Low strength is the key factor that keeps Mg-Li alloys from further applications. Herein, a Mg-6Li-3Al-0.4Ce alloy fabricated via rotary swaging exhibits an ultimate tensile strength of 411 MPa, yield strength of 335 MPa, uniform elongation of 11 %, and specific strength of 258 kN·m·kg-1, respectively. The high yield strength is attributed to the dislocations, twins, and stacking faults (SFs) strengthening contributions. The interactions between the twin and grain boundary enhance the strain-hardening capacity. Moreover, the dislocations and soft β-Li phase with sufficient slip systems can effectively relax the stress concentration induced by twin-twin interactions, and therefore improve the ductility.

The dual-phase Mg-9Li-1Zn-2Gd-1.2Mn alloys were prepared by traditional hot extrusion at 200 °C, 250 °C, and 300 °C, respectively. The microstructure of as-extruded Mg-9Li-1Zn-2Gd-1.2Mn alloy is remarkably refined, and the mechanical properties are significantly improved compared with the as-cast alloy. The Mg-9Li-1Zn-2Gd-1.2Mn alloy extruded at 200 °C exhibits the best comprehensive mechanical properties among the alloys with the yield strength (YS), ultimate tensile strength (UTS), and elongation to failure (εef) are 141 MPa, 166 MPa, and 57%, respectively. The dispersed second phases and Zn segregation along the grain boundary inhibit the growth of recrystallized grains and reduce the grain size, contributing to high ductility. Then, the unstable stacking fault energy of {0001}<11 2‾ 0> slip system (γusf(basal)) and surface energy of {0001} plane (γs(basal)) in Mg and Mg-Li-Gd-Zn supercells are characterized by first-principles calculation. The results indicated that the value of γusf(basal) decreased from 259 mJ/m2 to 249 mJ/m2, while the value of γs(basal) increased from 537 mJ/m2 to 597 mJ/m2. The lower γusf(basal) promotes the initiation of basal slip and higher γs(basal) leads to a lower cracking tendency, revealing the ductility improvement by adding Li, Zn, and Gd elements. This work provides an effective strategy to prepare high-ductility Mg-Li alloys.

To improve the properties of as-rolled Mg–3Y alloy, the microstructure was tailored by annealing at the temperature of 250 °C, 300 °C, 350 °C and 400 °C for 1 h, respectively. With the increase of annealing temperature, the deformed grains were transformed to equiaxed grains and average grain size decreases from 24.3 μm to 8.6 μm first and then increases to 30.1 μm. The elongation of alloy increases from 0.9% to 27.3% whereas tensile strength gradually decreases. The test alloy annealing at 300 °C has the best comprehensive properties with the ultimate tensile strength (UTS) and elongation (EL) of 222.4 MPa and 17.1% respectively, combined with favorable corrosion resistance. The excellent properties are mainly attributed to the bimodal structure with coarse deformed grains and fine recrystallized grains in Mg–3Y alloy via annealing at the temperature of 300 °C. This work comprehensively tailors the microstructure-properties and helps for the design the lean Mg alloys with high strength-ductility synergy and good corrosion-resistant property.

The weakening of basal texture is beneficial to improve the formability and mechanical properties of deformed magnesium alloys. In this paper, the microstructure and texture evolution of single pass rolled Mg-1.1Mn-0.5Al alloys with various reduction of 10%-60% at 200 degrees C were observed to reveal twin variants selection and mediated dynamic recrystallization (DRX) mechanism. The results showed that the type and volume fraction of activated twins were strongly related to rolling reduction. Primary {1012} tensile twins (TTWs), which were mainly activated in the 10% reduction rolled alloys, were not sufficient to induce recrystallization due to the absence of cumulative dislocation and lower plastic strain energy. In contrast, {1011}/ {1013} compression twins (CTWs) and {1011} -{1012}/ {1013} -{1012} double twins (DTWs) were preferred for recrystallization because of higher dislocation accumulation and stored strain energy. The occurrence of DRX was beneficial to absorb stored energy, relax stress concentration and weaken basal texture in adjacent domains. Due to the sufficient stress provided by massive basal slip dislocations, the type I and type II DTWs were more commonly observed than the type III and type IV variants, which involved much more dissociations of the mixed dislocations in deformed magnesium alloys.(c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Optimizing the mechanical properties and damping capacity of the duplex-structured Mg-Li-Zn-Mn alloy by tailoring the microstructure via hot extrusion was investigated. The results show that the Mg-8Li-4Zn-1Mn alloy is mainly composed of α-Mg, β-Li, Mg-Li-Zn, and Mn phases. The microstructure of the test alloy is refined owing to dynamic recrystallization (DRX) during hot extrusion. After hot extrusion, the crushed precipitates are uniformly distributed in the test alloy. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of as-extruded alloy reach 156 MPa, 208 MPa, and 32.3%, respectively, which are much better than that of as-cast alloy. Furthermore, the as-extruded and as-cast alloys both exhibit superior damping capacities, with the damping capacity (Q−1) of 0.030 and 0.033 at the strain amplitude of 2 × 10−3, respectively. The mechanical properties of the test alloy can be significantly improved by hot extrusion, whereas the damping capacities have no noticeable change, which indicates that the duplex-structured Mg-Li alloys with appropriate mechanical properties and damping properties can be obtained by alloying and hot extrusion.

The industrial applications of Mg alloys are greatly limited by their trade-off of high strength and ductility. In this work, conventional extrusion and rotary swaging (RS) were applied to Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca (wt.%) alloy to obtain high strength-ductility synergy Mg alloys. The microstructure evolution and mechanical properties of as-extruded and as-swaged alloys at different (2, 6 and 10) RS passes were investigated. The results show that large quantity of dislocations occur in twin lamellae and original dynamic recrystallized (DRXed) grains after RS. Those dislocations promote the formation of low-angle grain boundaries (LAGBs) and subgrains. As the RS process continue, these subgrains transform into fine grains with high-angle grain boundaries (HAGBs), which result in grain refinement. Compared to the as-extruded alloys, the strength of as-swaged alloys increases significantly. The edge region of the as-swaged Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy after 10 passes exhibits comprehensive excellent mechanical performance with a yield strength (YS) of 403 MPa, an ultimate tensile strength (UTS) of 427 MPa and a fracture elongation (FE) of 9.1%. The high strength of as-swaged alloys is the results of the combination of dislocation strengthening, fine grain strengthening and dispersion strengthening. The deformed grains deflected to ED and the tensile twins produced during RS enhance the basal texture and reduce the plasticity of the alloy.

High-strength Mg–5Li-5.3Al-0.7Si alloys were prepared by applying a combination of conventional extrusion with an extrusion ratio of 25:1 at 320 °C and subsequent rotary swaging (RS) with 0.2 mm reduction per pass in diameter at room temperature. The microstructural evolution was characterized and mechanical properties were investigated by tensile tests. The EBSD results showed that the grain size of the alloy decreased remarkably after extrusion and RS. Meanwhile, the yield strength (YS) of the as-extruded alloy was significantly improved from 161 MPa to 301 MPa by 2 passes RS, with only a slight reduction in ductility. The grain refinement during RS should be attributed to the activation of twins and continuous dynamic recrystallization (CDRX). The texture evolution during RS was investigated by EBSD. The number of grains with <0001> parallel to extrusion direction (ED) decrease significantly after RS. These grains are subjected to multi-directional stress and deformation, which rotate and develop a stronger texture component with <101‾0> - <112‾0> parallel to ED during RS, leading to the optimization of grain orientation. The phase evolution was investigated by SEM, EDS and TEM. Extrusion and RS effectively crush and disperse the second-phase particles of Mg2Si and Al0.89Li0.11, leading to their homogenization and refinement. The main mechanisms for strengthening the as-swaged alloy include grain refinement strengthening, dislocation strengthening, and second-phase strengthening. Grain refinement strengthening plays a dominant role in the as-swaged alloy.

The extruded Mg-6Li-4Zn-xMn(x=0,0.4,0.8,1.2 wt％)alloys were prepared,and the microstructure of the test alloys was investigated by optical microscopy,scanning electron microscopy and transmission electron microscopy.The corrosion prop-erties were determined by electrochemical measurements and immersion measurements in 3.5％NaCl solution.The results indicate that the extruded Mg-6Li-4Zn-xMn alloys are mainly composed of α-Mg phase,β-Li phase,Mn precipitates and some intermetallic compounds(MgLi2Zn).With the addition of Mn,stable corrosion products were formed on the surface of the test alloy,which can effectively inhibit further corrosion progress and improve the corrosion resistance.Mg-6Li-4Zn-1.2Mn alloy exhibits the best corrosion resistance,attributed to grain refinement,the improvement of the stability of corrosion product film and uniform distribution of fine second phases.