A Study on the Brittle-to-Ductile Transition Temperature of Forged β-Solidifying TiAlMn and TNM Alloys

Abstract

To further determine the brittle-to-ductile transition temperature, the microstructures and mechanical properties of typical forged β-solidifying Ti-42Al-5Mn (TiAlMn) and Ti-43Al-4Nb-1Mo-0.5B (TNM) alloys were studied. The results show that the microstructures of both heat-treated alloys consist of γ/α2 lamellar colony, equiaxed γ phase, and β0 phase. In addition, the globular α2 phase appears in the TNM alloy. The yield strength of TiAlMn alloy increases gradually with the testing temperature, whereas a significant drop from 605 MPa to 469 MPa occurs between 650 °C and 700 °C. In contrast, the TNM alloy exhibits a declining trend with the increasing testing temperature, and a remarkable reduction is observed in the temperature range of 700 °C–750 °C. Moreover, the fracture mode transition from transcrystalline cleavage to intercrystalline with increasing testing temperature was applied to the auxiliary judgment of brittle-to-ductile transition. As a result, the brittle-to-ductile transition temperatures of TiAlMn alloy and TNM alloy are about 650 °C–700 °C and 700 °C–750 °C, which may provide a reference for service temperature range of both alloys.

Evaluation of Forged TiAl Alloy Usefulness Based on Their Impact Resistance

“…%; the notation of at. % will be omitted hereafter) [4][5][6] is a representative forged TiAl alloy with a high β-phase content (area ratio of 10% or more [7]). Ti-42Al-5Mn is well suited for the production of large components because it can be hotforged (high-speed deformation in open space); therefore, it is used for the production of large structural components for defense applications, and this product is still in production.…”