Al-Cu-Mg包共晶合金凝固组织演变及凝固路径研究

Investigation of Solidification Structure Evolution and Solidification Path of Ternary Quasiperitectic Al-Cu-Mg Alloy

选取初生相在不同相区的成分为Al-15.0Mg-9.6Cu(wt.%,下同)和Al-19.5Mg-17.8Cu的三元包共晶合金,进行了不同冷却速度下的凝固试验,而后对其凝固路径、组织演化规律以及凝固机制进行了分析。试验结果表明,两种合金在凝固过程中发生了三元包共晶反应,凝固路径为别为(L+α-Al)→(L+α-Al+S)→(L+S+α-Al+T)→(L+α-Al+T)和(L+S)→(L+α-Al+S)→(L+S+α-Al+T)→(L+α-Al+T)。合金Al-19.5Mg-17.8Cu和Al-15.0Mg-9.6Cu的初生相分别为S相和α-Al相,而且两相共晶组织(α-Al+S)和(α-Al+T)均为离异共晶,呈团块状,而包共晶组织(α-Al+T)呈灰黑相间的条带状共生形貌。两种合金的凝固组织中均发现残余的S相,并且初生相为S相的Al-19.5Mg-17.8Cu合金的残余S相数量和尺度都要大于Al-15.0Mg-9.6Cu合金。

Two ternary quasiperitectic alloys with composition of AI-15.0Mg-9.6Cu （in wt. %, hereinafter inclusive） and AI-19.5Mg-17.8Cu were selected to carry out solidification experiments under different cooling rates. And then the solidification path, microstructure evolution and solidification mechanism were analyzed. The experimental results show that the solidification paths of the two alloys are （L＋α-A1）→ （L＋α-AI＋S） （L＋S＋α-AI＋T）→ （L＋α-AI＋T） and （L＋S）→（L＋α-AI＋S）→ （L＋S＋α-AI＋T）→ （L＋α-AI＋T）. The primary phase of AI-19.5Mg-17.8Cu and AI-15.0Mg-9.6Cu alloy are S and a-A1, respectively, while the two-phase eutectic （α-Al＋S） and （α-Al＋T） are divorced eutectic with blocky dendrite morphology, and quasiperitectic eutectic （oL-AI＋T） are in grey and black coupled strip morphology. Residual phases S is found in the solidification structures oft he two alloys, and the amount and size of the residual S of AI-19.5Mg-17.8Cu alloy with the primary S phase are more and larger than those of the A1-15.0Mg-9.6Cu alloy.