Grain refinement of Mg-Ca alloys by native MgO particles

In Mg-Ca alloys the grain refining mechanism,in particular regarding the role of nucleant substrates,remains the object of debates.Although native MgO is being recognised as a nucleating substrate accounting for grain refinement of Mg alloys,the possible interactions of MgO with alloying elements that may alter the nucleation potency have not been elucidated yet.Herein,we design casting experiments of Mg-xCa alloys varied qualitatively in number density of native MgO,which are then comprehensively studied by advanced electron microscopy.The results show that grain refinement is enhanced as the particle number density of MgO increases.The native MgO particles are modified by interfacial layers due to the co-segregation of Ca and N solute atoms at the MgO/Mg interface.Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy,we reveal the nature of these Ca/N interfacial layers at the atomic scale.Irrespective of the crystallographic termination of MgO,Ca and N co-segregate at the MgO/Mg interface and occupy Mg and O sites,respectively,forming an interfacial structure of a few atomic layers.The interfacial structure is slightly expanded,less ordered and defective compared to the MgO matrix due to compositional deviations,whereby the MgO substrate is altered as a poorer template to nucleate Mg solid.Upon solidification in a TP-1 mould,the impotent MgO particles account for the grain refining mechanism,where they are suggested to participate into nucleation and grain initiation processes in an explosive manner.This work not only reveals the atomic engineering of a substrate through interfacial segregation but also demonstrates the effectiveness of a strategy whereby native MgO particles can be harnessed for grain refinement in Mg-Ca alloys.

Extraction of lithium from salt lake brine by aluminum-based alloys

Salt lake brine was reacted with activated aluminum-based alloys and lithium was precipitated.The effects of aluminum-based alloys on precipitating lithium were investigated and the reasonable alloy used to extract lithium from brine was obtained.The effects of the mole ratio of Al to Li and Ca content of Al-Ca alloy,the initial concentration of lithiumion ion in solution,reaction temperature and reaction time on the adsorption rate of lithium were studied,and the optimized process parameters were determined.The results show that the mole ratio of Al to Li and Ca content of Al-Ca alloy and reaction temperature have great influences on the precipitation rate of lithium.The precipitation rate of lithium reaches 94.6% under the optimal condition,indicating that Al-Ca alloy is suitable for the extraction of lithium from salt lake brine.

Corrosion degradation behavior of Mg-Ca alloy with high Ca content in SBF

The corrosion degradation behavior of a Mg-Ca alloy with high Ca content aiming for a potential bone repair material in the simulated body fluid（SBF） was investigated.The microstructure and phase constitution of the pristine Mg-30%Ca（mass fraction） alloy were characterized with scanning electron microscopy（SEM） and X-ray diffraction（XRD）.The Mg-30%Ca alloy samples were immersed in the SBF for 90 d,and the morphology,composition and cytotoxicity of the final corrosion product were examined.It is found that Mg-30%Ca alloy is composed of α-Mg and Mg2 Ca phases.During the corrosion process in the SBF,the Mg2 Ca phase acts as an anode and the α-Mg phase acts as a cathode.The final corrosion product of the Mg-30%Ca alloy in SBF includes a small amount of black precipitates and white suspended particles.The white suspended particles are Mg（OH）2 and the black particles are believed to have a core-shell structure.The cytotoxicity experiments indicate that these black precipitates do not induce toxicity to cells.

Effect of extrusion speed on microstructure and mechanical properties of the Mg-Ca binary alloy

This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360MPa to∼258MPa as the ram speed increases from 0.4mm/s to 2.4 mm/s,and the elongation increases from∼3.9%to∼12.2%.The microstructure changes from bimodal grain feature to the complete dynamical recrystallization(DRX)with increase of the extrusion speed.The ultrafine DRXed grains in size of∼0.85μm,the numerous nano-Mg_(2)Ca particles dispersing along the grain boundaries and interiors,as well as the high density of residual dislocations,should account for the high strength.It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys.

Effect of fluoride treatment on corrosion behavior of Mg-Ca binary alloy for implant application

The influence of hydrofluoric acid（HF） treatment on the corrosion behavior of the Mg-0.5Ca alloys was investigated by immersion specimen in sodium hydroxide and HF solutions with various concentrations and durations at room temperature.Microstructural evolutions of the specimens were characterized by atomic force microscopy,X-ray diffraction,field-emission scanning electron microscopy.The corrosion resistance was examined through potentiodynamic polarization and immersion test in Kokubo solution.The results revealed that the fluoride treated Mg-0.5Ca alloys produced by immersion in 40% HF provided more uniform,dense and thicker coating layer（12.6 μm） compared with the 35% HF treated specimen.The electrochemical test showed that the corrosion resistance of fluoride treated specimen was 35 times higher compared with the untreated Mg-0.5Ca alloy specimen in Kokubo solution.In vitro degradation rate of the fluoride treated specimens was much lower than untreated Mg-0.5Ca alloy in Kokubo solution.After immersion test the surface of 40% HF treated sample showed a few corrosion dots,while untreated specimens were fully covered by corrosion products and delamination.Fluoride treated Mg-0.5Ca alloy with 40% HF is a promising candidate as biodegradable implants due to its low degradation kinetics and good biocompatibility.

On ignition point of Mg-Ca alloy under nitrogen atmosphere

The production cost will be greatly reduced if nitrogen can be used instead of inert gas in the spray forming process of magnesium alloys, but the heat from the reaction between magnesium alloys and nitrogen makes magnesium alloy burn easily. To solve the problem above, the ignition point of Mg-Ca alloy under nitrogen atmosphere was studied using a home-made experimental device and DSC-DTA. Results show that under nitrogen atmosphere, Ca addition has a great effect on the ignition point of Mg alloy. The ignition point of the Mg-5Ca bulk even exceeds 1,030℃, and the alloy can be held for 30 min at 900℃ without burning;while the average ignition point of Mg-5Ca powders is lower than 700℃, and it increases with the increasing particle size. Moreover, the purity of nitrogen must be in a certain scope;Mg-Ca alloy shows a higher ignition point under nitrogen with a purity of 99.5%. Based on the experimental results, the best adding content of Ca and the purity of nitrogen were determined, and the security and economic performance of preparing magnesium alloys by spray deposition were improved with nitrogen as atomizing gas.

A review on recent advancements in biodegradable Mg-Ca alloys

The binary Mg-Ca alloys are drawing increasing attention as temporary implant materials because of their excellent biocompatibility,biodegradability, and good mechanical properties. However, their applications are limited due to their high degradation rates in the human physiological environment, the consequent release of hydrogen gas, and rapid loss in mechanical properties. Furthermore, biocompatibility depends upon the degradability of the material. Various researchers have demonstrated that these issues can be addressed by control of Ca content, thermo-mechanical processing to obtain suitable microstructures, deposition of surface coatings, etc. In this manuscript, a detailed review of published literature on Mg-Ca alloys is presented. The challenges and future directions of research in this area are also described.

Preparation and characterizations of Mg-Ca alloys as degradable biomaterials

Mg-Ca alloys have been proposed to be a new candidate for biodegradable metal materials in the present study.Mg-1Ca,Mg-5Ca and Mg-20Ca(wt%)have been prepared and the primary properties related to their biomedical application have been investigated by X-ray diffraction,SEM observation,tensile,electrochemical and immersion tests.The experimental results show that with the increase of Ca concentration,the working ability of Mg-Ca alloy becomes worse.Only Mg-1Ca and Mg-5Ca alloy specimens can be hot rolled i...

Study of the degradation behavior and the biocompatibility of Mg-0.8Ca alloy for orthopedic implant applications

Mg-Ca alloys have recently attracted great attention towards the research in the field of orthopedic biodegradable implants.This study presents an in vitro degradation assessment of Mg-0.8Ca(0.8 wt.%of Ca)alloy in Hank’s balanced salt solution(HBSS).Immersion,hydrogen evolution and electrochemical behavior was studied as well as the cytotoxicity of the degradation products.Morphology and phase composition of the corrosion products were studied using SEM,EDX and XRD techniques.Degradation in HBSS resulted in the formation of the needle-shaped carbonated hydroxyapatite which was similar to the biological apatite in the human bone.Degradation kinetics showed that Mg-0.8Ca alloy had approximately 3-fold faster degradation rate than the pure Mg(1.08±0.38 mm/year for Mg-0.8Ca and 0.35±0.17 mm/year for pure Mg),as observed in two independent experiments.Both,pure Mg and Mg-0.8Ca alloy were biocompatible,generating no cytotoxic degradation products against human-derived HEK 293 cells.Thus,the Mg-0.8Ca alloy was found to be a promising biodegradable implant in terms of bioactivity and compatibility with human cell lines.Depending on the application of the implant and the estimated healing time of the bone,the desired degradation rate of an implant can be controlled by the Mg-Ca composition of such alloys.

Separation of primary solid phases from Al-Si alloy melts

The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical,physical and chemical properties of the alloys should be removed.On the other hand,Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process.One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts.This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation,draining,filtration,electromagnetic separation and centrifugal separation,focused on the iron removal and on the separation of silicon in the solvent refining process.

Electrolytic production of Cu-Ni alloys in CaCl_2-Cu_2S-NiS molten salt

An alternative metal/alloy production method,known as direct electrochemical reduction(DER),was introduced for the fabrication of CuNi alloys from mixed sulfides(Cu2S,NiS)under both galvanostatic and potentiostatic conditions.The influences of the process parameters(e.g.,cell voltage and current)on the compositions of the reduced compounds were investigated to yield industrially desirable alloys,namely,CuNi10,CuNi20,and CuNi30.The electrochemical behaviors of Cu2S and NiS in CaCl2 melt were examined at a temperature of 1200°C via cyclic voltammetry(CV).Based on the CV results,the cathodic reduction of Cu2S occurred in one step and cathodic reductions of NiS occurred in two steps,i.e.,Cu2S?Cu for copper reduction and NiS?Ni3S2?Ni for nickel reduction.Galvanostatic studies revealed that it was possible to fabricate high-purity CuNi10 alloys containing a maximum sulfur content of 320×10-6 via electrolysis at 10 A for 15 min.Scanning electron microscopy along with energy-dispersive X-ray spectrometry and optical emission spectroscopy(OES)examinations showed that it was possible to fabricate CuNi alloys of preferred compositions and with low levels of impurities,i.e.,less than 60×10-6 sulfur,via DER at 2.5 V for 15 min.

Tunable surface plasmon-polariton resonance in organic light-emitting devices based on corrugated alloy electrodes

We report a feasible method to realize tun able surface plasm on-polarit on(SPP)res onance in orga nic light-emitt ing devices(OLEDs)by emplo ying corrugated Ag-Al alloy electrodes.The excited SPP res onance in duced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes.With an appropriate composition ratio of the corrugated alloy electrode,the photons trapped in SPP modes are recovered and extracted effectively.The 25%in creaseme nt in luminance and 21%enhan ceme nt in curre nt efficie ncy have bee n achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.

In vitro and in vivo degradation,biocompatibility and bone repair performance of strontium-doped montmorillonite coating on Mg-Ca alloy

Poor bone growth remains a challenge for degradable bone implants.Montmorillonite and strontium were selected as the carrier and bone growth promoting elements to prepare strontium-doped montmorillonite coating on Mg-Ca alloy.The surface morphology and composition were characterized by SEM,EDS,XPS,FT-IR and XRD.The hydrogen evolution experiment and electrochemical test results showed that the Mg-Ca alloy coated with Sr-MMT coating possessed optimal corrosion resistance performance.Furthermore,in vitro studies on cell activity,ALP activity,and cell morphology confirmed that Sr-MMT coating had satisfactory biocompatibility,which can significantly avail the proliferation,differentiation,and adhesion of osteoblasts.Moreover,the results of the 90-day implantation experiment in rats indicated that,the preparation of Sr-MMT coating effectively advanced the biocompatibility and bone repair performance of Mg-Ca alloy.In addition,The Osteogenic ability of Sr-MMT coating may be due to the combined effect of the precipitation of Si4+and Sr^(2+)in Sr-MMT coating and the dissolution of Mg^(2+)and Ca^(2+)during the degradation of Mg-Ca alloy.By using coating technology,this study provides a late-model strategy for biodegradable Mg alloys with good corrosion resistance,biocompatibility.This new material will bring more possibilities in bone repair.

Niobium Extraction from Baotou Iron Ore Containing Niobium

The experimental results of niobium enrichment in laboratory and in blast furnace in Baotou Iron and Steel Corporation were reported.The effects of temperature,constituents of slag and silicon content in hot metal on niobium recovery were studied and the results have been verified by blast furnace operation.Optical and electronic microscopy and EPMA was observed that at the metal-slag interface there is NbC deposit layer obstructed Nb entering into the metal,By raising the temperature of hearth and agitating the bath,the reduc- tion of niobium oxide in slag could be speeded up,the solubility of Nb in hot metal could increase and the deposited NbC layer became thinner and even disappeared,in result,Nb recovery was increased.A compre- hensive extraction process combining ore dressing with pyro-hydro-metallurgy was suggested for Baotou niobium resource which was difficult to be concentrated formerly.The methods of increasing niobium recovery were also suggested.

The Inhibition Effect of Cinnamon Extract on Leaching of Aluminum Cook Wares in NaCl Solutions at Quasi-Cooking Condition

The contribution of cinnamon extract on leaching of aluminum (Al) cook wares was investigated using two aluminum alloys (Indian and Egyptian) and pure Al. The cinnamon (Cin) was extracted by heating the Cin sticks at 90&degC in distilled water for an hour to make the 10% stock solution. This study was done in aqueous solutions in presence and absence of 1% NaCl using weight loss at 90&degC. Moreover surface study (SEM and EDX) and electrochemical methods (Open Circuit Potential and Tafel plot) were applied. The addition of Cin solutions to 1% NaCl decreased the corrosion rates in weight loss and electrochemical method compared to 1% NaCl solutions which showed an inhibitive property of Cin solution. The inhibition was found to obey the modified Langmuir isotherm with a negative Langmuir ΔGads indicating the spontaneous nature of adsorption even at 90&degC. The EDX surface analysis of the Al surface immersed in Cin + NaCl revealed the composition of the pits formed. From Tafel method, it was found that the corrosion current density of pure Al was more than that of the Egyptian alloy. The apparent activation energy values for Cin, Cin + NaCl and NaCl solution were evaluated and discussed.

Superelasticity of Cu–Ni–Al shape-memory fibers prepared by melt extraction technique

In the paper, a melt extraction method was used to fabricate Cu–4Ni–14Al（wt%） fiber materials with diameters between 50 and 200 μm. The fibers exhibited superelasticity and temperature-induced martensitic transformation. The microstructures and superelasticity behavior of the fibers were studied via scanning electron microscopy（SEM） and a dynamic mechanical analyzer（DMA）, respectively. Appropriate heat treatment further improves the plasticity of Cu-based alloys. The serration behavior observed during the loading process is due to the multiple martensite phase transformation.

钛合金在油气开采中的应用及研究现状

我国目前现有的油井管用钛合金都是在其他行业所用钛合金的基础上进行改进设计的,普遍存在抗腐蚀性能较差、成本较高等缺点,并且钛合金在我国油气开采领域还未得到大规模的生产与应用。总结了钛合金油井管在油气开采领域的应用以及油井管用钛合金抗腐蚀能力的研究成果,并且梳理了我国目前油井管用钛合金材料抗腐蚀性能的不足,为后续的研究提供参考。

Introducing MagBERT:A language model for magnesium textual data mining and analysis

Magnesium(Mg)based materials hold immense potential for various applications due to their lightweight and high strength-to-weight ratio.However,to fully harness the potential of Mg alloys,structured analytics are essential to gain valuable insights from centuries of accumulated knowledge.Efficient information extraction from the vast corpus of scientific literature is crucial for this purpose.In this work,we introduce MagBERT,a BERT-based language model specifically trained for Mg-based materials.Utilizing a dataset of approximately 370,000 abstracts focused on Mg and its alloys,MagBERT is designed to understand the intricate details and specialized terminology of this domain.Through rigorous evaluation,we demonstrate the effectiveness of MagBERT for information extraction using a fine-tuned named entity recognition(NER)model,named MagNER.This NER model can extract mechanical,microstructural,and processing properties related to Mg alloys.For instance,we have created an Mg alloy dataset that includes properties such as ductility,yield strength,and ultimate tensile strength(UTS),along with standard alloy names.The introduction of MagBERT is a novel advancement in the development of Mg-specific language models,marking a significant milestone in the discovery of Mg alloys and textual information extraction.By making the pre-trained weights of MagBERT publicly accessible,we aim to accelerate research and innovation in the field of Mg-based materials through efficient information extraction and knowledge discovery.

基于信号融合的镁合金激光焊接熔透状态监测

针对目前研究中缺乏镁合金激光焊接熔透状态监测的现状,提出了一种基于声图信号融合的镁合金激光焊接熔透状态监测方法;使用麦克风和高速相机监测激光焊接过程,将提取的声音、图像特征进行特征级融合,并输入反向传播神经网络中,实现镁合金熔透状态准确识别,准确率达100%。结果表明,与单独使用声音或图像特征进行监测相比,声音图像信号融合监测能获得更高的识别准确率;将声图融合特征输入经典机器学习方法中,均获得了较高的准确率;该方法准确识别了镁合金激光焊接熔透状态,有助于提高焊接质量。

复杂铂铱铑合金的活化溶解及铑提取工艺研究

针对复杂铂铱铑合金处理过程中存在的溶解效率低、精炼周期长等问题,开展了合金活化溶解、TBP萃取分离、阳离子交换、还原制备铑粉的工艺路线及技术条件探索。结果表明:采用铝粉为活化剂、合金与活化剂质量比为1∶9、反应温度1300℃、反应时间3 h,活化后合金中铂、铱、铑的溶解率均达到99%以上;采用TBP为萃取剂,控制萃前液中铂铱总浓度为15~20 g/L,电位1100 mV以上,可实现铂铱与铑的高效分离;采用甲酸配合聚乙烯吡咯烷酮还原法可快速制备出铑粉,铑粉的平均粒径为1~3μm,晶体结构为面心立方,与矿产一次资源中提取的铑粉性质相同。