On the Growth Dynamics of Nearly-Locked Grain in the Three-Phase In-Bi-Sn Eutectic System


Mohagheghi S., Serefoglu M.

METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, vol.50A, no.11, pp.5221-5233, 2019 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 50A Issue: 11
  • Publication Date: 2019
  • Doi Number: 10.1007/s11661-019-05426-3
  • Title of Journal : METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
  • Page Numbers: pp.5221-5233

Abstract

Solidification microstructures are significantly affected by the anisotropy of crystal/crystal interphase energy. A recent experimental work on a three-phase eutectic system by the authors suggested that two distinguishable eutectic grains, i.e., quasi-isotropic and locked, form when crystal/crystal interphase energies contain negligible and strong anisotropy, respectively (Mohagheghi and Serefoglu in Acta Mater 2018, vol. 151, pp. 432-42, 2018). In two-phase eutectic systems, in addition to these two grain types, another class of eutectic grain called nearly-locked (NL) was reported. In order to investigate the existence of the NL grain in three-phase eutectic systems, real-time directional solidification (DS) and rotating directional solidification (RDS) experiments are performed on thin samples of In-Bi-Sn eutectic alloy. It is found that NL grains also form in three-phase eutectics and they contain some characteristic features of both quasi-isotropic and locked grains. The anisotropy is strong enough to tilt the lamellar pattern with respect to the thermal gradient axis, as in the case of locked grains; however, the NL grains also retain some of the characteristic features of the quasi-isotropic grains, such as lambda-diffusion, systematic eutectic spacing adjustment, and recovery mechanisms. As a result, these grains tend to form a relatively uniform ABAC-type growth pattern, similar to quasi-isotropic grains. Using the equilibrium shapes extracted from the interphase traces of RDS patterns, the gamma plot of the anisotropic interphase, which contains 2 twofold smooth and distinct minima, is determined. (C) The Minerals, Metals & Materials Society and ASM International 2019