Microstructure Research And Performance Improvement Of AZ80 Magnesium Alloy Wheel

Mg alloy, as the lightest metallic material, has attracted considerable interest due to its low density, high specific strength, high specific stiffness, good thermal conductivity and high damping properties.Therefore, it is considered as "the green engineering material of the 21 st century".Magnesium alloy wheel has become a new research direction of wheel molding technology on lightweighting of automobile.The AZ80 alloy, as an available forging wheel materaisl, has been systematically inverstigated in this paper, including chemical composition, microstructure evolutionat different condition and the effects of forging and heat treatment on the performance improvement.The conclusions are summarized as follow:The microstructure evolution of the AZ80 as-cast ingot.The grainof the as-cast ingot is obviously refined by the minor addition of rare earth elements, such as Ce, Y and Gd.Moreover, the grain size become 100-200 μm when the rare earth elements are less than 1wt%. Moreover, the segregation of the as-cast ingot is elimated by homogenization treatment.AZ80 forging process optimization.The form ability of AZ80 ingot is excellent when the processing temperature is between 380℃~400℃.The deformation speed of AZ80 alloy under hydraulic press can reach 2-6 mm/s, and the slow deformation speed is appropriate.The mould should be heated to 350-380 ℃ consistent with the deformation temperature.,The deformation of the ingot should be step by step according to the height difference beteewn the ingot and the product, and the deformation is less than 40% each time.The effects of forging and heat treatment on microstructure and mechanical property of AZ80 alloy.The columnar grain and coarse dendrite become refined, dispersed and elongated after forging deformation.Meanwhile, dynamic recrystallization occurs during deformation process.The refined grain is about 20-40μm;The grain refinement and dynamic recrystallization by forging deformation can effectively improve the mechanical properties more than 100% of AZ80 alloy.The diffusion of Mg17Al12 particels is extremely slow by T6 heattreatment. And few Mg17Al12 particels are insufficient to stengthen the alloy. Therefore, T6 heat treatment is not available for AZ80 magnesium industrial application.The Mg17Al12 particels increasingly precipated after long timeT5 heat treatment.As a result, the yield tensile strength and ultimate tensile strength are improved. However, the dtrength is still lower than that of forging treatment.The texture and anisotropy become more intense after the forging treatment. T6 heat treatment cannot eliminate the texture and anisotropy. However, the addition of rare earth elements, grain refinement and T5 treatment can reduce the texture and anisotropy.