The local microstructural heterogeneities in a single layer of laser clad hypereutectic Al-50Si alloy over Al7075 substrate has been studied over different applied laser powers. The general microstructure of the laser clad layer, irrespective of the applied laser power, could be described by three distinctive regions from the deposited bead/substrate interface to the top – i) columnar primary Al-dendritic region, ii) Al-Si near-eutectic region, and iii) non-equilibrium three phase region composed of Si primary particles, fine Al-rich dendrites and interdendritic Al-Si eutectic. A spatial heterogeneity in the cooling rates is inferred within the single clad layer based on the microstructural length scales – the bulk Al-Si shows two orders of magnitude higher cooling rate than interface. A distinct difference in the orientation of the clad microstructure near the bead/substrate interface and size and distribution of Si particles in the deposited layer is seen with different applied laser power. Such microstructural differences have been explained on the basis of the melt pool solidification conditions of the hypereutectic alloy under different laser power.

在不同的激光功率下，研究了Al7075基体上单层激光熔覆过共晶Al-50Si合金中的局部微观结构异质性。激光熔覆层的一般微观结构，与所施加的激光功率无关，可以通过从沉积的磁珠/基体界面到顶部的三个不同区域来描述-i）柱状主要Al树枝状区域，ii）Al-Si附近-共晶区；和iii）由硅一次颗粒，细小富铝枝晶和枝晶间Al-Si共晶组成的非平衡三相区。根据微观结构的长度尺度，可以推断出单层覆层中冷却速率的空间异质性–块状Al-Si的冷却速率比界面高出两个数量级。在施加不同的激光功率的情况下，可以看到包层微结构在珠/衬底界面附近的取向以及沉积层中Si颗粒的大小和分布的明显差异。已经根据过共晶合金在不同激光功率下的熔池凝固条件解释了这种微观结构差异。