Influence of scanning strategy and parameter on microstructural feature, residual stress and performance of Sc and Zr modified Al–Mg alloy produced by selective laser melting

Abstract

Selective laser melting (SLM), due to its track-by-track and layer by layer localized additive manufacturing process nature, has significant requirements for the optimization of laser scanning strategy and parameter. In this work, rare earth element Sc- and Zr- modified Al–Mg alloy was processed by SLM using an “island” scanning strategy with different island sizes. The influence of island size on surface quality, microstructural feature, residual stress, tensile property and corrosion resistance of SLM-processed Al–Mg-Sc-Zr alloy was systematically investigated. Experimental results indicated that the surface smoothness was enhanced as the island size decreased, but the influence of island size on microstructural development and tensile properties was not distinct. Considerably high tensile properties above 500 MPa combined with elongations of 10%–12% were generally obtained for Al–Mg-Sc-Zr specimens processed under different island sizes. Minimum residual stress was generated at a moderate island size of 2.4 mm and the residual stress increased both at a small and a large island size. A similar tendency was also observed for the corrosion resistance of SLM processed Al–Mg-Sc-Zr specimens, where a superior corrosion resistance (icorr = 6.82 × 10−6 A cm−2) was generated at the middle island size. The different temperature gradient and thermal behaviors under different island sizes contribute to the variation of surface conditions and residual stresses. The change in corrosion behaviors under different island sizes was related to the different molten pool configurations. These findings provided the knowledge of the relationship between laser scanning strategy and properties of SLM processed Al–Mg-Sc-Zr alloy, which further facilitated process optimization and engineering applications of laser additive manufacturing of high-performance Al–Mg-Sc-Zr alloy.