Design of compositionally modulated materials for controlled strain release during deformation through phase-field simulations

Impurity segregation and solute partitioning, which can lead to microscale concentration modulations (microCMs), are common phenomena in materials processed through various methods. Traditionally, these microCMs have been viewed as undesirable, necessitating costly homogenization treatments for their removal. However, in this study, we introduce an innovative alloy design strategy that capitalizes on the potential benefits offered by microCMs, as revealed through phase-field simulations. The majority of our simulation predictions have received strong support from experimental investigations, and these predictions have guided the development of new experimental designs for microCM alloys with exceptional properties. We highlight two notable examples. The first example demonstrates how microCMs can be strategically employed to regulate martensitic transformations, transforming them from typical sharp first-order transitions into broadly smeared continuous transitions. This modification results in quasi-linear superelasticity with an exceptionally low apparent Young’s modulus, as well as Invar and Elinvar anomalies. The second example showcases how microCMs can be harnessed to activate various solid-state phase-transformation mechanisms in distinct locations, including congruent transformation, pseudospinodal decomposition, and nucleation-and-growth, leading to microstructurally modulated materials with excellent comprehensive mechanical properties. These studies challenge the conventional view of microCMs as unwanted byproducts, demonstrating their potential as a valuable resource for designing alloys with outstanding characteristics.