INSITU HIGH-RESOLUTION ELECTRON-MICROSCOPY OBSERVATION OF THE MELTING PROCESS OF IN PARTICLES EMBEDDED IN AN AL MATRIX

The melting process of In particles embedded in an Al matrix has been observed continuously using an in situ heating experiment in a high-resolution high-voltage electron microscope. The crystalline In particles are cubo-octahedral in shape, bounded by eight {111}Al,In and six {100} Al,In facets. Cavities are attached to most of the In particles. Melting started either at the cavity or at one of the {100} facets and proceeded into the interior of the In particle. The process took place in six stages, in each of which one {100} facet became covered by the liquid phase. In particular, at the very beginning of the melting process, the liquid droplet, nucleated at a {100} facet, assumed two configurations alternately before the liquid reached the next {100} facet. The time spent in this stage was much longer than that spent in the rest of the process, and it is concluded that this stage is the rate-controlling process.