Effect of hot rolling on microstructure and tribology behaviors of Ti-50.8Ni alloy
(1. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China;
2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China)
2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China)
Abstract: We link different microstructures to tribological behaviors of Ti-50.8Ni (mole fraction, %) in reciprocating mode at room temperature (20 °C). Hot-rolled alloys with B2 phase exhibit lower coefficient of friction and wear rate compared to the ones with B19？. Stress-induced martensitic transformation occurs during sliding. However, multi-pass hot rolling weakens the wear resistance. In this study, microstructures were characterized through electron backscatter diffraction and transmission electron microscopy (EBSD/TEM). From the concept of energy conservation, the effects of weak intensity of hot-rolled textures on the wear resistance are minimal. Based on the result that the alloy with a higher portion of coincidence site lattice boundaries shows lower martensitic start transformation temperature in the DSC curves than that with higher KAM values, the delay on B2-B19？ transformation from {112}B2 twins outweighs dislocations. Moreover, widely distributed small-angle grain boundaries owing to dynamic recovery improve the wear resistance effectively compared to those that are well-recrystallized.
Key words: Ti-50.8Ni alloy; tribological performance; small angle grain boundaries; coincidence site lattice (CSL) boundary