Strengthening mechanisms of Mo–Nb–Ti and Ta–Nb–Ti complex-concentrated alloys: Data-driven insights from atomic descriptors and short-range order

The design of refractory complex-concentrated alloys (RCCAs) requires a comprehensive understanding of how alloying elements govern microstructure and mechanical response. Here, we report an integrated approach combining high-throughput experiments on Mo-Nb-Ti and Ta-Nb-Ti thin-film alloy libraries with molecular dynamics simulations to examine short range order (SRO). Composition dependent X-ray diffraction and electron microscopy investigations reveal that Mo-Nb-Ti alloys maintain fine grain sizes with minimal temperature dependence, whereas Ta-Nb-Ti alloys undergo substantial grain growth at elevated temperature. Nanoindentation mapping shows that Mo-Nb-Ti alloys consistently exhibit higher hardness and hardness-to-modulus ratios than Ta-Nb-Ti alloys, with strengthening largely affected by solid-solution effects. In contrast, the hardness reduction in Ta-Nb-Ti films deposited at high temperature is directly correlated with grain coarsening. Molecular dynamics simulations further demonstrate that SRO plays a critical role in strengthening and plasticity.