Magnesium alloys are characterized by their low density (approximately 1.8 g/cm 3 for magnesium alloys), high strength, large modulus of elasticity, good heat dissipation, good shock absorption, greater ability to withstand impact load than aluminum alloys, good corrosion resistance to organic matter and alkalinity. According to the statistical analysis of literature data collected by Web of Science Core Collection, it can be found that the growth rate of publications on magnesium alloy during 2008-2018 is significantly higher than the overall growth rate of alloy research papers. In the past 11 years, the Web of Science Core Collection has collected 21,440 papers on magnesium alloys, averaging nearly 2000 papers annually, of which 2768 papers were collected in 2018, an increase of 206% over 2008, accounting for more than one fifth of the total literature on alloy research. Magnesium alloys have become an important lightweight metallic structural material and have been widely studied worldwide. As the only journal focusing on magnesium alloy research which devoted to the coverage and dissemination of global research on magnesium alloys. This article statistically analyzes all the academic articles published by Journal of Magnesium and Alloys (JMA) from 2013 to 2018 and compares them with all the articles containing magnesium alloy in their titles on the Web of Science during this period. The development trends of magnesium alloys are summarized based on these articles, and the influence and academic value of the articles published by JMA are summarized as well. This paper hopes to better realize the value of JMA, help better spread the academic research of magnesium alloys, and promote the development of global magnesium alloy research. (C) 2019 Published by Elsevier B.V. on behalf of Chongqing University.

Research on magnesium alloys continues to attract great attention, with more than 3000 papers on magnesium and magnesium alloys published and indexed in SCI in 2020 alone. The results of bibliometric analyses show that microstructure control and mechanical properties of Mg alloys are continuously the main research focus, and the corrosion and protection of Mg alloys are still widely concerned. The emerging research hot spots are mainly on functional magnesium materials, such as Mg ion batteries, hydrogen storage Mg materials, and bio-magnesium alloys. Great contributions to the research and development of magnesium alloys in 2020 have been made by Chongqing University, Chinese Academy of Sciences, Central South University, Shanghai Jiaotong University, Northeastern University, Helmholtz Zen-trum Geesthacht, etc. The directions for future research are suggested, including: 1) the synergistic control of microstructures to achieve high-performance magnesium alloys with concurrent high strength and superior plasticity along with high corrosion resistance and low cost; 2) further development of functional magnesium materials such as Mg batteries, hydrogen storage Mg materials, structural-functional materials and bio-magnesium materials; 3) studies on the effective corrosion protection and control of degradation rate of magnesium alloys; 4) further improvement of advanced processing technology on Mg alloys. (C) 2021 Chongqing University. Publishing services provided by Elsevier B.V.

Laser additive manufacturing is widely recognized to be an effective method to form complicated and custom metallic components. The existing research on metal additive manufacturing utilizes traditional alloy grades, which are designed based on the assumption that solidification occurs at equilibrium; thus, these materials are not well suited to the nonequilibrium metallurgical dynamics that are present in additive manufacturing techniques. Common issues, such as high crack susceptibility, low toughness, and low fatigue capability, as well as anisotropy, frequently occur during the fabrication of additively manufactured metallic parts. It is therefore necessary to conduct research on the design of new materials designed specifically for laser additive manufacturing in order to fully realize the potential advantages and value of the ultrafast solidification conditions. In this article, the technical bottlenecks, material design methods, and the development of new materials that are applicable to laser additively manufactured metal materials are reviewed; these materials include aluminum alloys, titanium alloys, iron-based alloys, and magnesium alloys. Finally, the potential future direction of research related to laser metal additive manufacturing is discussed.

Mg alloys are attractive in the fields of aerospace, automotive, and biomedical engineering, owing to the advantages of light weight, high specific strength, excellent damping property, good biocompatibility, and in vivo degradable property. However, conventional methods for manufacturing Mg alloys, such as casting and deformation processing, yield low-quality large-scale monolithic and complex structures, which hinder the applications of Mg parts. Additive manufacturing (AM) is a burgeoning alternative to manufacture monolithic parts through layer-by-layer deposition of metallic materials using 3D model data. In this paper, the latest research progress in AM of Mg alloys, which focuses on technological processes and influencing factors, macro and microstructures, mechanical properties, and corrosion properties of parts manufactured primarily by selective laser melting (SLM) and wire and arc AM (WAAM), are comprehensively reviewed. Currently, additively manufactured Mg parts with a relative density > 99% have been achievable through both SLM and WAAM after process optimization, and their mechanical properties and corrosion resistance have been comparable to those of casting and wrought parts, indicating a great potential for engineering applications. Finally, the future development trend and research direction of AM of Mg alloys are proposed from the perspectives of materials design, process improvement, and performance evaluation.

镁合金具有轻质、比强度高、阻尼减振、生物相容性好、体内可降解等优点，在航空航天、汽车轻量化、生物医疗等领域应用潜力巨大。然而传统的镁合金铸造成形和变形加工技术在制备一体化复杂结构件上具有一定的局限性，制约了镁合金在上述领域的应用普及。增材制造是一种根据三维模型数据逐层熔化沉积的先进技术，有望成为镁合金复杂构件制备的重要技术途径。本文概述了近年来增材制造镁合金的研究进展，重点对选区激光熔化(SLM)和电弧增材制造(WAAM) 2种主要增材制造的工艺研发现状和影响因素、微观组织、力学性能及耐蚀行为进行分析与总结。研究表明，工艺优化后SLM和WAAM等技术均可获得致密度> 99%的镁合金试件，并且能够获得与传统制造镁合金相当的力学性能和耐蚀性能，增材制造镁合金表现出极大的工程应用潜力。最后，从材料优化、工艺改进及性能评价等方面对增材制造在镁合金中的未来发展趋势与研究方向进行了总结与展望。

In this work, the microstructure and tensile properties of DD32 single-crystal (SC) superalloy repaired by laser metal forming (LMF) using pulsed laser have been studied in detail. The microstructures of the deposited samples and the tensile-ruptured samples were characterized by optical microscopy (OM), transmission electron microscope (TEM) and scanning electron microscope (SEM). Due to high cooling rate, the primary dendrite spacing in the deposited area (17.2 μm) was apparently smaller than that in the substrate area (307 μm), and the carbides in the deposited samples were also smaller compared with that in the substrate area. The formation of (γ+γ′) eutectic in the initial layer of repaired SC was inhibited because of the high cooling rate. As the deposition proceeded, the cooling rate decreased, and the (γ+γ′) eutectic increased gradually. The (γ+γ′) eutectic at heat-affected zone (HAZ) in the molten pool dissolved partly because of the high temperature at HAZ, but there were still residual eutectics. Tensile test results showed that tensile behavior of repaired SC at different temperatures was closely related to the MC carbides, solidification porosity, γ′ phase, and (γ+γ′) eutectic. At moderate temperature, the samples tested fractured preferentially at the substrate area due to the fragmentation of the coarse MC carbide in the substrate area. At elevated temperature, the (γ+γ′) eutectic and solidification porosity in the deposited area became the source of cracks, which deteriorated the high-temperature properties and made the samples rupture at the deposited area preferentially.

Selective laser melting (SLM) additive manufacturing technology holds the broad prospect for the preparation of high-performance complex metal components owing to its high processing accuracy, short manufacturing cycle, and high material usage. Magnesium (Mg) alloys are the lightest metal structural material and provide the benefits of low density, substantial specific strength and specific stiffness, good damping and shock absorption performance, and good biodegradability. Thus, it is worthwhile to employ SLM to manufacture Mg alloys, which is predicted to widen the application scope of Mg alloys. In this study, a comprehensive review on SLM of Mg alloys focusing on the preparation of Mg alloy powders, SLM process parameters, metallurgical defects, microstructure and mechanical properties of the as-built state, post-processing, and special equipment developed for SLM of Mg alloys is given. Finally, the future development trends of the SLM of Mg alloys are explored.

选区激光熔化(SLM)增材制造技术由于其加工精度高、制造周期短、材料利用率高等优点，在制备高性能复杂金属构件方面具有广阔的应用前景。镁合金是最轻的金属结构材料，具有密度低、比强度和比刚度高、阻尼减震性能好、生物降解性良好等优点。因此，采用SLM技术制备镁合金具有重要的研究价值，有望拓宽镁合金的应用范围。本文针对镁合金SLM增材制造技术，详细介绍了镁合金粉末制备、SLM工艺参数、冶金缺陷、SLM态的显微组织和力学性能、后处理、镁合金专用SLM设备方面的研究进展，并展望了未来镁合金SLM研究的发展方向。

Commercial purity as-cast magnesium was hot rolled and subsequently annealed at different temperatures in order to investigate its grain growth behavior and link it to the texture evolution. Annealing at an intermediate temperature of 220 °C gave rise to abnormal grain growth with a few grains reaching a grain diameter 10 times larger than the mean. Increasing the annealing temperature to 350 °C yielded normal grain growth. Both types of grain growth revealed a strengthening of the (0001) <$11\overline{2}0$> texture component. It is hypothesized that a dislocation density gradient after recrystallization grants (0001) <$11\overline{2}0$> grains a size advantage during early stages of growth. The type of growth will be, however, determined by the mobility of the present grain boundaries and triple junction drag, which are strongly dependent on the annealing temperature. The above hypothesis of the interplay between these parameters was explored through curvature- and residual dislocation-density-gradient-driven grain growth simulations using a formerly developed level-set approach. The simulation outcome suggests that application of such a modeling approach in microstructure studies of magnesium can provide valuable new insights into the problem of grain growth and associated texture evolution.

This study investigates the effects of fine and coarse undissolved particles in a billet of the Mg-7Sn-1Al-1Zn (TAZ711) alloy on the dynamic recrystallization (DRX) behavior during hot extrusion at low and high temperatures and the resultant microstructure and mechanical properties of the alloy. To this end, partially homogenized (PH) and fully homogenized (FH) billets are extruded at temperatures of 250 and 450 °C. The PH billet contains fine and coarse undissolved Mg2Sn particles in the interdendritic region and along the grain boundaries, respectively. The fine particles (<1 μm in size) retard DRX during extrusion at 250 °C via the Zener pinning effect, and this retardation causes a decrease in the area fraction of dynamically recrystallized (DRXed) grains of the extruded alloy. In addition, the inhomogeneous distribution of fine particles in the PH billet leads to the formation of a bimodal DRXed grain structure with excessively grown grains in particle-scarce regions. In contrast, in the FH billet, numerous nanosized Mg2Sn precipitates are formed throughout the material during extrusion at 250 °C, which, in turn, leads to the formation of small, uniform DRXed grains by the grain-boundary pinning effect of the precipitates. When the PH billet is extruded at the high temperature of 450 °C, the retardation effect of the fine particles on DRX is weakened by their dissolution in the α-Mg matrix and the increased extent of thermally activated grain-boundary migration. In contrast, the coarse Mg2Sn particles in the billet promote DRX during extrusion through the particle-stimulated nucleation phenomenon, which results in an increase in the area fraction of DRXed grains. At both low and high extrusion temperatures, the extruded material fabricated using the PH billet, which contains both fine and coarse undissolved particles, has a lower tensile strength than that fabricated using the FH billet, which is virtually devoid of second-phase particles. This lower strength of the former is attributed mainly to the larger grains and/or absence of nanosized M2Sn precipitates in it.