偏晶系Al-Bi合金的自生复合行为

In Situ Composite of Al-Bi Monotectic Alloy

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 6 0× 1 0 9K·s/m2 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λ2 V =C。

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 L 2(Bi) dropletsrandom dispersion of L 2 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 L 2 fibers or L 2 droplets in the aluminum matrix is obtained at G/V more than 1 6×10 9 K·s/m 2 .The relation of the inter fiber spacing λ of L 2 with the growth rate V is λ 2V=C .