Fluctuations of chemical composition of austenite and their consequence on shape memory effect in Fe–Mn–(Si, Cr, Ni, C, N) alloys

• Published in: Acta materialia 2004-09, Vol.52 (16), p.4791-4799
• Main Authors: Bliznuk, V.V., Gavriljuk, V.G., Kopitsa, G.P., Grigoriev, S.V., Runov, V.V.
• Format: Article
• Language: English
• Subjects: AUSTENITE; CHEMICAL COMPOSITION; Chemical homogeneity; CHROMIUM ALLOYS; EXPERIMENTAL DATA; FCC LATTICES; Fe–Mn–Si alloys; IRON BASE ALLOYS; MANGANESE ALLOYS; MATERIALS SCIENCE; NEUTRON DIFFRACTION; NEUTRONS; NICKEL ALLOYS; NITROGEN ADDITIONS; PHASE TRANSFORMATIONS; POLYCRYSTALS; Shape memory; SHAPE MEMORY EFFECT; SILICON ALLOYS; Small angle polarised neutron scattering; SMALL ANGLE SCATTERING; SOLID SOLUTIONS; STRAINS
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2004.06.036

Polycrystalline samples of shape memory iron-based alloys containing 17, and 30 mass% Mn and alloyed with Si, Cr, Ni, C, N were studied by means of small angle scattering of polarized neutrons (SAPNS). A direct correlation between chemical homogeneity of the Fe–Mn, Fe–Mn–Si, Fe–Mn–Si–Cr, Fe–Mn–Si–Cr–Ni solid solutions and the values of reversible strain caused by the γ → ε → γ martensitic transformation was found. The addition of silicon to the Fe–Mn alloys significantly improves chemical homogeneity of the fcc solid solution on the scale of larger than several nm, which correlates with the essential increase of reversible strain. A similar to silicon but weaker effect was observed in the case of nitrogen addition to the Fe–Mn–Si–Cr, Fe–Mn–Si–Cr–Ni alloys. Based on the obtained experimental data and in consistency with the previously expressed idea by Sade et al., the positive effect of silicon and nitrogen on chemical homogeneity and SME in Fe–Mn alloys is attributed to the short-range atomic ordering induced by these elements.