Deformation mechanisms in a β-quenched Ti-5321 alloy: In-situ investigation related to slip activity, orientation evolution and stress induced martensite

Abstract

The deformation behavior of β-quenched near β Ti-5321 (Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe) alloy was systematically studied using in-situ tensile test monitored by the scanning electron microscopy (SEM). Besides, the electron backscatter diffraction (EBSD) was performed to thoroughly discuss the deformation mechanisms. The results indicated that slip activities, crystal rotation and stress induced martensite transformation were the major deformation mechanisms in the β-quenched Ti-5321 alloy during in-situ tensile testing. The slip activities were investigated by using the EBSD-trace analysis, which demonstrated that {110}<111>, {112}<111> and {123}<111> slip systems were activated and the {110}<111> slip system dominated. Besides, β grains rotated about 7.8° to accommodate the increased macrostrain. Notably, the stress induced martensite α″ which was related to the double yielding behavior during tensile process exhibited multiple characteristics. The different α″ variants divided the β matrix into smaller β blocks with a typical zigzag morphology, in which one α″ variant passed through another one by deflecting its initial growth direction. Moreover, the deformation twinning in martensite α″ and slip bands cutting through martensite α″ effectively accommodated the local strain. These systematically analysis can provide insightful information about the deformation mechanisms in near β titanium alloys.