超轻α固溶体基Mg-6Li-3Zn合金的位错蠕变

来源期刊：金属学报2010年第6期

论文作者：曹富荣 管仁国 丁桦 李英龙 周舸 崔建忠

文章页码：715 - 722

关键词：Mg-Li-Zn合金； 位错蠕变； 准超塑性； 力学性能； 空洞

Key words：Mg-Li-Zn alloy； dislocation creep； quasi-superplasticity； mechanical property； cavity

摘    要：采用熔铸和大变形轧制制备了Mg-6Li-3Zn合金板材,研究了合金的高温变形行为、显微组织、空洞与位错蠕变机制.在623 K和1.67×10^-3s^-1条件下获得了300%的最大延伸率.OM,TEM和SEM观察显示,合金带状晶粒组织在573 K和1.67×10^-3s^-1)条件下发生显著的动态再结晶,亚晶轮廓不清晰,位错分布比较均匀.合金在573-623 K和1.67×10^-3s^-1条件下断裂形式为韧性断裂.获得了新型的位错黏性滑移与位错攀移转变蠕变机制图,表明Mg-6Li-3Zn合金带状晶粒组织在573 K和1.67×10^-3s^-1条件下高温变形机制为晶格扩散控制的位错黏性滑移,其应力指数为3(应变速率敏感性指数0.33),变形激活能为134.8 kJ/mol,与Mg的晶格扩散激活能相同.获得了新型的考虑聚合的空洞长大图,合金在573 K和1.67×10^-3s^-1条件下的空洞长大机制为塑性控制的空洞长大.

Abstract: Mg-6Li-3Zn alloy was prepared by Jackson’s melting and casting method and the sheets of 1.2 mm in thickness processed by hot rolling at 573 K and cold rolling with a total reduction of more than 92% were obtained.The high-temperature mechanical behavior at temperatures ranging from 423 to 673 K and initial strain rates ranging from 1.67×10^-3 to 5×10^-2s^-1 were investigated. The microstructure evolution,such as grains,subgrains,dislocations,cavities and fracture morphology, were investigated by OM,TEM and SEM.Yavari-Langdon model describing the transition between dislocation viscous glide and dislocation climb was used to construct a new dislocation creep mechanism map which consists of Cottrell’s solute atmosphere breakaway dislocation climb regime,dislocation viscous glide regime and Cottrell’s solute atmosphere incorporated dislocation climb regime.A new cavity growth map considering cavity coalescence was obtained according to the cavity growth models. The maximum elongation to failure of 300%was demonstrated at 623 K and an initial strain rate of 1.67×10^-3s^-1.Significant dynamic recrystallization occurred in band-like structure at 573 K and an initial strain rate of 1.67×10^-3s^-1,the subgrain contour was ambiguous and dislocation distribution was relatively uniform.Fracture mode of the alloy at 573-623 K and an initial strain rate of 1.67×10^-3s^-1 is ductile fracture.It is shown by the dislocation creep mechanism map that the high-temperature deformation mechanism in Mg-6Li-3Zn alloy sheet with band-like structure at 573 K and an initial strain rate of 1.67×10^-3s^-1 is dislocation viscous glide controlled by lattice diffusion,the stress exponent is 3(strain rate sensitivity exponent 0.33) and deformation activation energy is 134.8 kJ/mol, which is the same as the lattice diffusion activation energy of Mg.The cavity growth mechanism of the alloy at 573 K and an initial strain rate of 1.67×10^-3s^-1 is plasticity controlled cavity growth.