A Cu-based bulk amorphous alloy composite reinforced by carbon nanotube

Bulk Cu50Zr40Ti10 amorphous alloy composites reinforced with carbon nanotube （CNT） were successfully fabricated by hot pressing technique. Their density, thermal conductivity, and mechanical properties were systemically investigated. The density and the compression strength of the compacts both decrease with increasing CNT content. The thermal conductivity of the compacts decreases when the CNT content is less than 0.10% or exceeds 0.60% （mass fraction）, while increases when the CNT content is in the range of 0.1%-0.6%. The strain limit and the modulus of the compacts are obviously improved when the CNT content is less than 1.0% and then decrease significantly when the CNT content exceeds 1.00%. The optimum CNT addition is less than 0.20% at the comprehensive properties point of view.

Effect of consolidation parameters on mechanical properties of Cu-based bulk amorphous alloy consolidated by hot pressing

Cu50Zr40Ti10 bulk amorphous alloys were fabricated by hot pressing gas-atomized Cu50Zr40Ti10 amorphous powder under different consolidation conditions without vacuum and inert gas protection. The consolidation conditions of the Cu50Zr40Ti10 amorphous powder were investigated based on an L9（34） orthogonal design. The compression strength and strain limit of the Cu50Zr40Ti10 bulk amorphous alloys can reach up to 1090.4 MPa and 11.9 %, respectively. The consolidation pressure significantly influences the strain limit and compression strength of the compact. But the mechanical properties are not significantly influenced by the consolidation temperature. In addition, the preforming pressure significantly influences not the compression strength but the strain limit. The optimum consolidation condition for the Cu50Zr40Ti10 amorphous powder is first precompacted under the pressure of 150 MPa, and then consolidated under the pressure of 450 MPa and the temperature of 380 °C.

Microstructure of Cu-based Amorphous Composite Coatings on AZ91D Magnesium Alloy by Laser Cladding

To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM （scanning electron microscopy）, EDS （energy dispersive X-ray spectroscopy）, XRD （X-ray diffraction） and TEM （transmission electron microscopy） techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.

Accelerated prediction of Cu-based single-atom alloy catalysts for CO_(2) reduction by machine learning

Various strategies,including controls of morphology,oxidation state,defect,and doping,have been developed to improve the performance of Cu-based catalysts for CO_(2) reduction reaction(CO_(2)RR),generating a large amount of data.However,a unified understanding of underlying mechanism for further optimization is still lacking.In this work,combining first-principles calculations and machine learning(ML)techniques,we elucidate critical factors influencing the catalytic properties,taking Cu-based single atom alloys(SAAs)as examples.Our method relies on high-throughput calculations of 2669 CO adsorption configurations on 43 types of Cu-based SAAs with various surfaces.Extensive ML analyses reveal that low generalized coordination numbers and valence electron number are key features to determine catalytic performance.Applying our ML model with cross-group learning scheme,we demonstrate the model generalizes well between Cu-based SAAs with different alloying elements.Further,electronic structure calculations suggest surface negative center could enhance CO adsorption by back donating electrons to antibonding orbitals of CO.Finally,several SAAs,including PCu,AgCu,GaCu,ZnCu,SnCu,GeCu,InCu,and SiCu,are identified as promising CO_(2)RR catalysts.Our work provides a paradigm for the rational design and fast screening of SAAs for various electrocatalytic reactions.

Formation Mechanism of Curved Martensite Structures in Cu-based Shape Memory Alloys

The curved martensite structures have been observed in CuZnAI-based shape memory alloys by both transmission electron microscope and optical microscope. It was found that the curved martensite structures observed in as-solution treated, as-aged and as-trained alloys usually occurred around dislocation tangles or precipitate, at the plate boundary or grain boundary, and when the growing plates collided with each other or alternate mutually.

Application of Fe-Based Amorphous Alloy in Industrial Wastewater Treatment:A Review

Amorphous alloy(MGs)is a solid alloy with disordered atomic accumulation obtained by ultra-rapid solidification of alloy melt.The atom deviates from the equilibrium position and is in metastable state.Up to now,a large number of MGs have been applied to the treatment of dye and heavy metal contaminated wastewater and ideal experimental results have been obtained.However,there is no literature to systematically summarize the chemical reaction and degradation mechanism in the process of degradation.On the basis of reviewing the classification,application,and synthesis of MGs,this paper introduces in detail the chemical reactions such as decolorization,mineralization,and ion leaching of Fe-based amorphous alloy(Fe-MGs)in the degradation of organic and inorganic salt wastewater through direct reduction or advanced oxidation mechanism.Compared with crystalline materials,the higher reaction rate of Fe-MGs can be attributed to lower activation energy,negative redox potential,loose product layer,and band structure with downward shift of valence band top.Finally,some suggestions and prospects are put forward for the limitations and research prospects of MGs in the environmental field,which provides a new idea for the synthesis of new environmental functional materials.

Preparation and properties of novel Cu-based bulk metallic glasses Cu_(55-x)Zr_(37)Ti_8In_x

The glassy rods were successfully fabricated in the Cu-Zr-Ti-In alloy system by casting into a copper mold. The value of ATx reaches a maximum of 66 K for the BMG CusoZraTTi8In5 alloy. The reasons for enhancing glass forming ability of Cu-based BMGs with the addition of indium were discussed from atomic size and thermodynamics. Alternatively, the BMG Cu52Zra7Ti8In3 exhibits the highest compressive strength （1981 MPa） and the best plasticity among glassy Cu55-xZra7TisInx （x_〈5）. The total plastic deformation of Cu52Zr37TisIn3 before fracture approaches 1.2%.

THE FAILURE MECHANISM OF REVERSE SHAPE MEMORYEFFECT IN A Cu-BASE ALLOY

The interior structural evolution accompanying reverse shape memory effect (RSMEin a Cu-Zn-Al alloy was studied by means of transmission electron microscopy. It was found that RSME is closely related to bainitic transformation in this alloy during the isothermal reaction at moderate temperatures. At a given temperature and a certain external constraint stress, the shape memory effect depends mainly on the aging time.During the early stage, the shape memory effect enhances with the increase of reactiotn time. Then it will decrease gradually apon further aging. If the alloy is overaged, the stacking faults of bainite will disappear gradually by the motion of partial dislocations through which long range diffusion of solute atoms takes place, giving rise to the deterioration of RSME. When all the bainite transforms to α phase, RSME will lose completely.

Comparison of Cu−Al−Ni−Mn−Zr shape memory alloy prepared by selective laser melting and conventional powder metallurgy

This work aimed to investigate and critically analyze the differences in microstructural features and thermal stability of Cu−11.3Al−3.2Ni−3.0Mn−0.5Zr shape memory alloy processed by selective laser melting(SLM)and conventional powder metallurgy.PM specimens were produced by sintering 106−180μm pre-alloyed powders under an argon atmosphere at 1060°C without secondary operations.SLM specimens were consolidated through melting 32−106μm pre-alloyed powders on a Cu−10Sn substrate.Mechanical properties were measured through Vickers hardness testing.Differential scanning calorimetry was conducted to assess the martensitic transformation temperatures.X-ray diffraction patterns were collected to identify the metallurgical phases.Optical and scanning electron microscopy was used to analyze the microstructural features.b′1 martensite was found,irrespective of the processing route,although coarser martensitic variants were present in PM-specimens.In conventional powder metallurgy samples,intergranular eutectoid constituents and stabilized austenite also formed at room temperature.PM-specimens showed similar average hardness values to the SLM-specimens,albeit with high standard deviation linked to the porosity.The specimens processed by SLM showed reversible martensitic transformation(T0=171°C).PM-processed specimens did not show shape memory effects.

Semi-solid processing of aluminum and magnesium alloys:Status,opportunity,and challenge in China

Owing to its low cost,short process and low energy consumption,semi-solid processing(SSP)of aluminum(Al)and magnesium(Mg)alloys has been considered as a competitive approach to fabricate complicated components with excellent performance.Over the past decade,significant progress has been achieved in deeply understanding the SSP process,the microstructure and performance of the fabricated components in China.This paper starts with a retrospective overview of some common slurry preparation methods,followed by presenting the performance and the underlying mechanisms of SSP fabricated alloys.Then,the mainstream opinions on the microstructure evolution and rheological flow behavior of semi-solid slurry are discussed.Subsequently,the general situation and some recent examples of industrial applications of SSP are presented.Finally,special attention is paid to the unresolved issues and the future directions in SSP of Al and Mg alloys in China.

Corrosion behavior of Cu-Al-Mn-Zn-Zr shape memory alloy in NaCl solution

The corrosion behavior of a copper-based shape memory alloy(Cu-Al-Mn-Zn-Zr) in 3.5 wt.% Na Cl solution was investigated by means of potentiodynamic polarization measurements, electrochemical impedance spectroscopy(EIS) and X-ray photoelectron spectroscopy(XPS). At the beginning of corrosion, oxidation products formed on the surface of the shape memory alloy and constantly covered the reaction surface, resulting in the decrease of corrosion rate. After 4 d of immersion in NaCl solution, the corrosion product layer became thick and porous, leading to the increase of corrosion rate, and the corrosion reaction mechanism changed from polarization control to diffusion control. The diffusion impedance increased with increasing thickness of the oxide layer for the samples immersed in NaCl solution for 6-15 d. During the whole corrosion process, the reaction mechanism of the alloy changed and the corrosion resistance was improved continuously. The corrosion products mainly contained CuO, ZnO, Al2O3, MnO/Mn2O3, MnO2 and Al(OH)3. Transition of the corrosion products from Cu2O to CuO and Al2O3 to Al(OH)3 occurred during corrosion.

Relieving segregation in twin-roll cast Mg-8Al-2Sn-1Zn alloys via controlled rolling

Twin-roll casting(TRC)of Mg alloys with high Al content has unique advantages and broad development prospects.However,the severe segregation of high-alloyed Mg caused by TRC technology is difficult to solve at present,which restricts its practical application.In this work,the homogenization of coarse segregated phases in a twin-roll cast Mg-8Al-2Sn-1Zn(ATZ821)alloy was successfully achieved by a method combining solid-solution heat treatment and controlled rolling,which is suitable for industrial-scale production.In addition,the evolution of the microstructure was studied in detail.It was found that phases dynamically precipitated and dissolved repeatedly during the hot rolling process,and the evolution of entire second phases can be classified into three stages,i.e.,the net dissolution,balancing and net precipitation stages.During the process,the large-size chain-like eutectic phases evolved into a fine and nearly spherical(∼0.4μm)morphology that was uniformly dispersed in the Mg-matrix due to the thermodynamic coupling and the Ostwald ripening effect.Moreover,a fine grain microstructure(∼4μm)was obtained.The formidable segregation problem of twin-roll cast Mg alloys with high Al content was solved,which is an important finding for the industrial application of high-alloyed twin-roll cast sheets.©2020 Published by Elsevier B.V.on behalf of Chongqing University.

MARTENSITIC TRANSFORMATION AND THERMAL STABILITY IN Cu-Al-Co AND Cu-Al-Zr ALLOYS

Cu-Al-Co and Cu-Al-Zr alloys were explored with Co or Zr additions in Cu-Al alloys for high temperature shape memory alloys. Samples were quenched after homogenized at 850℃ for 48h. It was found that both Cu-Al-Co and Cu-Al-Zr show AlCus martensitic phase at room temperature and exhibit martensitic transformation temperatures higher than 200℃, showing the potentials for developing as high temperature shape memory alloys. Thermal cycles were performed by DSC instrument on both Cu-Al-Co and Cu-Al-Zr alloys. The results show that Cu-Al-Co loses its martensitic transformation after five thermal cycles, and Cu-Al-Zr exhibits no martensitic transformation in the second thermal cycle.

Interfacial Microstructure between WC-Based Cermet and Cu Alloy

A WC-TiC-Co/CuZnNi composite layer was produced on 1045 steel substrate by means of inside-furnace brazing technique. The microstructure, phase constituent and interfacial diffusion behavior between cermet and CuZnNi alloy were investigated by means of scanning electron microscopy (SEM), transmission electron microscope (TEM), electron probe microanalyzer (EPMA) and X-ray diffraction. The results showed that microstructure of matrix was α and β phases. Cermet particies were surrounded by the α+β phases in the composite layer and their sizes were almost similar to those in original state. The interfacial zone was formed by the mutual diffusion of elements under the condition of high temperature. The interface consists of WC, TiC, CuZn, and CuNi phases, and there are no microcracks and inclusions near the interface.

Corrosion behavior of magnesium and magnesium alloys

The automotive industry has crossed the threshold from using magnesium alloys in interior applications such as instrument panels and steering wheels to unprotected environment such as oil pan, cylinder head and wheels. The expanding territory of magnesium leads to new challenges: mainly environmental degradation of the alloys used and how they can be protected. The present critical review is aimed at understanding the corrosion behavior of magnesium and magnesium alloys in industrial and marine environments, and the effect of microstructure, additive elements and inhibitors on the corrosion mechanism.

Texture Development of a Cold-rolled CuZnAl Alloy

In this paper, the textures of a CuZnAl alloy, produced d by cold rolling in the dual phase state, were studied. The alloy was heat-treated to obtain a microstructure of dual phases, then, cold-rolled with intermediate annealings. The pole figures of a and 3 phases were measured separately by the texture goniometer at the surface and center of rolled sheets. The orientation distribution function analysis showed that the a phase possessed a weak texture, and the 3 phase possessed a strong a-fiber texture. Compared the textures between the center and surface it was indicated that the textures were as a whole homogeneous. The formation of such two phase textures depended mainly on the volume percents of both phases as well as the recrystallization annealing.

THE TYPE II DEFECT IN 18R MARTENSITE IN A Cu-Zn-Al ALLOY

Type H defect in 18R martensite in a Cu-Zn-Al alloy has been studied by high resolution electron microscopy. It was found that Type H defect is not fault internal to martensite plate; rather,it is a stack of plates A and C. The rare observation of Type H defect is considered to be due to the fact that thc slice is too thin to exist for self-accommodation.

镁合金腐蚀和控制技术的基础问题

耐蚀性差是制约镁合金广泛应用的瓶颈问题,行业关注的腐蚀痛点问题包括镁合金连接件的电偶腐蚀、表面防护涂层破损后易腐蚀以及镁合金在力学/化学交互作用下的腐蚀问题,分析了这些腐蚀痛点背后的原因,提出了需要进一步研究的镁合金腐蚀科学问题,包括镁合金电化学腐蚀的控制步骤、多因素耦合作用下的电偶腐蚀规律、力学/化学交互作用下的腐蚀机制、实用低成本防护涂层的构筑及响应机制等,并建议从腐蚀机理→材料→服役环境→加工制备→服役性能→表面防护→方法论等方面全方位思考,从本质上澄清镁合金的腐蚀机理,开发出低成本、高耐蚀、多功能的镁合金防护涂层,促进其广泛应用。

金属材料钛合金在化工与医药领域的应用

随着化工生产与材料学的高速发展,金属材料钛合金在化工与医药领域的应用越来越广泛,成功解决了传统工艺在这两大领域面临的一系列难题。而钛合金作为一种新型的金属材料,在石油工业、燃料电池、化工设备装置、海水淡化、骨科、牙科、药物释放动力学等诸多领域显示出了广阔的应用前景。本文旨在全面综述钛合金材料在化工与医药领域的应用,为实际生产和科学研究提供可靠的参考依据。

激光选区熔化适配型铝合金的研究及应用现状

使用激光选区熔化(Selective laser melting,SLM)技术制备的铝合金构件具有形状复杂、晶粒细小、力学性能优异等特点,在航天航空、轨道交通等领域有着广泛应用。然而,目前可用于SLM成形的铝合金材料仍面临着可打印种类有限、成形过程易产生冶金缺陷等问题,严重制约了SLM高性能铝合金的发展。本文基于承力构件的实际需求,综述了目前适配于SLM技术的铸造铝合金、稀土改性铝合金及铝基复合材料的研究现状,重点从适用于SLM技术的材料设计角度出发,概述所制备材料的独特微观组织及力学性能,并就SLM铝合金部件的国内外应用现状进行总结,点出现阶段SLM铝合金原材料仍多采用传统铸造材料为主的局限性,适于SLM技术的新材料、新产品在标准化以及规模化等方面仍需进一步细化和拓展。