Enhancing creep formability and comprehensive property in Al–Mg–Si alloy by combinatorial pre-ageing and large pre-deformation

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 826; p. 141967
• Main Authors: Chen, Kailiang, Liu, Chunhui, Ma, Peipei, Yang, Jianshi, Zhan, Lihua, Huang, Minghui, Hu, Jianhua
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 05.10.2021; Elsevier BV
• Subjects: Aging (natural); Aluminum base alloys; Al–Mg–Si alloy; Chemical precipitation; Cold; Cold rolling; Cold working; Combinatorial analysis; Corrosion resistance; Creep forming; Creep strength; Deformation; Dislocation; Dislocation density; Ductility; Formability; Grain boundaries; Magnesium; Metallurgy; Precipitation; Predeformation; Silicon; Creep forming; Precipitation; Al–Mg–Si alloy; Cold-rolling; Dislocation
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2021.141967

A thermal-mechanical route proceeding by pre-ageing and heavy cold-rolling has been developed to significantly improve both the creep formability and comprehensive properties in an Al–Mg–Si alloy. The uniform creep deformation increases by 2–5 times and the strength enhances by 60–140 MPa without sacrificing ductility compared to the conventional treatment. The pre-ageing at 180 °C could tune the density, mobility and distribution of the dislocations generated during cold-rolling. A physical metallurgical picture of the pre-ageing-dependent creep ageing in the cold-worked Al–Mg–Si alloy is established based on complementary transmission electron microscopy, differential scanning calorimetry and X-ray diffraction. Concurrent solutes precipitation and dislocation recovery contribute to the exceptional creep ageing response in the heavily cold-deformed Al–Mg–Si alloy. The high density dislocations could substantially promote the creep deformation and improve the strength-ductility balance. The fragmentation of grains and the inhibition of continuous precipitation along the grain boundary lead to a superior resistance to inter-granular corrosion. Our results demonstrate the application potential of solutes precipitation control before large pre-deformation in creep age forming of Al alloy components with unusual figures of merit. •Combined pre-ageing and large pre-deformation is proposed to improve creep-ageing.•Pre-ageing at 180 °C renders larger enhancement in both creep strain and strength.•The fundamental modification of the microstructure evolution is revealed in detail.•The high dislocation density determines the enhanced creep formability and property.