拉伸温度和应变速率对细晶纯镁力学行为和微观组织的影响

Effect of Tensile Temperature and Strain Rate on Mechanical Behavior and Microstructure of Fine Grain Pure Magnesium

在冰水条件下利用四道次等通道转角挤压(ECAP)制备细晶纯镁,并进行中高温拉伸试验。研究了经ECAP变形后纯镁在拉伸温度为室温至250℃和应变速率为3.33×10^-4、6.67×10^-4、3.33×10^-3s^-1下的力学行为及微观组织演变。结果表明:峰值应力随拉伸温度的升高和应变速率的降低而下降。当应变速率为3.33×10^-4s^-1,断裂伸长率随拉伸温度的上升先升高后降低;当拉伸温度为200℃,断裂伸长率达到最大98.3%,而在250℃有所下降,从断口形貌来看,这是由于微裂纹的形成恶化了塑性。

Fine grain pure Mg was prepared by four passes equal channel angular pressing(ECAP) at the ice-water temperature. The mechanical behavior and the evolution of microstructure of ECAP processed Mg in the range from room temperature(RT) to 250 ℃ and strain rates of 3.33×10^-4 s^-1, 6.67×10^-4 s^-1, 3.33×10^-3 s^-1 were investigated. The results show that the peak stress decreases with the increase of tensile temperature and the decrease of strain rate. When the strain rate is 3.33 ×10^-4 s^-1, the fracture elongation first increases and then decreases with the increase of tensile temperature. The specimen exhibits the best fracture elongation, reaching 98.3% at tensile temperature of 200 ℃, but the fracture elongation decreases at 250℃. The fracture morphology indicates that the deterioration of the plasticity is mainly due to the formation of micro-cracks.