STUDY AND MODELING OF HOT TEARING FORMATION

As for most of the topics in the field of solidification, Mert Flemings has always pioneered new ideas. While much of the understanding of hot tearing formation was already known about 30 years ago, he devised with Metz an interesting apparatus for studying the resistance of mushy zones to compression and shearing [1,2]. Part of the results of these tests lead Flemings to become interested in semi-solid processing of metallic alloys, with the success we know today (e.g., production of automobile components by thixocasting). Probably because of that, hot tearing criteria and models have not progressed very much since. However, with the advent of refined stress and solidification models, one sees today renewed interest in hot tearing. The present contribution, after recollecting some of the early work of Flemings in this area, presents recent SEM observations of hot tears in aluminum alloys and in-situ observations of hot tearing formation in organic systems. A recent model of hot tearing, which combines deformation of the mushy zone and interdendritic liquid flow, is also summarized.