Abstract
AbstractAluminium alloys of 6xxx series are widely used in the fabrication of light weight structures especially, where high strength to weight ratio and excellent weld-ability characteristics are desirable. Gas metal arc welding (GMAW) is the most predominantly used welding process in many industries due to the ease of automation. In this investigation, an attempt has been made to identify the best variant of GMAW process to overcome the problems like alloy segregation, precipitate dissolution and heat affected zone (HAZ) softening. Thin sheets of AA6061-T6 alloy were welded by cold metal transfer (CMT) and Pulsed CMT (PCMT). Among the two joints, the joint made by PCMT technique exhibited superior tensile properties due to the mechanical stirring action in the weld pool caused by forward and rearward movement of the wire along with the controllable diffusion rate at the interface caused by shorter solidification time. However, softening still exists in the welded joints. Further to increase the joint efficiency and to minimize HAZ softening, the joints were subjected to post weld heat treatment (PWHT). Approximately 10% improvement in the tensile properties had been observed in the PWHT joints due to the nucleation of strengthening precipitates in the weld metal and HAZ.
Highlights
The fabrication of the light weight structures demands the necessity of aluminium alloys in the automobile sector
The joint made by Pulsed CMT (PCMT) technique exhibited superior tensile properties due to the mechanical stirring action in the weld pool caused by forward and rearward movement of the wire along with the controllable diffusion rate at the interface caused by shorter solidification time
Welding of heat treatable aluminium alloys by conventional fusion welding processes are limited in usage in the industrial applications due to the dissolution or coarsening of strengthening precipitates caused by the excess heat input [1]
Summary
The fabrication of the light weight structures demands the necessity of aluminium alloys in the automobile sector. Javier Serrano Perez et al [12] observed that by employing post weld heat treatment (PWHT) for the gas metal arc welded aluminium alloy joints, the softening gets reduced drastically in the weld metal zone and opined that it was due to the generation of Mg and Si elements caused during the artificial aging treatment that facilitates the formation of β′′ precipitates. They concluded that there is a drastic improvement in the mechanical properties of the GMA welded aluminium alloy joints due to the PWHT. This stimulated to carry out this research work to study the effect of PWHT on tensile properties of cold metal transfer arc welded AA6061-T6 aluminium alloy joints
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