Statistical thermodynamic approach to austenitic Fe_1-yNb_yN_xsystem

Abstract

Available equilibrium P -T -C(pressure -temperature -composition) relationships reported for fcc (face centred cubic) Fe 12 y Nb y N x alloys with Nb content y up to 0 . 00561 were analysed on the basis of statistical thermodynamics. The reported P -T -C relationships showed a trend of rising N level x with increasing Nb content y under comparable conditions of temperature T and nitrogen partial pressure p(N 2 ). Statistical models assuming several types of atom clustering modes were compared. A model in which interstitial N atoms were preferentially consumed rst to form Nb -N dipoles in the Fe 12 y Nb y lattice, and then the remaining N atoms were distributed over O sites (octahedral interstitial sites) surrounded by six Fe atoms without Nb, was concluded to be the most realistic one.MST/5313

Statistical Thermodynamic Analysis for Hydrogen Absorption Behaviour in a Four Monolayers (4 ML) Thick <i>bcc</i> Vanadium (110) Superlattice Being in Contact with Molybdenum Layer

“…1) In the earlier statistical thermodynamic analyses for solution of interstitial element X into the substitutional alloy lattice A 1¹y B y , suppressed solubility of X in the alloy A 1¹y B y compared with that in the metal lattice A was represented by the decreased ª in the A 1¹y B y compared with that in the pure metal A 3,4,9,10,20) and, on the contrary, the enhanced solubility of X in the alloy A 1¹y B y compared with that in the metal lattice A was represented by the increased ª in the A 1¹y B y compared with that in the pure metal A. 9,14,15,19) According to available information, 3,4,20) alloying with the VIa-group elements such as Mo and W into lattice of Vagroup metals like V, Nb and Ta would lead to decrease of ª for H solubility in the alloy phase. For example, ª for bcc Nb 1¹y Mo y H x lattice was determined to be 0.75 for y = 0, 0.45 for y = 0.1, 0.30 for y = 0.2 and 0.20 for y = 0.3.…”

Empirical Expression of Phosphorus Solubility in Molten Fe1-yCry Given as Functions of Temperature and Phosphorus Activity

“…This feature might look strange at first glance but, with reference to the available atom clustering models for some Fe 1Ϫy M y X x systems, [6][7][8][9][10][11][12] the observed apparently confusing y-dependence of a P -x isotherm shift pattern along a P direction must be interpreted in terms of change-over of cluster type surrounding P atom in the interstitial site (probably octahedral interstitial site). In the range of y smaller than 0.12, Cr-P dipole (or 1Cr/5Fe type cluster) might have formed while, in the range of y higher than 0.12, 4Cr/2Fe type cluster might have formed with reference to the information gathered by statistical thermodynamic consideration for this type of alloys.…”

“…In the range of y smaller than 0.12, Cr-P dipole (or 1Cr/5Fe type cluster) might have formed while, in the range of y higher than 0.12, 4Cr/2Fe type cluster might have formed with reference to the information gathered by statistical thermodynamic consideration for this type of alloys. [6][7][8][9][10][11][12] Anyway, to gain more concrete quantitative information, a P -T-x relationships estimated in this work for respective y for Fe 1Ϫy Cr y P x must be subjected to detailed statistical thermodynamic analysis. This line of analysis might be made in future as a separate work.…”