Microstructure and tensile properties of large-size 7055 aluminum billets fabricated by spray forming rapid solidification technology

• Large size as-deposited billets of 7055 Aluminum alloy was successfully fabricated by spray forming technology.
• The microstructure observation showed that there were equiaxed grains with the size of about 50 μm.
• The detrimental dendrite microstructure was suppressed completely in our as-deposited 7055 alloys.
• After extruding, the peak-aged 7055 alloys showed high tensile strength (667 MPa) and enhanced elongation (10%).
• The microscopic fracture morphology of as-extruded specimens was the transgranular dimple fracture.

In this study, high-quality large billets of 7055 aluminum alloy were successfully fabricated by spray forming rapid solidification technology. Microstructure observation showed that there were equiaxed grains with the size of about 50 μm in diameter. The dendrite microstructure was suppressed and the undesirable macrosegregation did not exist in the as-deposited 7055 alloys, attributable to rapid solidification effects. The secondary phases were the main η-Mg(Zn,Cu,Al)2 expansion phases and the very small amounts of AlxFe3Cu Iron-bearing phase. As-deposited 7055 billet was subsequently processed by hot extrusion, solid solution treatment at 450 °C/24 h and aging at 120 °C for 12 h. The as-aged alloy was then subjected to tensile testing. The results revealed that yield strength, tensile strength and elongation rate of the alloy reached 608 MPa, 667 MPa and 10%, respectively. After extruding, the observation of the microscopic fracture morphology of as-extruded specimens manifested that fracture mode was the transgranular dimple fracture.