The effect of heat treatment on the precipitation hardening in FeNiCoAlTa single crystals

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 784; p. 139327
• Main Authors: Czerny, M., Maziarz, W., Cios, G., Wójcik, A., Chumlyakov, Y.I., Schell, N., Fitta, M., Chulist, R.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.05.2020; Elsevier BV
• Subjects: Aging; Annealing; Beta phase; Chemical composition; Coherence; Heat treating; Iron-based shape memory alloys; Martensite; Martensitic transformations; Morphology; Phase transformation; Precipitates; Precipitation; Precipitation hardening; Precipitation heat treatment; Single crystal; Single crystals; Superelasticity; Phase transformation; Precipitation; Iron-based shape memory alloys; Superelasticity; Single crystal
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2020.139327

The main goal of this work was to examine the effect of aging process on the precipitation behavior including phase morphology, chemical composition and degree of coherence in Fe–28Ni–17Co-11.5Al-2.5Ta single crystals. The nano-sized and coherent γ′ precipitates were used for strengthening process. The particles were investigated with transmission and scanning electron microscopies along with high energy X-ray diffraction. The single crystalline material of [100] (001) orientation was subjected to three different heat treatments: slowly cooled, quenched and then annealed with various aging conditions. Aging at 973 K for short times results in coherent 2-6 nm-sized γ′ precipitates and fully reversible superelastic strains while annealing at 973 K for 5 h and longer times leads to the precipitation of larger γ’ particles formed together with β phase which significantly reduces the transformed martensite volume fraction.