Understanding the deformation mechanism of individual phases of a dual-phase beta type titanium alloy using in situ diffraction method

An in situ tensile X-ray diffraction (XRD) set-up with an area detector was employed to characterize deformation behaviors of individual phases in a commercial dual-phase β-Ti alloy. A developed analytical approach based on the modified Williamson-Hall plot accounting for dislocation evolution was proposed to elucidate the deformation mechanism of each phase from the in situ XRD data. A commercial purity titanium (alpha type, α-Ti) alloy was examined as a comparison to assist identifying the influence of inter-phase interaction on the deformation behavior of the β-Ti alloy. We found that the small amount of the fine lamella shaped hcp (α) precipitates, which is only 5% in volume, has great effects on the deformation mechanism of the bcc (β) matrix in the β-Ti alloy due to the Burger's orientation relationship (BOR) between the two phases. Due to the reason that slip on the coherent plane of (211)β of the β phase (i.e. (10 1̅0)α plane of the α phase) is more predominant than that of (110)β plane (i.e. (0002)α plane) in a hcp ploycrystal, slip on (211)β plane is easier than that on (110)β plane in the β-Ti alloy (cf. {110} < 111 > is the typical slip system in single phase bcc polycrystals). Although slip on (211)β plane is the most facile, lattice strain on (211)β plane is not the smallest, manifesting that stress/strain redistribution between α precipitates and β matrix occurred to accommodate the inter-phase interaction.