Prof. Elena Pereloma
UOW Electron Microscopy Centre
University of Wollongong
Metastable β-Ti (body centered cubic, bcc) alloys exhibit a unique combination of strength and ductility as they accommodate deformation via stress-induced phase transformation and twinning in addition to slip. The matrix bcc β phase typically transforms during loading to α” martensite (orthorhombic) and ω (hexagonal close packed, hcp) phases. The relative activities of the operative deformation mechanisms depend on several factors including the stability of the β phase, loading path and deformation conditions (temperature and strain rate).
In the present ongoing research project, various in-situ and ex-situ experimental techniques are used to evaluate the effects of the β matrix stability, strain and loading path (tension, compression, cyclic tension-compression and bending) on the microstructure evolution and the associated deformation mechanisms in metastable β Ti-V-Fe-Al alloys. The matrix stability was manipulated by the formation of different volume fractions of α phase (hexagonal close packed, hcp) and the associated rejection of β-stabilisers back into the β matrix. The evolution of microstructures during in-situ bending test in scanning electron microscope were followed. In-situ neutron diffraction during monotonic tension and cyclic tension-compression loading (±2% strain) of fully β microstructure was also carried out. The effects of β phase stability, strain and strain path were analysed and discussed.