Structure and Properties of Nano-Crystalline Ti-Base Alloys Obtained by Vacuum Hot Pressing
The cp-Ti and Ti-base alloys with additions of Ta and Nb were ball milled and consolidated using vacuum hot pressing. This novel technique allowed to obtain a high level of densification of milled powders up to about 98% and the nanometric grain size level. In the samples of vacuum hot compacted cp-Ti grain size of a single α phase was estimated at 140 nm. With the increase of content the β-stabilizing elements in alloys such as Ta and Nb, structure and a grain size has been changed. In the case of Ti-5Ta-5Nb alloy, also single α phase was observed but with grains size was much smaller, close to 85 nm. The further increasing of the content of Ta and Nb caused further refinement of grain size down to 60 nm and change of structure into two phase α+β and β in case of Ti-10Ta-10Nb and Ti-15Ta-15Nb alloys respectively. The hardness and Young Modulus were measured using the dynamic hardness tester and calculations of hardness and elastic modulus values were based on Oliver and Pharr model.