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.