Keyhole mode induced simultaneous improvement in strength and ductility of Sc modified Al-Mn alloy manufactured by selective laser melting

摘要

The effect of melting modes on microstructure evolution and tensile properties of selective laser melted (SLM-ed) Sc modified Al-Mn alloy (Al-5Mn-0.6Sc) is investigated in this work. With the transition of melting mode from conduction to keyhole by coinstantaneous increasing the laser power from 200 W to 380 W and the scanning speed from 800 mm/s to 1400 mm/s, the columnar grain width significantly decreases by 88% from 34.9 urn to 4.2 μm. Consequently, the yield strength and the elongation increase simultaneously from 266 MPa and 10% to 308 MPa and 17%, which increase by 16% and 70%, respectively. The refinement and orientation diversification of the grains caused by keyhole mode simultaneously improve the strength and elongation by inducing the Hall-Petch effect and enhancing the crack path tortuosity. This work reveals the feasibility and the mechanism of changing melting mode acts as a method to regulate the SLM-ed microstructure and mechanical properties.