Precipitate Behavior and Microstructure Characterization of An Al-Zn-Mg-Cu Alloy Prepared by Spray Forming Process

摘要

A high Zn content Al-Zn-Mg-Cu alloy was prepared by spray forming process and the precipitate behavior and microstructure of the extruded alloy were also investigated. The precipitate sequence of the spray-formed alloy could be described as 'α-solid solution →GPI zone → GPII zone (also called Metastable η' )→ Stable η (MgZn_2)' during artificial ageing treatment. In the early stage of artificial ageing treatment, the GPI zone was the main strengthening phase and kept coherent relationship with the matrix. With the increasing of ageing time, η' phase dominate strengthening phase and kept semi-coherent relationship with the matrix. With the further increasing of ageing time, η phase took the place of η' phase, and dominated the strengthening phase in the alloy. The grain size of the spray deposit is finer than that of cast alloys. The ultimate tensile strength of the alloy is over 810MPa in peak ageing condition.