摘要
研究镍基高温合金在近服役条件下的力学性能与内在变形机理具有重要意义,但现有研究主要集中于单轴加载下的力学行为,多轴加载相关研究报道较少。为此,本工作对比研究了单轴和复合加载下多晶镍基高温合金GH4169的力学性能变化规律及其微观变形机制差异。在25℃下对多晶镍基高温合金GH4169进行拉伸-扭转复合加载,结合SEM、TEM、EBSD和中子衍射研究了加载方式对其力学性能、微观组织以及变形机理的影响。结果表明,拉伸样品的屈服强度和极限强度均随预扭转角度增加而增大(增幅分别约为150%和13%);在20%预拉应变下,扭转样品的屈服强度和延伸率均有所增加(增幅分别约为31%和16%)。拉伸和扭转变形后样品中的位错密度明显增大;同时复合加载下位错密度相较于单轴加载略小,表明存在位错湮灭效应。预加载产生的位错强化效应提高了屈服强度,而随后复合加载下位错湮灭效应使预拉伸扭转样品的极限强度有所降低。预扭转形成梯度结构的力学强化作用一定程度上抵消了位错湮灭效应的影响。研究表明,多轴加载方式可调控材料微观结构和变形机制,进而实现材料强度和韧性的协调提升。
GH4169 superalloys are used in gas turbine engines and power plants owing to their excellent mechanical properties and corrosion resistance at temperatures exceeding 600℃.Because of their service condition,involving high temperature and complex stress,much attention has been attracted to the effect of temperature and loading mode on the mechanical properties and deformation mechanism.The effect of the loading mode,especially the multiaxial or coupled loading,on the mechanism of plastic deformation is still an outstanding open question despite numerous investigations on the effect of temperature on mechanical properties.In this study,the effect of tension-torsion coupled loading on deformation behavior was investigated,where the microstructures and underlying mechanism were revealed using SEM,TEM,EBSD,and neutron diffraction.It is found that the mechanical properties are dependent on the tension-torsion loading.For the tension specimens,the yield and ultimate strengths increase with the pretorsion angle;for instance,at the pretorsion angle of 720°,the increase rate is approximately 150% and 13%,respectively.At the pretension strain of 20%,the yield strength and elongation increase by approximately 31% and 16%,respectively.The density of dislocations increases in those samples after tensile and torsional deformations compared to the undeformed samples.Moreover,the density of dislocations for specimens deformed under the coupled loading is lower than those deformed under axial loading,indicating the dislocation annihilation effect.The yield strength is enhanced due to the strengthening effect of the initial dislocations produced during the preloading.The ultimate strength for the torsional specimens after pretension decreases because of the dislocation annihilation effect during the subsequent coupled loading.However,for the tensile specimens after pretorsion,such dislocation annihilation effect can be counteracted to some extent by the strengthening effect of the formed gradient structure by pretorsion on mechanical strength.These findings provide some insight into the regulation of the microdeformation mechanism process of materials through designing the coupled or multiaxial loading modes and the coordinated improvement of strength and toughness based on the achievement of gradient or hierarchical microstructure.
作者
杨俊杰
张昌盛
李洪佳
谢雷
王虹
孙光爱
YANG Junjie;ZHANG Changsheng;LI Hongjia;XIE Lei;WANG Hong;SUN Guang'ai(Key Laboratory for Neutron Physics,Institute of Nuclear Physics and Chemistry,Chinese Academy of Engineering Physics,Mianyang 621999,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第1期30-42,共13页
Acta Metallurgica Sinica
基金
国家科技重大专项项目No.2019-VII-0019-0161
国家自然科学基金项目No.U1930121。
关键词
多晶镍基高温合金
复合加载
力学性能
变形机理
中子衍射
polycrystalline nickel-based superalloy
coupled loading
mechanical property
deformation mechanism
neutron diffraction
