Uncharacteristic second order martensitic transformation in metals via epitaxial stress fields

TL;DR

This paper demonstrates that epitaxial stress can alter the order of martensitic transformations in metals from first to second order, revealing critical behavior and continuous phase evolution.

Contribution

It introduces a novel way to modify phase transition order in metallic alloys using epitaxial stress, supported by molecular dynamics simulations.

Findings

Epitaxial stress changes martensitic transformation from first to second order.

Transformation exhibits critical behavior with power-law scaling.

Results align with recent experimental and computational studies.

Abstract

While most phase transformations, e.g. ferroelectric or ferromagnetic, can be first or second order depending on external applied fields, martensitic transformations in metallic alloys are nearly universally first order. We demonstrate that epitaxial stress originating from the incorporation of a tailored second phase can modify the free energy landscape that governs the phase transition and change its order from first to second. High-fidelity molecular dynamics simulations show a remarkable change in the character of the martensitic transformation in Ni-Al alloys near the critical point. We observe the continuous evolution of the transformation order parameter and scaling with power-law exponents comparable to those in other ferroic transitions exhibiting critical behavior. Our theoretical work provides a foundation to recent experimental and computational results on martensites near critical points.