Mg15Al镁合金ECAP变形过程中β相的碎化机理及动态析出行为

摘要

In order to improve the morphology, size and distribution ofβ-Mg17Al12 phase in the Mg-Al alloy and fulfill the precipitation strengthening effect of β-Mg17Al12 phase, Mg15Al high-aluminum magnesium alloy was processed by equal channel angular pressing. The evolution of β-Mg17Al12 phase in the MglSAl high-aluminum magnesium alloy after equal channel angular pressing (ECAP) for different passes was investigated by XRD, SEM, EDS and TEM. The results show that the coarse network eutectic β-Mg17Ml2 phase in Mgl5Al high aluminum-magnesium alloy can be effectively fragmentized by ECAP. With increasing extrusion passes, the size of β-Mg17Al12 decreases. After ECAP for 4 passes, β phase is fragmentized into small lump-shaped particles with size of less than 5 μm and the distribution of β phase becomes more homogeneous. Meanwhile, due to the large shear stress and high temperature, the dissolution of β phase in matrix occurs after ECAP for 2 passes and a large number of granular β phase with the size below 200 nm precipitates from the matrix after ECAP for 4 passes.%为了改善Mg-Al系合金中β-Mg17Al12相的形态、大小和分布,充分发挥其沉淀强化作用,利用能产生强塑性变形的等通道转角挤压法挤压Mg 15Al高铝镁合金；采用XRD、SEM、EDS和TEM研究不同道次ECAP挤压后Mg 15Al高铝镁合金中β-Mg17Al12相的演变.结果表明:ECAP强塑性变形能够有效地碎化Mg 15Al高铝镁合金中粗大的网状共晶β-Mg17Al12相；随挤压道次的增加,β-Mg17Al12相尺寸逐渐减小,挤压4道次后,网状共晶β-Mg17Al12相被破碎成尺寸在5μm以下的小块,分布得到一定改善；由于高应力与高温的共同作用,挤压2道次后,部分β-Mg17Al12相发生回溶,挤压4道次后,在α-Mg基体中动态析出许多尺寸在200 nm以下的粒状β-Mg17Al12相.