偏晶系Al-Bi合金的自生复合行为

在定向凝固条件下，研究了偏晶系Al-Bi合金的自生复合行为，考察了凝固速度和温度梯度对其自生复合行为的影响。试验结果表明偏晶反应可以生成两相有序排列的共生组织。在一定的温度梯度下，随着凝固速度的提高，组织由规则形态的纤维(或串状)组织向弥散分布的不规则组织转变。当G／V＞1．60×109K·s／2时，能得到规则的组织；反之，则得到不规则的弥散分布的组织，纤维间距与凝固速度的关系满足λ2V=C。

In Situ Composite of Al-Bi Monotectic Alloy

Monotectic Al-Bi alloys were solidified unidirectionally at various growth rates and temperature gradients. When a temperature gradient is constant, the microstructure changes in the sequence with increasing growth rates: fibrous composite structure→regular array of L2 (Bi) droplets→random dispersion ofL2 droplets in the aluminum matrix. The critical growth rate to form regular composite structure increases, as the temperature gradient increases. The monotectic composite structure i. e., the regular arrangement of L2 fibers or L2 droplets in the aluminum matrix is obtained at G/V more than 1.6×109 K·s/m2. The relation of the inter-fiber spacingλof L2 with the growth rate V is λ2V＝ C.