Influence of solid solution hardening effects on the thermomechanical properties of Cu-Mn, Cu-Sn and Cu-Zn alloys after severe plastic deformation

高压扭转（HPT）等剧烈塑性变形工艺允许金属合金的结构细化。HPT变形产生材料依赖的饱和晶粒尺寸，并且可以实现小于100 nm的晶粒尺寸。纳米结构合金在高度塑性变形后的机械性能的特征在于非常高的强度和良好的延展性。此外，观察到合金的应变速率敏感性增加。纳米晶合金的变形行为的关键是位错和晶界机制之间的复杂相互作用，这还没有完全理解。晶界作为位错的源和汇，仍然受到机械和热迁移过程。已经表明，UFG金属在升高的温度和低应变速率下可以表现出比粗晶状态更低的强度。因此，在低应变速率和升高的温度下，纳米结构合金存在从细晶粒硬化到热激活软化的转变。上述效应是复杂的，并且在本申请中将通过基于Cu固溶体合金（Cu-Mn、Cu-Sn、Cu-Zn）的实验设计来研究，所述Cu固溶体合金通过高压扭转变形（HPT）转变成纳米晶状态。通过选择合金元素，可以彼此独立地调节合金的固溶体硬化和堆垛层错能。固溶硬化效应反过来又影响到螺位错的错动和孪晶的形成，以及剧烈塑性变形过程中的晶界迁移和组织发展。这些合金系统的微观结构的发展和热机械性能是用来提供一个更好的金属物理理解的纳米晶合金中的晶界和位错之间的相互作用过程。

Severe plastic deformation processes such as high-pressure torsion (HPT) allow a structural refinement of metallic alloys. HPT deformation produces a material-dependent saturation grain size and grain sizes smaller than 100 nm can be achieved. The mechanical properties of nanostructured alloys after highly plastic deformation are characterized by very high strength in combination with good ductility. Furthermore, an increased strain rate sensitivity of the alloys is observed. Crucial for the deformation behavior of nanocrystalline alloys are complex interactions between dislocation and grain boundary mechanisms, which are not yet fully understood. The grain boundaries serve as sources and sinks for dislocations and are still subject to mechanical and thermal migration processes. It has been shown that UFG metals can exhibit lower strength than the coarse grained states at elevated temperatures and low strain rates. Thus, there is a transition from fine grain hardening to a thermally activated softening of the nanostructured alloys at low strain rates and elevated temperatures. The effects mentioned above are complex and shall be investigated in this application by means of an experimental design based on Cu-solid solution alloys (Cu-Mn, Cu-Sn, Cu-Zn), which are transformed into the nanocrystalline state by means of high-pressure torsion deformation (HPT). By selecting the alloying elements, the solid solution hardening and the stacking fault energy of the alloys can be adjusted independently of each other. The solid solution hardening effects, in turn, influence the cross slip of screw dislocations and twin formation, as well as the grain boundary migration and structure development during the severe plastic deformation. The microstructure development and the thermomechanical properties of these alloy systems are to be used to provide a better metal-physical understanding of the interaction processes between grain boundaries and dislocations in nanocrystalline alloys.