(1. 中南大学粉末冶金国家重点实验室，长沙 410083；
2. 中南大学粉末冶金研究院，长沙410083；
3. 中南大学航空航天学院，长沙410083)
摘 要: 以热挤压态镍基粉末冶金高温合金FGH96为研究对象，研究该合金横向(垂直于挤压方向)和纵向(沿挤压方向)试样的显微组织及力学性能，分析断裂机制和变形后的显微组织。结果表明：FGH96合金横向及纵向试样均为无明显织构的等轴晶组织，且平均晶粒尺寸及γ′相体积分数基本一致。在应变速率1×10-4 s-1时，横向和纵向拉伸试样抗拉强度在25~650 ℃温度区间内随温度升高缓慢降低，当温度高于650 ℃时，抗拉温度下降速率显著增加；且横向试样的抗拉强度低于相同实验条件下纵向试样的抗拉强度，差值为150~200 MPa；失效机制为从室温条件下的穿晶断裂转变为混合断裂模式，横向试样的转变温度为400 ℃左右，纵向试样的转变温度约为650 ℃；横向试样变形后，显微组织有高密度的位错缠结及层错；纵向试样拉伸断裂后，显微组织则主要为孪晶及位错与γ′相的交互作用。
关键字: 粉末冶金高温合金；晶粒尺寸；γ′析出相；抗拉强度；失效机制；变形组织
（1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. Research Institute of Powder Metallurgy, Central South University, Changsha 410083, China;
3. School of Aerospace and Astronautics, Central South University, Changsha 410083, China）
Abstract:The deformed microstructure and mechanical properties of hot extruded nickel base P/M superalloy FGH96 were investigated. The transverse direction was defined as being vertical to the direction of hot extrusion, and the longitudinal direction was parallel to that of extrusion. The results indicate that both transverse and longitudinal specimens show equiaxed metallographic microstructure without obvious texture, and the average grain size as well as volume fraction of γ′ precipitation are out of distinct difference. Furthermore, under the condition of strain rate of 1×10-4 s-1 , the ultimate tensile strength of both transverse and longitudinal direction specimens of FGH96 superalloys decreases slightly with the temperature elevating from 25 ℃to 650 ℃, while drops sharply when the temperature is higher than 650 ℃. However, the ultimate tensile strength of transverse specimens is lower than that of longitudinal samples under the same test conditions. The failure mechanisms show a transition from transgranular fracture at 25 ℃ to a mixed mode which includes both transgranular facture and intergranular fracture at higher temperature. The transition temperature of transverse specimens is roughly 400 ℃, while that of longitudinal specimens is around 650 ℃. Tangled dislocations and stacking faults exist clearly in the deformed transverse samples, and it is mainly the twin and interaction between dislocations and γ′ precipitations that occur in the longitudinal specimens after tensile deformation.
Key words: P/M superalloy; grain size; γ′ precipitate; ultimate tensile strength; failure mechanism; deformed microstructure
