Effect of ultrasonic vibration on Fe-containing intermetallic compounds of hypereutectic Al-Si alloys with high Fe content

The Fe-containing intermetallic compounds with high melting point in hypereutectic Al-Si alloys can improve the heat resistance and wear resistance at elevated temperatures. However, the long needle-like Fe-containing compounds in the alloys produced by conventional casting process are detrimental to the strength of matrix. The effect of ultrasonic vibration （USV） on the morphology change of Fe-containing intermetallic compounds in the hypereutectic Al-17Si-xFe （x=2, 3, 4, 5） alloys was systematically studied. The results show that, the Fe-containing intermetallic compounds are mainly composed of long needle-like β-Al5FeSi phase with a small amount of plate-like δ-Al4FeSi2 phase in Al-17Si-2Fe alloy produced by conventional casting process. With the increase of Fe content from 2% to 5% in the alloys, the amount of plate-like or coarse needle-like δ-Al4FeSi2 phase increases while the amount of long needle-like β-Al5FeSi phases decreases. In Al-17Si-5Fe alloy, the Fe-containing intermetallic compounds exist mainly as coarse needle-like δ-Al4FeSi2 phase. After USV treatment, the Fe-containing compounds in the Al-17Si-xFe alloys are refined and exist mainly as δ-Al4FeSi2 particles, with average grain size ranging from 26 μm to 37 μm, and only a small amount of β-Al5FeSi phases remain. The mechanism of USV on the morphology of Fe-containing intermetallic compounds was also discussed.

Growth kinetics of interfacial intermetallic compounds formed in SnPbInBiSb high entropy alloy soldered joints on Cu substrates

The growth behavior of the complex intermetallic compounds(IMCs)formed at the interface of Cu/SnPbInBiSb high entropy alloy solder joints was explored.The growth inhibition mechanism of the IMCs at the Cu/SnPbInBiSb solid−liquid reaction interface was revealed.The results showed that the growth rate of the complex IMCs obviously decreased at the Cu/SnPbInBiSb solid−liquid reaction interface.The maximum average thickness of IMCs only reached up to 1.66μm after reflowing at 200℃for 10 min.The mechanism for the slow growth of the complex IMCs was analyzed into three aspects.Firstly,the high entropy of the liquid SnPbInBiSb alloy reduced the growth rate of the complex IMCs.Secondly,the distorted lattice of complex IMCs restrained the diffusion of Cu atoms.Lastly,the higher activation energy(40.9 kJ/mol)of Cu/SnPbInBiSb solid−liquid interfacial reaction essentially impeded the growth of the complex IMCs.

Magnesium-rare earth intermetallic compounds for high performance high power aqueous Magnesium-Air batteries

Magnesium alloys are light structural materials and promising anode candidates for Mg-air batteries.However,application of Mg-air batteries is limited by poor performance at large current density and severe H2 generation side reactions.In this study,we pioneered magnesium-rare earth Mg_(3)RE(RE=La,Ce,Pr and Nd)intermetallic compounds as anodes to provide higher power density and more stable discharge performance.Especially,Mg_(3)Pr alloy exhibits high discharge voltage of 0.91 V and peak power density of 54.4 mW cm^(−2) at 60 mA cm^(−2) with anodic efficiency of 60%,far better than other Mg alloys.We reveal an activation mechanism of Mg_(3)RE-based anodes during discharge,which significantly accelerates mass transfer process as well as enhances discharge activity.The results improve the performance of high-power Mg-air batteries and promote the value-added application of abundant rare earth elements such as Ce and La.

Effects of heat treatment on the intermetallic compounds and mechanical properties of the stainless steel 321–aluminum 1230 explosive-welding interface

The effects of heat treatment on the microstructure and mechanical properties of intermetallic compounds in the interface of stainless steel 321 explosively bonded to aluminum 1230 were investigated in this study. Experimental investigations were performed by optical microscopy, scanning electron microscopy, and microhardness and shear tensile strength testing. Prior to heat treatment, increasing the stand-off distance between samples from 1 to 2.5 mm caused their interface to become wavy and the thickness of intermetallic layers to increase from 3.5 to 102.3 μm. The microhardness increased from HV 766 in the sample prepared at a stand-off distance of 1 mm to HV 927 in the sample prepared at a stand-off distance of 2.5 mm; in addition, the sample strength increased from 103.2 to 214.5 MPa. Heat treatment at 450°C for 6 h increased the thickness of intermetallic compound layers to 4.4 and 118.5 μm in the samples prepared at stand-off distances of 1 and 2.5 mm, respectively. These results indicated that increasing the duration and temperature of heat treatment decreased the microhardness and strength of the interface of explosively welded stainless steel 321-Al 1230 and increased the thickness of the intermetallic region.

Twinning in Intermetallic Compounds Are Long Shear Vectors and/or Shuffles Really Necessary?

In this paper the geometric description and general theory of mechanical twinning are reviewed, the twins in general lattices and superlattices are summarized, and the kinetic process by which mechanical twins form is revisited. A case study of mechanical twinning of HfV2+Nb, (cubic) Laves phase, is presented and the synchroshear of selected atomic layers is proposed to explain the physical process of twin formation. If the twins form in this way, then long shear vectors and / or atomicshuffles are not really necessary.

Remarkably reducing carbon loss and H2 consumption on Ni–Ga intermetallic compounds in deoxygenation of methyl esters to hydrocarbons

Ni–Ga alloy(Ni/Ga atomic ratio of 8),Ni3Ga and Ni5Ga3 intermetallic compounds(IMCs)catalysts were prepared from Ni–Mg-Al-Ga layered double hydroxides(LDHs)for the deoxygenation of methyl esters to hydrocarbons.In the alloy and IMCs,the presence of Ga reduced the surface Ni atom density,and the charge transfer from Ga to Ni increased the electron density of Ni.In the deoxygenation of methyl laurate,the Ni catalyst gave a complete hydrogenolysis of methyl laurate to CH4at 330°C and 3.0 MPa,while the presence of Ga promoted the HDO pathway and suppressed C–C bond hydrogenolysis and methanation.The Ni5Ga3 catalyst exhibited the best desired performance.Even at 400°C,it gave the yield of C11 and C12 hydrocarbons of ~99%,and the selectivity to CH4(SCH4) was only 2.4%.In the deoxygenation of methyl octanoate and methyl palmitate,the Ni5Ga3 catalyst also gave the yield of hydrocarbons above95%.Reactivity evaluation and methyl propionate-TPD and TPSR results indicate that the C–OCH3 bond instead of the O–CH3 one was cleaved on both Ni and bimetallic Ni–Ga catalysts.It is highlighted that methanol,derived from the C–OCH3 bond hydrogenolysis,mainly decomposed to CO and H2 on IMCs,while it was converted to methane on metallic Ni and alloy.It is of great significance that H2 could be yielded from the methyl ester itself.In short,the utilization of Ni–Ga IMCs can effectively reduce carbon loss and H2 consumption,all of which are ascribed to the geometric and electronic effects of Ga.

ONE-CELL-STATE METHOD FOR DETERMINATION OF ELECTRONIC STRUCTURE OF INTERMETALLIC COMPOUNDS

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SURFACE REACTION，HYDROGEN DIFFUSIVITY AND ENVIRONMENTAL EMBRITTLEMENT OF INTERMETALLIC COMPOUNDS Ni_3Al AND Fe_3Al

The effect of boron doping on the sensitivity to environmental embrittlement of Ni3Al-based alloys was investigated in this paper. The results show that the ductilizing effect of boron in Ni3Al is partly to suppress moisture-induced hydrogen embrittlement.The mechanism of this suppressing effect of boron relates to its severely decreasing the hydrogen diffusivity by boron segregated at the grain boundaries. The surface reaction of Fe3Al with water vapor and oxygen was experimentally confirmed by AES and XPS analysis. The kinetics of these reactions can be used to explain the different ductility behavior of aluminides in various environments.

Brittle and ductile characteristics of intermetallic compounds in magnesium alloys: A large-scale screening guided by machine learning

In the present work,we have employed machine learning(ML)techniques to evaluate ductile-brittle(DB)behaviors in intermetallic compounds(IMCs)which can form magnesium(Mg)alloys.This procedure was mainly conducted by a proxy-based method,where the ratio of shear(G)/bulk(B)moduli was used as a proxy to identify whether the compound is ductile or brittle.Starting from compounds information(composition and crystal structure)and their moduli,as found in open databases(AFLOW),ML-based models were built,and those models were used to predict the moduli in other compounds,and accordingly,to foresee the ductile-brittle behaviors of these new compounds.The results reached in the present work showed that the built models can effectively catch the elastic moduli of new compounds.This was confirmed through moduli calculations done by density functional theory(DFT)on some compounds,where the DFT calculations were consistent with the ML prediction.A further confirmation on the reliability of the built ML models was considered through relating between the DB behavior in MgBe_(13) and MgPd_(2),as evaluated by the ML-predicted moduli,and the nature of chemical bonding in these two compounds,which in turn,was investigated by the charge density distribution(CDD)and electron localization function(ELF)obtained by DFT methodology.The ML-evaluated DB behaviors of the two compounds was also consistent with the DFT calculations of CDD and ELF.These findings and confirmations gave legitimacy to the built model to be employed in further prediction processes.Indeed,as examples,the DB characteristics were investigated in IMCs that might from in three Mg alloy series,involving AZ,ZX and WE.

Ceramic bonding and joint's strengthening through forming intermetallic compounds in situ

The transient liquid phase diffusion bonding of Si 3N 4 ceramics with Ti/Ni/Ti and Al/Ti/Al multiple interlayers was performed. The formation of intermetallic compounds in situ and their effects on the joints strengths were investigated. The Ti/Ni/Ti interlayers produce NiTi and Ni 3Ti layers with considerable room temperature ductility and high elevated temperature strength to strengthen the bonding zone metals and the joints. The joints with 142 MPa shear strength at room temperature and 88 MPa shear strength at 800 ℃ are achieved under appropriate parameters, respectively. Al/Ti/Al interlayers transform into a special bonding zone metal with a large amount of Al 3Ti particles and a small amount of Al based solid solution, and in this case, the joints are strengthened significantly. Their strengths at room temperature and 600 ℃ reach 90 MPa and 30 MPa, respectively.

Sliding wear and friction behavior of ZA-27 alloy reinforced by Mn-containing intermetallic compounds

A ZA 27 alloy reinforced with Mn containing intermetallic compounds was prepared and its tribological behaviors were investigated. By adding Mn, RE, Ti and B into ZA 27 alloy, the test alloy (ZMJ) was fabricated by sand casting. Microstructural analysis shows that considerable amount of Mn containing intermetallic compounds such as Al 5MnZn, Al 9(MnZn) 2 and Al 65 Mn(RE) 6Ti 4Zn 36 are formed. Compared to ZA 27, ZMJ shows better wear resistance, lower friction coefficient and lower temperature rise of worn surface under lubricated sliding condition. ZMJ also shows the lowest steady friction coefficient under dry friction condition. The wear resistance improvement of ZMJ is mainly attributed to the high hardness and good dispersion of these Mn containing intermetallic compounds. It is indicated that the intermetallic compounds play a dominant role in reducing the sever adhesive and abrasive wear of the ZA 27 alloy.

Effect of Si on growth kinetics of intermetallic compounds during reaction between solid iron and molten aluminum

The effect of Si on the growth kinetics of intermetallic compounds during the reaction of solid iron and molten aluminum was investigated with a scanning electron microscope coupled with an energy dispersive X-ray spectroscope, and hot-dip aluminized experiments. The results show that the intermetallic layer is composed of major Fe2Al5 and minor FeAl3. The Al-Fe-Si ternary phase, rl/rg, is formed in the Fe2Al5 layer. The tongue-like morphology of the Fe2Als layer becomes less distinct and disappears finally as the content of Si in aluminum bath increases. Si in the bath improves the prohibiting ability to the growth of Fe2Als and FeAl3. When the contents of Si are 0, 0.5%, 1.0%, 1.5%, 2.0% and 3.0%, the activation energies of Fe2Al5 are evaluated to be 207, 186, 169, 168, 167 and 172 kJ/mol, respectively. The reduction of the activation energy might result from the lattice distortion caused by Si atom penetrating into the Fe2Al5 phase. When Si atom occupies the vacancy site, it blocks easy diffusion path and results in the disappearance of tongue-like morphology.

FORMABILITY CRITERIA OF INTERMETALLIC COMPOUNDS CONTAINING TRANSITION METAL SYSTEMS

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Effects of Fe-Al intermetallic compounds on interfacial bonding of clad materials

The growth of intermetallic compounds at the interface between solid Al and Fe and the effects of intermetallic compound layers on the interfacial bonding of clad materials were investigated. The results showed that the interface between the solid Fe and Al formed by heat-treatment consisted of Fe2Al5 and FeAl3 intermetallic compound layers, which deteriorated the interfacial bonding strength. Fractures occurred in the intermetallic compound layer during the shear testing. The location of the fracture depended on the defects of microcracks or voids in the intermetallic compound layers. The microcracks in the intermetallic compound layer were caused by the mismatch of thermal expansion coefficients of materials during cooling, and the voids were consistent with the Kirkendall effect. The work will lay an important foundation for welding and joining of aluminum and steel, especially for fabrication of Al-Fe clad materials.

Surface Properties of Cu Doped La-Ni Intermetallic Compounds

A series of Cu-doped La-Ni intermetallic compounds(LaN5-xCux, x = 0-4) was studied. The bulk structure and surface composition of the samples were detected before and after they were used as catalyst for nitrobenzene hydrogennation. The catalytic properties of the intermetallic compounds depend on the surface region composition, especially on the valence of the metal ions.

ELECTRONIC STRUCTURE OF Cu-DOPED RECo_5 TYPE INTERMETALLIC COMPOUNDS

Based on the feature of crystal sites occupied by alloying elements,a model cluster,investi- gating the interaction mechanisms of nonmagnetic element Cu in RECo_5 type alloy,has been presented.The electronic structure has been calculated with SCF-X_a-SW method.The calcu- lating results show that,after Cu replaced 2c crystal site Co,the energy spectrum of the mod- el cluster will move towards a shallow trap po.tential,the energy gap becomes small,the charge among the atoms will redistribute,and some new states to which impurity contributes will pro- duce.Partial-wave local density of states gives the interaction between atoms.Results of Hellmman-Feynman force show that the thermal expansion anisotropy of the model cluster decreases considerably after Cu substitutes for 2c crystal site Co.

Microstructure and Mechanical Behaviour of Proton-and Ion-irradiated Ll_2 Intermetallic Compounds

The results of mechanical testing and transmission electron microscopy on the ordered intermetallic Ll2 compounds1Zr3Al, Ni3Al, Ni3Si and Ni3Ge after irradiation with protons or heavy ions at high or low tem peratu re are presented and discussed. Using a minjaturjzed disk-bend test. it was found that proton irradiation of Zr3Al. Ni3Al and Ni3Si raises their yield strength :a single test of Ni3Ge shows no effect on the fracture stress of this brittle intermetallic The Vickers microhardness of all four alloys is raised by proton irradiation. The irradiations cause all the alloys to disorder. the extent of which is dependent on irradiation temperature Microstructural defects are produced by the irradiations Some exhibit strain-field contrast under dynamic two-beam diffracting conditions. Other distinct defect clusters are imaged only in dark-field using su perlattice reflections, These latter defects are discussed in the context of current arnorphization models. The strength increase of Zr3Al, Ni3Al and Ni3Si is attributed to a combination of disordering and strengthening from defects. The lack of an effect of irradiation on the fracture stress of Ni3Ge. in which voids were observed, requires further experiments

PtCoNi ternary intermetallic compounds anchored on Co,Ni and N co-doped mesoporous carbon:Synergetic effect between PtCoNi nanoparticles and doped mesoporous carbon promotes the catalytic activity

Highly active and robust electrocatalysts are desired for proton exchange membrane fuel cells.Pt-based intermetallic compounds(IMCs) have been recognized as one of the most promising low-platinum catalysts for fuel cells(FCs).Herein,we report a high-performance IMCs by anchoring ordered PtCoNi ternary nanoparticles on the N,Co and Ni co-doped dodecahedral mesoporous carbon(DMC).While the introduced Co and Ni participate in the formation of PtCoNi IMCs,some of them are doped in the mesoporous carbon and coordinated by N to form Co-N_(y)/Ni-N_(z)dual active centers,which further enhances the electrocatalytic activity towards oxygen reduction reaction.Moreover,the addition of Ni results in a negative shift of the d-band center of Pt as compared to the Pt/DMC and Pt_(3)Co/DMC,making it easier to adsorb oxygen on the surface.As expected,our optimal sample Pt_(3)Co_(0.7)Ni_(0.3)/DMC exhibits excellent performance with mass activity and specific activity of 1.32 A mgPt-1and 1.98 mA cm^(-2)at 0.9 V,which are 7.33and 6.19 times that of commercial Pt/C,respectively.The Pt_(3)Co_(0.7)Ni_(0.3)/DMC also reveals much better cathodic performance in an H2-air single fuel cell than commercial Pt/C catalyst with a power density of0.802 W cm^(-2).This work provides critical sights into constructing efficient catalysts by ternary intermetallic strategy and synergetic effect between active components and support.

Effect of uniform magnetic field on crystallization of intermetallic compound layers between Cu and liquid SnZn alloys

Crystallization of intermetallic compound layer between Cu and SnZn alloy under uniform magnetic field was studied. The effect of magnetic field density on the growth behavior of the intermetallic layer such as microstructure, crystal orientation and composition was analyzed by scanning electron microscopy, X-ray diffraction and electron-probe microanalysis, respectively. Compared with the intermetallic layer without magnetic field, 0.1 T of magnetic flux density decreases the layer thickness. However, further increasing magnetic flux density promotes the layer growth. Application of magnetic field also changes the crystal orientation of intermetallic layer, but has no obvious influence on the layer composition. This phenomenon can be attributed to the role of thermo-electromagnetic convection and Lorentz force on the Cu dissolution as well as the accumulation of Cu solute at the interface front.

Mechanism of anti-arterial thrombosis of Dahuangzhecong Fang screened by Ti-Al intermetallic compound porous material

The mechanism of antithrombotic of Dahuangzhechong Fang separated and purified by Ti-Al intermetallic compound porous material (TAICPM) was researched. Dahuangzhechong Fang, which was isolated and screened by TAICPM, was used to oral rats. At the end of study, their blood and thrombus were collected. The results show that TAICPM with the pore size of 1-5 μm can screen Dahuangzhechong Fang well. Dahuangzhechong Fang can increase 6-keto-PGF1α, lower content of TXD2 and platelet. Dahuangzhechong Fang has good effect to resist arterial thrombosis.