Interdiffusion in the Fe-Ni System Using Powder Compact

Abstract

The interdiffusion coefficients of the Fe-Ni system were determined in hydrogen atmosphere over the temperature range from 1000°to 1350°C on four couples with different combinations of plate and powder compact. The concentration gradients were measured with an electron probe microanalyser, and the diffusion coefficients were calculated by the Matano analysis. The results showed that the activation energy for the interdiffusion in the couple of Fe/Ni plate varies from 60 to 70 Kcal/mol with the decreasing nickel contents, while it is about 50 Kcal/mol in the couple of Fe/Ni powder compact. This suggests that the diffusibility of both elements are enhanced in the powder side zone of the couple. The enhanced diffusibility is also observed on both couples of Fe plate/Ni powder compact and Fe powder compact/Ni plate.The Kirkendall marker movement in a couple of powder compact indicates that iron atoms diffuse more rapidly than nickel atoms, and the ratio of the intrinsic diffusion coefficient of iron and nickel is about 2 at 1300°C. Furthermore, there exist a highly porous zone on the iron side and a highly densified zone on the nickel side across the initial interface.