Abstract: Solution+peak aging treatment (470 ℃× 2 h, water cooling, 120 ℃× 24 h, air cooling) was carried out on spray formed and extruded 7075 aluminum alloy, and microstructure and compressive properties of the alloy were characterized. The results show that the microstructure of the alloy consists of aluminum matrix and coarse rod-shape η(MgZn₂) phase distributed along the extrusion direction. After solution and peak aging treatment, the recrystallization occurs and the recrystallized grain size is 20-30 μm, and a large number of nanoscale strengthening phases η′(MgZn₂) and GP zones are precipitated. The compressive stress of the alloy slowly increases with the increase of strain. The compressive strength and compressive stress of the spray formed and extruded and peak aged alloy (at a compressive strain of 0.5) are 475.8-540.6 MPa and 700.1-807.7 MPa, respectively. The nanoscale strengthening phase in peak aged alloy inhibits dislocation movement, significantly improving the compression properties of the alloy. The compressive stress of the alloys in two states at room temperature is insensitive to the quasi-static strain rate. The fracture mechanism of the spray formed and extruded alloy is a mixed mode of transgranular fracture and intergranular fracture, and the peak aged alloy shows an intergranular fracture. The key to ensuring the ultra-high strength and overcoming the poor plasticity of the 7075 aluminum alloy is the uniform microstructure and the supersaturated solid solution obtained by spray forming and extrusion, and the fine recrystallized grains obtained by the solution and peak aging treatment.

Key words: spray forming, 7075 aluminum alloy, peak aging, microstructure, compression properties