Magnetic-field-assisted deep cryogenic treatment (MDCT) for simultaneous strengthening and toughening of TiAl alloy

Achieving a simultaneous improvement in strength and ductility of TiAl alloys at both room temperature (RT) and elevated temperatures remains a major challenge due to their inherent brittleness and limited hot workability. In this work, a magnetic field-assisted deep cryogenic treatment (MDCT, 3 T pulsed field, 4–16 h at −196 °C) was applied to a full-lamellar TiAlX alloy to enhance its mechanical properties. The results demonstrate that MDCT induces microplastic deformation and magnetic fragmentation, leading to microstructure refinement (an 82.8% reduction in lamellar colony size), an increase in dislocation density, a decrease in lattice parameters, and the formation of equiaxed γ grains at colony boundaries. These microstructural changes promote the α₂ → γ phase transformation and modify the γ-phase texture. The MDCT12 specimen (12 h treatment) exhibits the optimal performance, with tensile strength and elongation reaching 382.2 MPa (+24.1%) and 4.7% (+67.9%) at RT, and 808.0 MPa (+55.6%) and 14.5% (+34.3%) at 800 °C, respectively. The enhanced mechanical properties are attributed to a multi-scale synergistic mechanism involving lattice contraction, dislocation-mediated phase transformation, and interface-dominated deformation twinning/dynamic recrystallization. This study provides a novel strategy for multi-field processing of intermetallic materials, offering significant potential for industrial applications in aerospace and automotive sectors.