Understanding of surface segregation of Cu and Zn on nano Si precipitates to the mechanical property improvement of high pressure die casting Al9Si3CuFe alloy

• Published in: Journal of alloys and compounds 2022-02, Vol.895, p.162219, Article 162219
• Main Authors: Zhang, Yijie, Wang, Shihao, Lordan, Ewan, Dou, Kun, Zhou, Xiaorong, Hashimoto, Teruo
• Format: Article
• Language: English
• Subjects: Aging (metallurgy); Al alloys; Aluminum base alloys; Chemical precipitation; Copper; Die casting; Heat treating; High pressure; high pressure die casting; Mechanical properties; mechanical property; Precipitates; Precipitation heat treatment; Scanning transmission electron microscopy; Si precipitate; Silicon; Zinc
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.162219

To understand Si precipitation and its influence on mechanical property improvement in high pressure die casting (HPDC) Al9Si3CuFe alloy under direct ageing heat treatment, the precipitates in Al9Si3CuFe alloy containing in-situ MgAl2O4 particles is analyzed via atomic-resolution scanning transmission electron microscopy. It is shown that lath-like Si precipitates form in an average size of 50 nm in length, and a good orientation relationship of {010} Al//{111}Si is observed between Si precipitate and matrix. Interestingly, Cu and Zn are observed to segregate onto Si/Al interface, which has a coarsening resisting effect on precipitate growth. The presence of these Si precipitates is the main factor contributing to the further improvement of mechanical properties of Al9Si3CuFe alloy, which results in an increase of 70 MPa in yield strength compared to the alloy without Si precipitates. •Cu and Zn are observed to segregate onto Si/Al interface.•The segregation has a coarsening resisting effect on Si precipitate growth.•The presence of Si precipitates results in a further improvement of 70 MPa in yield strength.