Effect of plastic deformation on material properties and martensite structures in Ti–Nb alloys

Abstract

Abstract The purpose of this study was to investigate and discuss the effect of plastic deformation on material properties, such as Young’s modulus and internal friction, of the martensite structures in Ti–Nb alloys. A characteristic of the structure of Ti–10Nb alloys is the twin α structure. For Ti–15Nb alloys, it is the α′ martensite structure and for Ti–20Nb alloys, it is the α″ martensite structure. In the twin α structure, Young’s modulus decreased slightly and the internal friction increased gradually with an increase in the rolling reduction rate. In the α′ martensite structure, Young’s modulus decreased slightly and the internal friction decreased gradually with an increase in the rolling reduction rate. On the other hand, in the α″ martensite structure, Young’s modulus decreased and the internal friction increased drastically at a weak plastic deformation. After that, Young’s modulus was almost stable and the internal friction decreased with further deformation. The change in the material properties of the α′ martensite structure was considered to be caused by a decrease in the lattice constants, like a reverse transformation from α′ to α or the emission of a dislocation. The change in the material properties of the α″ martensite structure was considered to be caused by the change in the internal microstructure, such as the increase in the dislocation or twin.