Detection and analysis of basic variables during linear friction welding of GH4169 superalloy

By monitoring the line voltage and current of the driving motor during linear friction welding （ LFW） of GH4169 superalloy, the frictional power of the rubbing interface between two components to be joined was detected. The data was recorded by a data acquisition card and processed by the LabVIEW software. By analyzing the evolution of frictional power, the joint formation mechanism was discussed. The curves of the measured basic variables （frictional power, axial shortening, interfacial temperature and axial pressure） reflected the characteristics of the LFW process and offered an effective way for welding parameter optimization.

SUPERPLASTIC FORMING AND AP-PLICATION OF GH4169 SUPERALLOY

The superplastic forming and application of GH4169 superalloy are studied. It is shown that for the typical superplastic forming strain rates of 10- 3 s 1 to 10- 4 s -1, the available engineering strains of the fine-grain GH4169 superalloy are always higher than 250% within wide temperature scopes (920 -980℃), and the maximum elongation to failure obtained is 513%. Dynamic grain growth is presented during superplastic deforming for the alloy, and the grain becomes larger with the increase of the strain. A GH4169 fuel manifold of an aerocraft is superplastically formed, and the superplastically formed GH4169 mainfold is tested by 30 MPa hydraulic pressure for 10 min. So some GH4169 alloy complex components can be superplastically formed in the aerospace industry to decrease the costs of fabricating these components.

Stress Relaxation Behavior of GH4169 Superalloy

GH4169 superalloy stress relaxation test was investigated to study its characteristics of stress relaxation curves at various temperatures( 550,650,and 750 ℃). These curves presented jointly two distinct stages,the stage of inner stress relaxing quickly,and the stage of inner stress relaxing slowly and closing to the stress relaxation limit. And these curves obtained could be fitted by second order exponential decay function well. Based on the experimental stress relaxation curves,the relationship between stress relaxation rate and time were derived, which showed that the higher relaxation temperature and the greater initial rate of stress relaxation. The whole process presented two different stages,the stage of stress relaxation rate falling rapidly and the stage of stress relaxation rate slowing down and tending to be constant. The relation curve between creep strain rate and stress of GH4169 superalloy can be divided into three stages,low stress stage,transition stage,and high stress stage.Both the high stage and the low stage present linear correlation.

Effect of linear friction welding process on microstructure evolution,mechanical properties and corrosion behavior of GH4169 superalloy

Linear Friction Welding(LFW)technology was used to realize the welding of GH4169 superalloy,and the effect of welding parameters on the microstructure,mechanical properties and corrosion behavior of the joint was analyzed.The results show that there is a positive correlation between the weld hardness and the tensile strength.With the gradual increase of heat input and welding pressure,the joint quality is gradually improved,but the heat affected zone is not significantly increased.The smaller the grain size of the weld,the higher the strength and plasticity of the joint.With the increase of the joint shortening amount,the corrosion resistance of the weld first gradually increases.However,when the shortening reaches a certain level,the corrosion resistance of the joint becomes little changed.With the increase of solution temperature,the corrosion current density increases and the polarization impedance decreases.The higher the corrosion temperature,the worse the corrosion resistance of the joint.There is no significant correlation between the joint strength and the corrosion resistance.The corrosion resistance of the joint can be enhanced without changing the joint mechanical properties by reducing the welding frequency and amplitude or increasing the welding pressure.

Kinematics and Dynamics Model of GH4169 Alloy for Thermal Deformation

The stress-strain curves and microstructure properties of superalloy GH4169 was tested by thermal simulation experiment with different parameters,which were deformation temperature and strain rate and strain and original grain size.The influence of technology parameters on crystal grain size of dynamic recrystallization（DRC）was analyzed.The kinematics model of superalloy GH4169 was established,in which the relation between grain size of dynamic recrystallization and function Z（Zener-Hollomon）and parameters was described.The dynamics model of superalloy GH4169 was put forward,which described the relation between the quantity of dynamic recrystallization and function Z and parameters.The research results showed that the grain size of dynamic recrystallization increased with increasing the temperature and decreasing the strain rate.And the grain size of DRC bore no relationship to original grain size.And the quantity of dynamic recrystallization decreased with increasing the original grain size.