Ti and Ni Grain Boundary Diffusion in B2 NiTi Compound

Abstract

The radiotracer technique was used to measure the grain boundary diffusion of44Ti and63Ni in slightly Ni-rich polycrystalline NiTi compound in the temperature range of 673 - 923 K. The temperature dependence of the grain boundary triple productP(P=sδDgb,sis the segregation coefficient,δis the grain boundary width, andDgbis the grain boundary diffusion coefficient) for Ti and Ni was determined. The triple products of both Ti and Ni grain boundary diffusion in NiTi reveal a unique behavior with significant deviations from an Arrhenius-type dependence. Probable evolution of the grain boundary structure with temperature was used to interpret this phenomenon.