Critical driving force for martensitic transformation fcc(γ)→hcp(ε) in Fe−Mn−Si shape memory alloys
- 120 Downloads
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 N γ =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 C γ→ε , 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 C γ→ε =−100.99 J/mol in Fe−27.0Mn−6.0Si and ΔG C γy→ε =−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 C γ→ε =A·γ+B, where γ is the stacking fault energy (SFE) andA andB are constants related to materials.
Keywordscritical driving force martensitic transformation Fe−Mn−Si alloy
Unable to display preview. Download preview PDF.
- 1.Hsu, T. Y. (Xu Zuyao), On ferrous shape memory alloys (part 1,2,Shanghai Metals (in Chinese), 1993, 15 (2): 1; 15 (3): 1.Google Scholar
- 6.Hillert, M., Jarl, M., A model for alloying effects in ferromagnetic metals,CALPHAD, 1978: 227.Google Scholar
- 7.Inden, G., The role of magnetism in the calculation of phase diagrams,Physica, 1981, 103B: 82.Google Scholar
- 8.Hsu, T. Y. (Xu Zuyao), Thermodynamic properties of β(γ)→ε martensitic transformation,Acta Metall. Sin., 1980, 16: 430.Google Scholar
- 12.Murakami, M., Otsuka, H., Suzuki, H. G. et al., Complete shape memory effect in polycrystalline Fe−Mn−Si alloys, inProc. ICOMAT-86, Jpn. Inst. Metals, Sendai: Jpn. Inst. Metals, 1987, 985–990.Google Scholar