Study On Quenching Sensitivity And Thermal Simulation Properties Of Cast 7085 Aluminum Alloy

Al-Mg-Zn-Cu aluminum alloy,as a time-strengthening aluminum alloy,whose strength limit up to 550N/mm2 above,began in 1944 as the aerospace field of the main structural materials.However,its performance has a direct relationship with the post-solution quenching process.The element content of the alloy is relatively high,and the decrease in the cooling rate often leads to a decrease in the overall performance when the slab is quenched.In order to improve the comprehensive properties of thick materials,the quench-sensitive properties of the alloys need to be studied.This article uses optical microscope,scanning electron microscopy,hardness testing,electrical conductivity testing,DSC thermal analysis,isothermal thermal compression simulation and other experimental tools and methods,using as-cast 7085 aluminum alloy as the research object to determine the content of main alloying elements,heat treatment process parameters The high-temperature rheological behavior of the alloy was studied and the following conclusions were obtained.(1)the effects of main alloying elements Zn,Mg,and Cu on the quenching sensitivities are studied.It is found that when the Mg and Cu contents are similar,the decrease in Zn content has a lower influence on the quench sensitivity,and the Mg content increases,at 1.12wt%?1.33wt%,it promotes more phases in the slow rate quenching of the alloy,and at the same time it promotes the precipitation of T and S phases and improves the quenching sensitivity of the alloy;when the content continues to increase to 1.546wt%,the quenching sensitivity of the alloy is reduced.The increase of Cu content can promote the precipitation of S phase in the microstructure and reduce the mechanical properties of the quenched alloy.Therefore,in order to improve the overall performance of the alloy(good mechanical properties and quenching sensitivity),the content of Mg should be in the vicinity of7.8 wt%,the content of Mg in the alloy is1.33wt%?1.57wt%,and the content of Cu is moderate.To reduce the range as much as possible,are conducive to reducing the quenching sensitivity of the alloy.(2)The as-cast 7085 aluminum alloy has the characteristics of steady state rheology and dynamic softening during the thermal simulation test.The heat deformation activation energy of as-cast 7085 aluminum alloy is 152.7 KJ/mol,and the appropriate homogenization system can effectively reduce the activation energy.Size;when the deformation temperature is low,dynamic recovery is the main;when the temperature is higher,dynamic softening and dynamic recrystallization are the main factors.According to the observation of the microstructure of the experimental alloy,the grain size,shape,and size of the alloy have great differences under different deformation conditions.With the decrease of InZ,the grains are gradually elongated along the radial direction,and the number of precipitation phases decreases.Recrystallized grains grow.(3)The effect of improving the quenching sensitivity of the 7085 aluminum alloy by a two-stage homogenizing system with slow rate heating is obvious compared with the rapid temperature increasing two-stage homogenization or single-stage homogenization system,but the hardness of some alloys is sacrificed.