CO2 laser welding of aluminium matrix composites

The development of suitable welding techniques is a key-point for the use of Metal Matrix Composites in engineering applications. High energy welding techniques. such as laser beam, may have both positive and negative effects (high cooling rates, so minimum time is available for matrix-reinforcement reactions, but also high temperature, with strong beam-reinforcement interactions). This work is focussed on the set up of CO, laser welding processes for discontinuously reinforced Aluminium Matrix Composites. Both unalloyed Al and an At-Si casting alloy (A354) have been used as matrices, reinforced by particulate Silicon Carbide (5 and 15%vol). The composites have been submitted to penetration tests (traverse speed = 3.7 m/min, laser beam power = 4 kW). Two kinds of filler wires (ER4043 and ER4047) have been also employed. Microstructural characterisations have been carried out on the beads, leading, together with an analytical thermal model of the process, to the definition of guidelines for obtaining good welded joints on such composites.