水冷对普通铸造Mg-Zn-Zr-Y镁合金准晶相形成的影响及铸态组织研究

Effects of Water-Cooling on Quasicrystal Formation of As-Cast Mg-Zn-Zr-Y Alloys and the Microstructure

摘要:

通过普通凝固方法，在铸锭冷却过程中进行水冷制备准晶强化Mg-Zn-Zr-Y镁合金，并研究不同Zn和Y含量(Y/Zn比相同) 对通过这种制备方式获得的Mg-Zn-Zr-Y合金显微组织、显微硬度和热裂倾向的影响。结果表明：一定Y/Zn比的Mg-Zn-Zr-Y合金通过水冷冷却可获得更大的冷却速度，有利于获得更大体积分数的I-相(Mg3YZn6)。Y元素的添加使合金的成分过冷度增大，是铸态合金显微组织细化的主要原因。α-Mg基体中固溶的Zn含量是Mg-Zn-Zr-Y铸态合金基体硬度值的主要决定因素，I-相具有远高于α-Mg基体的硬度。Y元素引起合金液相线温度的大幅下降，固相线温度没有变化，从而减小了合金凝固区间，降低了铸锭的热裂倾向

Abstract:

Mg-Zn-Zr-Y alloys containing quasicrystal phase were prepared by an as-cast method with water-cooling. On this base, the effects of different Zn and Y content (the same Zn/Y ratio) on microstructure and micro-hardness were also discussed. The results show that the increase of cooling rate by water-cooling can increase the volume fraction of quasicrystal phase (I-phase, Mg3YZn6) of Mg-Zn-Zr-Y alloy. The decreasing of grain sizes of the as-cast alloy is due to the increase of constitutional supercooling by Y addition. The solid solubility of Zn in α-Mg matrix mainly affects the hardness of the matrix, and the hardness of I-phase is much higher than that of the matrix. The liquidus temperature decreases substantially while the solid temperature does not change with Y addition, which weakens the hot cracking tendency of the ingot due to the decrease of freezing range.