Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 564, Issue -, Pages 369-380Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2012.11.076
Keywords
Friction stir spot welding; Fatigue; Magnesium alloy
Categories
Funding
- USAMP Magnesium Front End RD Project [DE-EE0003583]
- Department of Energy and the National Energy Technology Laboratory [DE-FC26-02OR22910]
- agency of the United States Government
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In this paper the fatigue behavior of the friction stir spot welded (FSSW) coupons of magnesium AZ31 alloy manufactured under different welding process conditions is investigated. Two sets of lap-shear coupons were made based on variation in plunge depth, tool rotation speed and tool geometry. Metallographic analysis of the untested FSSW coupons revealed differences in weld geometry and microstructure. Interfacial hooking of the faying surface was found to vary significantly between the two sets of process conditions. Microhardness test data revealed a large gradient in hardness profile. Results from the load controlled cyclic tests showed that lower tool rotation and shallower shoulder plunge depth led to better fatigue performance. Optical fractography of the fatigued coupons revealed that fatigue cracks initiated at the weld interface in both sets of coupons. However, the fracture mode showed variability between the two process conditions. The fractography analysis suggests that the effective top sheet thickness, interfacial hook and microstructure, which are largely determined by the process conditions, significantly affect the fatigue behavior of the friction stir spot welds in magnesium alloys. (c) 2012 Elsevier B.V. All rights reserved.
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