(1. 中南大學(xué)粉末冶金國家重點實驗室，長沙 410083；
2. 中南大學(xué)粉末冶金研究院，長沙410083；
3. 中南大學(xué)航空航天學(xué)院，長沙410083)
摘 要: 以熱擠壓態(tài)鎳基粉末冶金高溫合金FGH96為研究對象，研究該合金橫向(垂直于擠壓方向)和縱向(沿擠壓方向)試樣的顯微組織及力學(xué)性能，分析斷裂機制和變形后的顯微組織。結(jié)果表明：FGH96合金橫向及縱向試樣均為無明顯織構(gòu)的等軸晶組織，且平均晶粒尺寸及γ′相體積分?jǐn)?shù)基本一致。在應(yīng)變速率1×10-4 s-1時，橫向和縱向拉伸試樣抗拉強度在25~650 ℃溫度區(qū)間內(nèi)隨溫度升高緩慢降低，當(dāng)溫度高于650 ℃時，抗拉溫度下降速率顯著增加；且橫向試樣的抗拉強度低于相同實驗條件下縱向試樣的抗拉強度，差值為150~200 MPa；失效機制為從室溫條件下的穿晶斷裂轉(zhuǎn)變?yōu)榛旌蠑嗔涯Ｊ剑瑱M向試樣的轉(zhuǎn)變溫度為400 ℃左右，縱向試樣的轉(zhuǎn)變溫度約為650 ℃；橫向試樣變形后，顯微組織有高密度的位錯纏結(jié)及層錯；縱向試樣拉伸斷裂后，顯微組織則主要為孿晶及位錯與γ′相的交互作用。
關(guān)鍵字: 粉末冶金高溫合金；晶粒尺寸；γ′析出相；抗拉強度；失效機制；變形組織
（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
