Effect of Sb on the microstructure and mechanical properties of AZ91 magnesium alloy

Effects of Sb addition on the microstructure, mechanical properties, and fr acture behaviors of AZ91 magnesium alloy, as well as the sensitivity to sec tion thickness of the structure and mechanical properties, have been studie d. The results show that when Sb is added into the AZ91 alloy, the grain is refined, the Mg17Al12 phase is refined and granulated, and a new Mg3Sb2 ph ase is formed and becomes coarse needle-shaped as Sb content increases. The room-temperature tensile strength, elongation, and impact toughness increa se first, and then decrease with increasing Sb content. The study on sensit ivity to section thickness shows that, when composition is constant, the ro om-temperature tensile strength and elongation increase with the reduction of section thickness; when section thickness is constant, the room-temperat ure tensile strength and elongation increase first, and then decrease with increasing Sb content. Additionally, the Sb addition improves the tensile s trength of the AZ91 alloy at 100 degreesC and 150 degreesC. The room-temper ature tensile and impact fractographs of the AZ91 alloy show intergranular fracture. With increasing Sb content, the tearing deformation zones on the both fractographs enlarge at first, and then diminish, which is consistent with the change of tensile strength, elongation, and impact toughness incre asing first, and then reducing with increasing Sb content.