Effect of Al and Mo Redistribution on α/β Interface Stability in Dual-Phase Titanium Alloys During Plastic Deformation

The TC11 α + β dual-phase titanium alloy exhibits limited room-temperature ductility (3.3 × 10−4 s−1: elongation 13.8%) but achieves significant superplasticity at 900 °C (3.3 × 10−4 s−1: elongation 314%), which correlates strongly with the mechanical response of α/β interfaces. These interfaces, which often crack at room temperature, undergo extensive sliding while preserving structural integrity during superplastic deformation. Combining microstructural analysis with first principles calculations, this study reveals how the stability of the α/β interface is dominated by the redistribution of alloying elements, thereby leading to distinct mechanical behaviors. Energy-dispersive X-ray spectroscopy results and calculated solution energies demonstrate that Mo preferentially dissolves in the β phase, whereas Al exhibits comparable solubility in both phases with a slight preference for the α phase. During high-temperature deformation, the α→β transformation drives Mo redistribution away from the interface toward newly formed β phases. This redistribution of Mo lowers the interfacial energy, strengthens the interface, suppresses stress-induced cracking, and ensures macroscopic continuity. Our study provides a theoretical perspective for Ti alloy design through interfacial engineering.