Excellent room-temperature ductility and formability of rolled Mg–Gd–Zn alloy sheets

In order to develop new magnesium alloy sheets with high formability at room temperature, the microstructure, texture, ductility, and stretch formability of rolled Mg–2%Gd–1%Zn and Mg–3%Gd–1%Zn sheets were investigated. The microstructures of these rolled sheets consist of fine recrystallized grains with a large amount of homogeneously distributed tiny particles in the matrix. The basal plane texture intensity is quite low and the basal pole is tilted by about 30° from the normal direction toward both the rolling direction and the transverse direction. The sheets exhibit an excellent ultimate elongation of ∼50% and a uniform elongation greater than 30%, and the Erichsen values reach ∼8 at room temperature. The flow curves of the two Mg–Gd–Zn alloys sheets display a remarkable linear hardening after an obvious yield point. The majority of the grains in the tilted texture have an orientation favorable for both basal slip and tensile twinning because of a high Schmid factor. The excellent stretch formability at room temperature can be attributed to the non-basal texture and low texture intensity, which led to the following characteristics: a lower 0.2% proof stress, a larger uniform elongation, a smaller Lankford value and a larger strain hardening exponent.

Research highlights▶ The Mg–Gd–Zn sheets have an oval-shaped distribution of basal poles by the addition of Gd. ▶ The basal texture intensity of the sheets is effectively weakened by the addition of Gd. ▶ The sheets exhibit a large elongation-to-failure (nearly 50%) at room temperature. ▶ The sheets exhibit a uniform elongation (larger than 30%) at room temperature. ▶ The sheets exhibit a high Erichsen values (nearly 8) at room temperature.