Microstructure and properties of hypereutectic casting Al-Si alloy remelted by A-TIG

The A-TIG remelting progress with different actived fluxes applied on the surface of cast aluminum alloy for pistons was used to investigate the effect of actived fluxes on microstructures and mechanical properties of the remelted zone. OM and SEM were carried out to study the microstructures of the remelting zone,and wear resistance tester and universal mechanical tester were performed to measure their mechanical properties. The experimental results indicate that different actived fluxes can increase the weld penetration,refine the grain,and enhance wear resistance and mechanical properties of the remelted zone. The remelted zone with SiO₂ flux reaches the maximum penetration of 8. 05 mm. The combined actived flux with SiO₂,BaCl₂,MgF₂ can lead to the lowest value of SDAS and the finest primary silicon. The wear resistance is significantly improved that the wear volume of the remelted zone with SiO₂-BaCl₂-MgF₂ flux and Zn O-CuO-MgF₂ flux is reduced to 9. 7% and 6. 8% of the substrate,respectively. The tensile strength of the remelted zone with SiO₂-BaCl₂-MgF₂ flux is increased from 225. 9 MPa to 328. 3 MPa,which is considered to get the best overall performance.