Performance of different TIG remelting processes in hypereutectic Al-Si cast alloy

Abstract

The various tungsten inert gas welding (TIG) remelting processes applied on the surface of hypereutectic cast aluminum alloy were used to investigate the effect of remelting method on microstructures and mechanical properties of the remelted layer. Optical microscope and scanning electron microscope were carried out to study the penetration and microstructures of the remelted layers, and the micro hardness tester and universal mechanical tester were performed to measure their mechanical properties. The experimental results indicated that the remelting could refine the structure and enhance the hardness and mechanical properties of the remelted layers. The remelted layer with activating flux TIG (A-TIG) reached the deeper penetration of 3.9 mm, the lowest secondary dendrite arm spacing (SDAS) of 3 μm and the finest primary silicon particles. The hardness of A-TIG remelted layer was lower because of the reduction of hard Si phases, while the ultimate tensile strength increased from 163 MPa of the substrate to 236 MPa, which was considered to get the best overall performance.