Microstructure and mechanical properties in multi-directionally forged 7075 and 7N01 aluminum alloy

Abstract

The microstructure and mechanical properties of 7075 and 7N01 alloys after multi-directional forging (MDFing) and subsequent aging were systematically investigated. The number density of the precipitates in the aged samples after MDFing were lower than that of the aged sample without MDFing. The aged 7075 and 7N01 alloys after MDFing showed the ultimate tensile strengths of 556 MPa and 428 MPa, respectively. The fatigue tests were conducted in air and 3.5% NaCl aqueous solution to investigate the effect of MDF on the fatigue properties of 7000 series alloys. As a result of fatigue test in air, the fatigue strength of the MDFed 7N01 alloy was slightly lower than that of non-MDFed one, but that of the 7075 alloy showed no difference before and after MDFing. Two alloys had no significant difference in fatigue crack growth rate in air and 3.5% NaCl aqueous solution.