7075-T6铝合金的高温成形性能和微观组织

采用等温拉伸试验,研究了温度对7075-T6铝合金板材力学性能的影响规律.通过金相观察和断口形貌分析,讨论了7075-T6铝合金板材高温拉伸变形的微观组织变化和断裂失效机制.结果表明,随温度升高,材料强度和硬度逐渐降低,断后伸长率总体上呈上升趋势,但在250℃时出现低值.温度低于200℃,应力随应变先快速增加后缓慢增加...

High temperature formability and microstructure of 7075-T6 aluminum alloy

Influence of temperature on mechanical properties of the 7075-T6 aluminum alloy sheet was studied by means of isothermal tensile tests. The microstructure change and fracture failure mechanism of the 7075-T6 aluminum alloy sheet during high temperature deformation were discussed by metallographic observation and fracture morphology analysis. The results show that with the increase of temperature, the strength and hardness of the material decrease gradually, and the elongation after fracture shows an upward trend with a low-lying level appears at 250 ℃. When the temperature is lower than 200 ℃, true stress increases rapidly with the strain and then grows slowly, during this process, strain hardening mechanism is dominant, and the main softening mechanism is dynamic recovery. As the temperature reaches 200 ℃, true stress keeps stable after the peak value, which is mainly attributed to balance between the strain hardening and the recovery softening processes. When the temperature exceeds 200 ℃, true stress increases rapidly to the peak with the strain and then gradually decreases. This is due to the contribution of dynamic re-crystallization to material softening. At 250 ℃, because the dynamic recrystallization softening dominates, the stress decreases and the plasticity decreases significantly. When temperature rises to 300 ℃, the re-crystallization process nearly completes, the grains are elongated along the tensile direction, the depth of dimples on the fracture surface increases, and their average sizes grow. In macroscopical sight, the plasticity of the material improves.