The Effect of Time during Post Weld Heat Treatment (PWHT) on Mechanical Properties of Copper Alloy with Gas Metal Arc Welding (GMAW)

In this project the effect of time during post weld heat treatment on the mechanical properties of copper alloy was studied using gas metal arc welding (GMAW) technique. Gas metal arc welding technique is a welding technique that uses heat energy to combine metal parts. Copper aluminum also known as aluminum bronze is selected as the representative for copper alloy electrode in this study. It is an inevitable fact that mechanical properties of a material changes when it undergoes heat treatment. In this project, post weld heat treatment at a constant temperature and varying time period were conducted upon welding to 6 test samples. The effect of time during post weld heat treatment on the welded joint was studied using Charpy Impact test in accordance with ASTM E23. Furthermore, hardness test and microstructure observation have been conducted on the welded material to observe the changes in the mechanical properties of the welded material at the weld joint and heat affected zone. The size and pattern of the microstructure at the joint are the primary factors that affect the impact strength of the joined metal parts. The results obtained from this study shows that the impact toughness increases at the weld joint when the time of post weld heat treatment is increased. The hardness at the weld joint is improved significantly with increase in time of post weld heat treatment and only a slight increase in hardness is observed at the base metal close to the welded joint. In the microstructure observation it is observed that grain growth has occurred and grain migration have occurred reducing the residual stresses at the joint.