通过在Mg-2.0Zn-0.3Zr镁合金中添加不同含量的稀土元素Y,研究Y元素及其含量对合金组织和力学性能的影响及机制.结果表明:当Y含量从0.9%增加到1.9%(质量分数, 下同)时,组织明显细化,晶间化合物呈连续细网状;当Y含量达到3.7%时,晶间化合物呈不连续的粗网状.当Y从1.9%增加到5.8%时,合金强度逐步提高.Y含量为0.9%时,Y的细化作用及适当的W-相含量对塑性有利,延伸率达到最大值24.8%;Y含量为3.7%时,W-相的数量因X-相的出现而减少,晶间化合物变为不连续网状分布,对塑性有利,合金综合力学性能最佳,抗拉强度为232 MPa,屈服强度为124 MPa,延伸率为23.5%.添加Y后的Mg-2.0Zn-0.3Zr合金流变应力和挤压变形抗力提高,但可通过420 ℃, 12 h热处理和热变形温度提至450 ℃,改善合金的热成型性并获得更高的综合力学性能.
The effect of rare earth element Y and its content on the microstructure and mechanical properties of the Mg-2.0Zn-0.3Zr alloy and the mechanism were investigated by adding different contents of Y in the alloy. The results indicate that when the Y content changes from 0.9% to 1.9 % (mass fraction, similarly hereinafter), the microstructure becomes finer obviously and the intercrystalline compound looks like a continuous thin net; while when the Y content increases to 3.7%, the compound shows discontinuous thick net. The strength of the alloy is improved gradually when the Y content increases from 1.9% to 5.8%. The preferable plasticity with a maximal elongation of 24.8% is obtained when the Y content is 0.9%, due to the refinement effect of Y and proper W-phase content. When the Y content is 3.7%, the W-phase is less due to the presence of X-phase, while the intercrystalline compound becomes discontinuous thick net, which are favorable to improving plasticity of the alloy. The alloy with 3.7% Y has better comprehensive mechanical properties than others, with the tensile strength of 232 MPa, the yield strength of 124 MPa and the elongation of 23.5%. The Y element addition can lead to an increase of the flow stress and the deformation resistance of the alloy; annealing at 420 ℃ for 12 h and hot deformation at 450 ℃ can improve the extrudability and better comprehensive mechanical properties for the alloy can be obtained.
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