Observation of Inclusion in Aluminum Deoxidized Iron.

Abstract

Aluminum-deoxidized iron at 1 873 K was solidified at 3 different cooling speed; (1) the ultra-rapid cooling of iron using twin rollers, (2) the quenching of iron into copper mold, and (3) the quenching of the iron-bearing crucible in a water bath; the most rapid cooling rate achieved with (1), which was probably about 10 5 K/s, followed (2) and (3). Dendritic, maple-like, polygonal, network-like, coral-like and spherical inclusions were observed in the samples. The dendritic, maple-like and polygonal inclusions varied in size from several tens to a few pm and were classified as primary inclusions since their sizes were independent of cooling speed. However, the network-like and coral-like inclusions (in the sample cooled ultra-rapidly and quenched into copper mold), and spherical inclusions were classified as secondary inclusions since they decreased in size with increased cooling speed. A few large spherical inclusions, which would be primary inclusions, were also present. The analysis of the electronic diffraction of the inclusions established that the a, y, δ-alumina were present as secondary inclusions. An amorphous silica spherical inclusion was also observed.