Comparative X-ray and time-of-flight neutron diffraction studies of martensite crystal lattice in stressed and unstressed binary Ti–Ni alloys

Abstract

An X-ray and time-of-flight neutron diffraction study of a Ti–50.0 at.% Ni alloy was performed. The B19′ martensite lattice parameters are different for the quenched martensite and for the martensite formed from the austenite containing a well-developed dislocation substructure due to transformation-induced hardening. A tensile stress increases the “underrecovery” of the d h k l values of planes perpendicular to the axis of tension (and of the “apparent” martensite lattice parameters calculated from these d h k l values) after a cycle of transformation-induced hardening compared with the corresponding values of the initial quenched martensite. A probable cause for the differences between d h k l and lattice parameters of martensite formed from highly dislocated austenite and corresponding parameters of quenched martensite formed from recrystallized austenite are tensile components of stress fields generated by the dislocation substructure and/or residual stresses of different origin which are present in the initial austenite.