Microstructure Evolution of a Ternary Monotectic Alloy During Directional Solidification

doi:10.1007/s40195-014-0199-z

Abstract

Abstract:

A model was developed to describe the microstructure evolution in a directionally solidified ternary monotectic alloy. The directional solidification experiments were carried out on Al-3Pb-1Sn (wt%) alloys by using a Bridgman apparatus. The microstructure evolution in the directionally solidified sample was calculated. The numerical results agree well with the experimental ones. It is demonstrated that the nucleation of the minority phase droplets occur at two different positions. One corresponds to the liquid-liquid decomposition, which occurs in front of the solidification interface. The other is at the liquid/solid interface. The nucleation rate of the minority phase droplets at the liquid/solid interface is significantly higher than at the position in front of the solidification interface. The characteristic of the nucleation process leads to a bimodal size distribution of the minority particles in the directionally solidified sample.

Key words: Ternary monotectic alloy, Directional solidification, Modeling

Shu Chen, Jiu-Zhou Zhao, Hong-Xiang Jiang, Jie He. Microstructure Evolution of a Ternary Monotectic Alloy During Directional Solidification[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(3): 316-321.

Figures/Tables 8

Fig. 1 Microstructures of the Al-3 wt% Pb-1 wt% Sn alloys directionally solidified at different solidification rates: a 2 mm/s, b 5 mm/s, c 8 mm/s

Fig. 2 Size distribution of the (Pb, Sn)-rich particles in the Al-3Pb-1Sn alloy directionally solidified at the rate of 5 mm/s

Table 1 Average radius of the (Pb, Sn)-rich particles in the Al-3 wt% Pb-1 wt% Sn alloys solidified directionally at different solidification rates

Solidification rates (mm/s)	3D average radius (μm)
2	0.43
5	0.34
8	0.26

Fig. 3 Measured (squares) and calculated (solid line) temperature profile of the melt in front of the solidification interface along the central z axes of the sample

Fig. 4 Average radius of the (Pb, Sn)-rich particles in the Al-3 wt% Pb-1 wt% Sn alloy directionally solidified at different solidification rates

Fig. 5 Vertical cross-sectional phase diagram for Al-3Pb-xSn ternary alloys

Fig. 6 Supersaturation of the matrix melt and nucleation rate of the MPDs along the central z axes of the sample directionally solidified at the rate of 5 mm/s

Fig. 7 Number density and average radius of the MPDs along the central z axes of the sample solidified at the rate of 5 mm/s

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