Abstract
By the application of Chou's new geometry model and the available data from binary Fe−Mn, Fe−Si and Mn−Si systems, as well as SGTE DATA for lattice stability parameters of three elements from Dinsdale, the Gibbs free energy as a function of temperature of the fcc(γ) and hcp(ε) phases in the Fe−Mn−Si system is reevaluated. The relationship between the Neel temperature of the γ phase and concentration of constituents in mole fraction,T γN =67x Fe+540x Mn+x Fe x Mn[761+689(x Fe−x Mn)]−850x si, is fitted and verified by the experimental results. The critical driving force for the martensitic transformation fcc(γ)→hcp(ε), ΔG γ→εC , defined as the free energy difference between γ and ε phases atM s of various alloys can also be obtained with a knownM s . It is found that the driving force varies with the composition of alloys, e. g. ΔG γ→εC =−100.99 J/mol in Fe−27.0Mn−6.0Si and ΔG γy→εC =−122.11 J/mol in Fe−26.9Mn−3.37Si. The compositional dependence of critical driving force accorded with the expression formulated by Hsu of the critical driving force for fcc(γ)→hcp(ε) transformation in alloys with low stacking fault energy (SFE), i. e. ΔG γ→εC =A·γ+B, where γ is the stacking fault energy (SFE) andA andB are constants related to materials.
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Project supported by the National Natural Science Foundation of China (Grant No. 59671023).
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Jin, X., Xu, Z., Hsu, T.Y. et al. Critical driving force for martensitic transformation fcc(γ)→hcp(ε) in Fe−Mn−Si shape memory alloys. Sci. China Ser. E-Technol. Sci. 42, 266–274 (1999). https://doi.org/10.1007/BF02916772
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DOI: https://doi.org/10.1007/BF02916772