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通过调整合金中Sr和Mg的加入量、温度梯度和凝固速度,对Al-12.5Si合金进行一系列定向凝固试验。结果表明,Sr可以对共晶Si进行变质,得到规则界面,也可以引起界面失稳,因为和Mg一样,其溶质分配系数k01,增加了成分过冷。随Sr或Mg含量增加,共晶界面的演化过程为平界面→胞状晶→树枝晶→等轴晶;随凝固速度增大和温度梯度减小,界面前沿成分过冷变大,界面形貌经历了从失稳到胞晶、树枝晶和等轴晶的转变。
By adjusting the addition of Sr and Mg, temperature gradient and solidification rate, a series of directional solidification tests on Al-12.5Si alloy were carried out. The results show that Sr can degenerate eutectic Si to get regular interface, which can also lead to interface instability. Like Mg, the solute partition coefficient k01 increases the undercooling. With the increase of Sr or Mg content, the evolution process of eutectic interface is flat interface → cellular crystal → dendrite → equiaxed crystal. With the increase of solidification rate and temperature gradient, the frontal interface composition becomes supercooling and the morphology of interface undergoes From instability to the transformation of dendrites, dendrites and equiaxed grains.