Theoretical studies of transport and surface properties of liquid Fe-Mn and Fe-Co alloys
Date
2020-02
Authors
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Journal ISSN
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Publisher
Federal University of Technology, Owerri
Abstract
Transport and surface properties of liquid Fe−Mn and Fe−Co alloys were computed using the self-association model in conjunction with a model based on the hard sphere theory, the model of Moelwyn-Hughes and a statistical mechanical approach. Using the self-association model, the model parameters were determined from the experimental thermodynamic data at 1863 K. These model parameters were then used to compute the concentration-concentration fluctuations at the long wavelength limit (𝑆𝑐𝑐(0)), short range order parameter (𝛼1), mutual diffusivity, viscosity, surface concentration, surface tension and surface 𝑆𝑐𝑐(0) for the two alloys at 1863 K. Results obtained show that Fe−Mn alloy with low tendency of homocoordination exhibits ideal mixing below 0.25 and above 0.88 atomic fractions of iron. On the other hand, Fe−Co alloy shows ideal mixing property below 0.20 and above 0.88 atomic fractions of iron, homocoordination between 0.20 and 0.70 atomic fractions of iron (Fe) and weak ordering between 0.70 and 0.90 atomic fractions of iron (Fe). Throughout the entire concentration range, diffusion-related activities as reflected by mutual diffusivities are higher in Fe−Mn alloy than in Fe−Co alloy. The viscosities of the two liquid alloys exhibit negative deviations from Arrhenius’ law, with the negative deviation being more pronounced in the Fe−Co alloy. Calculations also indicate that more Mn-atoms segregate at the surface of Fe−Mn alloy whereas nearly equal concentrations of Fe-atoms and Co-atoms are at the surface of Fe−Co alloy. These observations possibly suggest that more Fe-atoms are present at the surface of Fe−Co alloy than that of Fe−Mn alloy. The surface tension of Fe−Mn alloy increases throughout the entire concentration range while for Fe−Co alloy, it initially decreases to around 0.59 atomic fraction of iron (Fe) before it rises rapidly. The results from the computation of surface concentration-concentration fluctuations at the long wavelength limit corroborate the results from bulk properties calculations.
Description
This thesis is for the award of Master of Science (MSc.) in Solid State Physics
Keywords
Mutual diffusivity, viscosity, surface concentration, surface tension, Fe−Mn alloy, Fe−Co alloy, homocoordination, Department of Physics, ideal mixing
Citation
Ogundeji, S. O. (2020). Theoretical studies of transport and surface properties of liquid Fe-Mn and Fe-Co alloys (Unpublished Master's Thesis). Federal University of Technology, Owerri, Nigeria