Abstract
In situ solidification experiments on Zn-6 wt pct Bi immiscible alloys were conducted to investigate the droplet evolution under high static magnetic fields (HSMFs). The results showed that a microstructure with extremely fine Bi-rich particles distributed in the matrix can be obtained under an HSMF of 29 T. The average diameter of the Bi-rich phase decreased with the increasing magnetic flux density. Stokes sedimentation disappeared when the HSMF was larger than 18 T. Starting at an HSMF of 18 T, Bi-rich droplets grew via pure diffusion in the liquid matrix. The HSMF decreased the spacing of the droplet arrays when the cooling rate (R) was approximately 1600 °C/min. The formation of a Zn-rich phase surrounded by a Bi-rich shell at HSMFs below 18 T, when R was approximately 60 °C/min, was attributed to the thermoelectric magnetic force.
Highlights
IMMISCIBLE alloys, which are known as monotectic alloys, have been of research interest for decades because of their excellent conductivity[1] and wear resistance.[2]
We previously showed that Stokes sedimentation could be markedly suppressed by applying high static magnetic fields (HSMFs) of 17.4 and 29 T to a Zn-4 wt pct Bi alloy.[18]
The region located approximately 2 to 3 mm from the bottom edge of the sample along the central axis, which was photographed in this study, was considered representative to estimate the segregation in each ingot
Summary
IMMISCIBLE alloys, which are known as monotectic alloys, have been of research interest for decades because of their excellent conductivity[1] and wear resistance.[2] in binary alloys, a solidified structure with segregation commonly forms under normal gravity conditions because of the Stokes sedimentation induced by the large density difference between the two elements. The formed minority liquid droplets settle or float because of the different specific densities of the liquid phases, and they migrate according to the temperature gradient. This droplet motion leads to severe phase segregation in the microstructure and even in the macrostructure of immiscible alloys.
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