Effect of heat input on microstructure and mechanical properties of Al-Mg alloys fabricated by WAAM

A wire and arc additive manufacture (WAAM) system, based on cold metal transfer (CMT) technology, was used to manufacture Al-Mg alloys. An aluminum-magnesium ER5356 wire was employed as the filler metal to build Al-Mg components with different heat input by adjusting wire feed speed (WFS) and travel speed (TS). The macroscopic morphology and microstructure of Al-Mg thick walled samples were characterized using optical micro-graphs (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS). Vickers hardness and tensile properties were performed and mechanical properties were investigated. From microstructural studies, grain size variations in the range of 42.9-88.7 mu m in inner-layer region (NLR) and 37.7-77.6 mu m in inter-layer region (TLR) were observed when the WFS was 7.0 m/min, and TS was 0.9 m/min, whereas larger grains in significant amount were observed in similar regions under other WFS/TS combinations. The main phases of samples were identified to be alpha-phase (Al) and beta-phase (Al3Mg2). The mechanical properties of the Al-Mg samples were relatively stable during different WFS/TS conditions; average micro-hardness showed a stability characteristic with the values ranging between 70-77Hv. The ultimate tensile strength (UTS), yield strength (YS) and elongation (%E) were found to be 255 +/- 5 MPa, 128 +/- 10 MPa and 23.2% +/- 3% in identified location1 (taken from front to the back of the thick walled samples) and location2 (taken from root to the top of thick walled samples), respectively. For all samples, the fractographs exhibited typical dimple fracture characteristics. From the present work, it is evident that parts manufactured by WAAM-CMT have a better performance than the 5356 conventional casting alloys.