Room-temperature ductility and anisotropy of two rolled Mg-Zn-Gd alloys

To develop new magnesium alloy sheets with high formability at room temperature, the microstructure, texture, ductility and anisotropy of rolled Mg-1%Zn-1%Gd and Mg-2%Zn-1%Gd sheets were investigated. The microstructures were characterized as fully recrystallized grains with a large amount of homogeneously distributed fine particles in the matrix. The sheets exhibit an excellent ultimate elongation of nearly 36% and an uniform elongation greater than 15%. The Mg-1%Zn-1%Gd sheet has a random basal texture and the basal pole is tilted by about 30° from the normal direction towards the transverse direction. The planar anisotropy is shown to be as low as 0. The flow curves of the two Mg-Zn-Gd alloys display an abrupt yielding with a remarkable linear hardening at high strain rate after a plastic strain of roughly 3%. The majority of grains in the tilted texture have an orientation favorable for both basal slip and tensile twining because of a high Schmid factor. The low planar anisotropy, the large uniform elongations and the high strain-hardening rate observed in the Mg-Zn-Gd sheets imply excellent room temperature formability.