Effect of cooling recrystallization annealing treatment on properties of an initial aged deformed GH4169 superalloy

In the authors’ previous study, a novel double-stage heat treatment method including an aging treatment and a cooling recrystallization annealing treatment (CRT) was proposed [1]. This method can evenly refine the deformed coarse grains of an initial solution-treated deformed GH4169 alloy. This study focuses on investigating the role of this method on the microstructural evolution and properties of an initial aged deformed GH4169 alloy. For the initial aged deformed GH4169 alloy, a similar double-stage heat treatment was designed and implemented first, and then the microhardness and uniaxial tensile tests were completed. The results show that the proposed double-stage annealing treatment can effectively increase the uniformity and refinement of the deformed coarse grains, and the hardness and strength of deformed GH4169 alloy. Among these CRT parameters, the initial temperature of CRT has a more obvious effect on the average grain size compared to the cooling rate and final temperature. Moreover, the hardness and strength of deformed GH4169 alloy are mainly affected by the average grain size. When the average grain size is 5.82 μm, both the hardness and strength reach the maximum value. Furthermore, owing to the encouraging effect of the δ phase on the nucleation of micropores, the elongation of GH4169 alloy at high temperatures increases slightly with the dissolution of the δ phase. Additionally, for the deformed GH4169 alloy after heat treatment, it is found that the fracture mode under the high-temperature tension demonstrates a shear fracture and shows a microvoid coalescence ductile fracture macroscopically. Based on an overall consideration, the optimal heat treatment process is "900°C × 12 h + 1010°C–2°C/min-970 °C".