Research On New Type Thermomechanical Treatment Process Of Spray Formed High Strength 7034 Aluminum Alloy

7034 aluminum alloy belongs to the Al-Zn-Mg-Cu super-strength aluminum alloy,which has the advantages of low cost,high strength ratio,good weldability and easy processing.At the same time,the alloy has the dual characteristics of heat treatment strengthening and deformation strengthening.It is widely used as structural materials in aerospace,national defense,military industry and other fields.In this paper,the effects of different deformable heat treatment processes on the microstructure and mechanical properties of jet deposited 7034 aluminum alloy were studied,and the strengthening and toughening mechanism was explored.OM,EDS,TEM,HRTEM,MH-3 microhardness tester and tensile test at room temperature were used.the grain size,dislocation and substructure evolution,morphology and size of precipitated phase,grain boundary morphology,hardness and mechanical properties of the alloy were investigated to further explore the strengthening and toughening mechanism.The research results show that isothermal deformation heat treatment can effectively bridge the gap of spray-deposited 7034 aluminum alloy.The dispersed phase and intragranular spherical massive MgZn₂ phase produced in the matrix provide the basis for alloy strengthening.The dislocations and substructures produced by the deformation further hinder the deformation of the alloy.The discontinuous grain boundary precipitation phase and the wide precipitation-free zone make the alloy exhibit higher strength and better plasticity.The best process are 40%pre-deformation and 40%thermal deformation followed by T6 aging,which the tensile strength is630.3MPa and the elongation is 11.5%.After isothermal deformation,cold deformation treatment was carried out,the grains were refined,resulting in fine-grain strengthening,the dislocation density increases,which promotes the increase of the flow stress of the alloy,thereby increasing the strength of the alloy.The number of intragranular precipitation phases has increased significantly,which helps to increase the strength of the alloy.The intragranular precipitation phases after T6 aging are all spherical and massive?'phases,while for RRA aging treatment,it mainly includes the spherical agglomerate?'phase and part of the rod-like?phase.The size of the precipitated phase at the grain boundary and the width of the precipitation-free zone were reduced,which increases the strength of the alloy and reduces the plasticity.T6 aging was performed when the pre-deformation,thermal deformation and cold deformation are 40%,35%,and 5%respectively,and the alloy's strong tensile strength reaches the maximum value of 876.3MPa,and the elongation is 2.8%.Co MPared with isothermal deformation heat treatment,the strengthened solution treatment after isothermal deformation significantly reduces the grain size,increases the dislocation density in the matrix,and was distributed in a network shape,and forms micron-level sub-crystals,which hinder alloy deformation.After different aging,the grains all contain spherical?'phase and rod-like?phase,but during RRA aging,the proportion of?phase was reduced co MPared with T6 aging,the size of the precipitated phase at the grain boundary and the width of the precipitation-free zone decrease,the strength of the alloy increases,and the plasticity decreases.Strengthening solid solution and RRA aging were carried out when the pre-deformation and thermal deformation are both 40%,and the alloy strength and plasticity reach the best,which are 837.6MPa and 4.5%respectively.