Study On Heat Treatment System Of 6082 Aluminum Alloy Used For High Speed Railway Cable Support

To improve the performances of 6082 aluminum alloy profiles used for high-speed railway cable supports,the microstructure and mechanical properties of6082 aluminum alloy profiles under different heat treatment conditions were studied.By means of electronic universal testing machine,Brinell hardness tester,metallographicmicroscope,scanningelectronmicroscope?SEM?,X-ray diffractometer?XRD?,electron back-scattered diffraction?EBSD?and other testing methods,the influence mechanism and internal rule of heat treatment on the microstructure and properties of the alloy were analyzed systemically.And on this basis the optimized heat treatment systems with the most practical use value and the best comprehensive performances were obtained.The main contents and results are as follows.?1?The studies on the microstructure and mechanical properties of 6082aluminum alloy profiles under different solution treatment systems indicate that the optimal solution performance of 6082 aluminum alloy profiles is 533°C/40 min.The intergranular compounds of the alloy profiles are well dissolved under this system as well as the unified grain size distribution is 7.02?m.The grain direction is deflected from?200?direction to?111?direction,and the obtained solid solution has a high degree of supersaturation.The Brinell hardness is 88 HB,tensile strength is 290 MPa,and yield strength is 171 MPa.?2?The results of microstructure and mechanical properties of 6082 aluminum alloy profiles under different aging treatment systems show that the best aging treatment system of 6082 aluminum alloy profiles is 175°C/8 h.Under this condition,the precipitated strengthening phase?Mg₂Si phase?particles are evenly distributed,and the average grain size is 9.80?m.At this time,the Brinell hardness of the alloy can reach 115 HB,the tensile strength can reach 375 MPa,the yield strength can reach 360 MPa,and the elongation can reach 15.5%.?3?The studies on the influence mechanism of residence time before hardness on the hardness and strength of 6082 aluminum alloy profiles show that the residence time of the 6082 aluminum alloy profile with the best comprehensive performance is optimized to be 0-4 h,and the hardness and strength of the sample reaches a maximum under the condition,which means the aging treatment should be carried out within 4 h after the solution treatment,as a result,the alloy material has the best performance.?4?XRD characterizations of 6082 aluminum alloy profiles show that the total strengthening of grain boundary strengthening and dislocation strengthening after aging treatment increase from 87.87 MPa to 99.97 MPa.The EBSD characterizations of the alloy indicate that the aging treatment can effectively remove the residual stress stored in the alloy during the extrusion process,the grains grow slightly,and the recrystallized grains ratio decreases from 45%to 28%.Meanwhile,the average grains boundary angle is lowered as well as the low angle grain boundary ratio is significantly increased.The average grain boundary angle decreases from 25.51°to16.06°,and the proportion of low-angle grain boundaries increases from 47.91%to67.47%.In addition,the aging treatment can significantly change the grain distribution in the{100}and{110}directions of the grains.Moreover,it significantly enhances the texture of the sample in the{100}and{110}directions.?5?Fatigue verification experiments of 6082 aluminum alloy profiles under optimized heat treatment parameters are carried out under the condition of stress 4 kN and frequency 10 Hz.The fatigue life is up to 610,000 times.As a conclusion,the heat treatment system of 6082 aluminum alloy profile is optimized as:the solution treatment is 533°C/40 min,residence time is less than 4h,and the aging treatment is175°C/8 h.Under this system of heat treatment,the material properties fully meet the performance requirements of high-speed railway cable supports.