combinatorial_mixing

Overview

This repository contains the computational framework and data for exploring compositionally complex alloys through combinatorial mixing. Our initial computational sampling employs a rotationally symmetric compositional contour centred on the equiatomic composition, with a gradient of approximately 5-50 at.% for each element. This methodology samples 69 distinct regions, each representing an individual alloy by its averaged composition and structure. By varying the arrangement of sputtering targets, we substantially expand the sampled compositional space.

Permutational Combinatorial Chemical Mixing

We consider the complexity of quinary variants, specifically the $\mathrm{Cr_x Fe_x Ni_x - X_x Y_x}$ variants, where elements X and Y are chosen from a pool of Co, V, Mn, Mo, Cu, Nb, W, Ti, Al, Si, and Ta. This approach yields 55 quinary elemental combinations. Each combination allows for the exploration of combinatorial chemical mixing across 120 target permutations, producing 69 unique alloys for each permutation. This leads to an initial computational analysis covering 455,400 alloy compositions.

Phase Stability Assessment

The phase stability of each alloy composition is evaluated using two Gibbs energy construction methods aimed at identifying single-phase FCC regimes. These regimes can be fabricated using either:

• Bulk casting-homogenisation: Conducting a full equilibrium search for a single-phase FCC temperature window between $900^\circ\text{C}$ and $1300^\circ\text{C}$.
• Combinatorial thin film: Performing a minimum Gibbs energy search across the compositional space at a lower temperature of $200^\circ\text{C}$, comparing FCC with other potential phases.

Solid Solution Strengthening Calculation

This repository also calculates solid solution strengthening, leveraging a generalised weak-pinning model that emphasises the statistical fluctuations in solute configurations for enhancing dislocation binding (Varvenne et al.). The methodology employs mechanical elasticity simplification, where solute atoms acting as centres of dilation or contraction introduce volume misfits. Calculations involve factors such as shear yield stress, energy barriers for thermally activated flow, and tensile yield strength at various temperatures and strain rates, utilising data from Pymatgen for modulus, Poisson's ratio, and the TCHEA4 database for molar volume.

Figures examples

Compositional Contour

Full Equilibrium Phase Map

Minimum Gibbs Energy Phase Map

Solid Solution Strengthening