Experimental investigations and comparative analysis of friction stir welded AA7075 alloy with and without copper as external alloying element in different forms

摘要

1Friction stir welding (FSW) experiments were conducted on AA7075 alloys under optimised conditions with copper as external alloy on the faying sides of the base material in thin strip and spray coating form. The idea behind the experimentation is to determine the influence of the formed inter metallic compound (IMC) in enhancing the weld strength, by providing uniform frictional heat input to the top and bottom sides of the plates. Test results of mechanical and metallurgical properties indicate that the interaction of AA7075 alloy with copper, in coating form, enhances the bond strength by formation of Al_2Cu and Al_4Cu_9 IMCs. Lack of metallurgical bond strength due to reduced material flow, caused by the difference in the developed friction heat between the top and bottom sides of the weld in conventional weldments, is considerably reduced by copper coating. High thermal conductivity of the copper in coating form has reduced the temperature gradient and maintained homogenous material flow in the weld zone. Reduction in weld strength is observed in copper strip inserted weldments due to interruption of the unmelted copper particles in aluminium matrix in the weld zone leading to a weak bond.