In the past two years, significant progresses have been achieved in high-performance cast and wrought magnesium and magnesium alloys, magnesium-based composites, advanced cast technologies, advanced ...processing technologies, and functional magnesium materials, such as Mg ion batteries, hydrogen storage Mg materials, bio-magnesium alloys, etc. Great contributions to the development of new magnesium alloys and their processing technologies have been made by Chongqing University, Shanghai Jiaotong University, Chinese Academy of Sciences, Helmholtz Zentrum Geesthacht, Queensland University, Brunel University, etc. This review paper is aimed to summarize the latest important advances in cast magnesium alloys, wrought magnesium alloys and functional magnesium materials worldwide in 2018–2019, including both the development of new materials and the innovation of their processing technologies. Based on the issues and challenges identified here, some future research directions are suggested, including further development of high-performance magnesium alloys having high strength and superior plasticity together with high corrosion resistance and low cost, and fundamental research on the phase diagram, diffusion, precipitation, etc., as well as the development of advanced welding and joining technology.
Covalent organic frameworks (COFs) hold great promise in molecular separations owing to their robust, ordered and tunable porous network structures. Currently, the pore size of COFs is usually much ...larger than most small molecules. Meanwhile, the weak interlamellar interaction between COF nanosheets impedes the preparation of defect-free membranes. Herein, we report a series of COF membranes through a mixed-dimensional assembly of 2D COF nanosheets and 1D cellulose nanofibers (CNFs). The pore size of 0.45-1.0 nm is acquired from the sheltering effect of CNFs, rendering membranes precise molecular sieving ability, besides the multiple interactions between COFs and CNFs elevate membrane stability. Accordingly, the membranes exhibit a flux of 8.53 kg m
h
with a separation factor of 3876 for n-butanol dehydration, and high permeance of 42.8 L m
h
bar
with a rejection of 96.8% for Na
SO
removal. Our mixed-dimensional design may inspire the fabrication and application of COF membranes.
The research and development status of casting magnesium alloys including the commercial casting alloys and the new types casting alloys are reviewed,with more attention to microstructure and ...mechanical properties of modified-AZ91,AM60 and WE43 alloys with various additions,and new types of low cost casting alloys and high strength casting alloys.The modification and/or refinement of Mg2 Si phase in Mg-Al-Si based casting alloys by various additions are discussed and new purifying technologies for casting magnesium alloys are introduced to improve the performance.The modified AZ81 alloy with reduced impurities is found to have the tensile strength of 280 ± 6 MPa and elongation of 16% ± 0.7%.The fatigue strength of AZ91 D alloy could be obviously improved by addition of Ce and Nd.The Mg-16Gd-2Ag-0.3Zr alloy exhibits very high tensile and yield strengths（UTS：423 MPa and YS：328 MPa）;however,its elongation still needs to be improved.
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 Zentrum 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.
Magnesium (Mg) alloys, as one of the lightest structural metallic materials, have attracted considerable attention in the automotive, aerospace, and microelectronic industries. However, wrought Mg ...alloys are easy to form a strong basal texture with the basal planes of hexagonal close-packed unit cells being parallel to the processing direction during hot processing. This extremely deteriorates the stretch formability of Mg alloy sheets at room temperature (RT) and limits their widespread industrial applications. To overcome this drawback, many studies have been devoted to controlling microstructures including grain sizes, texture characteristics and precipitates to achieve high-performance Mg alloy sheets via alloying and new processing techniques. In this review, we briefly summarize recent advances in enhancing the stretch formability of Mg alloy sheets at RT from two major aspects: (1) by the design of new alloy systems and (2) by the exploitation of advanced processing techniques. Both strategies hold great promise for developing high-performance and low-cost Mg alloy sheets with a superior combination of strength, ductility and stretch formability. Additionally, future research directions for the development of such high-performance Mg alloy sheets are suggested. We hope that this review can provide some insightful information for researchers who are committed to fabricating high-performance Mg alloys for lightweight structural applications in the transportation industry, so as to improve fuel efficiency and reduce climate-changing and health-compromising emissions.
In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites ...for strength enhancement. This paper reports an Aluminum–Graphene Nanoplatelets(Al/GNPs)composite using a semi-powder method followed by hot extrusion. The effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in this paper. It is demonstrated that 0.3 wt% Graphene Nanoplatelets distributed homogeneously in the matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monolithic aluminum(in tension), Al–0.3 wt% GNPs composite exhibited higher 0.2% yield strength(+14.7%), ultimate tensile strength(+11.1%) and lower failure strain( -40.6%). Surprisingly, compared to monolithic Al(in compression), Al–0.3 wt% GNPs composite exhibited same 0.2% compressive yield strength and lower ultimate compression strength(- 7.8%),and lower failure strain(- 20.2%). The Al–0.3 wt% GNPs composite exhibited higher Vickers hardness compared to monolithic aluminum(+11.8%).Scanning electron microscopy(SEM), Energy-Dispersive X-ray Spectroscopy(EDS) and X-ray diffraction(XRD) were used to investigate the surface morphology, elemental percentage composition, and phase analysis, respectively.
•The Mg-graphene/CNTs composites are fabricated in present work.•Synergetic effect of MW–CNTs and GNPs in magnesium matrix is investigated.•MW–CNTs intercalates between Graphene sheets to form 3D ...hybrid structures.
Graphene nanoplatelets (GNPs) are novel reinforcing fillers due to their fascinating mechanical properties. However, their unique mechanical properties rapidly devolve as the sheets aggregate due to strong van der Waals forces and π–π attractions, therefore limiting their applications in metal matrix composites. In present work, the rapid aggregation of two-dimensional GNPs is inhibited by intercalating one-dimensional multi-walled carbon nanotubes (MW-CNTs). The long and flexible MW-CNTs bridge adjacent GNPs to form three dimensional hybrid structures which prevent their aggregation, thus resulting in a high contact area between CNTs+GNPs hybrid structure and the matrix. The composite reinforced with hybrid (GNPs and CNTs) reinforcement exhibited higher failure strain than those reinforced with individual GNPs and MW-CNTs. Compared to pure Mg, the Mg–1Al–0.6wt.%(CNTs+GNPs) composite exhibited improvement in elastic modulus, 0.2% yield strength, ultimate tensile strength and failure strain (+17%; +19%; +15% and +137%, respectively). The impressive increase in tensile failure strain (%) confirmed significant synergetic effect between GNPs and MW-CNTs.
Magnesium alloys are characterized by their low density (approximately 1.8 g/cm3 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.
The effects of the base lubricant with and without nanoparticles on the tribological behavior of magnesium alloy/steel contacts were investigated using a reciprocating sliding ball-on-flat ...tribometer. Three sets of contact conditions were used to evaluate the effect of concentration, the capacity of carrying load and the stability of the lubrication film, respectively. The results showed that the tribological properties of the base lubricant have been improved by adding the nanoparticles. As compared with the SiO2 nanolubricants, the positive effect of the MoS2 nanolubricants is more pronounced in terms of the load carrying capacity and the lubrication film stability. Mechanisms by which the nanolubricants improve tribological behaviors are discussed.
•MoS2 and SiO2 nanoparticles are used as lubricant additives for magnesium alloy/steel contact.•The optimum concentration of nano-SiO2 or nano-MoS2 in base lubricant is obtained.•The MoS2 is more pronounced in terms of load carrying capacity and lubrication film stability.•The wear mechanisms are explained in light of the experimental results.
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