Tailoring strength and ductility of Mg97Y2Zn1 alloy through the architecture of heterogeneous lamellar structure by large-ratio hot extrusion

In this study, a heterogeneous lamellar structure is achieved in Mg97Y2Zn1 alloy via large-ratio hot extrusion of the alloys in as-cast (CE) and as-annealed (AE) stages. The ultimate tensile strength (UTS) of CE and AE alloys is 426.5 and 471.4 MPa, and their fracture elongation (FE) is 8.1% and 1.0%, respectively. Mechanical properties of the CE and AE alloys exceed that of the majority of wrought Mg97Y2Zn1 alloys due to the heterostructure induced strengthening. Both in the two extruded alloys, <<-Mg layers and LPSO layers acting as soft and hard domains, respectively, constitute the heterogeneous lamellar structure. As a result of the narrower spacing of <<-Mg and LPSO layers, more refined DRX grains and LPSO particles, and the increased volume fraction of LPSO phase, the strength of the AE alloy is higher than that of CE alloy. However, the AE alloy exhibits poor ductility owing to the easy aggregation of dislocations and stress at the interfaces of narrower layers. Based on discussion of the strengthening mechanisms, the preparation of Mg97Y2Zn1 alloys with tailored mechanical properties of high UTS ranging from 420 to 480 MPa, and FE 1 similar to 8%, could be realized via the combination of annealing (controlling the content of 14H phase) and large-ratio hot ex-trusion (promoting the formation of heterogeneous lamellar structure).(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

A heterogeneous lamellar structure is achieved in Mg97Y2Zn1 alloy through large-ratio hot extrusion, resulting in improved mechanical properties compared to other Mg97Y2Zn1 alloys. The alloys in as-cast and as-annealed stages have ultimate tensile strengths of 426.5 and 471.4 MPa, and fracture elongations of 8.1% and 1.0% respectively. The increased strength in the as-annealed alloy is attributed to narrower spacing of <<-Mg and LPSO layers, refined DRX grains and LPSO particles, and a higher volume fraction of LPSO phase. However, the as-annealed alloy has poor ductility due to the easy aggregation of dislocations and stress in the narrower layers. It is suggested that tailored mechanical properties can be achieved through annealing and large-ratio hot extrusion.