Yaw Delali Bensah | Searcharxiv

arXiv2017

Maximum entropy generation rate density and its application to microstructural evolution

A solidification model based on the principle of maximum entropy production rate (MEPR) is considered for the study of pure metals. The approach leads to the development of a breakdown criterion which is able to account for the solidification velocity and solid-liquid interface (SLI) thickness. The quantitative knowledge of the SLI thickness and the maximum entropy generation rate density obtained at breakdown gives an insight about the structure of the SLI during solid to liquid phase transformation. The formation of facet and non-facet morphology, and their transitions are accounted for, which is a function of solidification velocity, heat of fusion, density and the crystallographic growth plane.

cond-mat.mtrl-sci↗

arXiv2017

Interfacial instability of a planar interface and diffuseness at the solid-liquid interface for pure and binary materials

Topographical and diffuse interface reconfigurations occur with a change in the solidification rate. In this article we pursue the hypothesis that the interface configuration during solidification is determined by the rate of entropy production in the region between a rigorous solid and rigorous liquid phase. We posit that when an interface begins to migrate, there are several stable configurations that are possible. These include atomistically-planar, diffuse-planar, facet non-planar and cellular non-planar. The configuration and topographical condition that affords the maximum entropy production rate (MEPR) yields the most stable interface configuration. The principle of MEPR is applied to (1) describe atomistically smooth and diffuse interfaces, (2) provide quantitative results for the diffuse interface thickness and the number of pseudo-atomic layers in the interface region, and (3) predict the transition from planar to a non-planar facet or non-facet cellular morphology as a function of solidification velocity or temperature gradient. Numerous experimental investigations spanning over sixty years have failed to comprehensively validate any of the existing solid-liquid interface (SLI) growth instability models. With the MEPR model, for the first time, breakdown conditions are predicted with a fair degree of accuracy for a number of binary alloys where no previous theoretical model had predictability. The model considers steady state solidification at close-to and far-from equilibrium conditions.

cond-mat.mtrl-sci↗