Surface segregation modeling in the case of evaporation

A kinetic model is proposed to characterize surface segregation in the case of evaporation. The kinetics is formulated using the difference between the diffusion rate of solute atom in the bulk and the evaporation rate of solute atom from the surface layer. The first-order reaction equation is appli...

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Bibliographic Details
Published in:Journal of alloys and compounds 2019-08, Vol.797, p.640-651
Main Authors: Wang, Bo, Meng, Fangliang, Zheng, Lei, Wang, Minqing, Meng, Ye, Cui, Fenge, Liang, Xianghua, Gao, Yang, Yang, Sheng, Zhao, Yingchun
Format: Article
Language:English
Subjects:
Aluminum
Diffusion rate
Enrichment ratio
Evaporation
Evaporation rate
First-order reaction
Kinetics
Magnesium base alloys
Mathematical models
Parameters
Pressure
Reaction kinetics
Surface layers
Surface segregation
Vapor pressure
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Summary:A kinetic model is proposed to characterize surface segregation in the case of evaporation. The kinetics is formulated using the difference between the diffusion rate of solute atom in the bulk and the evaporation rate of solute atom from the surface layer. The first-order reaction equation is applied to quantify evaporation flux. A balanced state is quantified when the vapor and ambient pressure is equal and thus a complete quantification of the kinetics forms. The kinetic curve is convex prior to critical time and concave after. The maximum surface concentration decreases as evaporation parameter decreases. The kinetics of Mg surface segregation of Al-0.8 wt%Mg alloy is fitted. An enrichment ratio of 16.484 and evaporation parameter of 0.57 are the values that fit the experimental results the best. The balanced surface concentration of Mg is calculated and implies further evaporation with prolonged time. The proposed model can adequately describe surface segregation in the case of evaporation, and the formulated kinetics can satisfactorily quantify this phenomenon. [Display omitted] •A kinetic model is proposed for surface segregation in the case of evaporation.•Kinetics is formulated by the difference between diffusion rate and evaporation rate.•First-order reaction equation is applied to quantify evaporation flux.•A balanced state when vapor pressure equals to environmental pressure is quantified.•Theoretical calculations are in excellent agreement to experimental results.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2019.05.134