Lateral grain growth during reactive isothermal solidification in the Ni-Sn system

In this research lateral growth of Ni3Sn4 grains in the Ni-Sn system during isothermal solidification was investigated. Experiments involved multi-layered samples heat-treated for different durations at temperatures in the range 235–600◦C. During solidification Ni3Sn4 was the only intermediate phase found to grow as a layer at the solid/liquid interface. SEM and optical microscopy cross-sectional views of samples heat-treated at 500◦C and at 600◦C reveal that lateral grain growth occurs, the mean lateral grain size being proportional to √t(t-the duration of the heat treatment). This process was found to be connected with solution reprecipitation process between adjacent grains in order to equate the local curvature of the solid/liquid interface at groove zone. Rotation of the grain boundary groove due to this mass transfer induces a curvature of the grain boundary, which is the controlling mechanism for its migration. The process was numerically formulated, which provides quantitative fitting to the observed kinetics. The formulation includes a contribution due to the good wetting of the grain boundaries by the liquid phase supporting the observed enhancement in growth rate. C 2005 Springer Science + Business Media, Inc.