Munekazu Ohno 교수

An antitrapping current scheme for quantitative phase-field model [A. Karma, Phys. Rev. Lett. 87, 115701 (2001)] is extended to solidification process in a dilute binary alloy system involving diffusion in the solid. It is demonstrated in an asymptotic analysis that in the case of an arbitrary value of the solid diffusivity, five types of constraints exist between interpolating functions used in the phase-field model, which need to be satisfied simultaneously to eliminate all anomalous interface

A quantitative phase-field model is developed for simulating microstructural pattern formation in nonisothermal solidification in dilute multicomponent alloys with arbitrary thermal and solutal diffusivities. By performing the matched asymptotic analysis, it is shown that the present model with antitrapping current terms reproduces the free-boundary problem of interest in the thin-interface limit. Convergence of the simulation outcome with decreasing the interface thickness is demonstrated for n

Abstract A thermodynamic description of the Mg–Al–Mn system on the basis of critically assessed experimental data is presented. Particular attention is placed on the solubility of manganese in Mg-rich liquid alloys. The overall consistency between calculated and experimental phase equilibria is shown and the Calphad assessment enables a clear identification of consistency of various groups of data. In manganese-saturated liquid alloys the primary crystallizing phases are β-Mn and Al8Mn5 up to 23

Solid-liquid interfacial properties out of equilibrium provide the essential information required for understanding and controlling solidification microstructures in metallic materials. However, few studies have attempted to reveal all interfacial properties out of equilibrium in detail. The present study proposes an approach for simultaneously estimating all interfacial properties in a pure metal below the melting point on the basis of the Bayesian inference theory. The solid-liquid interfacial

This review presents the development of quantitative phase-field models for simulating the formation processes of solidification microstructures, with particular attention to the theoretical foundation and progress in modeling. The symmetry of interpolating functions required to reproduce the free-boundary problem in the thin-interface limit and the necessity of antitrapping current in the diffusion equation are discussed. In addition, new cross-coupling in the phase-field equation for two-sided

We analyzed the applicability of original Datta-Das proposal for spin-field-effect transistor (spin-FET) to nonballistic regime based on semiempirical Monte Carlo simulation for spin transport. It is demonstrated that the spin helix state in two-dimensional electron gas system is sufficiently robust against D'yakonov-Perel' spin relaxation to allow an operation of Datta-Das-type spin-FET in the nonballistic transport regime. It is also shown that the spin diffusion length of the spin helix state

A variational formulation of a quantitative phase-field model is presented for nonisothermal solidification in a multicomponent alloy with two-sided asymmetric diffusion. The essential ingredient of this formulation is that the diffusion fluxes for conserved variables in both the liquid and solid are separately derived from functional derivatives of the total entropy and then these fluxes are related to each other on the basis of the local equilibrium conditions. In the present formulation, the

We present the variational formulation of a quantitative phase-field model for isothermal low-speed solidification in a binary dilute alloy with diffusion in the solid. In the present formulation, cross-coupling terms between the phase field and composition field, including the so-called antitrapping current, naturally arise in the time evolution equations. One of the essential ingredients in the present formulation is the utilization of tensor diffusivity instead of scalar diffusivity. In an as