Particle engulfment and pushing by solidifying interfaces: Part 1. Ground experiments

Abstract

Directional solidification experiments have been carried out to determine the pushing/engulfment transition for two different metal/particle systems. The systems chosen were aluminum/zirconia particles and zinc/zirconia particles. Pure metals (99.999 pct A1 and 99.95 pct Zn) and spherical particles (500 µm in diameter) were used. The particles were nonreactive with the matrices within the temperature range of interest. The experiments were conducted so as to ensure a planar solid/liquid (SL) interface during solidification. Particle location before and after processing was evaluated by X-ray transmission microscopy (XTM) for the Al/ZrO2 samples. All samples were characterized by optical metallography after processing. A clear methodology for the experiment evaluation was developed to unambiguously interpret the occurrence of the pushing/engulfment transition (PET). It was found that the critical velocity for engulfment ranges from 1.9 to 2.4 µm/s for Al/ZrO2 and from 1.9 to 2.9 µm/s for Zn/ZrO2.