Alloy amorphization through nanoscale shear localization at Al-Fe interface

Achieving reliable metallic bonding directly between steel and aluminum alloys has a broad societal impact on sustainability from transportation systems to space exploration and biomedical devices. This is because steel and aluminum alloys are the top two most available and widely used metals. However, the development of detrimental intermetallic compounds (IMCs) at the Al-Fe interface has frustrated researchers and engineers for decades. Here, we present a new mechanism on how a nanoscale amorphous layer can be introduced at the Al-Fe interface without undesirable IMC: (i) a rapid sliding at the Al-Fe interface can generate a nanoscale premelting layer, leading to nanoscale shear localization; (ii) the resulting high shear strain rate within the premelting layer is high enough to suppress crystallization; (iii) as long as sufficiently high shear strain rate can be sustained within the premelting layer until the interfacial temperature is low enough, a stable amorphous can be retained without relying on rapid solidification. The findings provide a mechanistic basis for devising novel alloy amorphization and dissimilar metal joining techniques. (C) 2020 Elsevier Ltd. All rights reserved.