EXTENDED ABSTRACT: A high strength can be achieved in Mg alloys by conventional ultrafine-grains. However, it mightcause the tradeoff of corrosion resistance due to inclusion of a large number of non-equilibrium grain boundaries. The thick and low-density twin lamellas prepared by the traditional technology limited the improvement of strength. Therefore, preparation of dense ultraffne twins has become a critical bottleneck problem for twin-induced strengthening in magnesium alloy. In this study, a new technology of multi-pass and multi-directional cross compression with recycling of low strain and high strain is proposed, which exploits the change of strain path to promote the nucleation of twins and recycling of strains to inhibit the detwinning. An ultrafine grain structure (average grain size ~300 nm) consisting of dense ultrafine twins (average lamellar spacing ~200 nm) is prepared, giving a high yielding strength up to 469 MPa, which is comparable to that of many Mg alloys with a high content of rare-earth elements, which offers a new idea for producing high-strength magnesium alloys at low cost.The dense ultrafine twins not only greatly improve the strength, but also alter both the morphology and distribution of precipitates, which inhibits severe localized corrosion and decreases the corrosion rate by one order of magnitude. This technique has a high commercial viability as it can be readily implemented in industrial production. In addition, the study also mentions that alloy composition design and heat treatment were employed to improve the negative effects of natural aging in Al alloys. Currently, this technology is being used in cooperative enterprises, which brings enormous economic beneffts.

Keywords: Mg alloys; Twins; Mechanical and Corrosion properties

REFERENCES:

[1]Changjian Yan, et al. Nat. Commun., 12(1), (2021)4616;

[2]Yongquan Liu, et al. J. Mater. Res. Technol., 31, (2024)2972-2984.