MAX phases: Unexpected reactivity under impact

Abstract

This study reveals that MAX phase materials can exhibit extraordinary reactivity when subjected to impact loading. This previously unknown behavior was discovered and examined in a case study of TiSiC subjected to Split Hopkinson pressure bar (SHPB) testing. The employed methodology integrated SHPB coupled with thermal measurements and ex-situ spectroscopic analysis, yielding crucial quantitative insights into MAX phase reactivity and mechanical impact response. We observed a substantial release of high energy in the form of elevated temperatures upon impact and disintegration of the MAX phase. Surprisingly, it was found that oxidation, usually the prominent contributor to reactivity, only plays a secondary role. Instead, microstructural transformation emerges as the primary source of energy release. It is postulated that the transformative kinetic mechanism involves rapid kinking, delamination, and bond breakage within the bulk material. These findings shed light on the fundamental energetics of MAX phases and highlight their potential as versatile reactive structural materials.