Effect of cryogenic process on the microstructure and mechanical properties of Ti - 35Nb - (0,0; 2,5; 5,0; 7,5) Sn alloys

Titanium alloys have presented interesting properties as a substitute for bone tissue and so have been intensively studied. The present study evaluated the modifications of phases resulting from thermal treatments of solubilization, water quenching and cryogenic treatment (-198 deg C) using Vickers microhardness, metallography and image analysis techniques. The results show that the cryogenic treatment after hardening significantly increased the hardness of the alloy with less than 5.0% of tin, and for the higher content the treatment showed no significant difference. The results of the metallography and hardness showed that the cryogenic treatment after the tempering increased the number of martensite needles, responsible for the improvement of hardness properties, and the image analysis demonstrates in a quantitative way the same pattern. It is possible to conclude that the total transformation temperature for alloys with less than 5.0% of tin is lower than the ambient temperature