ANALYSIS OF TIG AND FSP PROCESSES OF ALUMINUM ALLOY

Abstract

Industries like aerospace, automotive industries, food packaging, maritime etc. use aluminium alloys in abundance because of the desirable properties such as light weight, good mechanical properties and corrosion resistance etc. The properties of aluminium alloys vary largely on alloying elements on one side and processes applied on them on the other side. Alloying elements help in selecting the type of aluminium to determine the alloy which is near to the desired properties but these properties may be varied during the process of producing the desired useable product. Process such as welding effects the properties of the aluminium alloy to the large extent. Welding of aluminium is generally associated with loss in yield strength. It is due to reason is that the temper of the aluminium will take place due to welding heat which will affect loss in yield strength. Weld crack, porosity, undercut, incomplete fusion, Incomplete penetration are common TIG welding defects in aluminium alloys. All these defects would reduce the strength of the weld. Many researchers investigated these defects by way of studying the the effect of various process parameters on the mechanical properties of aluminium alloys. The defects produced because of welding reduced the hardness and ultimate tensile strength of aluminium alloy; however, the literature is silent about the corrective measures to overcome the reduction in strength due to defects so produced. Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. This deformation is produced by forcibly inserting a non- consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. The present work is combination of experimental and optimisation techniques to analyse the TIG welding and Friction stir processing on TIG welded joints. The study has three parts. vii First part investigates the effect of various TIG welding process parameters on the quality of TIG welded joint of aluminum alloy AA 5083 by use of filler wire ER 4043, ER 4047 and ER 5356 in terms of Ultimate strength and hardness of the joint. The various process parameters include Current, feeding rod diameter and Gas flow rate which were applied as per Taguchi Design of Experiments. Ultimate strength and hardness of the joints produced with various filler wires were optimised by applying Regression analysis, S/N ratio, Grey Relational analysis and Grey relational Grade to determine the best filler wire and optimum TIG welding parameters. In the second part Friction stir processing was applied on TIG welded joint produced with best filler wire at optimum welding parameters as identified in the first part. FSP parameters such as Rotational speed, Tool Tilt angle and Traverse speed were employed as per Taguchi Design of Experiments. Same Optimisation techniques as applied in the first part were repeated to identify the optimum Friction stir processing parameters In the third part Friction stir processing was applied at the optimum Friction stir processing parameters (as identified in the second part) on TIG welded joint (with best filler wire as identified in first part) taking Time interval between TIG and FSP into consideration to determine the optimum TIG welding parameters. This way the best filler wire, optimum TIG welding parameters as well as optimum Friction stir processing parameters were identified.