Influence of aging in B2-austenite phase on stress-induced martensitic transformation for [001]B2-oriented Co35Ni35Al28Fe2 single crystals

The effect of aging in the high-temperature B2-phase on the martensitic transformation, the strength properties of L1₀-martensite, and the cyclic stability of superelasticity in compression in [001]_B2-oriented Co₃₅Ni₃₅Al₂₈Fe₂ single crystals was investigated. The B2-phase in quenched Co₃₅Ni₃₅Al₂₈Fe₂ single crystals remains stable without precipitation of secondary phases upon heating up to 520 K, which represents an increase of approximately 50 K compared to ternary Co₃₅Ni₃₅Al₃₀ alloys. Aging at 673 K leads to the precipitation of nanosized (Ni, Co)₅Al₃-particles providing dispersion strengthening. Short-term aging for 15 min decreases the start B2-L1₀ martensitic transformation temperature M_s by 140 K and significantly improves functional properties, resulting in a wide temperature range of superelasticity (345 K) and high strength properties of L1₀-martensite (> 1870 MPa) while maintaining cyclic stability of superelasticity.