Observation of atomically displacive transformation out of the boundary-reconstructive phase competition

TL;DR

This study uncovers a displacive martensitic transformation at a reconstructive phase boundary in a Ni-Co-Mn-V alloy, driven by critical phase competition and structural frustration, enabling phase control via external fields.

Contribution

It reveals a novel atomically displacive transformation occurring at a reconstructive boundary, expanding understanding of phase transition mechanisms in alloy systems.

Findings

Displacive transformation observed at reconstructive boundary.

Phase transition can be tuned by external fields.

Parent phase destabilization leads to new functional materials.

Abstract

During the phase transitions, diverse states evolve with multiplex phenomena arising from the critical competition. In this study, a displacive martensitic transformation with a lattice shear distortion was unexpectedly observed at the reconstructive phase boundary that usually connects multiple phases without crystallographic relation, in a Ni-Co-Mn-V all-d-metal alloy system. Experiments and theoretical calculations suggest that the parent phase becomes increasingly unstable when approaching the phase boundary. The lattice-distorted transformation with moderate first-order nature survives due to the critical phase competition from the structural frustration, in which the comparable energy and the diminished formation preference of different phases emerge. In this critical state, the phase selection including the martensitic phase transformation can be tuned by external fields such as rapid cooling, annealing and magnetic field. Our research reveals a novel manner to destabilize the parent phase, through which one could attain new functional materials based on the phase transitions.