Effect of Holding Pressure on Subsequent Aging Behavior of 7075 Aluminum Alloy
In order to explore the effect of holding pressure on the subsequent aging behavior of 7075 high strength alumi-num alloy in warm forming,combined with the characteristics of solid solution treatment of aluminum alloy,the work aims to simulate the cooling conditions in the actual hot forming process by plate pressure quenching experiment and study the 7075 high strength aluminum alloy under different holding pressure,in order to obtain the optimal holding pressure parameters of 7075 aluminum alloy plate after solid solution forming,as well as its age hardening behavior and microstructure evolution char-acteristics under different holding pressure conditions,thus providing theoretical guidance and process optimization reference for the hot forming-quenching integration process in actual production.The 7075 aluminum alloy plate was firstly subject to solid solution treatment and plate pressure quenching experiments,and then followed by aging treatment.The effects of different holding pressure on the mechanical properties and microstructure of the alloy after subsequent aging treatment were studied by metallographic observation,quasi-static uniaxial tensile test,micro-Vickers hardness tester and scanning electron microscope.With the increase of holding pressure,the grain size gradually decreased,the aging hardening response was significant,and the peak hardness gradually decreased.When the holding pressure was 10 MPa,the alloy had a relative balance between strength and plasticity after artificial aging at 150 ℃/6 h,and its tensile strength was 580.9 MPa,yield strength was 538.6 MPa and elongation after fracture reached 12.2％.The ideal matching of strength and plasticity could be obtained because when the hold-ing pressure was set to 10 MPa,the number of η'phases in the alloy increased and the distribution was relatively dispersed,which could hinder the dislocation movement and achieve the strengthening effect,but the plasticity of the alloy would be sacri-ficed to some extent.The tensile fracture analysis showed that when the holding pressure was constant,the number of alloy dimples under the same aging system decreased with the extension of aging time and the depth became shallow,and the plastic-ity of the material decreased.The holding pressure has a significant effect on the grain size,age hardening and mechanical prop-erties of the alloy.At the holding pressure of 10 MPa,the alloy shows a good balance between strength and plasticity,which provides an important reference for the optimization of hot forming-quenching process of 7075 aluminum alloy,especially in the selection of holding pressure.
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