Study on the surface layer formation of aluminum matrix composites and associated machinability in precision milling based on laser melting modification

SiCp/Al composites are extremely difficult to process due to excessive tool wear and poor surface integrity. This paper presents a novel material processing method combining laser surface melting modification and precision milling to improve the machinability and surface performance of this material. The surface layer laser modification experiments were carried out by controlling the parameters of the laser processing and the volume fractions of the reinforcements. The mechanisms of the laser surface modification at the optimized temperatures between 1397℃ and 2000℃ are revealed as follows: a) a portion of the SiC reinforced particles will react with the molten liquid Al matrix to form the needle-shaped Al4SiC4 ternary carbide and faceted Si particles, together with Al and Al-Si eutectics, constitute the laser modified zone; and b) the remaining SiC reinforced particles sink into the bottom of the Al matrix molten pool to form the particles accumulation zone. Then, the precision milling experiments were conducted to investigate the differences in cutting force, tool wear, and surface integrity between the modified zone and the original zone. When the total depth of cut doesn’t exceed the modified zone depth, the surface roughness and tool wear can be improved by 90.36 % and 61.03 %, respectively.