Microstructure And Properties Evolution Of Incoloy 925 Nickel Based Corrosion Resistant Alloys During Hot Working And Heat Treatment

Incoloy 925 corrosion-resistant alloy(hereinafter referred to as Alloy 925)is widely used in the manufacture of sea water pump shafts used in ships,and it is also the current advanced diesel engine and petroleum pipeline material.Based on the thermal simulation compression test,this paper studies the stress-strain curve of Alloy 925 under different deformation conditions,and then constructs the high temperature constitutive equation and thermal processing diagram of Alloy 925.It uses optical microscope,scanning electron microscope,transmission electron microscope and other equipment to explore the heat The evolution of the microstructure of Alloy 925 during the deformation process verified the accuracy of the processing map,discussed the influence of different deformation parameters on the hot deformation behavior of Alloy925,and constructed a dynamic recrystallization model based on the Z parameter.In addition,the Alloy 925 was aged for a long time based on different aging treatment temperatures and times,and the microstructure characteristics and precipitation laws of carbides and the second phase were analyzed.The specific experiments and research results are as follows:(1)Based on the flow stress-strain curve of Alloy 925 at a deformation temperature of 900-1150?and a strain rate of 0.01-10s^-1,a high-temperature constitutive equation based on the Arrhenius type of Alloy 925 is derived and established.The constitutive equations under all strains were coupled through polynomial fitting,and the predicted flow stress and experimental flow stress curves were fitted.The average relative error was 4.78%,indicating that the traditional Arrhenius-type high-temperature constitutive equation is useful for predicting The flow stress change law of Alloy 925 during hot deformation has certain accuracy.(2)Based on the flow stress-strain curve and constitutive equation of Alloy 925,the power dissipation diagram and rheological instability diagram of Alloy 925 are drawn,and the microscopic characteristics of the stable zone and the unstable zone are analyzed in combination with the microstructure observation,and the Alloy 925 is determined The optimal thermal processing window of the alloy is 1050-1150?and0.01-0.1s^-1.(3)The relationship between the recrystallization characteristic parameters and the Z parameter is established.The recrystallization characteristic parameters gradually decrease with the decrease of the strain rate and the increase of the deformation temperature.The recrystallization model was further constructed,and the change rule of the recrystallization volume fraction with strain rate and deformation temperature was predicted more accurately.The recrystallization volume fraction gradually decreased with the increase of strain rate and the decrease of deformation temperature.The constructed recrystallized grain size model predicts the recrystallized grain size accurately when the strain rate is low,and the recrystallized grain size increases with the decrease of the strain rate.(4)Based on the test of microstructure and mechanical properties of Alloy 925 at solution treatment temperature of 1100?,aging temperature of 650-900?and aging time of 0.5-240h,and through the thermodynamic calculation of the precipitated phase,the precipitation rule of the second phase was explored and discussed.The mass fraction of the precipitated phase changes with aging process parameters,and the second phase that may exist in the Alloy 925 at room temperature is analyzed:??,MC,M₂₃C₆,?,?.Combining hardness test and tensile test,it can be preliminarily judged that the best aging process parameter is 700?/50-100h.