Interdiffusion in Iron-Cobalt Alloys

Abstract

Interdijfusioll coifficiellts ill bcc alld fcc allo.ys qf the i7'01I-cobalt s..ystem were determilled as a f unctioll of coml)osition and temperatllre by use of all electron IJTobe X-ray microallalyser. Kirkendall effects were studied usillg alumina I)owder markers. The cOllcelltration del)elldellce of the illter-d~ffusioll coefficiellts shows the millimum at 25at 0 aCo ill the bcc regioll alld the maximum at 60at a aCo ill the fcc regioll. Apparellt activatioll ellerilies for illterdijfusioll have beell determilled fro m Arrhellills plots fllld are discussed ill cOllnectioll with the temperature depelldence of the therlllo-dYllamicfactor. It has beell showlI that the injluence of thisfactor in the bcc region is larger than that ill the fcc rrgioll. Intrinsic dijfusioll coifjicients calclila ted at marker cOIllI)oJitiollS were foulld to be larger for Fe than for Co ill agreemellt with the formatioll of voids ill Fe-rich side of the dif fusion cOlll)le. Self-diffusioll coifficients calculated fro m the illte/"diffusioll data by the methods of Balltiffi alld l\!lalllling were compared with experillielltal values de/ermined ky radiotracer method.

Diffusional Analysis for Growth of the Monosulfide Scale on Cobalt‐Iron Alloys

“…-7.6 Best fits were obtained using Eq. [13] which describes p as asymptotically approaching a high from low value with decreasing iron content of (CoFe)S -7.8 as shown in Fig. 6.…”

“…A flowchart for the computer simulation is given in Fig. p ----1.0 + 2.0 exp --{ (4 --0.55)/0.25} 2 [12] p ----2.4 for 4--0.65 [13] = 1.3 + 1.1 exp --{(4 --0.65)/0.07} 2 for 4--0.65…”

“…Calculations were first carried out to determine -7.2 which equation for p (Eq. [11], [12], or [13]) led to best representation of the measured iron contents of the (CoFe)S scales. A comparison of the fits obtained -Z4 for the composition profiles in scales formed on the 40% and 60% Fe alloys at T = 700~ and Ps2 = 2 • 10 .6 atm is shown in Fig.…”

Computer Simulation of the Diffusional Growth of Ternary Oxide Scales on Binary Alloys

“…where DAB is the alloy interdiffusion coefficient and the coordinate, u, is measured into the alloy from its original surface position u --= 0 at t = 0. This interdiffusion coefficient may be regarded as independent of alloy compositions encountered in the present investigation (20). Solution of Eq.…”

Etude rhéologique de l'influence de l'ordre et de la transformation ordre- désordre sur le fluage à haute température des solutions solides de surstructure du type B2. (Cu-Zn, Fe-Co, Ag-Mg, Fe3-Al et Ni-Al)

“…Au regard de la très faible différence existant entre D*9Fe et D* 60 c., les formules (5) et (6) conduisent au même résultat au terme ~ près. Pour la phase a, ç est proche de l'unité (0,77 à 800 °C par exemple) alors que Q~ ~ 0,2 eV [52]. En dessous de T, aucune valeur de ç n'est disponible dans la littérature.…”