Tooru Matsumiya

Analysis of solute distribution in dendrites of carbon steel with δ/γ transformation during solidification

Solute distribution in dendrites during solidification of carbon steel was analyzed by unidirectional solidification experiments and mathematical analysis. The characteristic of the mathematical analysis is that diffusion of solutes in solid and redistribution of solutes at solid/liquid andδ/γ interfaces are taken into consideration. Based on the observed and calculated results, it was found that phosphorus was redistributed fromγ-phase toδ-phase, and that manganese was slightly redistributed fromδ-phase toγ-phase. Therefore the concentrated region of phosphorus can be separated from that of manganese duringδ/γ transformation in the case of slow cooling. Moreover, it was concluded that rapid diffusion inδ-phase and the redistribution duringδ/γ transformation played an important role in the variation of the interdendritic concentrations of solutes with lower carbon concentration.

Estimation of thermodynamic properties of solutes in silicon II

This paper proposes a computational method for estimating activity coefficients and interaction parameters of solutes in dilute solution taking into consideration the excess entropy of mixing using the grand canonical Monte Carlo simulation. The proposed method was applied to oxygen in silicon solution and its activity coefficient was estimated where a three-body potential was used as inter atomic potentials to reduce computational time. The solubility limit of oxygen was obtained by the reciprocal of the calculated activity coefficient. The calculated value was significantly changed by taking into consideration the excess entropy of mixing.

Electronic structure analysis of magnetic properties of Fe16N2

SummaryThe magnetic properties of Fe16N2, bcc iron and bct iron were studied using the linear muffin tin orbital method in combination with the atomic sphere approximation (LMTO-ASA). The following results were obtained: The magnetovolume effect is the most important for the large magnetic moment of Fe16N2. The magnetic moment of iron increases with the distance from the nitrogen. The nitrogen atom plays a role in expanding the lattice. The effect of local lattice relaxation of the iron atoms that are first- and second-nearest neighbors to a nitrogen atom was examined.