Accelerated intermetallic phase amorphization in a Mg-based high-entropy alloy powder

Abstract: We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling. The presented methodology expedites the synthesis of amorphous alloy powder by strategically injecting entropic disorder through the inclusion of multi-principal elements in the alloy composition. Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a precursor intermetallic structure. This transformation, characterized by the emergence of antisite disorder, lattice expansion, and the presence of nanograin boundaries, signifies a departure from the precursor intermetallic structure. Additionally, this phase transformation is accelerated by the presence of multiple principal elements that induce severe lattice distortion and a higher configurational entropy. The atomic size mismatch of the dissimilar elements present in the alloy produces a stable amorphous phase that resists reverting to an ordered lattice even on annealing.