Intrinsic properties and mechanical behaviors of a W-free single crystal CoNiCr-based multicomponent alloy

CoNi-based alloys are critical structural materials for aerospace and gas turbine applications due to their outstanding oxidation and corrosion resistance. However, their relatively low strength at high temperature limits broad applications. Therefore, γ′-strengthened CoNi-based alloys have attracted considerable interest, which requires a fundamental understanding of their intrinsic properties and mechanical behaviors. In this study, a single crystal (SX) CoNiCr-based alloy with the composition Co–30Ni–10Cr–9Al–5Mo–2Ta-0.03B (at.%) without W, which is generally required for γ′ stabilization in CoNi-based alloys, is successfully grown by using Bridgman method. After solution and aging treatments, the alloy exhibits a typical γ/γ′ two-phase microstructure with spherical γ′ precipitates (∼50 vol%, ∼110 nm in diameter) uniformly distributed in the γ matrix. Intrinsic properties, such as density, melting point, elastic constants, Debye temperature, etc., are determined. Furthermore, the mechanical properties and deformation behavior are examined with the aid of advanced microscopy. The strength of the W-free SX alloy is comparable to that of typical Co–Al–W SX alloys. In the temperature range from room temperature to 1000 °C, the SX CoNiCr-based alloy exhibits excellent ductility with the elongation to fracture consistently exceeding 33 %. The deformation mechanisms resemble those of Ni-based SX superalloys, which are dominated by dislocation pairs below 800 °C and single dislocations above 900 °C.