The laser welding of A1-sic[p] metal matrix composites : an analytical estimate for the formation of aluminum carbide

The present research determined the critical thermal conditions for the formation of aluminum carbide during the laser welding of Al-SiC_{p/sub> metal matrix composites. The problem was studied using a combined experimental and analytical approach. The experimental approach included the performance of laser welding experiments on the composites and on the base matrix aluminum. Measurements of the thermal fields were made during laser processing and the weld profiles, weld areas and aluminum carbide areas were characterized in the samples after laser treatment.}

The analytical model was based on Rosenthal's line source solution obeying modified Beer Lambert's Law. It duplicated the experimentally determined weld profiles based on material properties, laser processing conditions and input parameters such as absorption efficiency and coefficients of absorption. The model was later verified by comparing the calculated thermocouple temperatures with the experimentally measured temperatures. The calibrated model was then used to calculate the thermal fields within the weld region and to determine the critical conditions for aluminum carbide formation.

Cooling rate was determined to be the most important factor for controlling the formation of aluminum carbide. It was determined that at a minimum formation temperature of 1100 K (827°C) , the critical cooling rate for the formation of aluminum carbide during laser processing of Al-SiC metal matrix composites was 12000 K/sec (12000°C/sec).