Superb strengthening behavior in a precipitation strengthened Co-rich CoCrNiAlTi medium entropy alloy with acceptable ductility. (July 2022)

• Record Type: Journal Article
• Authors: Du, X.H.; Gai, Y.H.; Li, W.P.; Chou, T.H.; Huang, J.C.; Shi, C.X.; Duan, G.S.; Wu, B.L.
• Is Part Of: Intermetallics. Volume 146(2022)
• Publication Date: 2022-07
• Subjects: Co-Cr-Ni base Medium-entropy alloy -- Mechanical properties -- Strengthening mechanism -- Twinning behavior; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2022.107582
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: For metallic materials, it is challenged to enhance the strain hardening rate under uniaxial tension when high flow stress is achieved. Here, we present a strategy enabling to obtain superior strain hardening ability via fabricating an incompletely recrystallized structure in a precipitation-strengthened Co-rich CoCrNiAlTi medium-entropy alloy. It involves to introduce a low-temperature ageing process in the CoCrNiAlTi alloy experienced high-strain cold rolling process. Accompanied with the formation of the partially recrystallized microstructure, high-density band-like L12 -type ordered phase has formed via discontinuous precipitation. During the plastic straining process, deformation twins have been triggered by the high-stress field owing to its metastable structure. As expected, the alloy demonstrates synergistically substantial strengthening and toughening effects, thus, a superb mechanical property combination with ultimate tensile stress of 2.20 GPa and ductility of over 5.0% has been achieved at ambient temperature. Highlights: A strategy enabling to obtain superior strain hardening ability in a precipitation-strengthened medium-entropy alloy has been presented. During the plastic straining process, multiple-mode twins have been triggered by the high-stress field owing to its metastable structure. The alloy demonstrates a superb mechanical property with ultimate stress of 2.25 GPa and tensile strain of 5.0% at ambient temperature.