Local melting in Al embedded with TiNi powder induced by microarea self-propagating high-temperature synthesis

Abstract

Microarea self-propagating high-temperature synthesis (microSHS) was ignited by the heat of mixing generated at the boundaries between an Al matrix and TiNi particles during plastic deformation at room temperature. The temperature of the boundaries was rapidly increased by microSHS; the temperature elevation resulted in local melting of the TiNi particle and the surrounding Al matrix, because the heat of mixing was localized in the vicinity of the TiNi particle although the amount of the heat of mixing was limited. Since the amount of the local melting region induced by microSHS is restricted, not only major elements (i.e. Al, Ti and Ni) but also impurities were involved in the solidification followed by local melting. As a result, FeNi nanoprecipitates, which have not been reported in SHS studies, were formed by inclusion of Fe, initially included as an impurity in raw materials. The formation mechanism of FeNi nanoprecipitates is discussed based on reference to the Al–Fe–Ni ternary alloy phase diagram. It is expected that local melting induced by microSHS is a key phenomonon for amorphization during severe plastic deformation of elemental sheets.