定向凝固条件下K对Al-Si共晶合金的变质作用

Modification of Al-Si Eutectic Alloy with Fotassium Under Unidirectional Solidification

介绍了定向凝固条件下K对Al-Si共晶合金固液界面稳定性、共晶Si形态尺寸及其生长动力学的影响,探讨了提高Al-Si合金机械性能的途径和K的变质机理。指出:(1)在强变质元素和一定凝固条件下,共晶Si由片状变为纤维状,并有向粒状转变的趋势。(2)K在Si晶体中和固液界面前沿的富集,封锁了孪晶生长台阶,降低了界面稳定性,使α相领先于共晶Si形核生长并促进Si产生孪晶分枝。

The effects of potassium on the solid-liquid interface stability and on the shape,size and growth dynamics of eutectic Si in Al-Si eutectic alloy have been investigated under unidirectional solidification. The ways to enhance the mechanical properties of the alloy and the mechanism of modification of patassiurn have also been discussed. It can be summarized that(l)The shape of eutectic Si tends to be transformed from lamellar to fibrous and to nodular under given, solidifying conditions with strong modifying elements. (2) The potassium atoms tend to accumulate on the L-S interface of Si (111) plane and to blockade the growth steps of that plane and to reduce the growth rate of Si and , in turn. to made the phase become the leading phase of growth and in same time to remote the branching of Si twins.