Effect of Cryogenic Deformation Treatment Before Solid Solution on Microstructure and Properties of 7050 Aluminum Alloy
WANG Lei1,2, YI Youping1,2, HUANG Shiquan1,2, DONG Fei1,2
1 College of Mechanical and Electrical Engineering, Central South University, Changsha 410083 2 State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083
Abstract: This study proposes a new cryogenic deformation process for 7050 aluminum alloy free forgings.That is, the alloy is placed in liquid nitrogen before heat treatment,after the alloy is lowered to the liquid nitrogen temperature, a single pass compression deformation is performed along the high direction. After heat treatment, hardness, room temperature tensile, electrical conductivity, intergranular corrosion, exfoliation corrosion test and metallographic microscope, scanning electron microscopy and transmission electron microscopy were used to study the effect of different cryogenic deformation on microstructure, mechanical properties and corrosion resistance of 7050 aluminum alloy.The results show that as the degree of cryogenic deformation increases, the recrystallization ratio of the alloy increases, the grains gradually refine, the spacing of the precipita-tion phase at the grain boundary decreases, and the discontinuous distribution changes to a continuous distribution, and the width of the precipitation zone is narrow. The tensile strength, yield strength and hardness of the alloy are obviously increased. The maximum lifting ranges are 33 MPa, 35 MPa and 10.5HV, respectively. The maximum elongation is 1.5%. The electrical conductivity shows a downward trend. The alloy resists intergranular corrosion and anti-flaking. Corrosion performance is reduced, the maximum depth of intergranular corrosion corresponding to 30% cryogenic deformation is 167 μm, and the peeling corrosion grade is EC.
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2019, Vol. 33 
