Study the correlation between Microhardness, Microstructure & In-situ thermal analysis of PCATIG weldedments of Al-SiC composite

Abstract

Activated TIG welding has been performed on Al – 8% SiC composite 5mm plate with various fluxes such as Al2O3, MnO2, CaO, MgO, SiO2 & TiO2. Microstructure, Micro hardness and cooling rate are observed. Correlation between micro hardness, microstructure and cooling rate of Pulsed Current TIG welding and Pulsed Current Activated TIG welding on Al-SiC composite has been studied. Combining the pulsed current TIG and activated TIG welding (PC-A-TIG) on Al-SiC composite showed very fine superior weld microstructure on PCATIG – SiO2 & PCATIG – TiO2 which resulted in higher micro hardness values around 70 – 75 Hv. Micro hardness are observed in different locations of weld surface such as 1mm, 2mm & 3mm below the weld surface and it also observed along the weld zone to heat affected zone upto 12mm for the profiling the micro hardness value around the weldment. Microstructure observed in weld centre for observed on weld zone & heat affected zone. Minimum micro hardness value between 63 – 65 Hv found in PCATIG – MnO2, PCATIG – CaO & PCATIG – MgO due to intermediate micro structure between coarse and fine. PCATIG – Al2O3 weld zone & heat affected zone and heat affected zone of PCATIG – MnO2, PCATIG – CaO & PCATIG – MgO shows coarse microstructure. This resulted in reduced micro hardness around 55 – 60 Hv. Coarse micro structure in weld zone and heat affected zone have least cooling rate. Fine micro structure in weld zone is due to higher cooling rate. Heat affected zone directly depends on temperature gradient between the weld centre and weldment heat affected zone.