The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing...The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing parameters on the positions of solid-liquid interfaces （SLIs） of copper and aluminum. It is found that mandrel tube length and mean withdrawing speed have significant effects on the SLI positions of both copper and aluminum. Aluminum casting temperature （TAI） （1003-1123 K） and secondary cooling water flux （600-900 L.h-1） have little effect on the SLI of copper but cause the SLI of aluminum to move 2-4 mm. When TA1 is in a range of 1043-1123 K, the liquid aluminum can fill continuously into the pre-solidified copper tube. Based on the numerical simulation, reasonable processing parameters were determined.展开更多
The influences of rolling reduction and aluminum sheet initial thickness(AIT)on the thickness fluctuation of aluminum layer(TFA)of embedded aluminum?steel composite sheet produced by cold roll bonding were investigate...The influences of rolling reduction and aluminum sheet initial thickness(AIT)on the thickness fluctuation of aluminum layer(TFA)of embedded aluminum?steel composite sheet produced by cold roll bonding were investigated,the formation mechanism of TFA was analyzed and method to improve the thickness uniformity of the aluminum layer was proposed.The results showed that when the reduction increased,TFA increased gradually.When the reduction was lower than40%,AIT had negligible effect on the TFA,while TFA increased with the decrease of AIT when the reduction was higher than40%.The non-uniformities of the steel surface deformation and the interfacial bonding extent caused by the work-hardened steel surface layer,were the main reasons for the formation of TFA.Adopting an appropriate surface treatment can help to decrease the hardening extent of the steel surface for improving the deformation uniformity during cold roll bonding process,which effectively improved the aluminum thickness uniformity of the embedded aluminum/steel composite sheets.展开更多
In this study, the effect of the processing route using a friction stir processing(FSP) method on the microstructure and mechanical behavior of a Mg-9Li-1Zn alloy was systematically investigated. In the FSP method, th...In this study, the effect of the processing route using a friction stir processing(FSP) method on the microstructure and mechanical behavior of a Mg-9Li-1Zn alloy was systematically investigated. In the FSP method, the odd-numbered(1st and 3rd) process directions and even-numbered(2nd and 4th) passes were alternated to distribute the strain throughout the whole processed zone uniformly. Consequently, the processed zone had a much more uniform microstructure and hardness distribution than the processed zone obtained using the conventional FSP method. Using this method, the grain size of a Mg-9Li-1Zn sheet alloy was refined from ~31 μm to ~0.21 μm with uniformly distributedα and β phases. The processed alloy exhibited a high strength-ductility synergy with an ultimate tensile strength(UTS) of 220.1 MPa and total elongation of 70.0% at a strain rate of 10^(-3)s^(-1), overwhelmingly higher than those of the base metal, 155.6 MPa in UTS and 36.0%in elongation. The in-situ SEM-DIC analysis and TEM observation demonstrated that such an outstanding ductility with moderate strength is caused by grain boundary sliding, the dominant deformation mechanism of the ultra-fine-grained sample after FSP. The processing route with reverse processing direction was proven to be efficient in producing the ultrafine grain size microstructure and improving the mechanical properties of superlight Mg-9Li-1Zn alloy.展开更多
Many non-toxic alloying elements,such as Fe,Ca,and Sr,have negligible solid solubilities in Zn matrix,leading to formation of coarse second phase particles.They exhibit low strengthening effects but highly detrimental...Many non-toxic alloying elements,such as Fe,Ca,and Sr,have negligible solid solubilities in Zn matrix,leading to formation of coarse second phase particles.They exhibit low strengthening effects but highly detrimental to ductility.So refining second phase is a common pursuit for Zn alloys.The present paper takes Zn-0.3Fe alloy suffered from coarse FeZn_(13) second phase particles as a touchstone to testify microstructure refining effect through solidification with an accelerated speed and multi-pass rolling.FeZn_(13) particles are refined from 24 to 2μm,and Zn grains are refined to 5μm.As a result,the strengthening effect of Fe is enhanced significantly,with yield strength and the ultimate tensile strength of the alloy increased from 132 to 218 MPa and from 159 to 264 MPa,respectively.Furthermore,corrosion non-uniformity and penetration are much alleviated.These results show that microstructure refinement,especially on coarse intermetallic second phases,has a great potential to improve mechanical and degradation properties of biodegradable Zn alloys.展开更多
Silver-based alloys are significant light-load electrical contact materials(ECMs).The trade-off between mechanical properties and electrical conductivity is always an important issue for the development of silver-base...Silver-based alloys are significant light-load electrical contact materials(ECMs).The trade-off between mechanical properties and electrical conductivity is always an important issue for the development of silver-based ECMs.In this paper,we proposed an idea for the regulation of the mechanical properties and the electrical conductivity of Ag-11.40Cu-0.66Ni-0.05Ce(wt%)alloy using in-situ composite fiber-reinforcement.The alloy was processed using rolling,heat treatment,and heavy drawing,the strength and electrical conductivity were tested at different deformation stages,and the microstructures during deformation were observed using field emission scanning electron microscope(FESEM),transmission electron microscope(TEM)and electron backscatter diffraction(EBSD).The results show that the method proposed in this paper can achieve the preparation of in-situ composite fiber-reinforced Ag-Cu-Ni-Ce alloys.After the heavy deformation drawing,the room temperature Vickers hardness of the as-cast alloy increased from HV 81.6 to HV 169.3,and the electrical conductivity improved from 74.3%IACS(IACS,i.e.,international annealed copper standard)to 78.6%IACS.As the deformation increases,the alloy strength displays two different strengthening mechanisms,and the electrical conductivity has three stages of change.This research provides a new idea for the comprehensive performance control of high-performance silver-based ECMs.展开更多
A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and...A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and terminative positions of deformation were dynamically identified during dieless drawing, and the global monitoring and online closed-loop control of the deformation zone were achieved. The dieless drawing process was systematically carried out on NiTi shape memory alloy wires. It is shown that the deformation measurement method of interframe displacement can track the axial displacement of the wires, but this cannot be achieved by traditional machine vision. The initial and terminative positions of deformation can be accurately identified by this method. The proposed rectifying control technology can effectively decrease the wire diameter fluctuation during dieless drawing, that is, the standard deviation of the wire diameter fluctuation could be decreased fi＇om 0.30 to 0.08 mm after three passes of dieless drawing, indicating that the control system has a good rectifying ability.展开更多
Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal s...Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...展开更多
A new horizontal continuous casting method with heating-cooling combined mold （HCCM） technology was explored for fabri- cating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microst...A new horizontal continuous casting method with heating-cooling combined mold （HCCM） technology was explored for fabri- cating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe 10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting （cooling mold casting） were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the pro- duction efficiency of a BFel0 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of {012}〈 621 〉. Compared with cooling mold casting （6 = 36.5%）, HCCM can improve elongation （3 = 46.3%） by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe 10 cupronickel alloy tube.展开更多
A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the com...A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the composite billet had good surface quality, metallurgical bonding interface between brass and pure copper as well as elongation of 53.1%. Synergistic deformation degree between pure copper wire and brass cladding layer was high during drawing. With an increase of the total deformation amount, the plastic deformation of the pure copper wire reduced triangular arc gaps between the pure copper wires and the triangular arc gaps were fully filled at 50%. When the total deformation amount was increased to 63%, dislocation cells and microbands successively formed in the pure copper wire. In the brass cladding layer, planar dislocation networks, twins and shear bands formed successively, and the main deformation mechanisms were dislocation sliding, twinning and shear deformation. The tensile strength increased from 240 MPa of the composite billet to 519 MPa of the one with the deformation amount of 63%, but the elongation decreased from 53.1% to 3.2%. A process of solid/liquid continuous casting and composite forming→drawing can work as a new compact method to produce brass cladding pure copper stranded wire composite as railway through grounding wire.展开更多
Crystallography of precipitates in Mg alloys is indispensable to explain and predict alloy microstructures and properties.In order to obtain a global understanding of diversified experimental results,a general theory ...Crystallography of precipitates in Mg alloys is indispensable to explain and predict alloy microstructures and properties.In order to obtain a global understanding of diversified experimental results,a general theory of singular interface is introduced,which provides the physical base and calculation methodology for interpreting precipitate morphology and orientation relationship(OR),especially useful for understanding irrational facets and ORs.Guided by the theory,recent experimental findings are systematically summarized,including thermally stable and metastable precipitates with various crystal structures.Then,theoretical advances inspired by the findings are introduced,which deepens our understanding on OR selection and preference of irrational facets.At last,future research directions in this field are proposed.展开更多
A new and effective semisolid slurry preparation process with air-cooled stirring rod(ACSR)is reported,in which the compressed air is constantly injected into the inner cavity of a stirring rod to cool the melt.The sl...A new and effective semisolid slurry preparation process with air-cooled stirring rod(ACSR)is reported,in which the compressed air is constantly injected into the inner cavity of a stirring rod to cool the melt.The slurry of a newly developed high thermal conductivity Al?8Si alloy was prepared,and thin-wall heat dissipation shells were produced by the ACSR process combined with a HPDC machine.The effects of the air flow on the morphology ofα1-Al particles,mechanical properties and thermal conductivity of rheo-HPDC samples were studied.The results show that the excellent slurry of the alloy could be obtained with the air flow exceeding3L/s.Rheo-HPDC samples that were produced with the air flow of5L/s had the maximum UTS,YS,elongation,hardness and thermal conductivity of261MPa,124MPa,4.9%,HV99and153W/(m·K),respectively.Rheo-HPDC samples show improved properties compared to those formed by HPDC,and the increasing rates of UTS,YS,elongation,hardness and thermal conductivity were20%,15%,88%,13%and10%,respectively.展开更多
The effects of Ni content（0–2.1wt%）on the cast and solid-solution microstructures of Cu-0.4wt%Be alloys were investigated,and the corresponding mechanisms of influence were analyzed.The results show that the amount...The effects of Ni content（0–2.1wt%）on the cast and solid-solution microstructures of Cu-0.4wt%Be alloys were investigated,and the corresponding mechanisms of influence were analyzed.The results show that the amount of precipitated phase increases in the cast alloys with increasing Ni content.When the Ni content is 0.45wt%or 0.98wt%,needle-like Be_（21）Ni_5 phases form in the grains and are mainly distributed in the interdendritic regions.When the Ni content is 1.5wt%or greater,a large number of needle-like precipitates form in the grains and chain-like Be_（21）Ni_5 and Be Ni precipitates form along the grain boundaries.The addition of Ni can substantially refine the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.The hindering effects of both the dissolution of Ni into the matrix and the formation of Be–Ni precipitates on grain-boundary migration are mainly responsible for refining the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.Higher Ni contents result in finer microstructures;however,given the precipitation characteristics of Be–Ni phases and their dissolution into the matrix during the solid-solution treatment,the upper limit of the Ni content is 1.5wt%–2.1wt%.展开更多
The effects of Ni content(0−2.10 wt.%)on the precipitated phase,strength and electrical conductivity of Cu−0.4wt.%Be alloy were investigated,and the influencing mechanism was analyzed.The results showed that the addit...The effects of Ni content(0−2.10 wt.%)on the precipitated phase,strength and electrical conductivity of Cu−0.4wt.%Be alloy were investigated,and the influencing mechanism was analyzed.The results showed that the addition of Ni promoted the precipitation of strengthening phase in the alloy and remarkably enhanced the strengthening effect.When the Ni content was increased from 0 to 2.10 wt.%,the strength of the aged alloy initially increased and then decreased,and approached the maximum when the Ni content was 1.50 wt.%.The peak-aging parameters of the alloy containing 1.50 wt.%Ni were the aging temperature of 400℃ and the aging time of 60 min,where the tensile strength and yield strength of the aged alloy were 611 and 565 MPa,respectively,which were 2.8 times and 6.1 times those of the alloy without Ni.The electrical conductivity of the alloy with Ni increased with the aging time,and decreased with the increase of Ni content.With an increase of the aging time at 400℃,phase transition sequence of the Cu−0.4Be−1.5Ni alloy wasγ″phase→γ′phase→γphase.For the aging time of 60 min,a large number of dispersed nano-scale coherentγ″phase andγ′phase formed in the alloy with a remarkable strengthening effect,which was mainly responsible for the high strength of the alloy.展开更多
The role of Cr in affecting the precipitates and the properties of aged Cu−Cr−P alloys was investigated and discussed.The results show that there are mainly three sizes of Cr phase in aged Cu−Cr−P alloys,among them,th...The role of Cr in affecting the precipitates and the properties of aged Cu−Cr−P alloys was investigated and discussed.The results show that there are mainly three sizes of Cr phase in aged Cu−Cr−P alloys,among them,the nano-sized Cr phase plays an important role in the strength of Cu−Cr−P alloys.The strengthening effect of Cr phase(less than 5 nm)with FCC structure completely coherent with the matrix is calculated to be about 200 MPa on the basis of dislocation cut-through mechanism.The strengthening effect of Cr phase(10−20 nm)with BCC structure incoherent with the matrix is calculated to be about 100 MPa on the basis of the Orowan dislocation bypass mechanism.The increase of Cr content changes the number and size of nano-sized Cr phase,which causes the mechanical properties of the Cu−Cr−P alloys to increase first and then decrease.The tensile strength of Cu−0.36Cr−0.01P alloy is 572 MPa and its electrical conductivity is 80%IACS after solid solution treatment at 980°C for 2 h followed by 95%cold rolling and then aging treatment at 450°C for 1 h.展开更多
In order to develop high strength,high damping and low density Al matrix composites,the Al/Zn composite bar samples with Zn mass fraction of 10%-40%were prepared by powder extrusion.The tensile strength and damping pr...In order to develop high strength,high damping and low density Al matrix composites,the Al/Zn composite bar samples with Zn mass fraction of 10%-40%were prepared by powder extrusion.The tensile strength and damping properties of the samples are improved by controlling both the Zn/Al diffusion degree and the precipitation of the interfacial phases.The results show that the tensile strength of the samples with Zn mass fraction of 10%-30%increases with the increases of both the Zn content and annealing temperature.When the Zn mass fraction increases to 40%,the tensile strength of the sample remains basically unchanged or decreases slightly,and the plasticity decreases gradually.Alloying of Al matrix and the formation of Zn/Al interface layer are mainly responsible for improving the strength of the annealed samples.The damping properties increase with the increases of both the Zn content and annealing temperature.The Zn/Al eutectoid lamella eliminates the detrimental effects on damping properties due to both alloying of the Al matrix and reduction of pure Zn in the Al matrix.The Al-30%Zn sample annealed at 350°C for 0.5 h has good comprehensive properties,including the tensile strength of 330 MPa,the elongation to failure of 10%and the room-temperature damping properties(tanθ)of 0.025.展开更多
Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces were fabricated by double rolling. The two surface morphologies of double-rolled copper foils are quite different, ...Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces were fabricated by double rolling. The two surface morphologies of double-rolled copper foils are quite different, and the surface roughness values are 61 and 1095 nm, respectively. The roughness value of matt surface can meet the requirement for bonding the resin matrix with copper foils used for flexible printed circuit boards, thus may omit traditional roughening treatment; the microstructure of double-rolled copper foils demonstrates an obviously asymmetric gradient feature. From bright surface to matt surface in thickness direction, the average grain size first increases from 2.3 to 7.4 μm and then decreases to 3.6 μm; compared with conventional rolled copper foils, the double-rolled copper foils exhibit a remarkably increased bending fatigue life, and the increased range is about 16.2%.展开更多
The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at ca...The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^(-1).Hollow billets under the same conditions were prepared,and their macro/microstructures were analyzed by an optical microscope and a scanning electron microscope.During the TZCC process,a circular fluid flow appears in front of the mushy zone,and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature gradient.The deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting speed.Experimental results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^(-1),while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed.2D12 aluminum alloy hollow billets with no macroscopic defects,the finest columnar crystals,and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^(-1),which is beneficial for the further plastic forming process.展开更多
The precipitation behaviours during the aging process and the corresponding strengthening mechanism of a Cu-0.4 wt%Sc alloy were systematically investigated in this study.The phase transformation sequence of the preci...The precipitation behaviours during the aging process and the corresponding strengthening mechanism of a Cu-0.4 wt%Sc alloy were systematically investigated in this study.The phase transformation sequence of the precipitation in the aging process of the Cu-0.4 wt%Sc alloy was found to be:supersaturated solid solution→Sc-enriched atomic clusters→metastable phase→Cu4Sc phase.The tetragonal structured lamellar Cu4Sc precipitates,with a habit plane parallel to the{111}plane of the Cu matrix and orientation relationships of(022)_(α)//(211)_(Cu4Sc)and[011]_(α)//[113]_(Cu4Sc),are found homogeneously distributed in the matrix.A combined process of cryogenic rolling(CR)and aging was designed for optimization of the mechanical and electrical properties.Excellent integration of yield strength(696 MPa)and electrical conductivity(62.8%IACS)of this alloy was achieved by cryogenic rolling and subsequent aging process at 400℃for 4 h.The significant precipitation strengthening effect of this alloy is attributed to the Cu4Sc precipitates with an extremely small size of only 1.5–3 nm.The leading strengthening mechanism is considered as the superposition of both coherent strengthening and Orowan strengthening effects.展开更多
Embedded aluminum-steel composite sheets used in heat exchanger were produced by cold roll bonding(CRB). The influences of annealing temperature and annealing time on the microstructure and the bonding strength of the...Embedded aluminum-steel composite sheets used in heat exchanger were produced by cold roll bonding(CRB). The influences of annealing temperature and annealing time on the microstructure and the bonding strength of the composite sheet were investigated. The recrystallization of the steel layer began at 525℃ and finished at 600℃. With the increase of the annealing temperature, the peel strength of the composite sheet whose original steel sheet surface was treated by scratch brush initially increased and then decreased, which was resulted from the competition of the mechanical locking and metallurgical bonding. After annealing, the cracks which formed between the broken work-hardened steel surface layer and its matrix during cold roll bonding remained. The composite sheet produced by CRB with the steel surface treatment of flap disc had less interfacial defects, higher bonding quality, higher diffusion rate of Al and Fe atoms at the interface and larger metallurgical bonding extent than the composite sheet produced by CRB with the steel surface treatment of scratch brush under the same conditions of annealing,which was helpful to shorten annealing time, reduce energy consumption and improve production efficiency.展开更多
The effects of warm-rolling process on the microstructure, ordering, mechanical properties and cold- rolling workability of Fe-6.Swt%Si alloy were investigated, where three processes of warm-rolling with the same tota...The effects of warm-rolling process on the microstructure, ordering, mechanical properties and cold- rolling workability of Fe-6.Swt%Si alloy were investigated, where three processes of warm-rolling with the same total reduction of 93% were used, including （1） 500 ℃/12 passes/total reduction of 93%, （2） 500 ℃13 passes/total reduction of 50% ＋ 400 ℃19 passes/total reduction of 86%, and （3） 500 ℃13 passes/total reduction of 50% ＋ 400 ℃15 passes/total reduction of 60% ＋ 300 ℃14 passes/total reduction of 64%. The results show that compared with process （1） warm-rolling with constant temperature of 500 ℃, process （2） and process （3） warm-rolling with gradually decreasing temperature can significantly improve the room temperature plasticity and cold-rolling workability of the Fe-6.5wt%Si alloy. For example, the three point bending fracture deflections are increased by 54.5% and 81.8% for processes （2） and （3）, respectively, and the maximum reductions of single pass cold-rolling without edge crack are increased from 50% of process （1） to 55% of process （2） and 62% of process （3）, respectively. The plasticity improvement of the Fe- 6.5wt%Si alloy can be attributed to both reductions of surface oxidation degree and order degree of the alloy by warm-rolling with gradually decreasing temperature.展开更多
基金financially supported by the National High Technology Research and Development Program of China (No. 2013AA030706 and No. 2009AA03Z532)the Fundamental Research Funds for the Central Universities of China (No. FRF-TP-12-146A)
文摘The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing parameters on the positions of solid-liquid interfaces （SLIs） of copper and aluminum. It is found that mandrel tube length and mean withdrawing speed have significant effects on the SLI positions of both copper and aluminum. Aluminum casting temperature （TAI） （1003-1123 K） and secondary cooling water flux （600-900 L.h-1） have little effect on the SLI of copper but cause the SLI of aluminum to move 2-4 mm. When TA1 is in a range of 1043-1123 K, the liquid aluminum can fill continuously into the pre-solidified copper tube. Based on the numerical simulation, reasonable processing parameters were determined.
基金Project(2013AA031301)supported by National High-tech Research and Development Program of ChinaProject(51104016)supported by National Natural Science Foundation of ChinaProject(BM2014006)supported by Jiangsu Key Laboratory for Clad Materials,China
文摘The influences of rolling reduction and aluminum sheet initial thickness(AIT)on the thickness fluctuation of aluminum layer(TFA)of embedded aluminum?steel composite sheet produced by cold roll bonding were investigated,the formation mechanism of TFA was analyzed and method to improve the thickness uniformity of the aluminum layer was proposed.The results showed that when the reduction increased,TFA increased gradually.When the reduction was lower than40%,AIT had negligible effect on the TFA,while TFA increased with the decrease of AIT when the reduction was higher than40%.The non-uniformities of the steel surface deformation and the interfacial bonding extent caused by the work-hardened steel surface layer,were the main reasons for the formation of TFA.Adopting an appropriate surface treatment can help to decrease the hardening extent of the steel surface for improving the deformation uniformity during cold roll bonding process,which effectively improved the aluminum thickness uniformity of the embedded aluminum/steel composite sheets.
基金partially supported by the JST-Mirai Program Grant Number JPMJMI19E5a Grant-in-Aid for Science Research from the Japan Society for the Promotion of Science。
文摘In this study, the effect of the processing route using a friction stir processing(FSP) method on the microstructure and mechanical behavior of a Mg-9Li-1Zn alloy was systematically investigated. In the FSP method, the odd-numbered(1st and 3rd) process directions and even-numbered(2nd and 4th) passes were alternated to distribute the strain throughout the whole processed zone uniformly. Consequently, the processed zone had a much more uniform microstructure and hardness distribution than the processed zone obtained using the conventional FSP method. Using this method, the grain size of a Mg-9Li-1Zn sheet alloy was refined from ~31 μm to ~0.21 μm with uniformly distributedα and β phases. The processed alloy exhibited a high strength-ductility synergy with an ultimate tensile strength(UTS) of 220.1 MPa and total elongation of 70.0% at a strain rate of 10^(-3)s^(-1), overwhelmingly higher than those of the base metal, 155.6 MPa in UTS and 36.0%in elongation. The in-situ SEM-DIC analysis and TEM observation demonstrated that such an outstanding ductility with moderate strength is caused by grain boundary sliding, the dominant deformation mechanism of the ultra-fine-grained sample after FSP. The processing route with reverse processing direction was proven to be efficient in producing the ultrafine grain size microstructure and improving the mechanical properties of superlight Mg-9Li-1Zn alloy.
基金financially supported by the National Natural Science Foundation of China(No.52071028)the Fundamental Research Funds for the Central Universities(No.FRF-TP-19-022A3Z)。
文摘Many non-toxic alloying elements,such as Fe,Ca,and Sr,have negligible solid solubilities in Zn matrix,leading to formation of coarse second phase particles.They exhibit low strengthening effects but highly detrimental to ductility.So refining second phase is a common pursuit for Zn alloys.The present paper takes Zn-0.3Fe alloy suffered from coarse FeZn_(13) second phase particles as a touchstone to testify microstructure refining effect through solidification with an accelerated speed and multi-pass rolling.FeZn_(13) particles are refined from 24 to 2μm,and Zn grains are refined to 5μm.As a result,the strengthening effect of Fe is enhanced significantly,with yield strength and the ultimate tensile strength of the alloy increased from 132 to 218 MPa and from 159 to 264 MPa,respectively.Furthermore,corrosion non-uniformity and penetration are much alleviated.These results show that microstructure refinement,especially on coarse intermetallic second phases,has a great potential to improve mechanical and degradation properties of biodegradable Zn alloys.
基金supported by the National Natural Science Foundation of China(Nos.52022011,52090041,and 51921001)the Beijing Nova Programs,China(No.Z191100001119125).
文摘Silver-based alloys are significant light-load electrical contact materials(ECMs).The trade-off between mechanical properties and electrical conductivity is always an important issue for the development of silver-based ECMs.In this paper,we proposed an idea for the regulation of the mechanical properties and the electrical conductivity of Ag-11.40Cu-0.66Ni-0.05Ce(wt%)alloy using in-situ composite fiber-reinforcement.The alloy was processed using rolling,heat treatment,and heavy drawing,the strength and electrical conductivity were tested at different deformation stages,and the microstructures during deformation were observed using field emission scanning electron microscope(FESEM),transmission electron microscope(TEM)and electron backscatter diffraction(EBSD).The results show that the method proposed in this paper can achieve the preparation of in-situ composite fiber-reinforced Ag-Cu-Ni-Ce alloys.After the heavy deformation drawing,the room temperature Vickers hardness of the as-cast alloy increased from HV 81.6 to HV 169.3,and the electrical conductivity improved from 74.3%IACS(IACS,i.e.,international annealed copper standard)to 78.6%IACS.As the deformation increases,the alloy strength displays two different strengthening mechanisms,and the electrical conductivity has three stages of change.This research provides a new idea for the comprehensive performance control of high-performance silver-based ECMs.
基金financially supported by the National Basic Research Priorities Program of China (No.2011CB606300)the National Natural Science Foundation of China (Nos.50634010 and 50674008)+1 种基金the Program for New Century Excellent Talents in Chinese Universities(No.NCET-06-0083)the Universities Fundamental Research Foundation of the Ministry of Education, China (No.FRF-TP-10-002B)
文摘A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and terminative positions of deformation were dynamically identified during dieless drawing, and the global monitoring and online closed-loop control of the deformation zone were achieved. The dieless drawing process was systematically carried out on NiTi shape memory alloy wires. It is shown that the deformation measurement method of interframe displacement can track the axial displacement of the wires, but this cannot be achieved by traditional machine vision. The initial and terminative positions of deformation can be accurately identified by this method. The proposed rectifying control technology can effectively decrease the wire diameter fluctuation during dieless drawing, that is, the standard deviation of the wire diameter fluctuation could be decreased fi＇om 0.30 to 0.08 mm after three passes of dieless drawing, indicating that the control system has a good rectifying ability.
文摘Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...
基金supported by the National High Technology Research and Development Program of China (No.2011BAE23B00)
文摘A new horizontal continuous casting method with heating-cooling combined mold （HCCM） technology was explored for fabri- cating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe 10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting （cooling mold casting） were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the pro- duction efficiency of a BFel0 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of {012}〈 621 〉. Compared with cooling mold casting （6 = 36.5%）, HCCM can improve elongation （3 = 46.3%） by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe 10 cupronickel alloy tube.
基金Project(51104016)supported by the National Natural Science Foundation of ChinaProject(51925401)supported by the National Natural Science Foundation for Distinguished Young Scholars of ChinaProject(2019B10087)supported by Ningbo Science and Technology Innovation 2025 Major Project,China。
文摘A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the composite billet had good surface quality, metallurgical bonding interface between brass and pure copper as well as elongation of 53.1%. Synergistic deformation degree between pure copper wire and brass cladding layer was high during drawing. With an increase of the total deformation amount, the plastic deformation of the pure copper wire reduced triangular arc gaps between the pure copper wires and the triangular arc gaps were fully filled at 50%. When the total deformation amount was increased to 63%, dislocation cells and microbands successively formed in the pure copper wire. In the brass cladding layer, planar dislocation networks, twins and shear bands formed successively, and the main deformation mechanisms were dislocation sliding, twinning and shear deformation. The tensile strength increased from 240 MPa of the composite billet to 519 MPa of the one with the deformation amount of 63%, but the elongation decreased from 53.1% to 3.2%. A process of solid/liquid continuous casting and composite forming→drawing can work as a new compact method to produce brass cladding pure copper stranded wire composite as railway through grounding wire.
基金Financially supported by the Fundamental Research Funds for the Central Universities(Project FRF-TP-19-022A3Z)National Natural Science Foundation of China(Project 51771022)
文摘Crystallography of precipitates in Mg alloys is indispensable to explain and predict alloy microstructures and properties.In order to obtain a global understanding of diversified experimental results,a general theory of singular interface is introduced,which provides the physical base and calculation methodology for interpreting precipitate morphology and orientation relationship(OR),especially useful for understanding irrational facets and ORs.Guided by the theory,recent experimental findings are systematically summarized,including thermally stable and metastable precipitates with various crystal structures.Then,theoretical advances inspired by the findings are introduced,which deepens our understanding on OR selection and preference of irrational facets.At last,future research directions in this field are proposed.
基金Project (2013B091300016) supported by the Department of Science and Technology of Guangdong Province,China
文摘A new and effective semisolid slurry preparation process with air-cooled stirring rod(ACSR)is reported,in which the compressed air is constantly injected into the inner cavity of a stirring rod to cool the melt.The slurry of a newly developed high thermal conductivity Al?8Si alloy was prepared,and thin-wall heat dissipation shells were produced by the ACSR process combined with a HPDC machine.The effects of the air flow on the morphology ofα1-Al particles,mechanical properties and thermal conductivity of rheo-HPDC samples were studied.The results show that the excellent slurry of the alloy could be obtained with the air flow exceeding3L/s.Rheo-HPDC samples that were produced with the air flow of5L/s had the maximum UTS,YS,elongation,hardness and thermal conductivity of261MPa,124MPa,4.9%,HV99and153W/(m·K),respectively.Rheo-HPDC samples show improved properties compared to those formed by HPDC,and the increasing rates of UTS,YS,elongation,hardness and thermal conductivity were20%,15%,88%,13%and10%,respectively.
基金financially supported by the National Key Research and Development Program of China (No.2016YFB0301300)
文摘The effects of Ni content（0–2.1wt%）on the cast and solid-solution microstructures of Cu-0.4wt%Be alloys were investigated,and the corresponding mechanisms of influence were analyzed.The results show that the amount of precipitated phase increases in the cast alloys with increasing Ni content.When the Ni content is 0.45wt%or 0.98wt%,needle-like Be_（21）Ni_5 phases form in the grains and are mainly distributed in the interdendritic regions.When the Ni content is 1.5wt%or greater,a large number of needle-like precipitates form in the grains and chain-like Be_（21）Ni_5 and Be Ni precipitates form along the grain boundaries.The addition of Ni can substantially refine the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.The hindering effects of both the dissolution of Ni into the matrix and the formation of Be–Ni precipitates on grain-boundary migration are mainly responsible for refining the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.Higher Ni contents result in finer microstructures;however,given the precipitation characteristics of Be–Ni phases and their dissolution into the matrix during the solid-solution treatment,the upper limit of the Ni content is 1.5wt%–2.1wt%.
基金The authors would like to thank the support from the National Key R&D Programme of China(No.2016YFB0301404)the National Natural Science Foundation of China(51925401,92066205)the National Ten Thousand Talents Programme of China and Ningbo“Science and Technology Innovation 2025”major project(No.2019B10087).
文摘The effects of Ni content(0−2.10 wt.%)on the precipitated phase,strength and electrical conductivity of Cu−0.4wt.%Be alloy were investigated,and the influencing mechanism was analyzed.The results showed that the addition of Ni promoted the precipitation of strengthening phase in the alloy and remarkably enhanced the strengthening effect.When the Ni content was increased from 0 to 2.10 wt.%,the strength of the aged alloy initially increased and then decreased,and approached the maximum when the Ni content was 1.50 wt.%.The peak-aging parameters of the alloy containing 1.50 wt.%Ni were the aging temperature of 400℃ and the aging time of 60 min,where the tensile strength and yield strength of the aged alloy were 611 and 565 MPa,respectively,which were 2.8 times and 6.1 times those of the alloy without Ni.The electrical conductivity of the alloy with Ni increased with the aging time,and decreased with the increase of Ni content.With an increase of the aging time at 400℃,phase transition sequence of the Cu−0.4Be−1.5Ni alloy wasγ″phase→γ′phase→γphase.For the aging time of 60 min,a large number of dispersed nano-scale coherentγ″phase andγ′phase formed in the alloy with a remarkable strengthening effect,which was mainly responsible for the high strength of the alloy.
基金The authors are grateful for the financial supports from National Key R&D Program of China(2016YFB0301303)Beijing Nova Program,China(Z191100001119125)the National Natural Science Foundation of China(51974028,U1602271).
文摘The role of Cr in affecting the precipitates and the properties of aged Cu−Cr−P alloys was investigated and discussed.The results show that there are mainly three sizes of Cr phase in aged Cu−Cr−P alloys,among them,the nano-sized Cr phase plays an important role in the strength of Cu−Cr−P alloys.The strengthening effect of Cr phase(less than 5 nm)with FCC structure completely coherent with the matrix is calculated to be about 200 MPa on the basis of dislocation cut-through mechanism.The strengthening effect of Cr phase(10−20 nm)with BCC structure incoherent with the matrix is calculated to be about 100 MPa on the basis of the Orowan dislocation bypass mechanism.The increase of Cr content changes the number and size of nano-sized Cr phase,which causes the mechanical properties of the Cu−Cr−P alloys to increase first and then decrease.The tensile strength of Cu−0.36Cr−0.01P alloy is 572 MPa and its electrical conductivity is 80%IACS after solid solution treatment at 980°C for 2 h followed by 95%cold rolling and then aging treatment at 450°C for 1 h.
基金Project(2016YFB0300901)supported by the National Key Research and Development Program of China
文摘In order to develop high strength,high damping and low density Al matrix composites,the Al/Zn composite bar samples with Zn mass fraction of 10%-40%were prepared by powder extrusion.The tensile strength and damping properties of the samples are improved by controlling both the Zn/Al diffusion degree and the precipitation of the interfacial phases.The results show that the tensile strength of the samples with Zn mass fraction of 10%-30%increases with the increases of both the Zn content and annealing temperature.When the Zn mass fraction increases to 40%,the tensile strength of the sample remains basically unchanged or decreases slightly,and the plasticity decreases gradually.Alloying of Al matrix and the formation of Zn/Al interface layer are mainly responsible for improving the strength of the annealed samples.The damping properties increase with the increases of both the Zn content and annealing temperature.The Zn/Al eutectoid lamella eliminates the detrimental effects on damping properties due to both alloying of the Al matrix and reduction of pure Zn in the Al matrix.The Al-30%Zn sample annealed at 350°C for 0.5 h has good comprehensive properties,including the tensile strength of 330 MPa,the elongation to failure of 10%and the room-temperature damping properties(tanθ)of 0.025.
基金financially support by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (No.2011BAE23B02)the Fundamental Research Funds for the Central Universities of China (No.FRF-TP-10-002B)
文摘Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces were fabricated by double rolling. The two surface morphologies of double-rolled copper foils are quite different, and the surface roughness values are 61 and 1095 nm, respectively. The roughness value of matt surface can meet the requirement for bonding the resin matrix with copper foils used for flexible printed circuit boards, thus may omit traditional roughening treatment; the microstructure of double-rolled copper foils demonstrates an obviously asymmetric gradient feature. From bright surface to matt surface in thickness direction, the average grain size first increases from 2.3 to 7.4 μm and then decreases to 3.6 μm; compared with conventional rolled copper foils, the double-rolled copper foils exhibit a remarkably increased bending fatigue life, and the increased range is about 16.2%.
基金the National Natural Science Foundation of China(No.U1703131,No.51674027,No.51974027 and No.52004028)Guangdong Basic and Applied Basic Research Foundation(2019A1515111126)the Fundamental Research Funds for the Central Universities(FRF-TP-18-005C1 and FRF-TP-18-041A1).
文摘The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^(-1).Hollow billets under the same conditions were prepared,and their macro/microstructures were analyzed by an optical microscope and a scanning electron microscope.During the TZCC process,a circular fluid flow appears in front of the mushy zone,and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature gradient.The deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting speed.Experimental results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^(-1),while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed.2D12 aluminum alloy hollow billets with no macroscopic defects,the finest columnar crystals,and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^(-1),which is beneficial for the further plastic forming process.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.FRF-IDRY-19-012)the National Natural Science Foundation for Distinguished Young Scholars of China(No.51925401)
文摘The precipitation behaviours during the aging process and the corresponding strengthening mechanism of a Cu-0.4 wt%Sc alloy were systematically investigated in this study.The phase transformation sequence of the precipitation in the aging process of the Cu-0.4 wt%Sc alloy was found to be:supersaturated solid solution→Sc-enriched atomic clusters→metastable phase→Cu4Sc phase.The tetragonal structured lamellar Cu4Sc precipitates,with a habit plane parallel to the{111}plane of the Cu matrix and orientation relationships of(022)_(α)//(211)_(Cu4Sc)and[011]_(α)//[113]_(Cu4Sc),are found homogeneously distributed in the matrix.A combined process of cryogenic rolling(CR)and aging was designed for optimization of the mechanical and electrical properties.Excellent integration of yield strength(696 MPa)and electrical conductivity(62.8%IACS)of this alloy was achieved by cryogenic rolling and subsequent aging process at 400℃for 4 h.The significant precipitation strengthening effect of this alloy is attributed to the Cu4Sc precipitates with an extremely small size of only 1.5–3 nm.The leading strengthening mechanism is considered as the superposition of both coherent strengthening and Orowan strengthening effects.
基金supported by the National High Technology Research and Development Program of China (2013AA031301)the National Natural Science Foundation of China (51104016)the Natural Science Foundation of Jiangsu Province (BK20161151)
文摘Embedded aluminum-steel composite sheets used in heat exchanger were produced by cold roll bonding(CRB). The influences of annealing temperature and annealing time on the microstructure and the bonding strength of the composite sheet were investigated. The recrystallization of the steel layer began at 525℃ and finished at 600℃. With the increase of the annealing temperature, the peel strength of the composite sheet whose original steel sheet surface was treated by scratch brush initially increased and then decreased, which was resulted from the competition of the mechanical locking and metallurgical bonding. After annealing, the cracks which formed between the broken work-hardened steel surface layer and its matrix during cold roll bonding remained. The composite sheet produced by CRB with the steel surface treatment of flap disc had less interfacial defects, higher bonding quality, higher diffusion rate of Al and Fe atoms at the interface and larger metallurgical bonding extent than the composite sheet produced by CRB with the steel surface treatment of scratch brush under the same conditions of annealing,which was helpful to shorten annealing time, reduce energy consumption and improve production efficiency.
基金financially supported by the National Basic Research Program of China(No.2011CB606300)the National HighTech Research and Development Program of China(No.2012AA03A505)
文摘The effects of warm-rolling process on the microstructure, ordering, mechanical properties and cold- rolling workability of Fe-6.Swt%Si alloy were investigated, where three processes of warm-rolling with the same total reduction of 93% were used, including （1） 500 ℃/12 passes/total reduction of 93%, （2） 500 ℃13 passes/total reduction of 50% ＋ 400 ℃19 passes/total reduction of 86%, and （3） 500 ℃13 passes/total reduction of 50% ＋ 400 ℃15 passes/total reduction of 60% ＋ 300 ℃14 passes/total reduction of 64%. The results show that compared with process （1） warm-rolling with constant temperature of 500 ℃, process （2） and process （3） warm-rolling with gradually decreasing temperature can significantly improve the room temperature plasticity and cold-rolling workability of the Fe-6.5wt%Si alloy. For example, the three point bending fracture deflections are increased by 54.5% and 81.8% for processes （2） and （3）, respectively, and the maximum reductions of single pass cold-rolling without edge crack are increased from 50% of process （1） to 55% of process （2） and 62% of process （3）, respectively. The plasticity improvement of the Fe- 6.5wt%Si alloy can be attributed to both reductions of surface oxidation degree and order degree of the alloy by warm-rolling with gradually decreasing temperature.
