采用差示扫描量热法(DSC)、扫描电镜(SEM)、电子探针(EMPA)等表征方法,对GH925合金的锻态相转变行为、固溶时效态热处理工艺性能及显微组织进行了研究.研究表明合金从室温25～1 100℃升温区间的相转变序列为:MC相(转变温度为540℃-终止析出温度为1 043℃,下同);γ'目(578～978℃);M23 C6-M7C3(679～758℃);σ相(723.5～879℃);η相(807～978℃).合金锻态组织经(990～1 010℃)×2h固溶+740℃-760℃×8h时效处理,可以获得最佳的综合力学性能.1 000℃×2h固溶+780℃×8h时效热处理,沿晶界有大量的脆硬针片状σ相析出,造成合金冲击韧性的急剧下降.
The phase transformation behaviors,solid-solution aging heat treatment processes,mechanic properties and microstructure of the forged GH925 alloy were investigated by means of differential scanning calorimetry (DSC),scanning clectron microscopy (SEM),electron probe microanalysis (EPMA) characterization meth ods,etc.The research results show that the phase transformation sequence of the forged alloy during elevated temperature from 25 to 1 100 ℃ is MC phase (initial transformation temperature is 540 ℃,terminated transformation temperature is 1 043 ℃,the same below),γ'phase (578-978 ℃),M23C6-M7C3 (679-758 ℃),σ phase (723.5-879 ℃) and η phase (807-978 ℃).The optimum comprehensive mechanical properties of the forged alloy can be obtained by 990-1 010 ℃ × 2 h solid-solution and 740-760 ℃ × 8 h aging heat treatment.An amount of hard and brittle needle flake σ phase precipitates along the grain boundaries after the heat-treatment of 1 000 ℃ ×2 h solid-solution and 780 ℃ ×8 h aging,resulting in a sharp decline of the aolly's impact toughness at this aging temperature.
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