Preparation And Heat Treatment Of Al-Zn-Mg-Cu Alloy By Spray Formed

Al-Zn-Mg-Cu alloy is a typical aging strengthening alloy,which is widely used in aerospace and automobile industries due to its light weight and high strength.However,alloys prepared by conventional casting methods have not achieve more excellent mechanical properties owing to the phenomenon of segregation with the increase of Zn content.Therefore,spray deposition process has been used to prepare the alloy.But the research on the heat treatment process of high Zn content of Al-Zn-Mg-Cu alloy prepared by spray deposition is not systematic.And the effect of elements on the high Zn content of Al-Zn-Mg-Cu alloy prepared by spray deposition is rarely reported.Hence,Al-11.5Zn-2.1Mg-1.6Cu alloy,Al-11.3Zn-1.9Mg-1.7Cu-0.19 Cr alloy and Al-11.6Zn-2.0Mg-1.6Cu-0.18 Zr alloy were prepared by spray-forming technology and the heat treatment process of Al-Zn-Mg-Cu alloys were investigated.The effects of Cr and Zr addition on the properties of Al-11.5Zn-2.1Mg-1.6Cu alloy were also analyzed.The mechanical properties and microstructure observation of Al-Zn-Mg-Cu alloys prepared by spray deposition after solution treatment were performed.The results showed that the effect of solution treatment changed for the different temperature and time of solution treatment.If solid solution temperature was too high,the alloy matrix appeared burning organization,impacting the mechanical properties of Al-Zn-Mg-Cu alloys.The performance of double solution treatment was better than single solution treatment.The hardness of Al-Zn-Mg-Cu alloys were increased after solution treatment.Moreover,the hardness of Al-Zn-Mg-Cu alloys after double solution treatment was higher than that after single solution treatment.The addition of Cr and Zr also affected the hardness of Al-Zn-Mg-Cu alloys.Based on the analysis of XRD and lattice constants,the addition of Cr and Zr elements changed the precipitates and the lattice constants in the alloy matrix,resulting in the change of hardness of in Al-Zn-Mg-Cu alloys.The mechanical properties and microstructure observation of Al-Zn-Mg-Cu alloys prepared by spray deposition after aging treatment were carried out.The results showed that the strength of Al-Zn-Mg-Cu alloys after aging treatment was greatly improved.The strength curve of Al-Zn-Mg-Cu alloys presented "double peak" phenomenon.Additionally,thehardness of Al-Zn-Mg-Cu alloys after aging time also presented "double peak" phenomenon.The addition of Cr and Zr could improved the strength of Al-11.5Zn-2.1Mg-1.6Cu alloys and the effect of Cr element was higher than that of the Zr element.However,the hardness of Al-11.5Zn-2.1Mg-1.6Cu alloys was declined by adding Cr and Zr.The microstructure observation showed that the precipitation phase was mainly GP zones at the first aging peak.The precipitation phase was changed to ? 'phase and ? phase at the second aging peak.The analysis of XRD and lattice constants showed that the type and amount of precipitates had a great influence on the strength of Al-11.5Zn-2.1Mg-1.6Cu alloys and the change of the hardness of Al-11.5Zn-2.1Mg-1.6Cu alloys was also related to the degree of distortion of the matrix.