Mg-4Al-2Ba-2Ca(ABaX422)合金的热锻及热加工图的构建（英文）

Hot forging of Mg-4Al-2Ba-2Ca(ABa X422) alloy and validation of processing map

将Mg-4Al-2Ba-2Ca(ABa X422)合金在300~500°C的温度范围内、0.01~10 mm/s的加工速率下热锻成杯型件,构建其热加工图,并研究其显微组织的演变。采用有限元法对该工艺进行模拟,估计加工余量的局部应变速率和平均应变速率范围。热加工图存在以下2个区域:(1)300~390°C,0.0003~0.001 s^(-1);(2)400~500°C,0.0003~0.3 s^(-1);这2个区域都存在动态再结晶(DRX)。该图表明,在高应变速率和低于400°C的温度下存在大范围的流动失稳区,在此区域会发生流动局部化。在上述2个区域条件下制备的锻件完好且组织均匀,在第一个区域条件下锻造所获锻件的晶粒尺寸更小。然而,当在流动失稳区锻造时,合金在最终成形前发生断裂。实验结果表明,上述2个区域条件下的荷载-行程曲线与模拟曲线吻合较好,而在失稳区获得的曲线则不平坦。

A cup-shaped component of Mg-4 Al-2 Ba-2 Ca（ABa X422） alloy was forged in the temperature range of 300-500 °C and at speeds in the range of 0.01-10 mm/s with a view to validate the processing map and study the microstructural development. The process was simulated through finite-element method to estimate the local and average strain rate ranges in the forging envelope. The processing map exhibited two domains in the following ranges：（1） 300-390 °C and 0.0003-0.001 s^-1, and（2） 400-500 °C and 0.0003-0.3 s^-1 and both represented dynamic recrystallization（DRX）. The map revealed a wide flow instability regime at higher strain rates and temperatures lower than 400 °C, in which flow localization occurred. Forgings produced under conditions of the above two domains were sound and symmetrical, and had finer grain sizes when being forged in the first domain. However, when being forged in the flow instability regimes, the alloy fractured before the final shape was reached. The experimental load-stroke curves for the conditions within the domains correlated well with the simulated ones, whereas the curves obtained in the instability regime were uneven.