The Role of Sm in Precipitates, Grain Sizes,and Tensile Properties of As-Cast and As-Extruded AZ31-0.3La Alloys

Herein, the effect of Sm on precipitates, grain sizes, and tensile properties of AZ31-0.3La alloy is investigated. Results indicate that Sm is almost dissolved in alpha-Mg matrix with 0.2% content, whereas Al2Sm with two kinds of morphologies forms with further Sm addition. The grain sizes of as-cast studied alloy increase first and then decrease with increasing Sm addition, whereas the dynamic recrystallization (DRX) grain sizes decrease first and then increase, and the DRX grain size distribution is uniform first and then uneven. During the hot extrusion process, the refinement of DRXed grains is attributed to the particle-stimulated nucleation (PSN) mechanism. The R-p0.2 (yield strength) of as-extruded studied alloy is changed from twin-dominated to slip-dominated by 0.2% Sm addition, and the basal texture is slightly weakened due to the refined DRX grains and even-distributed grain size distribution, and the minor solute Sm atoms segregating at grain boundaries. Finally, the R-p0.2 of the as-extruded AZ31-0.3La alloy is gradually enhanced with increasing Sm addition, and the A (elongation) is increased to 25% with 0.2% Sm addition and maintains to about 20% with 0.6-1.7% Sm addition.