Abstract
Two plates of thixoformed 7075 aluminum alloy were joined using Electron Beam Welding (EBW). A post-welding-heat treatment (PWHT) was performed within the semi-solid temperature range of this alloy at three temperatures, 610, 617 and 628 °C, for 3 min. The microstructural evolution and mechanical properties of EB welded plates, as well as the heat-treated specimens, were investigated in the Base Metal (BM), Heat Affected Zone (HAZ), and Fusion Zone (FZ), using optical microscopy, Scanning Electron Microscopy (SEM), EDX (Energy Dispersive X-ray Analysis), and Vickers hardness test. Results indicated that after EBW, the grain size substantially decreased from 67 µm in both BM and HAZ to 7 µm in the FZ, and a hardness increment was observed in the FZ as compared to the BM and HAZ. Furthermore, the PWHT led to grain coarsening throughout the material, along with a further increase in hardness in the FZ.
Highlights
7075 wrought aluminium alloys are used for a wide variety of applications in aerospace and automotive industries due to the outstanding characteristics that they possess, such as high-strengthto-weight ratio, ductility, toughness, low density, and resistance to fatigue [1,2,3,4]
Results indicated that after Electron-beam welding (EBW), the grain size substantially decreased from 67 μm in both Base Metal (BM) and Heat Affected Zone (HAZ) to 7 μm in the Fusion Zone (FZ), and a hardness increment was observed in the FZ as compared to the BM and HAZ
Al alloys have in the past been considered as difficult-to-weld materials through conventional arc welding techniques, improvements have removed these difficulties and quite few studies have focused on other technologies that offer improvements of weld performance, such as high-power density fusion joining, namely, laser beam welding (LBW) and electron beam welding [1,9,10], and, Friction Welding
Summary
7075 wrought aluminium alloys are used for a wide variety of applications in aerospace and automotive industries due to the outstanding characteristics that they possess, such as high-strengthto-weight ratio, ductility, toughness, low density, and resistance to fatigue [1,2,3,4]. Semisolid metal processing as a single step manufacturing method providing good quality near net shape products has been widely employed to aluminium alloys due to the advantages that this technology offers over the conventional casting techniques [5,6,7,8]. Al alloys have in the past been considered as difficult-to-weld materials through conventional arc welding techniques, improvements have removed these difficulties and quite few studies have focused on other technologies that offer improvements of weld performance, such as high-power density fusion joining, namely, laser beam welding (LBW) and electron beam welding [1,9,10], and, Friction Welding. Using EBW generates low distortions in the Fusion Zone (FZ), together with a narrow
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