Effect of annealing temperature on microstructure, mechanical properties and corrosion behavior of Al-Mg-Mn-Sc-Zr alloy

Abstract Al-Mg-Mn-Sc-Zr alloy possessing good weldability expected to be beneficial in aerospace field. Currently, the study of the corrosion behavior of this alloy at different annealing temperatures is insufficient. Here, the mechanical properties, exfoliation corrosion (EXCO), intergranular corrosion (IGC) behavior and microstructure of Al-Mg-Mn-Sc-Zr alloy were studied. The results demonstrated that with the increase of the annealing temperature, the strength of the alloy decreased and the elongation (El) increased, and the corrosion resistance of the alloy decreased first and then increased. The alloy was annealed at 300 °C for 1 h to obtain the best corrosion resistance and mechanical properties. Then, the IGC depth of the alloy was 10.36 μm, and the EXCO grade was PB. Additionally, the ultimate tensile strength (UTS), yield strength (YS) and El of the alloy were 422.63 MPa, 315.86 MPa and 15.44%, respectively. Specifically, the β phase diffused poorly to the grain boundary due to the quick recovery of the dislocation structure over 300 °C. This implied that the β phase has difficulty in the formation of a continuous network at grain boundaries, which thus significantly lowered the corrosion sensitivity of Al-Mg-Mn-Sc-Zr alloy. Moreover, the higher strength of the alloy can be attributed to the dispersion strengthening and the grain boundary strengthening.