Research On Cryogenic-Heat Treatment Control Of Processing Deformation Of High Strength Aluminum Alloy

At present,aerospace has higher and higher requirements for lightweight materials,so it is required to produce components with high specific strength and maintain long-term stable work on key components to save production,operation and maintenance costs.As a light alloy,the 7 series aluminum alloy is widely used because of its high strength.However,in the actual processing process,7-series aluminum alloys generally need to be solid solution-quenched and other heat treatments and cryogenic treatments to meet the performance requirements of strength and toughness.However,in the process of cold and heat treatment,due to the temperature gradient of the part surface and core,certain residual stress will inevitably be generated,which not only affects the subsequent machining process,but also seriously affects the dimensional stability of the part during actual use.In this paper,the residual stress generated by cold heat treatment of 7050 aluminum alloy leads to the subsequent machining deformation.The deformation and residual stress are measured by three-coordinate measurement and blind hole method respectively,and a relatively complete different cold heat treatment process route is obtained.The influence of residual stress on 7050 aluminum alloy and subsequent machining deformation,and the interaction between residual stress distribution and machining deformation is analyzed.The main conclusions are as follows:(1)By measuring the deformation of the fins of the T-piece after milling,it is found that the deformation of the fins of the specimens processed by SA and SAC is small;the deformation of the fins and the deformation of the specimens processed by SCA and SUQ within a certain period of time are floating The largest;the deformation and change amplitude of SACA specimens are small,and the dimensional stability after milling is relatively best.(2)By measuring the deformation of the bottom plate of the T-piece after milling,it is found that the deformation of the SCA sample is the largest among all the processes;the deformation of the bottom plate of the SACA sample is large,which does not correspond to the deformation of the ribs;the deformation of the bottom plate of the SC sample is relatively large.The deformation of SA and SUQ specimens is small;the deformation of SAC specimens is also large,and the deformation does not reach equilibrium with the extension of time.(3)By measuring the stress before and after milling of the rectangular parallelepiped sample,and combining the results of the deformation measurement,it is found that the greater the stress before milling,the greater the deformation.However,after milling,the stress of the sample with smaller deformation is larger,indicating that the stress release state is inseparable from the processing deformation of the workpiece and the subsequent dimensional stability.(4)By measuring the residual stress of samples of different shapes and sizes after different cold and heat treatments,it is found that for S samples,the larger the size,the greater the surface quenching stress;for SA samples,Samples of all sizes did not show obvious stress reduction;the stress of SC sample increased to a certain extent;the influence of SAC sample on the surface residual stress distribution in the actual measurement process was almost negligible,but it was along the depth direction The residual stress change rule on the above is different;the SCA sample shows different rules in the residual stress measurement of the special-shaped small block and the cube sample.SCA has a certain reduction effect on the residual stress of the special-shaped small block,but in the cubic There is no similar finding in the block.