Residual Stress Characterization And Relief Methods Of W/2A12 Composite

W/2A12 composite material is an excellent structural and functional material with excellent high-energy radiation resistance.In the process of manufacturing,W/2A12 composite materials inevitably undergo high-temperature processes,such as hot extrusion,heat treatment or work under high temperature and thermal cycling conditions.Solution quenching is an important heat treatment process for W/2A12 composite materials.In the quenching process,a large magnitudes of residual stress which has a great impact on the dimensional stability,stress corrosion resistance,fatigue strength and other properties will be introduced within the component,thus,great deformation will arise during the subsequent machining process.Therefore,it is of significance for regulating and predicting the residual stress in the W/2A12 composite material to improve the dimensional stability and other properties of the component.Based on the hot compression test,the constitutive equation of elevated-temperature deformation of the solution-quenched W/2A12 composite was established.Combining the end quenching method and the DFORM-HT iterative method,the heat transfer coefficients of the W/2A12 composite material and the heat transfer medium under three-dimensional heat transfer were obtained.The high-temperature deformation constitutive equation,heat transfer coefficients and measured material physical parameters were applied to the ABAQUS finite element software to establish the evolution model of the residual stress of the W/2A12 composite aluminum alloy during the conventional heat treatment process.The temperature and stress field evolution were simulated using ABAQUS software to study the effect of quenching water temperature on the stress distribution and magnitudes.The results show that increasing the quenching water temperature can more effectively achieve stress relief for tensile stress developed in intern region of component.In this paper,the method for determination of internal stress in W/2A12 composites was established based on the crack compliance method,utilized with finite element simulation to analyze the factors that cause the test error and then make corrections,and determine the interpolation function type and order selection criteria to minimize the errors of crack compliance method.XRD and hole-drilling method were carried out to determine the surface stress of the component,a comprehensive comparison of tested values using both methods was made to determine the selection principle of the determination of surface residual stress.Comparing the experimental values with the ABAQUS simulation results,the test results are in good agreement with the simulation results,confirming the accuracy and reliability of the residual stress simulation model established in this paper.According to the similarity of the quenching residual stress distribution within the component,the internal residual stress prediction based on the surface residual stress test data was realized,and the numerical model for predicting the residual stress of the quenched W/2A12 composite material is established.In addition,a new type of stress prediction method model for quenching and uphill-quenching process of complex shaped components was established.The maximum deviation between the model results and the experimental test results was less than 20%.The quenching residual stress relief treatment of W/2A12 composites was studied,and the residual stress and mechanical properties of the plates after various stress relief treatment were simultaneously characterized.The temperature of water has an apparent influence on the residual stress.Increasing the temperature of water can significantly reduce the residual stress of the component,and there was no significant change in the mechanical properties of the composite.Pre-stretching can significantly reduce the residual stress of the component,the lower limit of the amount of stretching should be set to 0.8%to make sure the apparent stress reduction.When the amount of stretching was 2%,the maximum tensile stress and maximum compressive stress were reduced by 89.8%and 88.5%,respectively.The uphill-quenching process using dimethyl silicone oil as the high-temperature medium can eliminate up to 60%of the quenching residual stress.The uphill-quenching treatment utilized immediately after quenching process can greatly reduce the residual stress in the sample,and the effect for stress relief of the first-time uphill-quenching process was most significant,the effect of uphill-quenching times on stress relief was not obvious.Moreover,the mechanical properties of the alloy have been optimized after uphill-quenching treatment.