共晶组织对2E12铝合金热变形行为及组织演变的影响

摘要

Two kinds of alloys whose microstructures were featured with supersaturated solid solution (alloy 1) and enriched with eutectics (alloy 2) were prepared by different heat-treatment methods, respectively. By combining isothermal hot compression test with microstructure observation, the hot deformation behaviors and microstructure evolution of both alloys were studied at temperature range of 340-490℃ and strain rate range of 0.001-10 s-1. The results show that alloy 2 possesses a higher peak-stress value deformed at 0.001-0.1 s-1, while alloy 1 possesses a higher peak-stress value deformed at 10 s-1. The main failure mode of alloy 1 is cracking at triple grain boundaries (GBs). When deformed at 340℃/10 s-1, the main failure modes of alloy 2 is the fracture of eutectics at GBs. When deformed at 490℃/0.001 s-1, the main failure modes of alloy 2 is the cracking caused by eutectic melting. The dynamic recrystallization takes place easier in alloy 1 and thus makes a smaller grain size. The dispersively distributed T-phase particles promote the homogeneous deformation of alloy and also refine grain size.%采用不同热处理方法制备过饱和固溶体(1号合金)和富含共晶组织(2号合金)这2种具有典型组织特征的2E12合金.结合热模拟实验和显微组织观察,针对2种合金铸锭在变形温度为340~490℃、应变速率为0.001~10 s-1下的变形行为以及组织演变特征进行研究.研究结果表明:在0.001~0.1 s-1的应变速率下,2号合金具有较高的峰值应力;在10 s-1的应变速率下,1号合金具有较高的峰值应力;1号合金在热变形过程中的主要失效形式表现为三叉晶界的失稳开裂;2号合金在340℃/10 s-1变形时的主要失效形式为晶界共晶组织的碎化;在490℃/0.001 s-1变形时的主要失效形式为晶界共晶组织的熔化开裂;在相同变形条件下,1号合金更容易发生动态再结晶且晶粒更细小;弥散分布的T相粒子可以促进合金均匀变形并且细化晶粒.