First-principles calculation of interface binding strength and fracture performance of β’/Al interface in Al–Mg–Si–Cu alloy

• Published in: Journal of alloys and compounds Vol. 830; p. 154515
• Main Authors: Chen, Bao, Zhang, Chuan-Hui, Jin, Ying
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.07.2020; Elsevier BV
• Subjects: Alloys; Aluminum base alloys; Atomic structure; Binding strength; Bonding strength; Charge transfer; Copper; Electronic structure; First principles; Fracture toughness; Griffith fracture; Griffith Irwin fracture; High strength alloys; Interface; Magnesium; Mathematical analysis; Mechanical properties; Mg9Si5 precipitate; Orientation relationship; Orientation relationships; Silicon; Griffith fracture; Orientation relationship; Binding strength; Mg9Si5 precipitate; Interface
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.154515

High strength and high toughness are the key requirements of Al–Mg–Si (6xxx) alloys, and the performance of the precipitate phase directly affect the mechanical properties of the alloys. Among them, the β’ (Mg9Si5) precipitate has the strengthening effect for Al–Mg–Si alloy which has not been systematically studied. Therefore, we explore the essential mechanism of simultaneously enhancing the mechanical strength and fracture resistance of alloy from the perspective of two kinds of orientation relationships (ORs) precipitate/matrix by using density functional method. In this study, we obtain the thermodynamically stable interface structures by the calculation of adhesion work and interface energy. By analyzing the micro-structure and bond charge transfer at the interface, it is found that the Si–Al bond and the Mg–Al bond play a key role in interfacial bind strength and toughness, respectively. Based on the Griffith fracture theory, we point out that the initial fracture in the alloy is related to the element composition ratio, and β′ will not trigger fracture preferentially. An in-depth analysis of the electronic structure of atoms at β’/Al interface indicates that the difference between Si–Al bond and Mg–Al bond interactions mainly lies in the decomposition of bond strength and orbital hybridization. This research extends our knowledge of improving the strength and toughness of Al–Mg–Si alloy. •The essential mechanism of simultaneously enhancing the mechanical strength and fracture resistance of alloy were explored.•The Si-Al bond and the Mg-Al bond play a key role in interfacial bind strength and toughness, respectively.•The initial fracture of alloy is related to the element composition ratio, and β’ will not trigger fracture preferentially.