Microstructure, mechanical properties, and corrosion resistance of friction stir welded Mg-Al-Zn alloy thick plate joint
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RESEARCH PAPER
Microstructure, mechanical properties, and corrosion resistance of friction stir welded Mg-Al-Zn alloy thick plate joints Fenjun Liu 1,2 & Jianbo Liu 1,2 & Yan Ji 1,2 & Yanxia Bai 1 Received: 28 March 2020 / Accepted: 12 October 2020 # International Institute of Welding 2020
Abstract Mg-Al-Zn (AZ31) of 10-mm thick plates were subjected to friction stir welding (FSW) using a conventional tool (CT) and bobbin tool (BT), respectively. The microstructure, room temperature tensile properties, dynamic compressive mechanical properties, and corrosion resistance of the base metal (BM) and various regions of the friction stir welded joints were investigated systematically. The mean grain size, dislocation density, and precipitate distribution in the various regions of the friction stir welded joints were various due to different thermal cycle and plastic deformation. Compared with the CT, a relatively more homogeneous microstructure, a larger number of high-density dislocations and precipitates were produced in the various regions of the joint prepared by the BT due to higher thermal cycle and strain rate. As a result, the friction stir welded joint prepared by the BT exhibits excellent tensile properties and dynamic compressive mechanical properties, and outstanding corrosion resistances compared to those of the CT. In addition to slight changes in tensile properties and dynamic compressive mechanical properties, the corrosion resistance of the joint prepared by the BT was significantly improved compared to the BM. FSW with BT was suggested to be the optimal method to weld AZ31 alloy thick plate. Keywords AZ31 alloy . Microstructure . Tensile properties . Dynamic compressive mechanical properties . Corrosion resistance . Thick plate
1 Introduction In addition to being known as a green engineering materials, magnesium alloys are also considered to be one of the most potential candidates to replace aluminum alloys in some mechanical and structural parts in the applications of aerospace and transportation for achieving lightweight design due to their low density [1–3]. In order to meet cost savings and widen application fields, a reliable welding process of magnesium alloys is inevitable. Magnesium alloys can be welded in
Recommended for publication by Commission III - Resistance Welding, Solid State Welding, and Allied Joining Process * Fenjun Liu [email protected] 1
College of Energy Engineering, Yulin University, Yulin 719000, China
2
Yulin Key Laboratory of Metal Matrix Composites and Remanufacturing Technology, Yulin University, Yulin 719000, China
a variety of processes, but welding magnesium alloys using conventional fusion process still faces many challenges such as evaporative loss of the alloying elements, hot crack, porosity, and high residual stress [4, 5]. Friction stir welding (FSW) is an innovative solid-state joining process, which can effectively alleviate the disadvantages of conventional fusion welding processes. FSW is considered by designers to be the most suitable for welding nonferr
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