搅拌铸造工艺制备Mg2B2O5/AZ63B镁基复合材料的热变形行为

Hot deformation behavior of Mg_2B_2O_5 whiskers reinforced AZ63B magnesium composite fabricated by stir-casting

在变形温度为250~400℃,应变速率5×10-5~0.5 s^(-1)范围内,研究了均匀化热处理态Mg_2B_2O_5/AZ63B镁基复合材料的热压缩变形行为,并利用双曲线正弦函数建立了其本构方程。结果表明:复合材料的峰值应力及其对应的应变均随温度的降低及应变速率的增加而增大;计算峰值应力与实验值的比较表明双曲正弦函数可以准确描述复合材料的本构关系;复合材料的应力指数n和激活能Q分别为5.5和221 kJ/mol,其变形机制为晶格扩散控制的位错攀移机制。热挤压试验表明:经过均匀化热处理,复合材料的最大及稳态挤压力与铸态相比分别下降了92 kN和80 kN。

Hot compression deformation behavior of homogenized Mg2B2O5 w / AZ63 B composite was investigated by compression test in the deformation temperature range of 250-400 ℃ with the strain rates from 5 × 10- 5-0.5 s^-1.The constitutive equation was established by hyperbolic sine law taking peak stresses as the function of temperature and strain rate.The results show that the peak stress and corresponding strain increase with the decreasing of the temperature and the increasing of the strain rate.By comparing the calculated flow stress and the measured flow stress,the results show that hyperbolic sine law equation is in good agreement with the experimental results.The stress exponent n and activation energy Q of the composite are 6.6 and 221 kJ / mol,respectively.The plastic deformation mechanism of the composite is the lattice diffusion controlled dislocation climb mechanism.The hot extrusion deformation of the composite shows that homogenization treatment before the extrusion reduces the peak and steady extrusion force by 92 kN and 80 kN,respectively,compared with that of the as-cast composite.