| As the lightest metal structural materials, magnesium alloys with the preferable properties such as high specific strength, good damping, and easy recycling and so on, have great application prospects in various fields, such as aerospace, defense industry, transportation, electronic products and so on. However, the absolute strength of magnesium alloy is still low, which hinder the development of magnesium alloy application. In recent years, Mg-RE-Zn series alloys have been developed, and its strength can reach more than 500 MPa, due to the composite strengthening effect combined LPSO phase and ageing precipitates. But researches on the plastic processing law of Mg-RE-Zn series alloys are still relatively shortage. Extrusion and rolling deformation can effectively improve the microstructure and properties of magnesium alloy, and can be applied to produce bars, pipes, profiles and sheets. It is of great significance to promote the production and application of magnesium alloy. So this paper researched the influence of extrusion and rolling deformation on microstructure and properties of the high strength Mg-9.23Gd-3.29Y-1.24Zn- 0.87Mn(wt%) alloy.Firstly, the impact of extrusion ratio(8, 11, 27 and 42) on microstructure and properties of as-homogenized alloy was investigated. After homogenization annealing, lots of layered LPSO phase was precipitated in the alloy. When extrusion ratio was 8 and 11, the degree of recrystallization was relatively low, the layered LPSO phase tended to parallel to extrusion direction, a large number of layered deformation organization was form, and then plasticity of the alloy was low. As the extrusion ratio increased, the degree of recrystallization increased gradually, and then the plasticity of the alloy increased gradually, but its ultimate tensile strength was almost the same. After aging treatment, the ultimate tensile strength of the alloys was different. The as-aged rod alloy with extrusion ratio of 11 had the highest strength after aging treatment, UTS = 502 MPa, YTS = 410 MPa, EL = 3.8%. In addition, the sheet alloy with extrusion ratio of 11 was prepared. Its microstructure was also mainly with layered deformation organization. And it also got good mechanical performance.Then, the influence of rolling deformation on microstructure and properties of the alloy was studied. When explored rolling deformation parameters of as-homogenized alloy, it can be found that the alloy was easy cracking rolling at 450℃,due to the recrystallization was hindered with layered LPSO phase. The deformed structure is still existed in the as-homogenized alloy after rolling at 520℃. And then its plasticity is poorer. For the as-cast alloy processed with “rolling + solution treatment + rolling”, its block-shaped LPSO phases were smaller and dispersive, its grains were relatively uniform, and then it had good plasticity. By contrast, the rolling with greater reduction can be processed easily with “rolling + solution treatment + rolling”.Finally, the impact of rolling deformation on microstructure and properties of as-extruded alloys was researched. For the extruded alloy with a lot of layered organization, the layered organization gradually reduced, and the recrystallization organization gradually increased during rolling deformation. But the grain size was not changed obviously. For the extruded alloy mainly with equiaxial grain organization, the grains slightly refined after rolling deformation. The yield strength of the extruded alloys improved, but the plastic sharply reduced, after rolling deformation. The rod alloy with extrusion ratio of 11 had the highest mechanical properties, UTS = 511 MPa, YTS = 430 MPa, EL = 2.6%, after processing with “rolling(thickness reduction 50%) + aging”. |
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