About this Abstract |
Meeting |
Advances in Welding and Additive Manufacturing Research 2022
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Symposium
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Advances in Welding and Additive Manufacturing Research 2022
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Presentation Title |
Effect of Tool Rotational Speed on Abnormal Grain growth of Friction Stir Welded Joint of 7075 Aluminum Alloy |
Author(s) |
Chirag Panwariya, Dheerendra Kumar Dwivedi |
On-Site Speaker (Planned) |
Chirag Panwariya |
Abstract Scope |
The friction stir weld joints of precipitation hardenable aluminium alloys invariably show abnormal grain growth (AGG) during the post-weld heat treatment like T6. AGG occurrence in weld nugget and heat-affected zone deteriorates the mechanical performance of the weld joint. Therefore, it is important to understand mechanisms leading to the AGG and device methods to avoid/minimize the same.
In this work, the effect of tool rotational speed on thermal instability of FSW joints was studied along with their mechanism. Friction stir welded joints of heat treatable 7075-T651 aluminum alloy were performed at six different tool rotational speeds (rpm), keeping traverse speed constant and followed by post-weld T6 heat treatment. Optical stereotype microscopic analysis, electron backscattered diffraction analysis, and micro-hardness were performed to characterize the weld joint.
Post weld T6 heat treatment resulted in catastrophic growth of the few grains at the expense of neighboring grains. Weld joint produced at higher tool rotational speed offered more uniform deformation compared to lower tool rotational speed, subsequently resulting in the uniform material flow and more nucleating sites so that grains grew in a continuous way and suppressed the AGG.
Presence of the diffuse texture in the EBSD analysis for the weld developed at higher rpm as compared to strong texture at low rpm helps in suppression of AGG. EBSD analysis reveals grain sub-divisional mechanism for the weld formation at higher rpm over the discontinuous grain growth for the weld formed at low rpm. AGG showed a lower micro-hardness value as compared to normally grown grains. Weld joint produced at optimum tool rotational speed showed a normal grain growth and higher micro-hardness of 197 HV, while AGG shows 117 HV and the base metal of 135 HV.
AGG results have been discussed in light of heat input and material flow behaviour and deformation.
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Proceedings Inclusion? |
Undecided |