Microstructure And Creep Behaviors Of Hot Continuous Rolling GH4169 Superalloy

In the paper,compared to the calcalation of creep activation energy and stress exponent,the influence of heat treatment regimes on the microstructure and creep properties of the forged and hot continuous rolling GH4169 alloy are investigated by means of heat treatment,creep properties measurment and microstructure observation,and the deformation mechanisms of the alloy during creep is discussed.Results show that,compared to the forged alloy,the finer grains is displayed in the hot continuous rolling alloy,and the finerγ″phase is dispersely precipitated within the grains after direct aged treatment(DA),but signficant amount carbides with short stick shape are discontinuously precipitated along the grain boundary.In the range of experimental temperatures and stresses,the activating energy of the forged alloy during creep is calculated as Q_a = 519.3kJ/mol.Compared to the forged alloy,the hot continuous rolling(HCR) alloy displays a better creep resistance,and the activation energies of DA-HCR and LTA-HCR alloys during creep are calculated to be Q_a = 559.2 kJ/mol and Q_a = 541.1 kJ/mol.Compared with other preparing technology,after direct aged treatment,the HCR alloy have a better creep resistance,and the creep lifetimes of the alloy is measured as 127 h in the applied stress of 700MPa at 660℃.During creep,the deformation feature of the forged alloy is twinning,the deformation mechanisms of the HCR alloy is the twinning and dislocations slipping within the twins,and the twinning plane activated during creep is determined as { 111 } plane.If the dislocations formed during hot rolling is defined as "pre-reserved ones,the ones may activate the creep dislocations occurring the single and double orientations slipping within the twinning to stave the stress concentrition, this is a main reason of enhancing the creep resistance and prolonging lifetimes of the alloy. After direct aged,the fracture modes of both forged and HCR alloys during creep are identified as the intergranular fracture,and appearring the smooth surface of the grain. During the later stage of creep,it is the fracture mechanism of the alloy during creep that the cracks are budded on the boundaries vertical to the applied stress axis,and expanded along the boundaries.But after crept up to fracture,the fracture of the long term aged HCR alloy displays a nonsmooth surface,thereinto,the carbides film formed on the boundaries has a few effect on the boundaries strength of the alloys,this is a main reason of prolonging the creep lifetimes of the alloy.