冷却速度对短纤维增强Al-4.5Cu合金复合材料的凝固偏析的影响

Effect of cooling rate on segregation during solidification in short fiber reinforced Al-4.5Cu alloy composite

用挤压铸造法制备Al2 O3f/Al— 4Cu复合材料 ,研究了冷却速度对复合材料凝固偏析的影响。结果表明 ,Al- 4Cu合金初晶在纤维间隙中生核长大 ,纤维不能作为α初晶非自发形核衬底 ;复合材料基体中存在由纤维间隙中心至纤维 /基体界面或晶界处渐增的Cu浓度梯度 ,纤维周围存在共晶第二相偏析 ;冷却速度增大 ,凝固偏析加剧 ;

Al 2O 3f/Al-4.5Cu composites were made by squeeze casting. The effect of cooling rate on solute segregation in composites was studied. The results indicate that the primary crystal of Al-4.5Cu alloy nucleates and grows in the interstice between fibers. The fiber surface can not serve as site for heterogeneous nucleation of α primary dendrite. In the composite exists the increasing copper concentration gradient from the center of the interstice between fibers to the interface or the grain boundaries. There are the eutectic phases around the fibers. The concentration segregation in the matrix is increased with cooling rate rising. The amount of eutectic phases followed by imbalance crystalline can be numerically calculated with formula Clyne-Kurz.