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

Authors: J. Kandasamy; M. Manzoor Hussain; S. Rajesham

Addresses: Department of Mechanical Engineering, MVSR Engineering College, Nadergul, Hyderabad, R.R. District – 501 510, India. ' Department of Mechanical Engineering, College of Engineering, JNTUH, Kukatpally, Hyderabad – 500 085, India. ' Pulla Reddy Institute of Technology, Vargal, Medak District – 509 217, Andhrapradesh, India

Abstract: Friction 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 Al2Cu and Al4Cu9 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.

Keywords: AA7075; aluminium alloys; friction stir welding; FSW; copper strip; spray coating; intermetallic compounds; IMC; mechanical properties; metallurgical properties; weld strength; bond strength; copper coating; temperature gradient; material flow.

DOI: 10.1504/IJMMP.2012.048524

International Journal of Microstructure and Materials Properties, 2012 Vol.7 No.4, pp.341 - 352

Published online: 14 Aug 2012 *

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