Microstructural Evolution and Mechanical Properties of As‐Cast and As‐Extruded Mg–14Li Alloy with Different Zn/Y and Zn/Gd Addition

Abstract

Magnesium-lithium alloy is the lightest metal engineering material, which possesses broad applications in the domains of aviation industries and military affairs because of its remarkable advantages, such as perfect electromagnetic shielding, damping properties, and superhigh specific stiffness and strength. Among those significant superiorities, its lower density is the most brilliant feature, which is 1/4-1/3 lighter than that of ordinary magnesium alloys, and almost 1/2 of aluminum alloys. [1-5] In addition, there exists an interest and important structure transformation from hexagonal close-packed (hcp) to bodycentered cubic (bcc) with the increasing Li content in binary Mg-Li alloys, which can reduce the crystal parameter (c/a ratio) of α-Mg and activate more non-basal slip systems. When the mass fraction of Li contents is more than 5.7 wt%, Mg-Li alloy presents a typical duplex-phase structure, which consists of α-Mg (hcp) and β-Li (bcc) phases. Moreover, when Li contents exceed 10.3 wt%, the microstructure of the alloy will be transformed from the duplex phase (α þ β) to single phase (β). [6-12] LA141 (Mg-14Li-1Al) is a kind of superlight alloy (1.333 g cm À3) among the commercial Mg-Li alloys. However, its wide uses are limited by existing problems involving low strength, weak anti-corrosion, and worse age hardening stability. Therefore, it has great significance to improve the performance of the superlight Mg-14Li-based alloy. [13-16] Optimal alloying addition might offer an attractive alternative. Shechtman was the first to discover quasicrystals in magnesium alloys in 1984. The atomic arrangement of quasicrystals is quite different from that of traditional crystals and amorphous alloys, which can significantly improve the comprehensive properties of magnesium alloys. [17-23] In recent years, the idea of quasicrystalline strengthening has been used for reference in the study of Mg-Li alloys. The addition of rare earth elements (RE), such as Y and Gd, to Mg-Li-Zn alloys can produce quasicrystalline strengthening phases with hightemperature stability and other kinds of mesophase strengthening matrices. In addition, Y and Gd have relatively higher solid solubility in the α-Mg matrix. [24] However, there are few reports about the strengthening effect of Zn/Y and Zn/Gd addition on Mg-Li alloy with single β-Li phase. Accordingly, elements Zn, Y, and Gd were added to the chosen Mg-14Li-based alloy. Therefore, Mg-14Li-2Zn-1Y (named LZY1421), Mg-14Li-3Zn-1Y (named LZY1431), Mg-14Li-6Zn-2Y (named LZY1462) and Mg-14Li-2Zn-1Gd (named LZG1421), Mg-14Li-3Zn-1Gd (named LZG1431), Mg-14Li-6Zn-2Gd (named LZG1462) alloys were prepared as

Ultra-high strength Mg-Li alloy with B2 particles and spinodal decomposition zones

“…For example, in the Mg-Li- x Al system, the solid solution decomposes into a DO 3 structure and spinodal decomposition zone [ 11 , 12 ]. Zn is the most commonly used alloying element, which has high solid solubility and exhibits a remarkable solid solution strengthening effect in Mg-Li alloys [13] , [14] , [15] . The addition of Zn should also change the free energy of the Mg-Li system, destroy the stability, promote solid solution decomposition and produce a microstructure that can strengthen the matrix.…”

High‐Cycle Fatigue Behavior of Deep Cryogenic–Elevated Temperature Cycling Treated Sand‐Cast Mg–6Gd–3Y–0.5Zr Alloy

“…Due to the low density, good machinability, high specific strength, and good damping capacity, magnesium alloys have received widespread attention as a recyclable structural material in the automotive and aerospace fields. [1][2][3][4] Compared with conventional aluminum and magnesium alloys, Mg-Gd-Y alloys have been reported to exhibit higher strength not only at ambient temperature, but also at elevated temperature and to display remarkable corrosion resistance and creep resistance. [5][6][7][8] Recently, abundant works have been conducted in relation to the Mg-Gd-Y system.…”