Effect of energy variation of proton beam on sharpening nitinol electrical resistivity increase at the martensitic transformation

The electrical resistivity of shape memory nitinol alloy before and after irradiation with 1.5-2 MeV was measured in the temperature range 220-350 K. The specimens were irradiated to a fluence of 6.6 x 10(15) cm(-2) over a period of 6 h. The change in electrical resistivity Delta rho = rho(f) - rho(s) at the martensitic transformation temperature T-c varied from 0.9 x 10(-5) Omega m, in the specimen irradiated with 1.5 MeV protons, to 77 x 10(-5) Omega m, when the energy of protons was 2 MeV. The relative electrical resistivity rho(f)/rho(s), of the specimen irradiated with 2 MeV protons is 20 times higher than that irradiated with 1.5 MeV, an indication that increasing the proton beam energy has enhanced the creation of defects produced by proton irradiation, due to the increase of the penetration range through the alloy, thus increasing the electrical resistivity at the martensitic transformation temperature T-c. The resistance increase in the martensitic transformation in the shape memory nitinol alloy becomes sharper when the proton beam energy is 1.875 MeV and higher. The proton beam energy proves to play an important role in the creation of defects and sharpening the resistance increase in the martensitic transformation in the shape memory nitinol alloy.