Under the laser directed energy deposition(LDED)process,the rapid melting and solidification usually lead to the emergence of pores and coarse columnar dendrites,which in turn compromise the properties of the deposite...Under the laser directed energy deposition(LDED)process,the rapid melting and solidification usually lead to the emergence of pores and coarse columnar dendrites,which in turn compromise the properties of the deposited alloys.This study introduced in-situ ultrasonic rolling(UR)as an innovative method to enhance the corrosion resistance of LDED specimens,and the microstructural characteristics and their correlation with corrosion resistance were deeply investigated.The findings reveal that the LDED-UR specimen exhibits a reduction in both the fraction and size of pores.Under the influence of severe plastic deformation generated by LDED-UR process,fully equiaxed grains appear with a reduced average size of 28.61μm(compared to63.98μm for the LDED specimen with columnar grains).The electrochemical corrosion resistance of the LDED-UR specimen is significantly enhanced compared to the LDED specimen.This enhanced corrosion resistance can be attributed to the low fraction of small-sized pores,the fine and uniformly distributed Cr-enriched ferrite phase,and the formation of a compact and thick passive film due to dense grain boundaries.The insight of the correlation between microstructure and corrosion behavior opens up a new pathway to enhance the corrosion resistance of LDED specimens.展开更多
Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstrea...Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.展开更多
Additive manufacturing provides achievability for the fabrication of bimetallic and multi-material structures;however,the material compatibility and bondability directly affect the parts’formability and final quality...Additive manufacturing provides achievability for the fabrication of bimetallic and multi-material structures;however,the material compatibility and bondability directly affect the parts’formability and final quality.It is essential to understand the underlying printability of different material combinations based on an adapted process.Here,the printability disparities of two common and attractive material combinations(nickel-and iron-based alloys)are evaluated at the macro and micro levels via laser directed energy deposition(DED).The deposition processes were captured using in situ high-speed imaging,and the dissimilarities in melt pool features and track morphology were quantitatively investigated within specific process windows.Moreover,the microstructure diversity of the tracks and blocks processed with varied material pairs was comparatively elaborated and,complemented with the informative multi-physics modeling,the presented non-uniformity in mechanical properties(microhardness)among the heterogeneous material pairs was rationalized.The differences in melt flow induced by the unlike thermophysical properties of the material pairs and the resulting element intermixing and localized re-alloying during solidification dominate the presented dissimilarity in printability among the material combinations.This work provides an in-depth understanding of the phenomenological differences in the deposition of dissimilar materials and aims to guide more reliable DED forming of bimetallic parts.展开更多
Conventional cast Al-Ce alloys are challenged by the increasing demand for improved mechanical properties.To address this issue,in this study,wire-arc directed energy deposition(WA-DED)is employed for the fabrication ...Conventional cast Al-Ce alloys are challenged by the increasing demand for improved mechanical properties.To address this issue,in this study,wire-arc directed energy deposition(WA-DED)is employed for the fabrication of Al-15Ce-3Mg(wt%)alloy components.We aimed to tune the microstructure and mechanical properties via the inherent sub-rapid-solidification effect of WA-DED.In addition to significant microstructure refinement,a decrease in arc heat input leads to a larger cooling rate,up to 346°C/s,and triggers the transition from hyper-eutectic to near-eutecticα-Al/Al_(11)Ce_(3)microstructures with the suppression of primary Al_(11)Ce_(3)intermetallics.Such microstructural modification improves the mechanical properties,resulting in higher yield and ultimate tensile strengths than those of the as-cast counterpart alloy.The fracture process involves the formation of dim-ples around Al11 Ce3,cracking of large Al11 Ce3 particles,and growth,merging,and fracture of pores.The strength increment is mainly contributed by particle-size strengthening mediated by microstructure refinement as well as the targeted formation of near-eutecticα-Al/Al_(11)Ce_(3)microstructures.展开更多
The microstructure characteristics and strengthening mechanism of Inconel738LC(IN-738LC) alloy prepared by using induction-assisted directed energy deposition(IDED) were elucidated through the investigation of samples...The microstructure characteristics and strengthening mechanism of Inconel738LC(IN-738LC) alloy prepared by using induction-assisted directed energy deposition(IDED) were elucidated through the investigation of samples subjected to IDED under 1050℃ preheating with and without hot isostatic pressing(HIP,1190℃,105 MPa,and 3 h).Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ’ phases in interdendritic and dendritic core regions.After HIP,grain morphology changed negligibly,whereas the size of the γ’ phase became increasingly even.After further heat treatment(HT,1070℃,2 h + 845℃,24 h),the γ’ phase in the as-deposited and HIPed samples presented a bimodal size distribution,whereas that in the as-deposited sample showed a size that remained uneven.The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%,respectively,due to the synergistic deformation of bimodal γ’phases,especially large cubic γ’ phases.Finally,the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.展开更多
Mg-Gd-Y-Zr alloy,as a typical magnesium rare-earth(Mg-RE)alloy,is gaining popularity in the advanced equipment manufacturing fields owing to its noticeable age-hardening properties and high specific strength.However,i...Mg-Gd-Y-Zr alloy,as a typical magnesium rare-earth(Mg-RE)alloy,is gaining popularity in the advanced equipment manufacturing fields owing to its noticeable age-hardening properties and high specific strength.However,it is extremely challenging to prepare wrought components with large dimensions and complex shapes because of the poor room-temperature processability of Mg-Gd-Y-Zr alloy.Herein,we report a wire-arc directed energy deposited(DED)Mg-10.45Gd-2.27Y-0.52Zr(wt.%,GW102K)alloy with high RE content presenting a prominent combination of strength and ductility,realized by tailored nanoprecipitates through an optimized heat treatment procedure.Specifically,the solution-treated sample exhibits excellent ductility with an elongation(EL)of(14.6±0.1)%,while the aging-treated sample at 200°C for 58 h achieves an ultra-high ultimate tensile strength(UTS)of(371±1.5)MPa.Besides,the aging-treated sample at 250°C for 16 h attains a good strength-ductility synergy with a UTS of(316±2.1)MPa and a EL of(8.5±0.1)%.Particularly,the evolution mechanisms of precipitation response induced by various aging parameters and deformation behavior caused by nanoprecipitates type were also systematically revealed.The excellent ductility resulted from coordinating localized strains facilitated by active slip activity.And the ultra-high strength should be ascribed to the dense nano-β'hampering dislocation motion.Additionally,the shearable nano-β1 contributed to the good strength-ductility synergy.This work thus offers insightful understanding into the nanoprecipitates manipulation and performance tailoring for the wire-arc DED preparation of large-sized Mg-Gd-Y-Zr components with complex geometries.展开更多
Laser Directed Energy Deposition (LDED) marks a critical advance in intelligent manufacturing, enabling efficient near-net shape production of metal parts. This method is especially beneficial for aerospace and defens...Laser Directed Energy Deposition (LDED) marks a critical advance in intelligent manufacturing, enabling efficient near-net shape production of metal parts. This method is especially beneficial for aerospace and defense applications that require high precision. However, issues such as deformation and heat accumulation during production still affect the quality of the final products, necessitating further optimization of process parameters. This paper studies the effects of three deposition strategies on 316L stainless steel parts using LDED. The three strategies based on unidirectional scanning (US), zigzag scanning (ZS), and square spiral scanning (SS) are investigated by solid samples and samples with a central hole. The surface smoothness, defects, and mechanical properties of 316L samples manufactured with the above strategies are discussed by means of surface topography tests and metallographic characterization. Experimental results indicate that the zigzag scanning strategy yielded better results for solid components, and the square spiral scanning strategy is suitable for samples with a central hole.展开更多
Wire-arc directed energy deposition(WA-DED)has emerged as a transformative technology for producing large-scale metal components owing to its capacity for cost-effective fabrication and suitable deposition rates.Recen...Wire-arc directed energy deposition(WA-DED)has emerged as a transformative technology for producing large-scale metal components owing to its capacity for cost-effective fabrication and suitable deposition rates.Recently,the focus has shifted to the WA-DED of magnesium alloys,which are promising lightweight structural materials in the aerospace transportation and military industries.This article systematically reviews recent advancements in magnesium alloys fabricated using WA-DED.It discusses aspects such as forming quality,internal defects,microstructural evolution,and mechanical properties.Prevalent internal defects such as pores and cracks in WA-DED magnesium alloys are identified and characterized.Additionally,strategies for enhancing the manufacturing quality are elucidated.Furthermore,this article comprehensively explores the underlying mechanisms of the interplay among process parameters,internal defects,and microstructural heterogeneity.The main objective is to provide insights into and strategies for defect elimination,microstructural homogenization,and property enhancement.Finally,some perspectives are proposed for further progress in the application of WA-DED magnesium alloy components for superior performance.展开更多
The static coarsening behavior of laser powder directed energy deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy and its effects on the alloy’s tensile properties were investigated.The static coarsening kinetics of...The static coarsening behavior of laser powder directed energy deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy and its effects on the alloy’s tensile properties were investigated.The static coarsening kinetics of the crab-like primary α(α_(P))and secondary α(α_(s))were satisfied by the Lifshitz-Slyozov-Wagner relationships.For the coarsening of the crab-like𝛼P,the coarsening efficiency(n)was satisfied at 0.25-0.35 for 910℃,whereas it was satisfied at 0.45-0.50 for 950 and 990℃.For the coarsening of the α_(s),the n was satisfied at 0.45-0.50 for 950℃ and 990℃.Compared to the as-built sample,the samples heat-treated at 910℃/2 h/air cooled and 950℃/2 h/air cooled exhibited good yield strength(930-1005.5 MPa),the highest elongation(14.5%-16.6%),and the lowest anisotropic ductility(0.6%)among all samples.The crab-like α_(P) and α_(s) increased the crack growth resistance and decreased the fracture difference in two different directions in the samples.展开更多
Additive manufacturing(AM)is a reliable technique for constructing highly complex metallic parts.Direct energy deposition(DED)is one of the most common technologies used for AM-printed metal alloys.However,issues such...Additive manufacturing(AM)is a reliable technique for constructing highly complex metallic parts.Direct energy deposition(DED)is one of the most common technologies used for AM-printed metal alloys.However,issues such as weak binding,poor accuracy,and rough surfaces still affect the final products.These limitations in the metal-feed DED process indicate that post-processing techniques are required to achieve high quality in terms of both mechanical properties and surface finish.Conventional contact-based post-processing methods have several drawbacks,including difficulties in accessing complex shapes,environmental impact,high time consumption and cost,and health risks for operators.To address these problems and improve surface quality,a laser polishing process has been proposed.By melting or ablating the material with a laser,the laser-polishing process enables the smoothing of the initial topography.It should be noted that there are currently no reviews focusing specifically on laser polishing as a surface treatment technology for the DED process.Therefore,this review presents a unique examination of the mechanisms and primary user-set parameters for both continuous wave(CW)and pulsed laser polishing.The objective is to demonstrate the capabilities of each process and the benefits of using them for the surfaces of DED metal parts.Additionally,existing knowledge and technology gaps are identified,and future research directions are discussed.展开更多
NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emph...NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emphasis on its phase composition,microstructure,mechanical property and deformation mechanism.The results show that the yield strength and ductility obtained by SLM are 100 MPa and 8%,respectively,which are remarkably different from DED result with 700 MPa and 2%.The load path of SLM sample presents shape memory effect,corresponding to martensite phase detected by XRD;while the load path of DED presents pseudo-elasticity with austenite phase.In SLM sample,fine grain and hole provide a uniform deformation during tensile test,resulting in a better elongation.Furthermore,the nonequilibrium solidification was studied by a temperature field simulation to understand the difference of the two 3D printing methods.Both temperature gradient G and growth rate R determine the microstructure and phase in the SLM sample and DED sample,which leads to similar grain morphologies because of similar G/R.While higher G×R of SLM leads to a finer grain size in SLM sample,providing enough driving force for martensite transition and subsequently changing texture compared to DED sample.展开更多
Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical properties.It is found that the localized remelting,reheat...Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical properties.It is found that the localized remelting,reheating,and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal,a gradient distribution of Ni4Ti3 precipitates along the building direction,and preferential formation of Ni4Ti3 precipitates in the columnar zone.The austenite transformation finish temperature(Af)varies from-12.65℃(Z=33 mm)to 60.35℃(Z=10 mm),corresponding to tensile yield strength(σ0.2)changed from 120±30 MPa to 570±20 MPa,and functional properties changed from shape memory effect to superelasticity at room temperature.The sample in the Z=20.4 mm height has the best plasticity of 9.6%and the best recoverable strain of 4.2%.This work provided insights and guidelines for the spatial characterization of DEDed NiTi.展开更多
In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major rea...In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major reason for this is the possibility of producing parts with a complex geometry as well as a fine-grained microstructure.While the process has been shown to be applicable for Mg-Al-Zn alloys,there is still a lack of knowledge in terms of the influence of the WAAM process on the age-hardening response.Consequently,this study deals with the aging response of a WAAM AZ91 alloy.In order to fully understand the mechanisms during aging,first,the as-built condition was analyzed by means of high-energy X-ray diffraction(HEXRD)and scanning electron microscopy.These investigations revealed a finegrained,equiaxed microstructure with adjacent areas of alternating Al content.Subsequently,the difference between single-and double-step aging as well as conventional and direct aging was studied on the as-built WAAM AZ91 alloy for the first time.The aging response during the various heat treatments was monitored via in situ HEXRD experiments.Corroborating electron microscopy and hardness studies were conducted.The results showed that the application of a double-step aging heat treatment at 325℃with pre-aging at 250℃slightly improves the mechanical properties when compared to the single-step heat treatment at 325℃.However,the hardness decreases considerably after the pre-aging step.Thus,aging at lower temperatures is preferable within the investigated temperature range of 250-325℃.Moreover,no significant difference between the conventionally aged and directly aged samples was found.Lastly,the specimens showed enhanced precipitation kinetics during aging as compared to cast samples.This could be attributed to a higher amount of nucleation sites and the particular temperature profile of the solution heat treatment.展开更多
We discuss novel advanced concepts suitable for the practical design of gamma-ray sources of directed energy. One concept is based on the self-channeling of a powerful optical laser in a gas within a metal tube. Anoth...We discuss novel advanced concepts suitable for the practical design of gamma-ray sources of directed energy. One concept is based on the self-channeling of a powerful optical laser in a gas within a metal tube. Another concept employs a direct excitation of a quadrupole nuclear level by a powerful optical laser. The third concept is based on the process of a high-order harmonic generation by an x-ray laser. All three concepts can be used for designing gamma-ray lasers that would have significant advantages over x-ray lasers. First, missile defense systems employing gamma-ray lasers would be weather independent. Second, the gamma-ray laser radiation can penetrate through the sand, which could be suspended in the air in a desert either naturally (due to strong winds) or artificially (as a protective “shield”). Besides, the first out of the three concepts can beemployed for creating non-laser gamma-ray sources of directed energy to be used for detecting stored radioactive materials, including the radioactive materials carried by an aircraft or a satellite. Last but not least: these concepts can be also used for remotely destroying biological and chemical weapons as a preemptive strike or during its delivery phase, as well as for distinguishing a nuclear warhead from decoy warheads. Thus, the defense capabilities of the proposed gamma-ray lasers can save numerous lives.展开更多
This paper presents a comprehensive review of the research studies on direct energy system effect on aircraft composite structures to develop a good understanding of state-of-the-art research and development in this a...This paper presents a comprehensive review of the research studies on direct energy system effect on aircraft composite structures to develop a good understanding of state-of-the-art research and development in this area.The review begins with the application of composite materials in the aircraft structures and highlights their particular areas of application and limitations.An overview of directed energy system is given.Some of the commonly used systems in this category are discussed and the working principles of laser energy systems are described.The experimental and numerical studies reported regarding the aircraft composite structures subject to the effect of directed energy systems,especially the laser systems are reviewed in detail.In particularly,the general effects of laser systems and the relevant damage mechanisms against the composite structures are reported.The review draws attention to the recent research and findings in this field and is expected to guide engineers/researchers in future theoretical,numerical,and experimental studies.展开更多
The layer-by-layer deposition strategy of additive manufacturing makes it ideal to fabricate dissimilar alloy components with varying functionality,which has promising application potential in a large number of indust...The layer-by-layer deposition strategy of additive manufacturing makes it ideal to fabricate dissimilar alloy components with varying functionality,which has promising application potential in a large number of industrial areas.In this study,two components composed of ERCuAl-A2 aluminum bronze(CuAl9)and Inconel 718 nickel-based superalloy were fabricated with different deposition orders by wire-arc directed energy deposition.Subject to changes in heat input and thermophysical properties of the substrate,the transition region of the deposited Cu-Ni component with the bottom half of CuAl9 and the top half of Inconel 718 is narrow and serrated.This region features a laminated intermetallic compound layer due to the convection and rapid cooling in the molten pool.In contrast,the Ni-Cu component deposited in the opposite order exhibits a 2 mm gradient transition zone.Within this region,a large number of diverse precipitates were found as well as regional variations in grain size due to the multi-layer partial remelting.Both two components show strong bonds and their tensile specimens tested along the vertical direction always fracture at the softer CuAl9 side.Excellent tensile properties along the horizontal direction were obtained for Cu-Ni(Ultimate tensile strength:573 MPa,yield stress:302 MPa,elongation:22%),while those of Ni-Cu are much lower due to the existence of the solidification cracks in the transition zone.The results from this study provide a reference for the additive manufacturing of Cu/Ni dissimilar alloy components,as well as their microstructure and mechanical properties control.展开更多
Here we propose to employ wire-arc directed energy deposition(WA-DED) to tune the microstructure and the mechanical property of Mg-Al-Si alloys, on the basis of its sub-rapid solidification effect. According to finite...Here we propose to employ wire-arc directed energy deposition(WA-DED) to tune the microstructure and the mechanical property of Mg-Al-Si alloys, on the basis of its sub-rapid solidification effect. According to finite element analysis, WA-DED shows higher cooling rate than conventional casting, reaching 598.3 K/s for Mg-Al-Si alloy, and the lower heat input, the larger cooling rate of WA-DED. Significant microstructure refinement is thus achieved, with reduced grain size and Mg_(2)Si particle diameter. The transition from hypereutectic to fully eutectic microstructure is triggered by reducing the heat input. Compared with the as-cast alloy, WA-DED alloys demonstrate higher ultimate tensile strengths(UTS) at both room-and high-temperature(150℃) properties, increasing by 50.1% and 30.3%, respectively. The superior strength-ductility synergy for Mg-Al-Si alloys results from the microstructure tuning via sub-rapid solidification of WA-DED.展开更多
Ti and its alloys have been broadly adopted across various industries owing to their outstanding proper-ties,such as high strength-to-weight ratio,excellent fatigue performance,exceptional corrosion resistance and so ...Ti and its alloys have been broadly adopted across various industries owing to their outstanding proper-ties,such as high strength-to-weight ratio,excellent fatigue performance,exceptional corrosion resistance and so on.Additive manufacturing(AM)is a complement to,rather than a replacement for,traditional manufacturing processes.It enhances flexibility in fabricating complex components and resolves machin-ing challenges,resulting in reduced lead times for custom designs.However,owing to distinctions among various AM technologies,Ti alloys fabricated by different AM methods usually present differences in mi-crostructure and defects,which can significantly influence the mechanical performance of built parts.Therefore,having an in-depth knowledge of the scientific aspects of fabrication and material properties is crucial to achieving high-performance Ti alloys through different AM methods.This article reviews the mechanical properties of Ti alloys fabricated by two mainstream powder-type AM techniques:powder bed fusion(PBF)and directed energy deposition(DED).The review examines several key aspects,en-compassing phase formation,grain size and morphology,and defects,and provides an in-depth analysis of their influence on the mechanical behaviors of Ti alloys.This review can aid researchers and engi-neers in selecting appropriate PBF or DED methods and optimizing their process parameters to fabricate high-performance Ti alloys for a wide range of industrial applications.展开更多
Columnar grain structure caused anisotropy in mechanical properties,especially in elongation,is an important concern for Ti-6Al-4 V alloy fabricated by directed energy deposition(DED).Several strategies have been prop...Columnar grain structure caused anisotropy in mechanical properties,especially in elongation,is an important concern for Ti-6Al-4 V alloy fabricated by directed energy deposition(DED).Several strategies have been proposed to reduce anisotropy by globularizing the grains,but these conventional approaches are costly and inefficient due to challenges faced during producing the columnarβ-grain structures.However,understanding the impact of columnar grain-related microstructures on the anisotropic deformation behavior is still necessary.Despite the recognition of the importance of grain boundary Widmannstättenαcolony(αWGB)as a grain-related microstructure,it has received limited attention in available literature on anisotropy in mechanical properties.This study employed in-situ induction heating during DED to controlαWGB formation,yielding three Ti-6Al-4 V samples with varyingαWGB sizes.Anisotropic deforma-tion ofαWGB and its impact on elongation in build and transverse directions were analyzed.αWGB width grew from 0.5μm to 32.4μm via diffusion-controlled growth due to reduced cooling rate.Transverse deformation led to dislocation movement and accumulation,causing early failure and worsened ductile anisotropy withinαWGB.Notably,largerαWGB size significantly exacerbated anisotropy in ductility.This work underscoresαWGB’s role in anisotropic deformation and offers insights for optimizing mechanical properties in DED-fabricated titanium alloys.展开更多
Investigations on the fabrication of large-size lightweight Mg alloy components by wire-arc directed en-ergy deposition(DED)are steadily flourishing.Nevertheless,most of these components still suffer from inferior per...Investigations on the fabrication of large-size lightweight Mg alloy components by wire-arc directed en-ergy deposition(DED)are steadily flourishing.Nevertheless,most of these components still suffer from inferior performance due to internal defects and inherent columnar grains.Herein,external ultrasound fields with different powers were successfully introduced into the wire-arc DED of AZ31 Mg alloy.The microstructure,defects,and mechanical properties of the fabricated components were carefully charac-terized and compared.The results show that the external ultrasound fields lead to decreased porosity,complete columnar to equiaxed transition(CET),and enhanced performance.Consequently,the UA90 samples exhibited a remarkable increase of~30%,~45%,and~189%in yield strength,ultimate tensile strength,and elongation,respectively.The dominant mechanisms of enhanced strength-ductility synergy were analyzed in detail.This study thus sheds new light on wire-arc DED of Mg alloy components with excellent performance via external ultrasound fields.展开更多
基金financial supports from the National Natural Science Foundation of China (No.52305440)the Natural Science Foundation of Changsha City (Nos.kq2208272,kq2208274)+1 种基金the Tribology Science Fund of the State Key Laboratory of Tribology in Advanced Equipment (SKLTKF22B09)the National Key Research and Development Program of China (2022YFB3706902)。
文摘Under the laser directed energy deposition(LDED)process,the rapid melting and solidification usually lead to the emergence of pores and coarse columnar dendrites,which in turn compromise the properties of the deposited alloys.This study introduced in-situ ultrasonic rolling(UR)as an innovative method to enhance the corrosion resistance of LDED specimens,and the microstructural characteristics and their correlation with corrosion resistance were deeply investigated.The findings reveal that the LDED-UR specimen exhibits a reduction in both the fraction and size of pores.Under the influence of severe plastic deformation generated by LDED-UR process,fully equiaxed grains appear with a reduced average size of 28.61μm(compared to63.98μm for the LDED specimen with columnar grains).The electrochemical corrosion resistance of the LDED-UR specimen is significantly enhanced compared to the LDED specimen.This enhanced corrosion resistance can be attributed to the low fraction of small-sized pores,the fine and uniformly distributed Cr-enriched ferrite phase,and the formation of a compact and thick passive film due to dense grain boundaries.The insight of the correlation between microstructure and corrosion behavior opens up a new pathway to enhance the corrosion resistance of LDED specimens.
基金supported by the 2022 MTC Young Individual Research Grants(Grant No.M22K3c0097)the Singapore Research,Innovation and Enterprise(RIE)2025 PlanSingapore Aerospace Programme Cycle 16(Grant No.M2215a0073)。
文摘Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.
基金supported by the National Natural Science Foundation of China(51975112,52375412)Fundamental Research Funds for Central Universities(N2203011)。
文摘Additive manufacturing provides achievability for the fabrication of bimetallic and multi-material structures;however,the material compatibility and bondability directly affect the parts’formability and final quality.It is essential to understand the underlying printability of different material combinations based on an adapted process.Here,the printability disparities of two common and attractive material combinations(nickel-and iron-based alloys)are evaluated at the macro and micro levels via laser directed energy deposition(DED).The deposition processes were captured using in situ high-speed imaging,and the dissimilarities in melt pool features and track morphology were quantitatively investigated within specific process windows.Moreover,the microstructure diversity of the tracks and blocks processed with varied material pairs was comparatively elaborated and,complemented with the informative multi-physics modeling,the presented non-uniformity in mechanical properties(microhardness)among the heterogeneous material pairs was rationalized.The differences in melt flow induced by the unlike thermophysical properties of the material pairs and the resulting element intermixing and localized re-alloying during solidification dominate the presented dissimilarity in printability among the material combinations.This work provides an in-depth understanding of the phenomenological differences in the deposition of dissimilar materials and aims to guide more reliable DED forming of bimetallic parts.
基金supported by National Natural Science Foundation of China(Grant No.52105319)The authors are grateful to the Analysis&Testing Center and the Micro-and Nanotechnology Center at the Beijing Institute of Technology for performing the XRM experiments.
文摘Conventional cast Al-Ce alloys are challenged by the increasing demand for improved mechanical properties.To address this issue,in this study,wire-arc directed energy deposition(WA-DED)is employed for the fabrication of Al-15Ce-3Mg(wt%)alloy components.We aimed to tune the microstructure and mechanical properties via the inherent sub-rapid-solidification effect of WA-DED.In addition to significant microstructure refinement,a decrease in arc heat input leads to a larger cooling rate,up to 346°C/s,and triggers the transition from hyper-eutectic to near-eutecticα-Al/Al_(11)Ce_(3)microstructures with the suppression of primary Al_(11)Ce_(3)intermetallics.Such microstructural modification improves the mechanical properties,resulting in higher yield and ultimate tensile strengths than those of the as-cast counterpart alloy.The fracture process involves the formation of dim-ples around Al11 Ce3,cracking of large Al11 Ce3 particles,and growth,merging,and fracture of pores.The strength increment is mainly contributed by particle-size strengthening mediated by microstructure refinement as well as the targeted formation of near-eutecticα-Al/Al_(11)Ce_(3)microstructures.
基金financial support of the National Natural Science Foundation of China(Nos.52130110 and U22A20189)the Research Fund of the State Key Laboratory of Solidification Processing(No.2023-TS-10)。
文摘The microstructure characteristics and strengthening mechanism of Inconel738LC(IN-738LC) alloy prepared by using induction-assisted directed energy deposition(IDED) were elucidated through the investigation of samples subjected to IDED under 1050℃ preheating with and without hot isostatic pressing(HIP,1190℃,105 MPa,and 3 h).Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ’ phases in interdendritic and dendritic core regions.After HIP,grain morphology changed negligibly,whereas the size of the γ’ phase became increasingly even.After further heat treatment(HT,1070℃,2 h + 845℃,24 h),the γ’ phase in the as-deposited and HIPed samples presented a bimodal size distribution,whereas that in the as-deposited sample showed a size that remained uneven.The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%,respectively,due to the synergistic deformation of bimodal γ’phases,especially large cubic γ’ phases.Finally,the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.
基金National Natural Science Foundation of China (52275374, 52205414)Xi’an Jiaotong University Basic Research Funds for Freedom of Exploration and Innovation-Student Programs (xzy022023066)+3 种基金Key Research and Development Projects of Shaanxi Province (2023-YBGY-361)Young Elite Scientists Sponsorship Program by CAST (2021QNRC001)State Key Laboratory for Mechanical Behavior of Materials (20212311)Xiaomi Foundation through Xiaomi Young Scholar Program
文摘Mg-Gd-Y-Zr alloy,as a typical magnesium rare-earth(Mg-RE)alloy,is gaining popularity in the advanced equipment manufacturing fields owing to its noticeable age-hardening properties and high specific strength.However,it is extremely challenging to prepare wrought components with large dimensions and complex shapes because of the poor room-temperature processability of Mg-Gd-Y-Zr alloy.Herein,we report a wire-arc directed energy deposited(DED)Mg-10.45Gd-2.27Y-0.52Zr(wt.%,GW102K)alloy with high RE content presenting a prominent combination of strength and ductility,realized by tailored nanoprecipitates through an optimized heat treatment procedure.Specifically,the solution-treated sample exhibits excellent ductility with an elongation(EL)of(14.6±0.1)%,while the aging-treated sample at 200°C for 58 h achieves an ultra-high ultimate tensile strength(UTS)of(371±1.5)MPa.Besides,the aging-treated sample at 250°C for 16 h attains a good strength-ductility synergy with a UTS of(316±2.1)MPa and a EL of(8.5±0.1)%.Particularly,the evolution mechanisms of precipitation response induced by various aging parameters and deformation behavior caused by nanoprecipitates type were also systematically revealed.The excellent ductility resulted from coordinating localized strains facilitated by active slip activity.And the ultra-high strength should be ascribed to the dense nano-β'hampering dislocation motion.Additionally,the shearable nano-β1 contributed to the good strength-ductility synergy.This work thus offers insightful understanding into the nanoprecipitates manipulation and performance tailoring for the wire-arc DED preparation of large-sized Mg-Gd-Y-Zr components with complex geometries.
文摘Laser Directed Energy Deposition (LDED) marks a critical advance in intelligent manufacturing, enabling efficient near-net shape production of metal parts. This method is especially beneficial for aerospace and defense applications that require high precision. However, issues such as deformation and heat accumulation during production still affect the quality of the final products, necessitating further optimization of process parameters. This paper studies the effects of three deposition strategies on 316L stainless steel parts using LDED. The three strategies based on unidirectional scanning (US), zigzag scanning (ZS), and square spiral scanning (SS) are investigated by solid samples and samples with a central hole. The surface smoothness, defects, and mechanical properties of 316L samples manufactured with the above strategies are discussed by means of surface topography tests and metallographic characterization. Experimental results indicate that the zigzag scanning strategy yielded better results for solid components, and the square spiral scanning strategy is suitable for samples with a central hole.
基金supported by National Natural Science Foundation of China(Grant Nos.52305331,U20B2031)China Postdoctoral Science Foundation(Grant No.2022M710298)Fundamental Research Funds for the Central Universities,China(Grant No.YWF-22-L-607).
文摘Wire-arc directed energy deposition(WA-DED)has emerged as a transformative technology for producing large-scale metal components owing to its capacity for cost-effective fabrication and suitable deposition rates.Recently,the focus has shifted to the WA-DED of magnesium alloys,which are promising lightweight structural materials in the aerospace transportation and military industries.This article systematically reviews recent advancements in magnesium alloys fabricated using WA-DED.It discusses aspects such as forming quality,internal defects,microstructural evolution,and mechanical properties.Prevalent internal defects such as pores and cracks in WA-DED magnesium alloys are identified and characterized.Additionally,strategies for enhancing the manufacturing quality are elucidated.Furthermore,this article comprehensively explores the underlying mechanisms of the interplay among process parameters,internal defects,and microstructural heterogeneity.The main objective is to provide insights into and strategies for defect elimination,microstructural homogenization,and property enhancement.Finally,some perspectives are proposed for further progress in the application of WA-DED magnesium alloy components for superior performance.
基金supported by National Key Research and Development Program of China(Grant No.2022YFB4602205).
文摘The static coarsening behavior of laser powder directed energy deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy and its effects on the alloy’s tensile properties were investigated.The static coarsening kinetics of the crab-like primary α(α_(P))and secondary α(α_(s))were satisfied by the Lifshitz-Slyozov-Wagner relationships.For the coarsening of the crab-like𝛼P,the coarsening efficiency(n)was satisfied at 0.25-0.35 for 910℃,whereas it was satisfied at 0.45-0.50 for 950 and 990℃.For the coarsening of the α_(s),the n was satisfied at 0.45-0.50 for 950℃ and 990℃.Compared to the as-built sample,the samples heat-treated at 910℃/2 h/air cooled and 950℃/2 h/air cooled exhibited good yield strength(930-1005.5 MPa),the highest elongation(14.5%-16.6%),and the lowest anisotropic ductility(0.6%)among all samples.The crab-like α_(P) and α_(s) increased the crack growth resistance and decreased the fracture difference in two different directions in the samples.
基金supported by National Key Research and Development Program of China(Grant No.2022YFB4600901).
文摘Additive manufacturing(AM)is a reliable technique for constructing highly complex metallic parts.Direct energy deposition(DED)is one of the most common technologies used for AM-printed metal alloys.However,issues such as weak binding,poor accuracy,and rough surfaces still affect the final products.These limitations in the metal-feed DED process indicate that post-processing techniques are required to achieve high quality in terms of both mechanical properties and surface finish.Conventional contact-based post-processing methods have several drawbacks,including difficulties in accessing complex shapes,environmental impact,high time consumption and cost,and health risks for operators.To address these problems and improve surface quality,a laser polishing process has been proposed.By melting or ablating the material with a laser,the laser-polishing process enables the smoothing of the initial topography.It should be noted that there are currently no reviews focusing specifically on laser polishing as a surface treatment technology for the DED process.Therefore,this review presents a unique examination of the mechanisms and primary user-set parameters for both continuous wave(CW)and pulsed laser polishing.The objective is to demonstrate the capabilities of each process and the benefits of using them for the surfaces of DED metal parts.Additionally,existing knowledge and technology gaps are identified,and future research directions are discussed.
基金Project(2020JJ2046)supported by the Science Fund for Hunan Distinguished Young Scholars,ChinaProject(S2020GXKJGG0416)supported by the Special Project for Hunan Innovative Province Construction,China+1 种基金Project(2018RS3007)supported by the Huxiang Young Talents,ChinaProject(GuikeAB19050002)supported by the Science Project of Guangxi,China。
文摘NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emphasis on its phase composition,microstructure,mechanical property and deformation mechanism.The results show that the yield strength and ductility obtained by SLM are 100 MPa and 8%,respectively,which are remarkably different from DED result with 700 MPa and 2%.The load path of SLM sample presents shape memory effect,corresponding to martensite phase detected by XRD;while the load path of DED presents pseudo-elasticity with austenite phase.In SLM sample,fine grain and hole provide a uniform deformation during tensile test,resulting in a better elongation.Furthermore,the nonequilibrium solidification was studied by a temperature field simulation to understand the difference of the two 3D printing methods.Both temperature gradient G and growth rate R determine the microstructure and phase in the SLM sample and DED sample,which leads to similar grain morphologies because of similar G/R.While higher G×R of SLM leads to a finer grain size in SLM sample,providing enough driving force for martensite transition and subsequently changing texture compared to DED sample.
基金the financial support of the Hunan Innovation Platform and Talent Plan(2022RC3033)Natural Science Foundation of Shandong Province(ZR2020ZD04)Ganzhou Science and Technology Planning Project(Grant No.Ganshikefa[2019]60)。
文摘Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical properties.It is found that the localized remelting,reheating,and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal,a gradient distribution of Ni4Ti3 precipitates along the building direction,and preferential formation of Ni4Ti3 precipitates in the columnar zone.The austenite transformation finish temperature(Af)varies from-12.65℃(Z=33 mm)to 60.35℃(Z=10 mm),corresponding to tensile yield strength(σ0.2)changed from 120±30 MPa to 570±20 MPa,and functional properties changed from shape memory effect to superelasticity at room temperature.The sample in the Z=20.4 mm height has the best plasticity of 9.6%and the best recoverable strain of 4.2%.This work provided insights and guidelines for the spatial characterization of DEDed NiTi.
基金supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020the financial support of the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant No.771146 TOUGHIT)funded within the AIT’s strategic research portfolio 2022 and by the European Commission within the framework INTERREG V-A Austria–Czech Republic in the project“ReMaP“(Interreg project no.ATCZ229)。
文摘In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major reason for this is the possibility of producing parts with a complex geometry as well as a fine-grained microstructure.While the process has been shown to be applicable for Mg-Al-Zn alloys,there is still a lack of knowledge in terms of the influence of the WAAM process on the age-hardening response.Consequently,this study deals with the aging response of a WAAM AZ91 alloy.In order to fully understand the mechanisms during aging,first,the as-built condition was analyzed by means of high-energy X-ray diffraction(HEXRD)and scanning electron microscopy.These investigations revealed a finegrained,equiaxed microstructure with adjacent areas of alternating Al content.Subsequently,the difference between single-and double-step aging as well as conventional and direct aging was studied on the as-built WAAM AZ91 alloy for the first time.The aging response during the various heat treatments was monitored via in situ HEXRD experiments.Corroborating electron microscopy and hardness studies were conducted.The results showed that the application of a double-step aging heat treatment at 325℃with pre-aging at 250℃slightly improves the mechanical properties when compared to the single-step heat treatment at 325℃.However,the hardness decreases considerably after the pre-aging step.Thus,aging at lower temperatures is preferable within the investigated temperature range of 250-325℃.Moreover,no significant difference between the conventionally aged and directly aged samples was found.Lastly,the specimens showed enhanced precipitation kinetics during aging as compared to cast samples.This could be attributed to a higher amount of nucleation sites and the particular temperature profile of the solution heat treatment.
文摘We discuss novel advanced concepts suitable for the practical design of gamma-ray sources of directed energy. One concept is based on the self-channeling of a powerful optical laser in a gas within a metal tube. Another concept employs a direct excitation of a quadrupole nuclear level by a powerful optical laser. The third concept is based on the process of a high-order harmonic generation by an x-ray laser. All three concepts can be used for designing gamma-ray lasers that would have significant advantages over x-ray lasers. First, missile defense systems employing gamma-ray lasers would be weather independent. Second, the gamma-ray laser radiation can penetrate through the sand, which could be suspended in the air in a desert either naturally (due to strong winds) or artificially (as a protective “shield”). Besides, the first out of the three concepts can beemployed for creating non-laser gamma-ray sources of directed energy to be used for detecting stored radioactive materials, including the radioactive materials carried by an aircraft or a satellite. Last but not least: these concepts can be also used for remotely destroying biological and chemical weapons as a preemptive strike or during its delivery phase, as well as for distinguishing a nuclear warhead from decoy warheads. Thus, the defense capabilities of the proposed gamma-ray lasers can save numerous lives.
文摘This paper presents a comprehensive review of the research studies on direct energy system effect on aircraft composite structures to develop a good understanding of state-of-the-art research and development in this area.The review begins with the application of composite materials in the aircraft structures and highlights their particular areas of application and limitations.An overview of directed energy system is given.Some of the commonly used systems in this category are discussed and the working principles of laser energy systems are described.The experimental and numerical studies reported regarding the aircraft composite structures subject to the effect of directed energy systems,especially the laser systems are reviewed in detail.In particularly,the general effects of laser systems and the relevant damage mechanisms against the composite structures are reported.The review draws attention to the recent research and findings in this field and is expected to guide engineers/researchers in future theoretical,numerical,and experimental studies.
基金supported by the Key Research and Development Program of Shaanxi Province(2023-YBGY361)the National Natural Science Foundation of China(52275374 and 52205414)+1 种基金the Postdoctoral Fellowship Program of CPSF(GZC20232098)as well as the Xiaomi Foundation through Xiaomi Young Scholar Program。
文摘The layer-by-layer deposition strategy of additive manufacturing makes it ideal to fabricate dissimilar alloy components with varying functionality,which has promising application potential in a large number of industrial areas.In this study,two components composed of ERCuAl-A2 aluminum bronze(CuAl9)and Inconel 718 nickel-based superalloy were fabricated with different deposition orders by wire-arc directed energy deposition.Subject to changes in heat input and thermophysical properties of the substrate,the transition region of the deposited Cu-Ni component with the bottom half of CuAl9 and the top half of Inconel 718 is narrow and serrated.This region features a laminated intermetallic compound layer due to the convection and rapid cooling in the molten pool.In contrast,the Ni-Cu component deposited in the opposite order exhibits a 2 mm gradient transition zone.Within this region,a large number of diverse precipitates were found as well as regional variations in grain size due to the multi-layer partial remelting.Both two components show strong bonds and their tensile specimens tested along the vertical direction always fracture at the softer CuAl9 side.Excellent tensile properties along the horizontal direction were obtained for Cu-Ni(Ultimate tensile strength:573 MPa,yield stress:302 MPa,elongation:22%),while those of Ni-Cu are much lower due to the existence of the solidification cracks in the transition zone.The results from this study provide a reference for the additive manufacturing of Cu/Ni dissimilar alloy components,as well as their microstructure and mechanical properties control.
基金National Natural Science Foundation of China (52105319)。
文摘Here we propose to employ wire-arc directed energy deposition(WA-DED) to tune the microstructure and the mechanical property of Mg-Al-Si alloys, on the basis of its sub-rapid solidification effect. According to finite element analysis, WA-DED shows higher cooling rate than conventional casting, reaching 598.3 K/s for Mg-Al-Si alloy, and the lower heat input, the larger cooling rate of WA-DED. Significant microstructure refinement is thus achieved, with reduced grain size and Mg_(2)Si particle diameter. The transition from hypereutectic to fully eutectic microstructure is triggered by reducing the heat input. Compared with the as-cast alloy, WA-DED alloys demonstrate higher ultimate tensile strengths(UTS) at both room-and high-temperature(150℃) properties, increasing by 50.1% and 30.3%, respectively. The superior strength-ductility synergy for Mg-Al-Si alloys results from the microstructure tuning via sub-rapid solidification of WA-DED.
基金the financial support provided by the industrial grant(No.G1006320).
文摘Ti and its alloys have been broadly adopted across various industries owing to their outstanding proper-ties,such as high strength-to-weight ratio,excellent fatigue performance,exceptional corrosion resistance and so on.Additive manufacturing(AM)is a complement to,rather than a replacement for,traditional manufacturing processes.It enhances flexibility in fabricating complex components and resolves machin-ing challenges,resulting in reduced lead times for custom designs.However,owing to distinctions among various AM technologies,Ti alloys fabricated by different AM methods usually present differences in mi-crostructure and defects,which can significantly influence the mechanical performance of built parts.Therefore,having an in-depth knowledge of the scientific aspects of fabrication and material properties is crucial to achieving high-performance Ti alloys through different AM methods.This article reviews the mechanical properties of Ti alloys fabricated by two mainstream powder-type AM techniques:powder bed fusion(PBF)and directed energy deposition(DED).The review examines several key aspects,en-compassing phase formation,grain size and morphology,and defects,and provides an in-depth analysis of their influence on the mechanical behaviors of Ti alloys.This review can aid researchers and engi-neers in selecting appropriate PBF or DED methods and optimizing their process parameters to fabricate high-performance Ti alloys for a wide range of industrial applications.
基金supported by the National Key Research and Development Program of China(Nos.2022YFB4600300 and 2022YFB4600301)the National Natural Science Foundation of China(No.52175364)+3 种基金the ND Basic Research Funds(No.G2022WD)the Shenzhen Science and Technology Plan Project(No.JCYJ20180508151903646)the Key Research and Development Program of Shaanxi(No.2023-YBGY-359)the Science and Technology Plan of Xi’an City(No.21ZCZZHXJS-QCY6-0001).
文摘Columnar grain structure caused anisotropy in mechanical properties,especially in elongation,is an important concern for Ti-6Al-4 V alloy fabricated by directed energy deposition(DED).Several strategies have been proposed to reduce anisotropy by globularizing the grains,but these conventional approaches are costly and inefficient due to challenges faced during producing the columnarβ-grain structures.However,understanding the impact of columnar grain-related microstructures on the anisotropic deformation behavior is still necessary.Despite the recognition of the importance of grain boundary Widmannstättenαcolony(αWGB)as a grain-related microstructure,it has received limited attention in available literature on anisotropy in mechanical properties.This study employed in-situ induction heating during DED to controlαWGB formation,yielding three Ti-6Al-4 V samples with varyingαWGB sizes.Anisotropic deforma-tion ofαWGB and its impact on elongation in build and transverse directions were analyzed.αWGB width grew from 0.5μm to 32.4μm via diffusion-controlled growth due to reduced cooling rate.Transverse deformation led to dislocation movement and accumulation,causing early failure and worsened ductile anisotropy withinαWGB.Notably,largerαWGB size significantly exacerbated anisotropy in ductility.This work underscoresαWGB’s role in anisotropic deformation and offers insights for optimizing mechanical properties in DED-fabricated titanium alloys.
基金National Natural Science Foun-dation of China(Nos.52275374,52205414)Xiaomi Founda-tion through the Xiaomi Young Scholar Program,the Key Research and Development Projects of Shaanxi Province(No.2023-YBGY-361)+2 种基金as well as the Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)State Key Laboratory for Mechan-ical Behavior of Materials(NO.20212311)as well as the Xi’an Jiaotong University Basic Research Funds for Freedom of Explo-ration and Innovation-Student Programs(NO.xzy022023066).
文摘Investigations on the fabrication of large-size lightweight Mg alloy components by wire-arc directed en-ergy deposition(DED)are steadily flourishing.Nevertheless,most of these components still suffer from inferior performance due to internal defects and inherent columnar grains.Herein,external ultrasound fields with different powers were successfully introduced into the wire-arc DED of AZ31 Mg alloy.The microstructure,defects,and mechanical properties of the fabricated components were carefully charac-terized and compared.The results show that the external ultrasound fields lead to decreased porosity,complete columnar to equiaxed transition(CET),and enhanced performance.Consequently,the UA90 samples exhibited a remarkable increase of~30%,~45%,and~189%in yield strength,ultimate tensile strength,and elongation,respectively.The dominant mechanisms of enhanced strength-ductility synergy were analyzed in detail.This study thus sheds new light on wire-arc DED of Mg alloy components with excellent performance via external ultrasound fields.
