纯铝板材限制模压变形强化后的热稳定性

Thermal stability of pure aluminum sheets strengthened by constrained groove pressing

借助拉伸试验、维氏显微硬度测试、TEM与EBSD等表征手段,研究了限制模压变形道次与变形后退火对纯铝板材微观组织与力学性能的影响规律。经过多道次的限制模压变形,材料晶粒尺寸由初始退火态的约30μm细化至亚微米级,强度、硬度显著提高。在回复阶段变形材料出现退火强化现象,且在300℃退火时仍保持良好的热稳定性。超细晶材料的退火强化现象主要由晶界位错源抑制强化引起,并与退火温度和应变累积量密切相关。材料晶粒组织在变形及退火过程中主要以小角度晶界为主,且应变累积的不均匀性始终存在。变形后期表面微裂纹的出现对材料的力学性能造成不良影响。2道次模压变形板材在300℃下退火1 h后的综合性能最优。

The effects of constrained groove pressing(CGP) pass and post-annealing temperature on microstructure and mechanical properties of pure aluminum sheets were studied by tensile tests,Vickers microhardness tests,TEM and EBSD.Grain size of the material is reduced to submicron level after multi-pass CGP from the initially annealed 30 μm,and both strength and hardness are greatly enhanced.Annealing strengthening happens in the recovery stage,which can be explained by dislocation source-limited strengthening and is closely related to annealing temperature and strain amount.The refined microstructure and superior properties are preserved up to 300℃.During CGP and subsequent annealing,the microstructure of the material mainly consists of low-angle boundary grains,and the distribution inhomogeneity of accumulative strain has not been eliminated.Surface micro-cracks occur in the late stage of CGP have undesirable effects on the evolution of mechanical properties.The optimum properties of material are obtained by 2-pass CGP with subsequent annealing at 300 ℃ for 1 h.