Grain Growth in Samples of Aluminum Containing Alumina Particles

A study of the two-dimensional and three-dimensional grain size distributions before and after grain growth treatments has been made in samples having a range of oxide contents. In order to collect statistically useful amounts of data, an automatic image analyzer was used and the resulting data were subjected to a series of statistical tests which evaluate the difference between related distributions. Normal grain growth was observed in samples of the lowest oxide content; as the oxide level was increased, a significant narrowing of the grain size distribution was observed. In the latter samples the maximum or limiting grain size measured after prolonged heat treatment is approximately one half that predicted by Zener and is in broad agreement with the values calculated from the models due to Hillert and Gladman. Anomalous grain growth has been observed in samples where normal grain growth is restricted and where the initial grain size distribution is very wide.