Manufacturing Technology Today

S. Ravikumar ¹, V. Seshagiri Rao ², S. Prakash ¹

Affiliations
1 Dept of Mech & Production Engg., Sathyabama University, Chennai, IN
2 Dept of Mech Engg., St.Joseph’s College of Engg., Chennai, IN

Abstract

This research presents the microhardness variations studies related to tool pin profiles on dissimilar joints of AA7075-T651 and AA6061-T651 aluminium alloys. The weld consolidation and quality was evaluated through observations of macro and micro structure. The microhardness variations were determined in the cross-section of the weld for different rotational and welding speeds. In all the specimens where the hardness distribution was measured, the AA7075 alloy was located at the Retreating side (RS) and the AA6061 alloy was in the Advancing side (AS). The Friction stir welded materials were joined under three different tool rotational speeds (800, 900 and 1,000 rpm) and three welding speeds (90, 100 and 110 mm/min), which are the two prime joining parameters in Friction stir welding (FSW). The axial load and the tilt angle parameters are kept constant at 12kN & 0°. Three different pin profiles (Taper cylindrical threaded, Taper square threaded and Square) tools were used to consolidate the weld in which the taper cylindrical threaded tool yields higher hardness of about 114.2 HV in the stirred zone with good mixing of these two alloys.

Keywords

Friction Stir Welding, Welding Speed, Rotational Speed, Macrostructure, Microstructure, Microhardness.

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D. Muruganandam ¹, S. Ravikumar ², V. Seshagiri Rao ³, Sushil Lal Das ⁴

Affiliations
1 Dept. of Mechanical Engg., Dhanish Ahmed College of Engg., Chennai, IN
2 Dept. of Mechanical and Production Engg, Sathyabama University, Chennai, IN
3 Dept. of Mechanical Engg., St. Joseph College of Engg., Chennai, IN
4 Jeppiaar Engg. College, Chennai, IN

Abstract

Aluminium alloys have gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to weight ratio and good corrosion resistance. Modern structural concepts demand reductions in both the weight as well as the cost of the production and fabrication of materials. Therefore welding processes have proven more attractive, and there is an urgency to study their potential. Compared to the fusion welding processes that are routinely used for joining structural aluminium alloys, friction stir welding (FSW) process, an emerging solid state joining process was invented in 1991 by TWI, in which the material that is being welded does not melt and recast. The major advantage in FSW process is that the maximum temperature reached is less than 80% of the melting temperature, i.e. the joint is performed in the solid-state and excessive micro structural degradation of the weld zone is avoided. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, axial force etc., and tool pin profile play a major role in deciding the joint strength. This paper focuses on mechanical properties evaluation and predicting the process parameters in varying rotational and welding speeds of friction-stir welding for the dissimilar precipitation hardenable aluminium alloys ie., between 6xxx (Al-Mg-Si) and 7xxx (Al-Zn-Mg).

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