고압비틀림 공정 처리된 Al7068 합금의 기계적 특성 및 미세조직 변화

• Published in: 대한금속·재료학회지, 61(1) Vol. 61; no. 1; pp. 1 - 8
• Main Authors: 오주희, Juhee Oh, 손수정, Sujung Son, 김형섭, Hyoung Seop Kim, 설재복, Jae Bok Seol, 성효경, Hyokyung Sung, 김정기, Jung Gi Kim
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 05.01.2023; 대한금속·재료학회
• Subjects: aluminum alloy; high-pressure torsion; mechanical property; microstructure; 재료공학
• ISSN: 1738-8228; 2288-8241

The combination of severe plastic deformation, deformational heat, and frictional heat generated during the high-pressure torsion process has a great effect on microstructural evolutions, including grain refinement, dynamic recrystallization and recovery. In particular, the low melting temperature metallic alloys (e.g., aluminum and magnesium) also induce nano-precipitations in the matrix during high-pressure torsion, which results in both unique microstructure and mechanical properties of the nanocrystalline metallic materials. In this study, the mechanical properties and microstructural evolution of high-pressure torsionprocessed aluminum 7068 alloy at room temperature were investigated. In the early deformation stage, both grain refinement and nano-precipitates were formed that increase the strength of ultrafine-grained aluminum alloy, and a maximum strength of 844 MPa was obtained for the 5T sample. However, in the later deformation stage, tensile strength decreases with the increase in shear strain due to grain growth, and coarse precipitates act as crack initiation sites during plastic deformation. In summary, the mechanical properties of highpressure torsion represent the strength-ductility trade-off as the increase of the number of revolutions. Their mechanical properties are superior to those of recent severe plastic deformation-processed aluminum alloys. This result shows that the severe plastic deformation of the HPT process positively contributes to their mechanical properties by inducing multiple strengthening paths, such as grain refinement and nanoprecipitation of the aluminum alloy. (Received 11 July, 2022; Accepted 4 October, 2022)