钠盐对铝硅合金的变质

采用高纯铝和硅（＞ ９９．９９％ ｗ ｔ）配制Ａｌ－１０％ Ｓｉ二元合金，经三元钠盐变质，研究合金中共晶硅相。结果表明：铝硅合金共晶凝固时，硅相滞后于铝相结晶。进行钠盐变质处理后，共晶凝固时硅相滞后更加明显，并使之由片状转变为纤维状。钠盐变质后的共晶硅中有较多的孪晶，孪晶轴为（１１１）Ｓｉ；孪晶方向为（２１１）Ｓｉ，共晶两相的位向关系符合〔１００〕Ａｌ∥〔１１０〕Ｓｉ。钠盐变质后的共晶硅以孪晶沟槽（ＴＰＲＥ）长大机制进行分枝、细化和弯曲，从而证明孪晶沟槽长大机制是产生变质结构的重要途径。

The Eutectic Si-phase in Al-Si Alloy Modified by Na-Salt

Al 10%wt Si alloy made of high purity aluminum and silicon(>99.99%wt)is modified by Na-Salt.The result from analuyzing.the eutectic Si phase indicates that the Si phase lags behind the Al phase when Al Si alloy eutectic solidified.modification not only changes the laminar Si phase to fibrous Si phase whose solidification lags more than the formar's,but also increases greatly the ednsity of twin crystal in Si phase.The twin crystal axis is(111) si .The crystal orientation is(211) si .The two phas,Si phase and Al phase in eutectic,accord with a regulation that100]al parallels to110] si .Further more,the modified eutectic Si phase branches,refines,flexes in accordance with TPRE growing mechanism,which is an importat approach to form modified crystallization structure.