Despite superior properties of ultrafine-grained (UFG) materials processed by severe plastic deformation (SPD), their thermal stability is a concern because of the supersaturated fractions of lattice defects. In this study, the microstructural stability of various UFG materials (2 alloys and 15 pure metals) after SPD processing through the high-pressure torsion (HPT) were investigated at room temperature for up to 10 years. While most of the metals with high melting temperatures remained stable, a softening by self-annealing occurred in pure silver, gold and copper (with moderate melting temperatures), and an unusual hardening occurred in pure magnesium, Al-Zn alloy and Mg-Li alloy (with low melting temperatures). These softening/hardening behaviors by grain coarsening were attributed to the contribution of grain boundaries to dislocation activity or grain-boundary sliding, respectively. It was shown that the self-annealing was accelerated by increasing the processing pressure and strain and by decreasing the processing temperature and stacking fault energy, due to the enhancement of stored energy and/or atomic mobility.

尽管通过严重的塑性变形（SPD）处理的超细颗粒（UFG）材料具有优越的性能，但由于晶格缺陷的过饱和部分，它们的热稳定性仍然值得关注。在这项研究中，在室温下长达10年的时间里，对通过高压扭转（HPT）进行SPD处理后的各种UFG材料（2种合金和15种纯金属）的微观结构稳定性进行了研究。虽然大多数具有较高熔化温度的金属保持稳定，但在纯银，金和铜中（具有中等熔化温度）通过自退火发生了软化，而在纯镁，Al-Zn合金和Mg-Li中则发生了异常硬化。合金（熔化温度低）。这些通过晶粒粗化的软化/硬化行为分别归因于晶界对位错活性或晶界滑动的贡献。结果表明，由于存储能量和/或原子迁移率的提高，通过增加处理压力和应变以及通过降低处理温度和堆积故障能来加速自退火。