Indian Journal of Science and Technology

Abstract

In the present study, an attempt has been made to study the effect of weld parameters on as-cast Al-SiC metal matrix composite plates using a newly developed active flux composition. Stir cast Al - 8% SiC plates were welded using different variants of TIG welding such as Constant Current TIG (CCTIG) welding, Pulsed Current TIG (PCTIG) welding, activated TIG (ATIG) welding and Pulsed Current Activated TIG (PCATIG) welding. Microstructure, macro structure, thermal profile, micro hardness and tensile properties were evaluated for different variants of TIG welding conditions and compared with each other. The combined effect of the active flux composition and pulsed current in PCATIG welding was compared with other variants such as TIG welding technique such as CCTIG welding, ATIG welding and PCTIG welding. Thermal profile revealed the increase in the peak temperature and the cooling rates for the PC-A-TIG weldments. Due to increased cooling rate, fine grain microstructure was observed in weld zone and heat affected zone. Fine grain microstructure of the PCATIG weldment is responsible for improved mechanical properties such as micro hardness, ultimate tensile strength, yield strength and elongation (%) compared to other welding variants. Maximum micro hardness value was found in weld zone in all the variants of TIG welding. PCATIG welding showed maximum weld zone hardness as 75HV, heat affected zone hardness values of the all TIG welding variants have more or less same value after 4mm away from weld centre. Due to active flux coating on PCATIG welding lead to increase in weld depth as 4.5mm. This increase in the weld depth directly increase the depth-towidth ratio (D/W = 0.82). Tensile strength of PCATIG welded sample showed (Ultimate Tensile Strength = 153MPa; Yield Strength = 137 MPa; elongation (%) = 16%). It confirms that the Al-SiC composite welded using PCATIG welding were improved mechanical behaviour than other TIG welding variants such as CCTIG welding, ATIG welding and PCTIG welding.
Keywords: Al-SiC Composite, ATIG Welding, Mechanical Properties, Microstructure, PCTIG Welding, TIG Welding