Improving Ti2AlNb deformation and ductility with single-step heat treatment

Researchers from China’s Harbin Institute of Technology, Suzhou Research Institute, and Chinese Academy of Sciences have published a paper in the Journal of Alloys and Compounds focusing on their success in producing a room-temperature strength-ductility matching Ti2AlNb via a post-processing heat treatment.

The as-sintered Ti₂AlNb intermetallic mainly contained the ‘O’ phase and small proportions of the B2 and α₂ phases, resulting in brittle characteristics, explained the researchers. After treating the intermetallic at 950°C for 2 h and subsequently quenching it, the brittle α₂ at the grain boundaries transformed into O phase and the O phase partially dissolved into the soft B2 phase, resulting in a much higher increase in elongation (10.4 %). The intermetallic yield strength remained at 867.3  MPa, comparable with sintered examples.

These structural changes allowed the team to improve the uniformity of deformation and allow more uniform slip transfer between O phase and B2 phase. The experimental analysis of the deformed region also revealed that the dominant deformation mode changed from single-system slip to a mix of single, double and cross slips after heat treatment. Furthermore, {110}_B2, {112}_B2, and {001}_O plane slips could also be activated during tensile tests; (021)_O and (02−1)_O twins contribute to the reduction of concentrated stress, thus improving the ductility.

‘Improving the uniform deformation ability and ductility of powder metallurgical Ti₂AlNb intermetallic with single-step solution heat treatment’ is available here.

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