The effects of γ-irradiation on Ti-Ni shape-memory alloy

The effect of gamma -irradiation on the martensitic transformation temperatures (MTTs) of Ti--Ni alloys was studied. Samples of Ti--51.0Ni were used in the investigations. Following aging at 480 deg C to gain a function of two way shape memory after solution treating at 700 deg C and water quenching, the samples were gamma -irradiated by a exp 60 Co source at room temperature up to a does of 2 x 10 exp 9 rad. Measurements of electrical resistivity vs. temperature were used to determine the MTTs for both irradiated and non-irradiated alloys. X-ray diffraction, optical microscopy, TEM and Doppler-broadening spectroscopy of positron annihilation were also used to analyze the microstructure. An upward shift of the MTTs were evidenced in the irradiated alloy. No evidence of variations of the grain size and ordering structure due to irradiation were detected. The possible role of point defects in the observed changes in the MTTs of the alloys studied is discussed.