变速定向生长条件下Pb－Sn共晶组织变化

STRUCTURE CHANGES OF DIRECTIONALLY SOLIDIFIED EUTECTIC Pb-Sn ALLOY UNDER VARYING GROWTH VELOCITY

利用改进后的定向凝固装置，研究了在阶跃增速和线性增、减速的变速生长条件下，Ｐｂ－Ｓｎ共晶合金定向凝固共晶组织的变化。实验结果表明：当共晶试样缓慢线性增速或减速时，定向生长共晶片间距的调节分别通过两相共晶片的逐步分叉或合并缓慢进行；当共晶试样增速和减速的加速度值相同时，实际共晶生长速度的变化过程呈对称的逆曲线。

The structure variety of directionally solidified eutectic Pb-Sn alloy under step and linear change of specimen displacement velocity was experimentally observed.The experiments were conducted on a directional solidification apparatus with an electronic varying velocity programmer for specimen displacement,which was designed and constructed by the authors.The experimental results show that,when the eutectic specimen moves with a slow and linear increase or decrease in velocity,the average laminar spacing of the directionally grown eutectic changes through progressive branching or merging of the eutectic laminae of both the two phases.The variation curves of the eutectic growth rates are approximately symmetric for the increase and decrease in the displacement velocity at the same acceleration.