半连续铸造AZTYM66310合金铸态与热处理后的相组成与拉伸性能研究

Phase Constitution and Tensile Properties of Semi-continuous Cast AZTYM66310 alloy at Casting State and Heat Treatment State

摘要:

摘 要: 研究了半连续铸造Mg-6Al-6Zn-3Sn-1Y-0.5Mn（AZTYM66310）镁合金在铸态以及固溶处理与时效处理后的微观组织结构演变和拉伸性能及失效机理。铸态AZTYM66310合金的微观组织中α-Mg初生相呈现典型的等轴枝晶形态，枝晶间分布大量的凝固过程中形成的第二相，包括Mg + Mg32(Al,Zn)49共晶、Mg2Sn离异共晶相以及Al2Y相和Al8Mn4Y相。铸态合金经过380℃×6h固溶处理后，大部分Mg32(Al,Zn)49相和部分Mg2Sn相溶入基体中，形成过饱和α-Mg固溶体，基体中Al、Zn、Sn元素含量显著提高，而Al2Y相和Al8Mn4Y相未发生明显变化。固溶处理显著提高了合金的抗拉强度，同时提升了合金的断后延伸率。经过380℃×6h+150℃×16h的时效处理后，合金组织中，尤其是晶界附近，析出大量的纳米尺度的颗粒增强相，强度提高，特别是屈服强度提高到187.4 MPa。合金在拉伸失效过程中，组织中的第二相首先破裂或者与基体分离，导致了微裂纹的产生，微裂纹沿着晶界扩展，最终导致样品发生断裂。

Abstract:

Abstract: The phase constitution, tensile properties and failure mechanism during tensile process of as-cast, as-solutioned and as-aged samples of a Mg-6Al-6Zn-3Sn-1Y-0.5Mn (AZTYM66310) magnesium alloy are investigated. The α-Mg primaries in the microstructure of as-cast AZTYM66310 alloy appear typical equiaxed dendrites morphology, and a large number of interdendritic phases formed during solidification, including Mg + Mg32 (Al, Zn) 49 eutectic, Mg2Sn divorced eutectic phases, Al2Y phases and Al8Mn4Y phases. After the solution treatment of 380℃ × 6h, the majority of Mg32(Al, Zn)49 phases and part of Mg2Sn phases were dissolved into the matrix, contributing the contents of Al, Zn and Sn in the matrix increasing significantly, while Al2Y phase and Al8Mn4Y phase not changing significantly. Solution treatment significantly improves the tensile strength and the elongation of the alloy. After aging treatment of 380 ℃ × 6h + 150 ℃ × 16h, a large number of nano-scaled particle reinforced phases precipitated in the alloy, especially near the grain boundary, contributing to the yield strength increasing to 187.4 MPa. During the tensile process of the alloy, the second phases in the structure first break or separate from the matrix, resulting in the generation of microcracks. And then these microcracks propagate along the grain boundaries, eventually causing the sample to fracture.