Effect Of Al-10Ti Addition On Microstructure And Mechanical Properties Of AZ102 Magnesium Alloys

Magnesium alloys AZ102 and alloys with Al-10Ti content ranged from 1% to 4% were prepared by fusion casting combined with progressive solidification and flash set. The alloys were conducted certain heat treatment and hot extrusion respectively. Optical microscope were employed to character the metallurgical structure, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) to character the phase composition and chemical constitution, and scanning electron microscope (SEM) to character the microstructure and feature of the fracture. Mechanical properties as Tensile Strength, Brinell Hardness and Extensibility were tested. Effect of Al-10Ti content on microstructure, mechanical properties, heat treatment and extruding of AZ102 alloys were discussed, and the mechanism of mechanical property improvement were analysed in this paper. The main conclusions are presented as follows:(1) The microstructure of five kinds of foundry magnesium alloys consists of a-Mg phase,β-Mg17Al12 phase and Al-Mn phase. The phase were not change by inequality Al-lOTi content, heat processing and extruding processing.(2) The property improvement of the magnesium alloy mainly based on the fine-grain reinforcement and the distribution of the second-phase. As the Al-10Ti content increased, the grain gets finer, the secondary dendrite arm spacing gets smaller, and the growth pattern changed from the former advanced dendrite to the refined equiax.(3) As the Al-lOTi content increased, the Tensile Strength, Extensibility and the fracture toughness property of the casted AZ102 magnesium alloys improved, but the Brinell hardness decreased. The AZ102-4,4% Al-10Ti content had the best property, with the extensibility 10.38%, Tensile strength217.7MPa, and Brinell hardness 62.4, which had well comprehensive property.(4) The addition of Al-10Ti caused the decrease in the solidus temperature, and with the increasing Al-10Ti content, the magnesium alloy AZ102 had lower heat treatment temperature or the shorter heat treatment time.(5) The heat treatment T4 had obvious reinforcement on the alloy. It made the alloy obtain the optimum comprehensive mechanical properties as the high tensile strength, good plasticity, and high hardness and so on. The T4 treatment of AZ102-3 obtained the best results. The phaseβ-Mg17Al12 distributed in dispersion way along the grain boundary, and with the homogeneous structure the alloy had the extensibility 10.22%, Tensile Strength 297.5MPa, and Brinell Hardness 74.34. The heat treatment T6 took the second place. The alloy 4% in Al-10Ti content, heat-treated with T2, obtained the best extensibility and harness and well tensile strength, which is 11.4%, HBS83.1 and 232.7 MPa respectively.(6) After the extrusion, the grains were obviously refined, and the extruding texture with clear machine direction was formed, which improved the microstructure and the comprehensive mechanical properties. The tensile strength was over 354 MPa, the extensibility over 7.6% and the Brinell hardness over HBS82.(7) The extruded magnesium followed with the heat treatment T6 had the optimum comprehensive mechanical properties. The magnesium AZ102-1heat-treated with T6 had the best properties, with the tensile strength 442.6 MPa, extensibility 5.1% and Brinell hardnessHBS105.5.