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通过OM,SEM及拉伸性能测试,研究了Mg-9.0Y-3.0MM-0.6Zr铸态合金均匀化温度与时间对显微组织的影响,确定该合金合适的均匀化工艺。结果表明:Mg-9.0Y-3.0MM-0.6Zr铸态合金显微组织主要由α-Mg基体相、Mg12(MM)相以及Mg24Y5相组成,晶粒度约为45μm;505,520℃均匀化温度较低,Mg-Y相分解不够完全;经535℃保温18 h均匀化处理后,仅在晶界处残留Mg12(MM)相,延长时间晶粒尺寸没有变化,可见Mg12(MM)相可有效抑制合金晶粒长大;535℃×18 h均匀化处理后合金的力学性能较铸态合金没有明显改变,均匀化态的合金经挤压后,力学性能大幅度提升,σ0.2,σb,δ分别为245,305 MPa和12.5%。均匀化处理后合金断口形貌与铸态合金相似,仅在局部存在少量的韧窝,室温下断裂方式为脆性断裂;挤压后的合金断口形貌呈典型的韧性断裂特征。
The effects of homogenization temperature and time on the microstructure of Mg-9.0Y-3.0MM-0.6Zr as-cast alloy were investigated by OM, SEM and tensile testing. The proper homogenization process was determined. The results show that the microstructure of as-cast Mg-9.0Y-3.0MM-0.6Zr alloy mainly consists of α-Mg matrix, Mg12 (MM) phase and Mg24Y5 phase with a grain size of about 45μm. The homogenization temperatures at 505 and 520 ℃ Low temperature and low temperature, the decomposition of Mg-Y phase is not complete enough. After being homogenized at 535 ℃ for 18 h, Mg12 (MM) phase remains only at the grain boundaries and the grain size does not change during the extension time. The mechanical properties of alloy after homogenized at 535 ℃ for 18 h did not change significantly compared with that of as-cast alloy. The mechanical properties of alloy homogenized after extrusion were greatly improved, and the mechanical properties of σ0.2, σb, δ Respectively 245,305 MPa and 12.5%. After homogenization, the fracture morphology of the alloy is similar to that of the as-cast alloy. Only a few dimples exist locally, and the fracture mode is brittle fracture at room temperature. The fracture morphology of the alloy after extrusion is typical ductile fracture.