The diffusion of niokel into iron wae meaeured in the temperature range 600-1050' C. Radioaotive Niw wee used ae the tracer element; the eurface-decreaee and the n&dual-aotivity seotioning m&bode were employed.
The di&eivity below the Curie temperature wae observed to be lower than that expected from an extrapolation of the diffusion data for paramagnetic alpha-iron.
The diffusion coefecienta may be expreeeed 88 follows (in cm*/eec):
Gamma
-iron, D = 0.71 exp (--87,OOO/RT) Patamagnetic alpha-iron above 800" C, D = 1.3 exp ( -6f3,OOO/RT) Ferromagnetic alpha-iron below 680' C, D = 1.4 exp (-58,7OO/RT). The anomal~ua decFeeee in the diffusion coefacient etarta at about 800" C, somewhat above the Curie temperature, and ia thought to be associated with the effect of abort range msgnetic order on the formation energy of vacancies. DIFFUSION DU NICKEL DANS LE FER La diffusion du nickel dane le fer a BtB rn& pour la g-e de temp&aturea a'&endant de 600 B 1060°C. Le? Ni" radio-a&if est utilise comme tweur; lea m&hodee employ& eont cellw de la diminution de la surfaca et de l'activiti tiiduelle. La diffueibilite en-deaeoue de la temp&ature de Curie ent inf&ieure 8~ que l'on po-it attendre de l'extrapolation dea donn&a exp&imentalee de la d&ion dana le fer 01 p aramagn&ique. Lea coe5cienta de diffusion peuvent rr'exprimer comme suit (en cm*/-). Fer gamma, D = 0,X' exp (-67.OOO/RT) Fer alpha p aramagnbtique au-deaeua de BOO"C, D = 1,3 exp (-66,OOO/RT) Fer alpha ferroma@tique en-d-us de 68O"C, D = I,4 exp (-66,7OO/RT) La diminution anormrrle du coefecient de diffusion dbbute aux environs de 8OO"C, c'est&dire un peu au-deaaua de la temp&ature de Curie. Elle peut Btre aasociBe B I'effet de l'ordre magn&ique B petite dietanca cur 1'6nergie de formation dea lacunee. DIFFUSION VON NICKEL IN EISEN Die Diiuaion von Nickel in Eisen wurde im Temperaturgebiet 600-1060°C gem-n. Ale Spurenelement wurde radioaktivee Ni" benutzt; dabei wurde eowohl die Abnahme der Aktivitet an der Ober&Bche wie die Reetaktivitat von Schnitten der Probe zur Meaeung verwandt. Die Diffueion&on&ante unterbalb der Curietemperatur iet niedriger, als man ee nach Extrapolation der Diffueionemeasungen fiir pcrramegnetiechee Alpha-Eieen erwartet. Die Diffueionekoefezienten lawen aich folgenderma6en auadrijcken (in cm*/aec): Gamma-Eieen D = 0.77 exp (-67,OOO/RT) Paramagnetischea Alpha-Eieen iiber 800°C D = 1.3 exp (-56,OOO/RT) Ferromagnetisches Alpha-Eiaen unter 680°C D = 1.4 exp (-&%,7OO/RT) Die anomale Abnahme dee Diffimionektienten beginnt bei etwa 800°C. etwae oberhalb der Curietemperatur, und hangt vermutlich mit dem Einfluea der magnet&hen Nahordnung aufdie Bildungaenergie von Lee&Hen zueammen. l This work wee sponsored by the U.S. Atomic Energy Commineion under Contract AT(30-l)-1076. Received Auguet 16. 1060. 7 Depertment of. Metallurgy, Massachusetts Inntitute of Teubno ogy, Cambridge.. Mace.
obtain an independent check on the influence of I) magnetic transformation on the diEuzivity.
EXPERIMENTAL PROCEDURE
High
-purity irons waz obtained in the form of &in. dia. forged bars, which were then machined to Q-in. dia. The bare were sealed in evacuafed Vjcor tubes and annealed at 86O'C for one week. The resultant grain size was 1% -) in. A few single q&ale were also made by a gradient anneal of baq that had been tenzile strained through the discontinuouz yielding. Disc specimens of &in. dia. and &in. thickness were machined from the bare and the z The analyeie e&owed (in wt. ye): 00.07 Fe, 0.007 C, 0.0056 0, 0.00013 N end lees than 0.006 Si.