Overcoming plasticity reduction in a severely deformed nano-grained metastable alloy

Most bulk metallic materials reveal an increased strength but a loss of ductility after cold deformation, a phenomenon known as the strength–ductility trade-off. In this study, we propose a strategy to overcome this problem by introducing a high density of crystalline defects into a Fe-based metastable alloy by refining grains to a nanometer scale. This procedure effectively enhances the kinetics and reduces the driving force for transformation-induced plasticity (TRIP). Consequently, the TRIP effect originally occurring at cryogenic temperature in the studied alloy becomes active at ambient conditions, contributing to a strength–ductility synergy and overcoming cold working induced sacrifice of ductility. High-density crystalline defects were introduced into a metastable alloy, leading to an increase in TRIP temperature. This helps to overcome the strength–ductility trade-off in the severely plastic-deformed alloys at ambient conditions.

绝大多数块体金属材料在冷变形后会表现出强度提升但塑性损失的现象，即所谓的强度-塑性权衡（strength–ductility trade-off）。本研究提出了一种破解该难题的策略：通过将铁基亚稳合金的晶粒细化至纳米尺度，引入高密度晶体缺陷。该工艺可有效改善相变诱导塑性（TRIP，transformation-induced plasticity）的动力学行为，并降低其相变驱动力。原本仅在低温环境下触发的TRIP效应，在本研究涉及的合金中得以在室温条件下激活，从而实现强塑协同，克服了冷变形引发的塑性损失问题。本研究通过向亚稳合金中引入高密度晶体缺陷，提升了TRIP效应的触发温度，进而解决了严重塑性变形合金在室温环境下的强度-塑性权衡难题。