Short-Term Splitting and Long-Term Stability of Cuboidal Nanoparticles in Ni44Co22Cr22Al6Nb6 Multi-Principal Element Alloy

Multi-principal element alloys (MPEAs) composed of thermally stable high-density cuboidal nanoparticles have revealed great potential for high-temperature applications. In this work, we systematically studied the growth behavior and coarsening kinetics of the cuboidal nanoparticles in Ni44Co22Cr22Al6Nb6 MPEA. In the initial stage of isothermal aging, the nanoparticles exhibit growth and split behavior, resulting in the improvement of mechanical performance, then the cuboidal nanoparticles retain superior thermal and mechanical stability during long-term isothermal aging. The 288 kJ/mol activation energy of Ni44Co22Cr22Al6Nb6 MPEA, which is higher than that in Ni-based superalloys, reveals the obvious elemental sluggish diffusion in Ni44Co22Cr22Al6Nb6 MPEA. Meanwhile, coarsening rate constant determined by the volume diffusion mechanism in Ni44Co22Cr22Al6Nb6 MPEA is 1-2 orders of magnitude less than that of the traditional Ni-based superalloys. The short-term regulation and long-term stability of the cuboidal nanoparticles endow the Ni44Co22Cr22Al6Nb6 MPEA with superior mechanical performance and thermal stability for high temperature applications.