Mechanical properties and microstructure evolutions of the SLM fabricated Al-Mg-Mn-Sc-Zr alloy when deforming at elevated temperatures

Abstract

The Al-Mg-Mn-Sc-Zr alloy is fabricated by selective laser melting (SLM), and the tensile deformation behaviors at 20 °C ∼ 300 °C are studied. The results indicate that the alloy exhibits significant softening when deformed at elevated temperatures. When the tensile temperature increases from 20 °C to 300 °C, the peak strength decreases from 592 MPa to 167 MPa, and the elongation increases from 13.6 % to 23.9 %, respectively. The decrease in strength is mainly due to the reduction in densities of dislocations and grain boundaries, as well as the weakening of pinning effects of dispersed Al₃(Sc,Zr) particles. The increase in elongation can be attributed to the alleviation of local stress concentration and enhancement on dislocation slip frequency during thermal deformation. In addition, the typical bimodal grain structures of the SLM alloys result in different deformation behaviors. The coarse grains usually deform preferentially under high temperatures due to their higher Schmid factors and lower strength. The unavoidable pore defects formed during the printing process will weaken the alloy's uniform plastic deformation ability and result in a deterioration of elongations, especially when the pore size further increases at higher temperatures. As a result, the improvement on elongations of the SLM fabricated Al-Mg-Mn-Sc-Zr alloys when deforming at elevated temperatures is not as significant as that of alloys fabricated by traditional methods.