Magnetic contribution to the interdiffusion coefficients in bcc (α) and fcc (γ) Fe-Ni alloys

Abstract

The interdiffusion coefficients in bcc (␣) and fcc (␥) Fe-Ni alloys below their Curie temperatures have been calculated based on the magnetic contribution to the free energy for interdiffusion. The free energy for interdiffusion due to magnetic ordering in bcc Fe-Ni alloys is positive. The calculated interdiffusion coefficients in bcc Fe-Ni alloys fit the experimental data quite well. In fcc Fe-Ni alloys, the magnetic contribution to interdiffusion depends on both temperature and composition and is abnormal for Ni compositions in the Invar region. The free energy of vacancy formation is positive and the free energy of vacancy migration is negative, due to the effect of magnetic ordering. The interdiffusion coefficient in the ferromagnetic phase is lower than that extrapolated from the paramagnetic phase for Ni compositions of 50 at. pct and greater and is higher than that extrapolated from the paramagnetic phase for Ni compositions of 40 at. pct and lower.

Metallographic cooling rates of the IIIAB iron meteorites

“…Yang and Goldstein (2004) developed a new method, which utilizes the effect of magnetic ordering on physical, magnetic and mechanical properties of Fe-Ni alloys, to calculate interdiffusion coefficients in kamacite as a function of temperature. The Yang and Goldstein (2004) calculated results are consistent with the most recent experimental diffusion measurements (Cermak et al, 1989), and are used in the numerical model.…”

“…These coefficients were fit by Saikumar and Goldstein (1988) and by Hopfe and Goldstein (2001) in their computer simulation models for Ni contents <50 wt%. In the current study, we employ the fit developed by Yang and Goldstein (2004) for Ni contents up to 70 wt% in binary Fe-Ni. Dean and Goldstein (1986) showed experimentally that P has a significant effect on the interdiffusion coefficients in kamacite and taenite.…”

“…In the last few years, the interdiffusion coefficients for the kamacite and taenite phases of the Fe-Ni system have been re-evaluated (Yang and Goldstein, 2004) and the formation mechanism and the nucleation temperature of the Widmanstatten structure (Yang and Goldstein, 2005) have been determined. These recent advances allow for a major improvement in the computer simulation program which is the heart of the metallographic cooling rate method.…”

Diffusion‐driven kinetic isotope effect of Fe and Ni during formation of the Widmanstätten pattern

“…Following the seminal studies of Wood (1964) and Goldstein and Ogilvie (1965), a great deal of work has been done on modeling the formation of the Widmanstätten pattern. This involved i) developing fast and stable computer algorithms for simulating phase growth in a finite system (Wood 1964;Goldstein and Ogilvie 1965;Goldstein and Short 1967;Willis and Wasson 1978;Rasmussen 1982;Saikumar and Goldstein 1988), ii) measuring Fe-Ni interdiffusion coefficients in taenite and kamacite as a function of temperature and composition of the alloy (Hirano et al 1961;Borg and Lai 1963;Goldstein et al 1964;Dean and Goldstein 1986;Cermak et al 1989;Meibom et al 1994;Yang and Goldstein 2004), iii) refining the Fe-Ni phase diagram in the temperature range 300-900 °C, including the influence of phosphorus on the positions of the phase boundaries (Goldstein and Ogilvie 1965;Doan and Goldstein 1970;Willis and Wasson 1978;Moren and Goldstein 1979;Romig and Goldstein 1981;Meibom et al 1994;Yang et al 1996;Yang and Goldstein 2006), and iv) identifying the conditions for nucleation of kamacite, which controls the degree of undercooling that affected the meteorite (Narayan and Goldstein 1985;Rasmussen et al 1995;Goldstein 2005, 2006).…”

Cu-Containing Fe-Ni Corrosion-Resistant Alloys Designed by a Cluster-Based Stable Solid Solution Model

“…[1,2] However, they suffer from severe pitting corrosion in high Cl -concentration environment, [3] which needs further surface coating or alloying. Among the many possible alloying elements, Cu is good for resisting Cl -corrosion but can only be used as a minoralloying element due to Cu-Ni spinodal decomposition [4][5][6] and to Cu-Fe immiscibility.…”