Fatigue strength and microstructure evaluation of Al 7050 alloy wires recycled by spray forming, extrusion and rotary swaging

Author(s)

de Salvo, Joao G. J. ^{[1, 2]} ; Afonso, Conrado R. M. ^[3]

Affiliation

^[1] Univ Fed Sao Carlos UFSCar, Programa Posgrad Ciencia & Engn Mat PPG CEM, Rod Washington Luiz, Km 235, BR-13565905 Sao Carlos, SP - Brazil

^[2] CTA, Div Mat, Inst Aeronaut & Espaco, Praca Marechal Eduardo Gomes 50, BR-12228904 Sao Jose Dos Campos, SP - Brazil

^[3] Univ Fed Sao Carlos USFCar, Dept Engn Mat DEMa, Rod Washington Luiz, Km 235, BR-13565905 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA; v. 30, n. 12, p. 3195-3209, DEC 2020.
• Web of Science Citations: 0

Abstract

Recycled high-strength aluminum alloys have limited use as structural materials due to poor mechanical properties. Spray forming remelting followed by hot extrusion is a promising route for reprocessing 7xxx alloys. The 7050 alloy machining chips were spray formed, hot extruded, rotary swaged and heat-treated in order to improve mechanical properties. Microstructures, tensile properties and fatigue strength results for a 2.7 mm-diameter recycled wire are presented. Secondary phases and precipitates were investigated by XRD, SEM, EBSD, TEM and DSC. As-swaged and heat-treated (solution and aging) conditions were evaluated. Mechanical properties of both conditions outperformed AA7050 aerospace specification. Substantial grain refinement resulted from the extensive plastic deformation imposed by rotary swaging. Refined micrometric and sub-micrometric A1 grains, as well as coarse and fine intermetallic precipitates were observed. Subsequent solution treatment resulted in a homogeneous, recrystallized and equiaxed microstructure with grain size of 9 mu m. Nanoscale GP(I) zones and eta' phase precipitates formed after aging at 120 degrees C, imparting higher tensile (586 MPa) and fatigue (198 MPa) strengths. (AU)

• FAPESP's process: 13/05987-8 - Processing and characterization of amorphous, metastable and nano-structured metallic alloys
• Grantee: Claudio Shyinti Kiminami
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 15/19978-6 - Advanced characterization through TEM of FIB prepared samples of nanocrystalline alloy coatings produced by thermal spray and laser cladding
• Grantee: Conrado Ramos Moreira Afonso
• Support Opportunities: Scholarships abroad - Research