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.

Magnetic Properties of Fe- and FeNi-based Amorphous Composite Ribbons

Ms-T curves and hysteresis loops were investigated for amorphous Fe78Si9B13, (FeNi)78(CrSiB)22, their lap-wound-cores, and their composite ribbons made by two-chamber-crucible technique. The properties of the lap-wound cores of the two kinds of ribbons are similar. For the composite ribbons, the intrinsic properties are the average of the two alloys. Their technological properties, i.e., hysteresis loops, however, are no longer the average of the two alloys. Instead, they show some dramatic changes compared to the lap-wound-cores. Especially, the shape of the hysteresis loop of the composite ribbon cores is largely different from that of lap-wound-cores. The reason for the difference is supposed to be internal stress induced from cooling after annealing.

Microstructure evolution of Ti_(48)Zr_(27)Cu_(6)Nb_(5)Be_(14)amorphous alloy after semi-solid isothermal treatment

The as-cast amorphous Ti_(48)Zr_(27)Cu_(6)Nb_(5)Be_(14)composites,comprising in situ formedβ-Ti ductile crystalline precipitates,were prepared by water cooled copper mold suction casting.Then,the semi-solid composites were obtained after the as-cast composites were treated by semi-solid isothermal treatment.The microstructure evolution and kinetics of the composites were examined.Results show that the microstructures of both the as-cast and semi-solid composites comprise ofβ-Ti crystal phases and amorphous matrix phases.Before and after treatment,the crystals evolve from fine granular or fine dendritic crystals to coarse crystals.As the treatment temperature increasing or the time prolonging,the average crystal size gradually increases and the surface morphology of the crystals gradually becomes regular.By studying the microstructural evolution and dynamics during the isothermal treatment process,it is found that the final morphology ofβ-Ti crystals is influenced by the isothermal treatment temperature and time(t),and theβ-Ti evolution rate increases with an increase in treatment temperature.In addition,a linear relationship was observed between the size of cubicβ-Ti crystals(D^(3))and t;the growth kinetics factor K is 3.8μm^(3)·s^(-1).As the K value closes to 4μm^(3)·s^(-1),it is inferred the morphology evolution ofβ-Ti crystals is a coarsening behavior controlled by the diffusion of solute elements.

Phase selection and performance of Mg–Cu–Y amorphous composite with different Mg/Cu ratios

In this article, Mg-Cu-Y alloys with two dif- ferent Mg/Cu ratios （in at%） were prepared using a water- cooled copper mold. Scanning electron microscopy and X-ray diffraction were applied to analyze the microstructure and phase composition. Moreover, corrosion resistance and wear resistance were studied systematically. The results show that both Mg65Cu25Ylo and Mg60Cu30Ylo alloys could form a composition of crystalline and amorphous phases. Although the microstructure of Mg65Cu25Ylo con- sists of an amorphous phase and ：t-Mg, Mg2Cu, and Cu2Y crystalline phases, the microstructure of Mg60Cu30Ylo alloy mainly consists of the amorphous phase and ：t-Mg, Mg2Cu. With reducing Mg/Cu ratio, the alloys have better corrosion resistance and wear resistance. The mechanism has also been discussed in detail.

Crystallization of Fe_(78)Si_9B_(13) Bulk Crystaline/ Amorphous(c/a) Composite

A metallic crystalline/amorphous （c/a） bulk composite was prepared by the slow cooling method after remelting the amorphous Fe78Si9B13 ribbon. By X-ray diffraction （XRD）, differential scanning calorimetry （DSC） and scanning electron microscope （SEM）, the composite consists of the primary dendrite α-Ee （without Si） as well as the amorphous matrix. After being anneal at 800 K, the uniform spheroid particles are formed in the c/a composite, which does not form in the amorphous ribbon under the various annealing process. Energy dispersive analysis of X-rays （EDAX）, SEM and XRD were applied to give more detailed information. The formation and evolution of the particle may stimulate the possible application of the Fe-matrix amorphous alloy.

Electrodeposition of Ni-W Amorphous Alloy and Ni-W-SiC Composite Deposits

Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induced codeposition. Effects of the bath composition, pH value, temperature and current density on the electrode position of Ni-W alloys and their composite deposits have been investigated, and the effect of heat treatment temperature on the hardness, structure and cohesive force of the amorphous Ni-W alloys and their composite deposits are also discussed. Results showed that the alloys containing more than 44 wt pct W content and the composite deposits containing 7.8 wt pct SiC content could be obtained by making use of the appropriate bath composition and plating conditions. Alloys and their composite deposits with over 44 wt pct W content show amorphous structure. The hardness of amorphous Ni-W alloys and their composite deposits increases obviously when heated, and can reach to 1350 HV and 1520 HV respectively for 46 wt pct W content. The cohesion on Cu, carbon steel and stainless steel is very good.

Microstructure and Corrosion Resistance of a Novel AlNiLa Lightweight Medium Entropy Amorphous Alloy Composites

A new type of lightweight AlNiLa medium entropy amorphous alloy composite ribbons(labled as MEAAC ribbons)were prepared by vacuum arc melting technology and high-speed single roller meltspinning method.The microstructure and thermal stability of MEAAC ribbons were examined using X-ray diffraction,differential scanning calorimeter,and scanning electron microscope.Meanwhile,the hardness and surface roughness of these ribbons were measured by Vickers microhardness tester and atomic force microscope.The potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS)were applied to investigate the corrosion behavior of these MEAAC ribbons in simulated seawater(3.5wt%NaCl corrosive solution)at room temperature.The results demonstrate that AlNiLa MEAAC ribbons in the as-received state are mainly composed of amorphous phase and intermetallic compounds.The hardness values of all melt-spun ribbons are above 310 HV_(0.1).With the increase of Al content,the linear polarization resistances of four various AlNiLa MEAAC ribbons are negligibly different numerically.It is also found that Al_(45)Ni_(27.5)La_(27.5) MEAAC ribbons have the most positive corrosion potential and the smallest corrosion current density at the same time;hence it may be a kind of potential material for metal surface protection in harsh ocean environment.

Critical state-induced emergence of superior magnetic performances in an iron-based amorphous soft magnetic composite

Soft magnetic composites(SMCs)play a pivotal role in the development of high-frequency,miniaturization and complex forming of modern electronics.However,they usually suffer from a trade-off between high magnetization and good magnetic softness(high permeability and low core loss).In this work,utilizing the order modulation strategy,a critical state in a FeSiBCCr amorphous soft magnetic composite(ASMC),consisting of massive crystal-like orders(CLOs,∼1 nm in size)with the feature ofα-Fe,is designed.This critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex dots.Superior comprehensive soft magnetic properties at high frequency emerge in the ASMC,such as a high saturation magnetization(Ms)of 170 emu g^(-1)and effective permeability(µ_(e))of 65 combined with a core loss(Pcv)as low as 70 mW cm^(-3)(0.01 T,1 MHz).This study provides a new strategy for the development of high-frequency ASMCs,possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.

Thermodynamic prediction of the composition of Fe-based amorphous alloys

The liquidus univariant lines of the Fe-Nb-B ternary system have been thermodynamically calculated by means of CALPHAD method and Fe-based thermodynamic data. It is found that there are two eutectic reactions in the Fe-rich corner,that is,（1） L（Fe-3Nb-15B） →α＋γ＋ M2B （1430 K）,and （2） L（Fe-10Nb-27B） → FeB ＋ Lc14 ＋ M2B （1575 K）. Moreover,the eutectic points are very close to the compositions with high glass forming ability determined experimentally. This means that it is feasible to design the compositions of multicomponent bulk metallic glasses by looking for the eutectic points in the Fe-Nb-B system by means of thermodynamic calculation.

Microstructure evolution and deformation mechanism of amorphous/crystalline high-entropy-alloy composites

High-entropy amorphous alloys present high hardness,but low tensile ductility.Here,deformation behavior of the amorphous/crystalline Fe Co Cr Ni high-entropy alloy(HEA)composite prepared by the previous experiment is investigated using atomic simulations.The result shows the partial dislocations in the crystal HEA layer,and the formation of shear bands in the amorphous HEA layer occurs after yielding.The strength of the amorphous/crystalline HEA composite reduces with increasing the thickness of the amorphous layer,agreeing with the previous experiments.The coupled interaction between the crystal plasticity and amorphous plasticity in amorphous/crystalline HEA composites results in a more homogeneous redistribution of plastic deformation to cause interface hardening,due to the complex stress field in the amorphous layer.The current findings provide the insight into the deformation behavior of the amorphous/crystalline HEA composite at the nanoscale,which are useful for optimizing the structure of the HEA composite with high strength and good plasticity.

Co-based Amorphous/Nanocrystalline Composite Coatings Deposited by Arc Ion Plating

Cobalt-based amorphous/nanocrystalline composite coatings have been grown by arc ion plating together with a specimen cooling system. With decreasing substrate temperature, the coatings undergo significant structure evolution. The degree of crystallization first decreases and subsequently increases as confirmed by X-ray diffraction. The cluster size first decreases and then remains constant as confirmed by transmission electron microscopy. The effect of substrate temperature on the evolution of the structure has been studied as a result of a competition between nucleation thermodynamics and kinetics of crystalline growth. With decreasing the substrate temperature, the microhardness and the critical load of the composite coatings firstly increased, and then remained almost constant. And the saturation magnetization revealed the opposite trend over the same range. The essence of these phenomena was ascribed to the microstructural variations caused by the decrease of the substrate temperature.

Mechanical properties of Fe-based amorphous–crystalline composite: a molecular dynamics simulation and experimental study

A new Fe-based amorphous–crystalline composite without non-metallic elements, Fe_(55)Cr_(15)Mo_(15)Ni_(10)W_(5), was prepared by melt-spinning. The formation ability and structure information were investigated by X-ray diffractometer(XRD), energy-dispersive spectrometer(EDS) and scanning electron microscope(SEM). The mechanical properties of the amorphous–crystalline composite were investigated by nanoindentation. A molecular dynamics simulation study was performed to simulate the formation of Fe_(55)Cr_(15)Mo_(15)Ni_(10)W_(5) amorphous alloy. The mechanical properties were obtained by compression simulations simultaneously. The results indicate that the Fe_(55)Cr_(15)Mo_(15)Ni_(10)W_(5) ribbon is an amorphous–crystalline composite structure with good ductility, and the hardness of the amorphous–crystalline composite is about 75%higher than that of master ingot. The simulation mechanical properties are in good agreement with the results of nanoindentation at the nanoscale.

Pulsed-Laser Annealing of NiTi Shape Memory Alloy Thin Film

Local annealing of amorphous NiTi thin films was performed by using an Nd：YAG 1064 nm wavelength pulsed laser beam. Raw samples produced by simultaneous sputter deposition from elemental Ni and Ti targets onto unheated Si （100） and Silica （111） substrates were used for annealing. Delicate treatment with 15.92 W/mm^2 power density resulted in crystallization of small spots; while 16.52 and 17.51 W/mm^2 power densities caused ablation of the amorphous layer. Optical microscopy, scanning electron microscopy, X-ray diffraction and atomic force microscopy were performed to characterize the microstructure and surface morphology of the amorphous/crystallized spot patterns.