Effect of Heat Treatment on the Mechanical Property and Deformation Mechanism of a Novel Cast Nickel-Based Superalloy

The microstructureMicrostructures, mechanical propertiesMechanical properties, fracture behavior, and deformation mechanismsDeformation mechanism of a novel cast nickel-based superalloySuperalloys subjected to various agingAging treatments were investigated. The microstructureMicrostructures of this new alloy K4800 consists of γ, MC, M23C6, and the γ′ in two sizes after conducting a heat treatmentHeat treatment of solution annealing and double-stage agingAging. It is found that an initial higher temperature agingAging process is beneficial and somewhat necessary to optimize the tensile and creepCreep properties of the alloy. The strength of alloy K4800 rises with the volume fraction of small-sized γ′ phase; meanwhile, the precipitationPrecipitation of large-sized γ′ phase has a desirable impact on the elevated temperature ductility of the alloy. However, the existence of large-sized γ′ phase may accelerate the ripening process of γ′ phase and decrease of creepCreep life of alloy K4800. Therefore, accurate control of the content and proportion of the γ′ phases in two sizes is the key to obtaining an optimal mechanical propertyMechanical properties of K4800. TEM microstructureMicrostructures investigations show that the main strengthening mechanismsStrengthening mechanisms of the alloy are APB cutting at room temperature and Orowan bypassing at high temperature. Additionally, based on the results of a long-term agingAging experiment at 800 °C up to 2000 h, the material is not expected to precipitate any undesirable phase like σ or η, exhibiting an outstanding microstructural stabilityMicrostructural stability.