Study of improvement of an aluminium alloy used in the aeronautical industry

• Autor(a) principal: Oliveira, João Lima
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/31244
• topic: Aeronautics; Aluminium alloy; Asymmetric rolling; Mechanical response; Crystallographic texture

The aeronautics industry is increasingly investing in the development of new materials that meet the high-performance requirements of this area. These developments are associated with a pursuit for more economical solutions. This work studies the possibility of improvement of the AA6061 aluminium alloy through asymmetric rolling processes and heat treatments. The effect of the various types of rolling (conventional and asymmetric), as well as other parameters of this process, is explored. Previously recrystallized samples are subjected to different ratios of the roll’s velocities (1, 3 and 1.36), thickness reduction per pass (20% and 50%) and forming routes (conventional, asymmetric continuous and asymmetric reverse). The mechanical properties and crystallographic texture of the samples were analysed in order to correlate the results obtained with the different process conditions. Data were obtained through hardness and uniaxial tensile tests, and EBSD analysis. After rolling and annealing, significant increases in hardness were observed in the samples. All samples show a large increase of yield and ultimate tensile stress, while the formability drastically decreases, being more pronounced for sample processed with a 50% rate reduction of thickness. The EBSD analysis reveals a formation of copper {112} <111>, shear 1 {001}〈110〉 and shear 2 {111}〈112〉 texture components which contribute to the increase of mechanical strength. It is concluded that the mechanical properties of this aluminium alloy can be enhanced originating strength values higher than the AA6061-T6 alloy. The limitations regarding the reduced material formability can be reviewed in the future by applying new heat treatments.