Thermal Deformation Behavior And Microstructure Analysis Of N06625 Nickel Base Alloy

N06625 Nickel base alloy is a solution strengthened nickel base superalloy with molybdenum and niobium as the main strengthening elements.It has good corrosion resistance,fatigue resistance,oxidation resistance,cold and hot working properties,and is widely used in petrochemical,aerospace,aerospace engineering and other fields,which is of great significance to the national economy and national defense construction.However,its high degree of alloying,narrow hot forming range,and problems such as coarse and uneven grains during processing seriously affect product performance.In this paper,N06625 nickel base alloy was taken as the research object,and the Gleeble-3800 thermal simulation testing machine,metallographic microscope,scanning electron microscope and other equipment were used to study its thermal deformation behavior at high temperature and high strain rate and the influence of deformation parameters on the evolution of alloy microstructure by means of rheological curve correction,constitutive model,hot working diagram and dynamic recrystallization model.The specific research contents and results are as follows:（1）The hot compression test was conducted on the N06625 nickel based alloy sample,and the obtained rheological curve showed two trends:one was a typical dynamic recrystallization characteristic;The other is a typical dynamic recovery feature.Consider the influence of friction and deformation temperature rise on rheological stress and make corrections.（2）Based on the modified data,the Johnson-Cook,Arrhenius,Hansel-Spittel constitutive models and Kumar-Prasad,Murty-Rao criterion hot processing maps are established.The strain compensated Arrhenius constitutive model has the highest fitting degree for the rheological curve of N06625 Nickel based alloy.（3）The microstructure evolution of N06625 Nickel based alloy in hot compression tests was analyzed using optical microscopy（OM）and electron backscatter diffraction（EBSD）.Continuous dynamic recrystallization（CDRX）at low deformation temperature is the main nucleation mechanism,and as the deformation temperature increases,the CDRX mechanism weakens.At higher deformation temperatures,discontinuous dynamic recrystallization（DDRX）is the main mechanism of dynamic recrystallization（DRX）,while CDRX can only serve as an auxiliary mechanism in the early deformation stage.（4）According to the microstructure,Murty Rao criterion is more suitable for N06625 nickel base alloy.The deformation area with a temperature of around1150-1200℃and a strain rate of 30-50 s^-1 is a fine-grained structure area,and the structure is more uniform.Plastic deformation in this area can obtain a more ideal grain structure.