Sequential phase transformations in Ta_0.4Ti₂Zr alloy via tensile molecular dynamics simulations with deep potential

Understanding the complex deformation mechanisms of non-equimolar multi-principal element alloys (MPEAs) requires high-fidelity atomic-scale simulations. This study develops a deep potential (DP) model to enable molecular dynamics simulations of the Ta_0.4Ti₂Zr (Ta_0.4) alloy. Monte Carlo simulations using this potential reveal Ta atom precipitation in the Ta_0.4 alloy. Under uniaxial tensile loading along the 100 direction in the NPT ensemble, the alloy undergoes a remarkable sequence of phase transformations: an initial body-centered cubic (BCC₁) to face-centered cubic (FCC) transformation, followed by a reverse transformation from FCC to a distinct BCC phase (BCC₂), and finally a BCC₂ to hexagonal close-packed (HCP) transformation. Critically, the reverse FCC to BCC₂ transformation induces significant volume contraction. We demonstrate that the inversely transformed BCC₂ phase primarily accommodates compressive stress. Concurrently, the reorientation of BCC₂ crystals contributes substantially to the observed high strain hardening. These simulations provide atomic-scale insights into the dynamic structural evolution, sequential phase transformations, and stress partitioning during deformation of the Ta_0.4 alloy. The developed DP model and the revealed mechanisms offer fundamental theoretical guidance for accelerating the design of high-performance MPEAs.