Influence of spinodal decomposition on structure and thermoelastic martensitic transition in MnCuAlNi alloy

• Published in: Materials letters Vol. 275; p. 128069
• Main Authors: Sun, L.Y., Vasin, R.N., Islamov, A.Kh, Bobrikov, I.A., Cifre, J., Golovin, I.S., Balagurov, A.M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-09-2020; Elsevier BV
• Subjects: Aging; Aging (metallurgy); Austenite; Copper; Cu-Mn alloys; Decomposition; Grain boundaries; Manganese; Martensite; Martensitic transformations; Materials science; Nanocrystalline materials; Neutron scattering; Neutrons; Phase transformations; Room temperature; Solid solutions; Spinodal decomposition; Temperature dependence; Thermodynamics and kinetics of spinodal decomposition; Water quenching; Grain boundaries; Cu-Mn alloys; Thermodynamics and kinetics of spinodal decomposition; Phase transformations; Nanocrystalline materials
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2020.128069

•Microstructure of Mn-19Cu-2Al-4Ni alloy is carefully examined.•Volume fraction and average volume of Cu-rich nanoclusters are quantified.•Martensitic transition temperatures are explained by degree of spinodal decomposition.
The effect of spinodal decomposition in Mn-19Cu-2Al-4Ni solid solution quenched from 830 °C after different ageing regimes is studied. After water quenching, face-centered cubic (f.c.c.) austenite is the only observed phase in the samples at room temperature, whereas, after different ageing regimes, the alloy has a two-phase state: face-centered tetragonal (f.c.t.) martensite and α-Mn body-centered cubic (b.c.c.) phase. Small-angle neutron scattering reveals that Cu-enriched clusters are formed in a Mn-enriched matrix due to spinodal decomposition during ageing in the austenitic state. With an increase in the Mn content in the matrix, temperatures of martensitic transition rise above room temperature, and a subsequent martensitic transformation upon cooling leads to the formation of f.c.t.-martensite. Temperatures for direct and reverse transitions are strongly dependent on ageing temperature and time, i.e., on the degree of chemical decomposition in austenite.