Laser welding of a SiC/Al-alloy metal matrix composite

The pulsed laser welding technique was used to process SiC particulate/Al-alloy metal matrix composites (MMC). The pulse on-time was constant at 20-msec and off-time was varied from 20 to 2-msec (duty cycles of 50-91%). The microstructural changes and the tensile behavior of laser processed MMC are characterized. Extent of microstructural changes varied from least to maximum for shorter (50%) to longer (91%) duty cycles respectively. Pulsed laser processing produced partial to complete dissolution of SiC particle and sometimes resulted in formation of aluminum carbide. It also produced a fine distribution of nonequilibrium complex precipitates due to the rapid cooling rate. In addition, the laser energy modified the SiC surface both physically and chemically. The results of tensile tests indicated that the modified SiC and the distribution of fine nonequilibrium precipitates enhance the mechanical properties of the laser processed composites. Optimum changes in microstructure and mechanical properties wer...