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研究了稀土Y在亚共晶铝硅合金中诱发稀土-铝共晶反应对铝合金初生α相的细化效应;应用Bramfitt提出的方法,计算了Al-Y共晶反应产物Al3Y与α-Al界面的二维点阵错配度,结果显示两者的二维错配度<6%,即Al3Y可作为α-Al的异质形核质点,且能达到中等有效形核而起到细化晶粒的作用,并通过实验验证计算结果如下:选用稀土元素Y作为A356合金细化剂的同时,将A356-Y熔体分别在稀土钇-铝共晶温度上、下10℃左右保温2 min后快速冷却,获得试样的金相组织照片后利用图像分析工具得到A356-Y合金初生α相的平均晶粒尺寸和平均形状因子。实验结果表明:A356-Y合金在Al-Y共晶温度之下保温,可获得较理想的初生α相形貌和较小的晶粒尺寸;结合二维错配的计算结果,可推断初生α相细化的主要原因为异质形核质点的增加:Al-Y共晶反应产物Al3Y与α-Al的二维点阵错配度在中等有效形核范围内,具有细化合金初生α相的作用;另一共晶产物α-Al与初生α相具有相同的晶体结构和点阵常数,则其也可作为异质形核质点而起到细化合金的作用。稀土Y可作为半固态A356合金中初生α相的优质细化剂。
The refinement effect of rare earth Y induced by rare earth-aluminum eutectic reaction on the α phase of aluminum alloy induced by rare earth Y was studied. The Al-Y eutectic reaction products of Al-Y and α-Al were calculated by Bramfitt’s method. Dimensional lattice mismatch, the results show that the two-dimensional mismatch between the two <6%, that Al3Y can be used as α-Al heterogeneous nucleation sites, and can achieve moderate and effective nucleation and refinement The experimental results show that when the rare earth element Y is used as the refiner of A356 alloy, the A356-Y melt is respectively retained for 2 min at about 10 ℃ under the rare earth yttrium-aluminum eutectic temperature After rapid cooling, obtaining the microstructure of the sample photograph after the use of image analysis tools to get A356-Y alloy primary α-phase average grain size and average shape factor. The experimental results show that the A356-Y alloy can be retained at the Al-Y eutectic temperature to obtain a better primary α-phase morphology and a smaller grain size. Based on the calculation results of the two-dimensional mismatch, it can be concluded that the primary α The main reason for the phase refinement is the increase of heterogeneous nucleation sites. The mismatch between Al3Y and α-Al in the Al-Y eutectic reaction is in the range of moderate effective nucleation, . The other eutectic α-Al has the same crystal structure and lattice constants as the primary α phase, which can also serve as a refinement alloy for the heterogeneous nucleation sites. Rare earth Y can be used as a fine refiner of primary alpha phase in the semi-solid A356 alloy.