Evolution And Interaction Of Microstructures Of Deformed Superalloy During Preparation Process And Thermo-mechnical Coupling Action

Deformed superalloy products have high cost performance,controllable structure and properties during production,high structure stability and excellent comprehensive mechanical properties during service,which are the main goals of industrial production of superalloys,and also the pratical and theoretical basis to develop hot-end components of aero-engine with higher thrust-to-weight ratio and longer service life.To achieve this goal,the in-depth understanding and control of the deformation behavior of cold and hot processing during production is undoubtedly the key,and the effects of complex service conditions on microstructure stability and improving the microstructure stability and reliability during service is a link that requires great attention.For this reason,this paper systematically studies the deformation behavior of typical microstructures at various stages of production and during serviceand their mutual influence to provide experimental and theoretical basis for the production and application of superalloy.The microstructure mutual influences and microstructure transfer between ascast and homogenized GH5605 during hot deformation were systematically studied.Based on the fact that the lighter element segeration is eliminated before(γ+M23C6)eutectic phase during homogenization at 1210℃,it is considered that the elimination of eutectic phase is the focus of the homogenization of GH5605 alloy.Based on the microstructure inheritance law between casting and forging,an economical homogenization process that prolonging the heating period before cogging to eliminate the eutectic phase is proposed.Furthermore,the interaction between grain boundaries and γ’ phase boundary of GH4720Li alloy on recrystallization and thermoplasticity during forging is clarified.The key control point of fine grains is the growth of recrystallized grains and even mixed grains at higher temperaturethan the resolubilization temperature of γ’,the key control of coarse grains is thermoplasticity and the recrystallization fraction.The thermal processing window for fine and coarse grains were constructured,and the adjustment principle of the hot processing control due to variation of initial grain size is proposed.A systematic study was carried out on the cold deformation behavior of grain,carbide and γ’.The microstructure evolution of grain,carbide strips and microstructure of GH5605 during cold rolling/annealing is revealed.The carbide strips formed after hot rolling/annealing gradually diminish with the increase of cold rolling/annealing passes,stacking faults and a small amount of twins d,while twins accompanied by strain-induced martensite transformation are hot and cold deformation mechanisms,respectively.Furthermore,systematic experimental and theoretical analysis on the rafting and cutting of γ’ along slip direction during room temperature compression of 617B alloy.It is clarified that the Young’s modulus of the y matrix has the most significant effect on the stress concentration at the γ/γ’interface.Based on this,the degree of solid solution strengthening of the matrix y should be fully considered to control cold deformation ability of γ’.Aiming at the deformation behavior of γ’ in the thermal-mechanical coupling process during service,different γ’ after different thermal exposures(600℃,650℃,730℃ to 3000 h)of FGH4720Li alloy was systematically analyzed,then the high temperature stretching,creep and fatigue testings were carried out.The influences of γ’ with different microstructural characteristics on the damage mechanisms under different stress and action time were elucidated.The results show that during the loading process of the alloy,the y matrix is more susceptible to the dissolution ofγ’Ⅱ and γ’Ⅲ,which makes the stress acting on the γ’i phase change significantly,resulting in different degrees of elongation and even fracture,for which it is believed that the stress redistribution between the γ’ and γ matrix is the main reason for different deformation characteristics of γ’.To sum up,this paper uses many experiments and theoretical analysis to obtain the microstructure evolution law and mutual influence behavior of typical microstructures in different processes during production of deformed superalloys,and reveal the influence of γ’ with different characteristics on fracture mechanisms under the action of thermo-mechanical coupling,based on which the relevant production and microstructure control principles are put forward,providing experimental and theoretical basis for industrial production and microstructure control of deformed superalloys.