Microstructural evolution of two binary β-titanium alloys during cold deformation

The deformation mechanism that reflects on the cold workability, of two beta-Ti alloys with chemical compositions of Ti-14Cr and Ti-17Mo in wt. % are studied in this work. The present alloys were solution treated at 900 degrees C for 1.8 ks. Followed by cold rolling with different reduction ratio from 5% to 30%. The microstructural evolution during cold deformation was followed using optical microscopy, X-ray diffraction and micro hardness. It was observed that the hardness and work hardening rate are affected significantly by the amount of cold deformation for the present Ti-alloys. It is apparent from the intensive microstructural observations that the deformation twinning (TWIP effect) is the dominant deformation mechanism in Ti-17Mo alloy at room temperature. However, the formation of slip bands and extended shear bands (SBs) were observed to be the deformation-induced microstructural features in Ti-14Cr alloy. The XRD analyses also revealed that the stress/strain induced martensitic transformation (TRIP effect) has not activated in the deformed Ti-alloys despite high deformation of 30%.