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Microstructure and mechanical properties of dissimiliar aluminum alloy/stainless steel joints prepared by friction stir spot welding (FSSW)

Lim , Yee Kai (2014) Microstructure and mechanical properties of dissimiliar aluminum alloy/stainless steel joints prepared by friction stir spot welding (FSSW). Masters thesis, Universiti Tun Hussein Onn Malaysia.

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Abstract

In this paper, the effects of welding parameter (tool rotational speed and tool penetration deep) on mechanical properties, failure mode and microstructure of dissimilar metal welding using friction stir spot welding were investigated. The rotating tool with different shoulder diameter of 10mm, 12mm and 14mm were used to weld aluminum alloy A6061-T6 and stainless steel 304 sheets with thickness of 1mm. The hardness profile and microstructure across the base metal (BM), heat affected zone (HAZ), thermo mechanically affected zone (TMAZ) and stir zone (SZ) were obtained. The failure mode analysis was conducted and co-related with the load displacement curve. The hook geometry formed in joint interface was investigated. The tensile shear strength and elongation increases with increasing of tool shoulder diameter, tool rotational speed and tool penetration depth. The Vickers hardness profile showed a W-shaped. The variation of Vickers hardness in each region of the weld was due to the effect of strain hardening, dissolution of strengthening phase and grain growth under high welding temperature. A plug type failure mode is observed at weld nugget and ductile fracture occur at the soft region of TMAZ and HAZ, which indicated a strong metallic bonding, was formed at the joint interface of aluminum alloy/stainless steel. The welding parameter was found to significantly affect the hook formation. Partial metallurgical bond (hook) was formed on the keyhole area and continues growth larger with increased of tool rotational speed and tool penetration depth. The interface of aluminum alloy and stainless steel weld nugget was bonded through mechanical mixing and formed partial metallurgycal bond and kissing bond.

Item Type: Thesis (Masters)
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA401-492 Materials of engineering and construction. Mechanics of materials
Depositing User: Normajihan Abd. Rahman
Date Deposited: 03 Sep 2014 04:31
Last Modified: 03 Sep 2014 04:31
URI: http://eprints.uthm.edu.my/id/eprint/5653
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