Zn-Cu-Ti变形锌合金异常力学行为研究

发现了 Zn-Cu-Ti 合金具有“加工软化”和“退火硬化”等异常力学行为. 采用 SEM、TEM、EDS 等手段对合金冷轧和热处理态显微组织进行观察和分析. 结果显示，该合金冷轧初始阶段（0 %~40.6 %）， 硬度略微升高，而继续提高变形率到 40.6 %~85.7 %，合金硬度明显下降，表现出剧烈的 “加工软化 ” 行为. 冷轧变形时，应变诱发动态再结晶，第二相析出增多，固溶 Cu、Ti 原子减少，固溶强化显著减弱，是引起合金“加工软化”的主要原因. 对经过 85.7 %冷轧变形的带材在 195 ℃和 215 ℃下退火，带材强度显著升高，表现出明显的“退火硬化”，且 215 ℃退火比 195 ℃退火同样时间的强度高. 退火时第二相分解，Cu、Ti 原子固溶于基体，固溶强化效应高于第二相强化，使合金表现出“退火硬化”行为. 

Abnormal mechanical behaviors of deformed Zn-Cu-Ti alloy

The abnormal mechanical behaviors of Zn-Cu-Ti alloy were discovered, such as working softening and anneal hardening. Microstructures of cold-rolled and annealed strips were observed and analyzed by SEM、 TEM and EDS. The results show that vickers hardness of the strips increases slightly as cold rolling deformation rate raising from 0 % to 40.6 %, and decreases significantly as cold rolling proceeding (40.6 %~85.7 %), the alloy exhibits a remarkable working softening. The facilitated precipitation induced by cold strain which weakens solid solution strengthening by reducing Cu and Ti solute atoms, along with dynamic recrystallization, resulting in working softening. Strength of the strips (cold deformation rate of 85.7 % ) increase significantly after being annealed at 195 ℃ or 215 ℃ , the alloy exhibits a remarkable anneal hardening. Strength of the strips soaking at 215 ℃ is higher than that at 195 ℃ for the same time period. The decomposition of second phase, the dissolution of Cu and Ti atoms during annealing and the effect of solid solution strengthening surpassing second phase strengthening result in anneal hardening of the alloy.