Inhibition Mechanism of the Interface Reaction in the Molten Pool of SiCp/Al Composites by Pulsed Laser Welding with Powder-Filling

Abstract

In the welding process of SiCp/Al composites, Al reacts with SiC particles in the molten pool to form Al4C3, a brittle phase, damaging the reinforcement and causing a sharp decline in the mechanical properties of weld joints. To mitigate this, a method of welding SiCp/Al composites by pulsed laser welding with powder-filling is proposed, inhibiting the interface reaction between Al and SiC particles in the molten pool. This study investigates the effect of pulse frequency on the temperature field of the molten pool, and combines thermal-fluid numerical simulation to analyze the peak temperature at different pulse frequencies, optimizing the Si content to ultimately inhibit the interface reaction in the molten pool. Results indicate that an appropriate pulse frequency achieves good welding formation and effectively regulates the peak temperature of the molten pool. Only a small amount of brittle phase is present in the weld joint, creating favorable conditions for the addition of alloying elements. The interface reaction is slowed down by adjusting the pulse frequency, though it is not completely inhibited. When the addition of Si content reaches 8%, the occurrence of the interface reaction is effectively inhibited. In weld joints with the addition of 8wt% Si powder, no Al4C3 brittle phase is present, and the tensile strength of the weld joint is 266 MPa, up to 70% of the base material.