Forming Ru containing eutectoid structure serves as the dislocation storage unit at the lamellar colony boundary of TiAl alloy

The lamellar colony boundary and lamellae interface are the priority locations for stress concentration, and how to alleviate the degree of stress concentration at these interfaces is an important part of overcoming the shortcomings of TiAl alloys. In this study, the eutectoid structure consisted of C15-Laves and τ₁ phases is formed at lamellar colony boundary in the 2.0Ru alloy. Gentle strain gradient at the C15-Laves/τ₁ and C15-Laves/β₀ interfaces indicates the insignificant lattice distortions, facilitating the great interfacial bonding and uniform stress distribution. The further enrichment of Ru in β₀ phase hinders the diffusion of other elements and promotes the C15-Laves phase precipitation with Ru deficiency. During tensile deformation process, dislocations are activated at the phase boundaries of the eutectoid structure and slip inward rather than accumulating at the phase interface. This kind of eutectoid structure serves as the unique dislocation storage unit delaying the fracture of TiAl alloys. As Ru content increases from 0 to 2.0 at %, the compressive strength and strain increase from 1605 to 2248 MPa and 29.2 to 39.9 %, respectively, and the tensile properties at room temperature also significantly improved. The ultimate tensile strength and elongation at 850 ℃ are simultaneously increased, especially the elongation increased by 8.3 times. The improvement of dislocation configuration by the eutectoid structure at the lamellar colony boundary, the toughening effect of γ_B and τ₁ phases, the refinement of lamellar spacing by Ru, and the solute solution of Ru are contributed to the mechanical properties.