Effect of homogenization treatment on microstructure of Mg-9.8Gd-3.5Y-2Zn-0.5Zr alloy

doi:10.13251/j.issn.0254-6051.2022.10.001

Abstract

Abstract: Microstructure evolution of Mg-9.8Gd-3.5Y-2Zn-0.5Zr alloy ingot after homogenization treatment at 505-535 ℃ for 0-84 h was studied by means of DSC, SEM, EDS and OM. The results show that the as-cast microstructure is dendrite, and the content of the second phase is 19.86%. The intergranular second phase mainly consists of white spot-like eutectic phase and massive LPSO phase, and the intragranular second phase consists of a small amount of needle-like LPSO phase, petal-like Zr cluster phase and square rare-earth rich phase. The morphology of LPSO phase after homogenization treatment is intergranular block and intragranular lamellar. The content of intragranular lamellar LPSO phase is affected by homogenization temperature and time. At 505-525 ℃, the growth rate of intragranular lamellar LPSO phase increases with the increase of homogenization temperature. The intragranular lamellar LPSO phase precipitates along the grain boundary into the matrix with the extension of holding time at the same temperature and begins to coarse after penetrating the grain. At 535 ℃, the intergranular massive LPSO phase transforms into W phase, and the intragranular lamellar LPSO phase dissolves into matrix. The intergranular LPSO phase plays a role of pinning relative to grain boundary migration. Homogenized at 505-525 ℃, with the extension of holding time, grain growth is not obvious. Homogenized at 535 ℃, the intergranular LPSO phase dissolved in large quantities and the grains begin to grow rapidly.

Key words: Mg-9.8Gd-3.5Y-2Zn-0.5Zr magnesium alloy, homogenization treatment, LPSO phase, microstructure

CLC Number:

TG146.22

Huang Yuanchun, Wang Zhou, Ma Shangkun. Effect of homogenization treatment on microstructure of Mg-9.8Gd-3.5Y-2Zn-0.5Zr alloy[J]. Heat Treatment of Metals, 2022, 47(10): 1-9.

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