Study On The Effect Of Two-stage Aging On The Microstructure And Properties Of Extruded 2A12 Aluminum Alloy

2A12 aluminum alloy is a deformable aluminum alloy that can be strengthened by heat treatment.In order to give full play to the role of plastic forming and heat treatment strengthening,and further improve the mechanical properties of parts,for aluminum alloy parts used in special equipment,this article uses two extrusion forming methods?reverse extrusion and annular channel extrusion?,research the effect of solution treatment and two-stage aging treatment on the mechanical properties and microstructure of molded parts.Through the optimization of the heat treatment process,the best process plan is obtained,which provides a theoretical basis for subsequent production.The metallurgical microscope?OM?,scanning electron microscope?SEM?,electron backscatter diffraction analysis?EBSD?and X-ray diffractometer?XRD?were used to analyze the microstructure and phase of the structure.With the help of tensile,hardness and other experiments for mechanical properties testing.The main findings are as follows:First,the experiment of upsetting deformation 2A12 aluminum alloy showed that the effect of double-stage aging on the improvement of alloy properties is more significant than that of single-stage aging.When the secondary aging parameters are unchanged,the primary aging temperature and time have little effect on the tensile strength;when the primary aging parameters are determined,it is concluded that the secondary aging temperature does not exceed 200°C and the holding time does not exceed 6h.The tensile strength keeps increasing.Finally,under the conditions of 495?×1h+100?×2h+180?×4h,the?and S phases are precipitated with aging,and the grains are fine,and the comprehensive performance of the material is excellent,which provides a reference for the aging scheme of the reverse extrusion component.Secondly,from the upsetting to the reverse extrusion process,the grain size increases slightly,the degree of fine recrystallized grains increases,and the performance is improved.After the heat treatment experiment,the alloy has excellent heat resistance.The residual eutectic phase is most fully dissolved under the solution parameter of 525?×1h,but the T phase is stable.Similarly,the performance improvement of double-stage aging on reverse extrusion alloy is significantly higher than that of single-stage aging,and the tensile strength?R_m?is close to 500MPa at 525?×1h+100?×2h+200?×5h,and the yield strength is(R_p0.2)421.71MPa,elongation?A?12%.The main strengthening phase of aging precipitation is nano-scale strip S phase?Al₂CuMg?,the secondary strengthening phase is?phase?Al₂Cu?,and the fracture analysis is mixed fracture.Compared with the initial state reverse extrusion member,the annular channel corner extruded member is relatively small in grain size,and there are more fine recrystallized grains distributed along the extrusion direction.After heat treatment at 525?×1h+100?×2h+200?×5h,the grain size increased slightly,and the precipitation-strengthening strengthening phase was strip-shaped S phase,mainly distributed along the grain boundary,consistent with the reverse extrusion.The mechanical properties test shows that R_m is492.98MPa,R_p0.20.2 is 225.43MPa,and A is 19.21%.Compared with reverse extrusion,the tensile strength was close,the yield strength was small,and the elongation was high,indicating that there is still room for significant improvement in performance.At the same time,it is concluded that 2A12 aluminum alloy combined with heat treatment under certain extrusion deformation will greatly improve performance and meet the strength requirements of aluminum alloy for special equipment.