激光作用下SiCP/A356 复合材料的快凝组织形成

对SiC 颗粒增强Al-Si 复合材料以及Al-Si 合金进行激光表面重熔处理, 分析了SiC 颗粒在快速凝固条件下的分布规律以及SiC 颗粒对合金基体凝固行为的影响。结果表明: SiC 颗粒不会被快速移动的凝固界面所推移; 颗粒对基体凝固组织中的相组成无影响, 但对凝固初生相的晶体生长有抑制作用。从颗粒与合金熔体的交互作用角度对实验结果进行了讨论。 

EVOLUTION OF RAPIDLY SOLIDIFIED MICROSTRUCTURE IN SiC_P/A356 COMPOSITES WITH LASER RADIATION

The presenTinvestigation is aimed to understand the microstructure evolution of SiC P/Al Si composites, i.e. , particle distribution and matrix microstructure in rapid solidification. Microstructures of SiC P/A356 composite and the monolithic alloy were comparatively studied through laser re melting process. ITis observed that the particle remains its original distribution after re solidification, indicating that rejection of particles by rapid solidification interface does not occur. The presence of particles does not lead to any change in the phase constitution in the matrix, but has a great effect on crystal growth of primary phase. For the monolithic alloy, primary phase dendrites arrange themselves closer to the heat flux direction. Raising the scanning velocity, the dendrites become finer but remain the characteristic of regular columnar epitaxial re growth. However, the arrangement of primary α Al in laser treated composite is somewhat chaotic. These results, in addition to some evidence of unstable branching dendritic structure and dendrites terminating at a particle, indicate that the particle with a size larger than the length scale of the sub grain structure forms a complete barrier to the crystal growth.