| GH4169 alloy is a nickel-based precipitation-strengthened alloy with excellent properties such as high temperature strength,corrosion resistance,oxidation resistance and good weldability.It has a wide range of applications in the aerospace industry.The alloy consists of ? matrix phase,???,?? and ? strengthening phase and NbC particles.NbC phase is the main carbide of GH4169 alloy,and obtaining fine dispersed NbC helps to improve the mechanical properties such as strength and creep of the alloy.In the flash welding of GH4169 alloy,it is found that the coarse NbC in the heat affected zone of the weld reduces the tensile properties of the weldment.The formation of the flash weld is to form a suitable temperature field from the weld end face to both ends after the flash,and then the upset Deformation,dynamic recrystallization occurs at the interface to form welds.It is found that the size,shape and quantity of NbC particles have regular distribution characteristics due to the gradient of welding temperature and deformation from weld to matrix.The method is to study the influence of temperature and deformation on the deformation of NbC in different areas of the welding specimen,so as to optimize the deformation parameters of the welding upset for the size,shape and quantity of NbC in the weld and heat affected zone.The technical solution of control meets the needs of high-performance GH4169 flash welded parts.(1)The flash welding process was simulated by thermal simulation experiment.The influence of thermal deformation on the variation of NbC particles was studied by means of OM,SEM and TEM.It was found that as the amount of deformation increases,the NbC particles are broken and partially re-dissolved,and the size and vol ?me fraction of the particles are correspondingly reduced.The adiabatic effect of the deformation causes the internal temperature of the metal to further increase,providing conditions for the re-dissolution of the NbC particles during the deformation process.The average spacing of NbC particles increases rapidly with the increase of deformation.The variation of NbC particles with the increase of deformation has the characteristics of chain?chain bending?chain direction?dispersion distribution.(2)For the GH4169 flash welding process,the thermal deformation of the sample with the fusion interface was carried out to study the characteristics of the weld formation.Based on the dynamic material model,the hot-worked drawing of GH4169 alloy with fusion interface was drawn.The combination of thermal processing and microstructure showed that the strain rate was 0.1 s-1,and the temperature was 1050 °C,which was the interface,which was beneficial to the formation of flash welding.Sewing feature organization.After thermal deformation,the distribution and size of NbC particles at the fusion interface to both ends,NbC particles gradually changed from diffuse distribution to strip-like distribution,and the average size of NbC increased first and then decreased.(3)According to the study of NbC particles and microstructure by thermal deformation,the parameters of GH4169 flash welding top section were optimized.Under the gradient temperature field formed by setting the flash parameters,the deformation of the weld was increased by increasing the upset stroke.And promote the dynamic recrystallization of the weld at a lower temperature,effectively suppressing the precipitation of coarse NbC in the heat-affected zone,and the tensile properties are obviously improved.The index is almost consistent with the performance of the original base metal,and the original welded specimen is stretched.The small,diffused dimples on the fracture are replaced by large,deep dimples. |
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