Determination of the Jackson-Hunt constants of the In-In2Bi eutectic alloy based on in situ observation of its solidification dynamics

We present a real-time observation study of lamellar patterns in thin-sample directional solidification of a near-eutectic In-In2Bi metallic alloy. The spacing range of stability is shown to extend from about 0.9λJH to 2.2λJH, where λJH is the Jackson-Hunt minimum undercooling spacing, in agreement with what was observed earlier in transparent eutectics. We analyze the time evolution of non-uniform spacing distributions using a previously established semi-empirical “spacing-diffusion” law [Akamatsu et al., Metal. Mater. Trans. A 35 (2004) 1815]. We obtain a quantitative estimate of the Jackson-Hunt constants and other material parameters relevant to eutectic growth, among which λJH2V=48±7μm3s-1 and D = 505 ± 75 μm2 s−1, where V is the solidification speed, and D is the solute diffusion coefficient in the liquid.