Additive manufacturing of a high strength Al-5Mg2Si-2Mg alloy: Microstructure and mechanical properties

Abstract

A novel Al-5Mg2Si-2Mg alloy was processed by selective laser melting (SLM) to understand its representative features of microstructural evolution and mechanical properties during additive manufacturing (AM). The as-SLM fabricated Al-5Mg2Si-2Mg alloy is found to deliver much less hot cracks and other defects. Meanwhile, excellent mechanical property is also achieved, i.e. 452 ± 11 MPa for ultimate tensile strength, 295 ± 14 MPa for yield strength, and 9.3 ± 2.5% for elongation. Clearly, these mechanical properties are better than that obtained by high pressure die casting (HPDC), and better than some other alloys obtained by SLM. The as-SLM fabricated Al-5Mg2Si-2Mg alloy is featured by the significantly refined microstructures in the compact primary α-Al, the divorced Mg2Si eutectic networks distributing at α-Al grain boundaries, and some α-AlFeMnSi phase in association with eutectic Mg2Si phase. The high strength and ductility of the alloy are attributed to its unique features including (a) the reduced solidification range, (b) the possible increase of the eutectic level in the microstructure, and (c) the shift of eutectic point and the maximum solubility point of Mg2Si in Al matrix.