Role of Zn on the room temperature formability and strength in Mg–Al–Ca–Mn sheet alloys

Abstract

We clarified the role of Zn on the mechanical properties and texture evolution in Mg-1.2Al-0.5Ca-0.4Mn-xZn (wt.%, x = 0, 0.8 and 1.6) alloy sheets fabricated by twin-roll casting and hot rolling. The room temperature stretch formability of the solution-treated sheet is improved with increasing Zn content, x. The Mg-1.2Al-0.5Ca-0.4Mn-1.6Zn alloy shows excellent stretch formability with the largest Index Erichsen value of 8.2 mm due to a weak transverse direction split texture. The development of the transverse direction split texture is attributed to the preferential nucleation of recrystallized grains at double twin boundaries promoted by the moderate segregation of Zn and Al. Subsequent artificial aging at 170 °C for 2 h (T6) leads to a substantial increase in strength without loss of ductility. The peak-aged Mg-1.2Al-0.5Ca-0.4Mn-1.6Zn alloy exhibits a high tensile yield stress of 210 MPa with an excellent elongation of 30.1% because of the dense dispersion of Guinier Preston zones within the Mg matrix. The insights gained in this work would establish a base for rational design and fabrication of bake-hardenable magnesium alloy sheet with excellent room temperature formability and high strength.