Diffusion mechanisms in B2 NiAl phase studied by experiments on Kirkendall effect and interdiffusion under high pressures Original Research Article

The intrinsic diffusivities of both components and the activation volume for interdiffusion in the B2 type NiAl phase have been measured in the high temperature region from 1473–1773 K. The activation volume for interdiffusion in 40–49 at%Al is found to be almost constant value of 1.0V0 (V0: molar volume of alloys) at 1473–1773 K, suggesting that divacancies contribute to the diffusion. Near 43 at%Al, the diffusion mechanism for Al atoms is most likely the triple defect mechanism with the activation energy of 320 kJmol−1, while that of Ni atoms is probably the anti-structure bridge mechanism with the smaller activation energy of 240 kJmol−1. However, at 50.5 at%Al, Al atoms diffuse by the nearest neighbor mechanism with the smaller activation energy (260 kJmol−1), whereas Ni atoms diffuse probably by the next nearest neighbor jump related to the triple defect with the larger activation energy (360 kJmol−1).