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http://hdl.handle.net/10397/94039
Title: | L12-strengthened multicomponent Co-Al-Nb-based alloys with high strength and matrix-confined stacking-fault-mediated plasticity | Authors: | Cao, BX Xu, WW Yu, CY Wu, SW Kong, HJ Ding, ZY Zhang, TL Luan, JH Xiao, B Jiao, ZB Liu, Y Yang, T Liu, CT |
Issue Date: | May-2022 | Source: | Acta materialia, May. 2022, v. 229, 117763 | Abstract: | This study presents the alloy development of a new class of L12-strengthened Co-Al-Nb-based alloys with high γ′-solvus temperatures together with superb strengths at both ambient and elevated temperatures. The L12-Co3(Al, Nb) phase was found to be in equilibrium with the γ-Co matrix and the B2-CoAl phase in the ternary Co-10Al-3Nb alloy after an isothermal aging at 700 °C; however, it transformed into the Laves phase as the aging temperature increased to 800 °C. Alloying additions of Ni helped to suppress the B2 phase formation, resulting in a clean γ-γ′ dual-phase microstructure. Ti and Ta elements further stabilized the L12 structure and increased the γ′-solvus temperature to 1150 °C without inducing the formation of any other deleterious intermetallic phases. The newly developed Co-Al-Nb-Ni-Ti-Ta multicomponent Co-rich alloy has demonstrated outstanding yield strengths at both ambient and elevated temperatures, reaching 1023 ± 27 MPa at 25 °C and 897 ± 53 MPa at 700 °C, respectively. Furthermore, electron microscopy analyses uncovered unique deformation substructures, in which plasticity is predominantly carried out via nanoscale matrix-channel-confined stacking faults. As determined by the first-principle calculations, the absence of particle shearing upon deformation at ambient temperature is ascribed to the ultrahigh planar fault energies of the multicomponent γ′ precipitates. High-density superlattice-stacking-fault shearing and their interactions are responsible for the yield anomaly at 700 °C. These findings not only provide the fundamental understanding of the deformation behavior of the L12-strengthened alloys, but also demonstrate the great potential for developing next-generation high-temperature structural materials based on the multicomponent Co-rich alloy systems. | Keywords: | Cobalt-based alloys Deformation mechanisms High-temperature strength Mechanical properties Phase stability |
Publisher: | Pergamon Press | Journal: | Acta materialia | ISSN: | 1359-6454 | DOI: | 10.1016/j.actamat.2022.117763 |
Appears in Collections: | Journal/Magazine Article |
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