Laser and electron beam welding of SiCp reinforced aluminum A-356 metal matrix composite

Abstract

This paper details the results of a comparative study of laser and electron beam welding of a cast aluminum metal-matrix composite (Al-MMC) reinforced with SiC particles (SiC[sub p]). Electron beam welding of 15% SiC[sub p] A356-MMC produces much less deleterious Al[sub 4]C[sub 3] than CO[sub 2] laser beam welding at the same input powers and travel speeds. The advantage of EB welding of 15% SiC[sub p] A356-MMC relative to laser beam welding due to the different mechanisms of energy absorption by the substrate material for the two processes. During laser beam welding, the SiC particles are dissolved into a homogeneous solution of liquid Al, Si, and C at high temperatures, and the Al[sub 4]C[sub 3] subsequently precipitates from this solution on cooling. During EB welding of SiC[sub p] Al-MMCs, neither phase preferentially absorbs the energy of the electrons, and heating is more uniform than with laser beam welding. As a result of the uniform heat transfer to each phase, dissolution and decomposition of the SiC is limited and little Al[sub 4]C[sub 3] is formed. It is recommended that sharp focus of the electron beam and high travel speeds be used to minimize Al[sub 4]C[sub 3] formation. The results of thismore » study can be more broadly interpreted to suggest that other high melting efficiency welding processes that allow for rapid welding cycles and minimal superheating can also be used to join SiC[sub p] Al-MMCs as long as the process is compatible with the material.« less