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采用2种不同铸造冷却方式制备成分相同、组织特征不同的Mg-4.4Zn-0.3Zr-0.4Y镁合金,研究不同铸造组织特征对挤压变形态合金组织和力学性能的影响。结果表明:与空冷铸造合金相比,水冷增大了熔体冷却速度,使合金铸态组织得到细化,抑制了W-相(Mg_3Y_2Zn_3相)的形核,并促进了I-相(Mg_3YZn_6相)的生成,获得了更大体积分数的准晶相(I-相)。经过挤压变形后,水冷铸造合金中的再结晶晶粒细小均匀,I-相颗粒经过挤压破碎后弥散分布在基体上,{0002}基面织构得到弱化,而■织构强度增强,从而使Mg-4.4Zn-0.3Zr-0.4Y挤压态合金的强度和塑性都得到了大幅提高。水冷铸造合金经过挤压变形后,屈服强度和抗拉强度分别达到297.0和327.3 MPa,与空冷铸造挤压态合金相比分别提高了46.4和21.4 MPa。水冷铸造挤压态合金的延伸率达到14.8%,与空冷铸造挤压态合金相比增大了4.7%。
Two different casting cooling methods were used to prepare Mg-4.4Zn-0.3Zr-0.4Y magnesium alloy with the same composition and different microstructures. The effects of different castings on the microstructure and mechanical properties were investigated. The results show that water cooling increases the cooling rate of the melt compared with the air-cooled cast alloy, and the as-cast microstructure of the alloy is refined, inhibiting the nucleation of the W-phase (Mg_3Y_2Zn_3 phase) and promoting the phase transformation of the I_ phase (Mg_3YZn_6 phase ), A larger volume fraction of quasicrystalline phase (I-phase) was obtained. After extrusion deformation, the recrystallized grains in the water-cooled cast alloy are fine and uniform, the I-phase particles are dispersed and dispersed on the matrix after being crushed and crushed, the texture of the base surface is weakened, and the texture strength is enhanced, As a result, the strength and ductility of Mg-4.4Zn-0.3Zr-0.4Y alloy have been greatly improved. The yield strength and tensile strength of the water-cooled cast alloy reached 297.0 and 327.3 MPa respectively after extrusion, which were 46.4 and 21.4 MPa higher than those of the air-cooled cast alloy. The elongation of water-cooled cast alloy reached 14.8%, which increased by 4.7% compared with air-cooled cast alloy.