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对比研究了Mg-2Nd-4Zn-1Zr合金在铸态和热处理态下显微组织结构的演变。借助TEM、SEM和XRD等研究发现,合金中的第二相有几种不同的种类特征。在铸态下,合金中存在的共晶化合物是由Mg、Nd和Zn构成的两种不同类型的三元相:T相和W相。然而,经过热处理,随着时间和温度的变化,T相几乎完全溶解进入α-Mg基体中,但W相仍然大量剩余在基体中。此外,随着热处理时间的延长,沿晶界分布的第二相的形貌由连续分布的网状逐渐转变为球状。在热处理过程中,合金中W相是一种高热力学稳定相,其数量随着热处理的进行而逐渐减少,并最终粗化、稳定地存在于基体中。
The evolution of microstructure of Mg-2Nd-4Zn-1Zr alloy under as-cast and heat-treated conditions was comparatively studied. With TEM, SEM and XRD and other studies have found that the second phase of the alloy has several different types of features. In the cast state, the eutectic compound present in the alloy is two different types of ternary phases consisting of Mg, Nd and Zn: the T phase and the W phase. However, after heat treatment, the T phase dissolves almost completely into the α-Mg matrix with time and temperature changes, but the W phase still remains largely in the matrix. In addition, with the extension of heat treatment time, the morphology of the second phase distributed along the grain boundaries gradually changed from the continuous distribution of reticular to spherical. During the heat treatment, the W phase in the alloy is a highly thermodynamically stable phase, the amount of which decreases gradually as the heat treatment progresses, and eventually becomes coarse and stable in the matrix.