Effect of heat treatment on structure and magnetic properties of Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk amorphous alloy

Abstract： This study deals with the Fe65.5Cr4Mo4Ga4P12C5B5.5 ferromagnetic bulk amorphous alloy. XRD analysis showed an amorphous structure of the as-cast sample. The same method revealed that, after annealing at 973 K for v=10 min, the sample displayed a crystalline structure with crystalline phases formed. The crystallization process of the alloy was examined by DTA analysis. It was shown that crystallization took place in the temperature range between 810 K and 860 K with the exo-maximum peak temperature at 846 K with a heating rate of 20 K.min-1. The method also showed that, at temperatures ranging from 753 K to 810 K, the alloy exhibited the properties of supercooled liquids. A correlation between heat-induced structural changes and magnetic properties of the alloy was determined by thermomagnetic measurements. Maximum magnetization M=3.7 Am2.kg-1 of the alloy was reached after its annealing at 733 K for τ=10 min. Upon annealing, the alloy exhibited a relaxed amorphous structure. Annealing the alloy above the crystallization temperature led to a decrease in bulk magnetization. After annealing at 973 K for r=10 min, the bulk magnetization of the alloy was M＇=0.45 Am2.kg-1. Accordingly, after crystallization and formation of new compounds, the magnetization of the alloy was decreased by a factor of about 7.7. The strength of the magnetic field applied during the measurements was H=10 kA.m-1. The samples were tested for changes in the microstructure and hardness of both the amorphous phase and the resulting crystalline phase.

Bone loss prevention in ovariectomized rats using stable amorphous calcium carbonate

In assessing the relationship between calcium supplementation and maintaining bone mass or reducing the risk of fracture, the effectiveness of calcium supplementation has never been decisive. Freshwater crayfish rely on amorphous calcium carbonate (ACC), an instable polymorph of calcium carbonate, as the main mineral in the exoskeleton and in the temporary storage organ, the gastrolith. Inspired by the crayfish model, we have previously shown an increase in calcium bioavailability in rats administered with synthetic stable ACC vs. crystalline calcium carbonate (CCC). The current study compared the effects of amorphous calcium derived from either gastrolith or synthetic ACC with those of crystalline calcium, found in commercial CCC or calciumcitrate supplements, in a bone loss prevention model. Rats were subjected to either sham or ovariectomy (OVX) operation (n^20/ group) followed by administration of food pellets supplemented with 0.5% calcium from either source over 12 weeks. Micro-computed tomography (μCT) and histomorphometric analyses revealed bone loss prevention by both gastrolith and ACC treatments, manifested by an increase in morphometric bone parameters, compared to both CCC-?and calcium citrate-treated groups. Both gastrolith and ACC treatments resulted in bone formation in the tibia cancellous bone, indicated by dynamic histomorphometry parameters, compared to either the CCC or calcium citrate treatments. Levels of urine deoxypyridinoline (DPD), suggested an anti-resorptive effect of ACC, which was also the only treatment that led to a significant increase in vertebral mechanical strength, as supported by μCT analysis of topology and orientation parameters of the vertebral trabeculae. To our knowledge, such levels of bone loss prevention by calcium supplements have never been reported. These findings thus suggest the potential of both natural (crayfish gastrolith) and, to a greater extent, synthetic ACC sources for the prevention of metabolic bone disorders and possibly of osteoporotic processes.

ELECTRONIC STRUCTURE OF CHALCOGENIDE COMPOUNDS

Empirical linear combination of atomic orbitals(LCAO)calculations are performed to investigate the electronic structure of Sb_(2)Se_(3),Sb_(2)Te_(3),In_(2)Se_(3) and In_(2)Te_(3).The bands of bonding p states are overlapped with the bands of lone pair states in these materials.The absorption edges of these materials correspond to indirect gap,and the calculation agrees with experimental values.

新宿琉璃光院白莲花堂,东京,日本

这座白色混凝土建筑仿佛是在承受来自天空的恩泽一般,从大地中长出,再不断向上空张开。为之命名白莲花堂,是取自弥陀净土中含苞待放的莲花蕾之意。而这座寺庙是在都市的喧嚣和楼宇的夹缝中静静开放的。从地下生出的中央结构体形成建筑的中心轴,将纳骨堂藏于其中,并向天空生长。寺庙的主要功能被安排在结构体上方，仿佛漂浮存空中一般。最具象征性的空间是被置于中心轴最上方的“空之屋”。来自圆形天窗的光线从空间中穿过。“空之屋”处于包含音乐厅、美术馆这些文化功能的整个寺庙空间的中心，将各处都连接起来，却不属于任何地方。它象征性地承受着来自天空的恩泽，是一处用于冥想的空间。

Design of FeSiBPCu soft magnetic alloys with good amorphous forming ability and ultra-wide crystallization window

The Fe_(81.3)Si_(4)B_(13–x)PxCu_(1.7) soft magnetic alloys with high Cu and proper P elements addition were synthesized with the aim of ensuring the amorphous forming ability(AFA)while expanding the crystallization window(CW).It is found that the atomic ratio of P/Cu of∼3 is advantageous for AFA whereas a small amount of P addition promotes the precipitation ofα-Fe grains and excessive P addition induces surface crystallization behavior of the present alloys.High Cu concentration can expand the annealing temperature(Ta)window whereas proper P addition effectively expands the annealing time(ta)window.The Fe_(81.3)Si_(4)B_(13-x)PxCu_(1.7) soft magnetic alloy was successfully synthesized with a large Ta window of up to 130°C and ta window of 90 min,which is a breakthrough for nanocrystalline alloys with high saturation magnetization.Microstructure analysis reveals that the ultra-wide CW is related to the unique nucleation mechanism,that is,theα-Fe grains are precipitated attaching to the Cu or CuP clusters and enveloping the Cu clusters,resulting in the high number density ofα-Fe nanocrystals.The ultra-wide CW promises the potential material in flexibly choosing the annealing process according to the performance.

Strong dependency of the tribological behavior of CuZr-based bulk metallic glasses on relative humidity in ambient air

Thanks to their outstanding mechanical properties,Bulk Metallic Glasses(BMGs)are new alternatives to traditional crystalline metals for mechanical and micromechanical applications including power transmission.However,the tribological properties of BMGs are still poorly understood,mostly because their amorphous nature induces counter intuitive responses to friction and wear.In the present study,four different BMGs(Cu_(47)Zr_(46)Al_(7),Zr_(46)Cu_(45)Al_(7)Nb_(2),Zr_(60)Cu_(28)Al_(12),and Zr_(61)Cu_(25)Al_(12)Ti_(2))underwent ball-on-disc friction tests against 100Cr6 steel balls(American Iron and Steel Institute(AISI)52100)at different relative humidities(RHs)ranging from 20%to 80%.Controlling humidity enabled to observe a high repeatability of the friction and wear responses of the BMG.Interestingly,the friction coefficient decreased by a factor of 2 when the humidity was increased,and the wear rate of BMGs was particularly low thanks to a 3rd-body tribolayer that forms on the BMG surface,composed of oxidized wear particles originating from the ball.The morphology of this tribolayer is highly correlated to humidity.The study also identifies how the tribolayer is built up from the initial contact until the steady state is achieved.

A revisit to the role of Mo in an MP35N superalloy:An experimental and theoretical study

Molybdenum(Mo)has been recognized as an essential alloying element of the MP35N(Co_(35.4)Cr_(22.9)Ni_(35.5)Mo_(6.2),at.%)superalloy for enhancing strength and corrosion resistance.However,a full understanding of the addition of Mo on microstructure and mechanical properties of the Mo-free parent alloy is lacking.In this work,we consider five(Co_(37.7)Cr_(24.4)Ni_(37.9))_(100-x)Mo_(x)(x=0,0.7,2.0,3.2,and 6.2)alloys,and reveal that yield/tensile strength and ductility are continuously increased for these alloys with increasing Mo content while a single-phase face-centered cubic structure remains unchanged.It is found that strong solid solution strengthening(SSS)is a main domain to the improved yield strength,whereas grain boundaries are found to soften by the Mo addition.The first-principles calculations demonstrate that a severe local lattice distortion contributes to the enhanced SSS,and the grain boundary softening effect is mostly associated with the decreased shear modulus.Both first-principles calculations and scanning transmission electron microscopy observations reveal that the stacking fault energy(SFE)reduces by the Mo addition.The calculated SFE value decreases from 0.4 mJ/m^(2) to-11.8 mJ/m^(2) at 0 K as Mo content increases from 0 at.%to 6.2 at.%,and experimentally measured values of SFE at room temperature for both samples are about 18 mJ/m^(2) and 9 mJ/m^(2),respectively.The reduction of SFE promoted the generation of stacking faults and deformation twins,which sustain a high strain hardening rate,thus postponing necking instability and enhancing tensile strength and elongation.

End-to-end differentiability and tensor processing unit computing to accelerate materials’ inverse design

Numerical simulations have revolutionized material design.However,although simulations excel at mapping an input material to its output property,their direct application to inverse design has traditionally been limited by their high computing cost and lack of differentiability.Here,taking the example of the inverse design of a porous matrix featuring targeted sorption isotherm,we introduce a computational inverse design framework that addresses these challenges,by programming differentiable simulation on TensorFlow platform that leverages automated end-to-end differentiation.Thanks to its differentiability,the simulation is used to directly train a deep generative model,which outputs an optimal porous matrix based on an arbitrary input sorption isotherm curve.Importantly,this inverse design pipeline leverages the power of tensor processing units(TPU)—an emerging family of dedicated chips,which,although they are specialized in deep learning,are flexible enough for intensive scientific simulations.This approach holds promise to accelerate inverse materials design.

Microstructure and soft-magnetic properties of FeCoPCCu nanocrystalline alloys

Fe(83.2-x)CoxP(10)C6Cu(0.8)(x=0,4,6,8 and 10)alloys with a high amorphous-forming ability and good softmagnetic properties were successfully synthesized.Saturation magnetic flux density(Bs)is effectively enhanced from 1.53 T to 1.61 T for as-quenched alloy by minor Co addition,which is consistent well with the result of the linear relationship between average magnetic moment and magnetic valence.For Cocontained alloys,the value of corecivity(Hc)is mainly determined by magneto-crystalline anisotropy,while effective permeability(μe)is dominated by grain size and average saturation polarization.After proper heat treatment,the Fe(79.2)Co4P(10)C6Cu(0.8)nanocrystalline alloy exhibited excellent soft-magnetic properties including a high Bsof 1.8 T,a low Hcof 6.6 A/m and a highμeof 15,510,which is closely related to the high volume fraction of α-(Fe,Co)grains and refined uniform nanocrystalline microstructure.

Deformation behavior of a TiZr-based metallic glass composite containing dendrites in the supercooled liquid region

The deformation behavior of a TiZr-based bulk metallic glass composite(BMGC)was characterized in the supercooled liquid region(SLR)from 623 K to 693 K.It was observed that the alloy exhibits the deformation behavior from work softening at low temperatures to work hardening at high temperatures.The yield stress and overshoot stress decrease remarkably with the increase of temperature,accompanied by superplasticity.The results showed that the crystallization occurred in the amorphous matrix for the post-deformation samples and the volume fraction of the corresponding crystallization products increased with increasing testing temperature.It is implied that the work hardening behavior was closely associated with the crystallization of the amorphous matrix.The tensile stress can accelerate the crystallization of amorphous matrix and the martensitic transformation of dendrite phases,which implies that the thermal stability of the alloy decreases under tension.These findings shed light on designing new BMGCs with high mechanical performance as well as the good SLR formability.

Structure characteristics and piezoresistive effect of nc-Si:H films

In recent years, using the ultra-vacuum PECVD system, we have successfully prepared the nano-crystalline silicon films (nc-Si:H). The nc-Si:H films are composed of a mass of fine microcrystallites with the mean grain size of 3—5nm and the volume crystalline fraction of X_c=(50±5)%. The spacing between grains is constituted by a great number of interfaces, as shown in fig. 1. From the figure, it is estimated that the thickness of the interfaces is 1—4 atomic layers (≤1nm) and the volume fraction of the interfaces is about 40%. It is obvious that the microstructure of the nc-Si:H films is quite diffe

Enhanced dye degradation capability and reusability of Fe-based amorphous ribbons by surface activation

The dye degradation capability and reusability of FeSiBNbCu amorphous ribbons are largely enhanced due to the surface activation by ball milling.The time required for degrading 50%of acid orange 7 solution by the activated FeSiBNbCu amorphous ribbons is only 1/6 of that by the as-quenched ribbons,while the reusable times of the activated ribbons is 6 times larger than that of the as-quenched ribbons.The superior degradation capability and better reusability of the activated FeSiBNbCu amorphous ribbons come from not only the uneven topography of the ribbon surface induced by ball milling,but also the stored deformation energy,including the structural rejuvenation and the enlarged residual stress.The structural rejuvenation in the activated FeSiBNbCu amorphous ribbons is verified by heat relaxation analysis,and the increased residual stress is confirmed by the magnetic domain measurements on the ribbon surfaces.Besides,the environmental adaptability of the activated FeSiBNbCu amorphous ribbons is also investigated.The possible pathways for degradation of acid orange 7 using the activated ribbons,including azo bond cleavage and hydroxylation of benzene ring,are proposed.This work provides a new method to effectively improve the degradation performance of amorphous ribbons.

Corrosion mechanisms of Zr-based bulk metallic glass in NaF and NaCl solutions

So far,some investigations related to the corrosion mechanism of Zr-based metallic glasses in solutions containing Cl-have been developed.However,few attentions have been paid to the situation in F--containing solution.This paper describes the corrosion behaviours of Zr52Al10Ni6Cu32 bulk metallic glass(BMG)in Na F and Na Cl aqueous solutions.The corrosion mechanism of Zr-based BMG in F–containing solution was proposed for the first time.It was found that in Na Cl solutions,Zr-based BMG samples underwent typical pitting corrosion.Selective dissolution of Zr,Al and enrichment of Cu were observed in corrosion pits.However,corrosion occurred in the form of general breakdown of passive film in Na F solutions.Such difference is interpreted in terms of the binding ability of anions to surrounding molecules,i.e.,Cl-with loose surrounding water passes through the passive film to cause pitting;F-with a tight surrounding molecules layer absorbs on passive film then coordinates with cations from matrix.

Correlation between deformation behavior and atomic-scale heterogeneity in Fe-based bulk metallic glasses

The correlation betweent deformation behavior and atomic-scale heterogeneity of bulk metallic glasses(BMGs)is critical to understand the BMGs'deformation mechanism.In this work,three typical[(Fe_(0.5)Co_(0.5))_(0.75)B_(0.2)Si_(0.05)]_(96)Nb_4,Fe_(39)Ni_(39)B_(14.2)Si_(2.75)P_(2.75)Nb_(2.3),and Fe_(50)Ni_(30)P_(13)C_(7)BMGs exhibiting different plasticity were selected,and the correlation between deformation behavior and atomic-scale heterogeneity of Fe-based BMGs was studied.It is found that the serrated flow dynamics of Fe-based BMGs transform from chaotic state to self-organized critical state with increasing plasticity.This transformation is attributed to the increasing atomic-scale heterogeneity caused by the increasing free volume and short-to-medium range order,which facilitates a higher frequency of interaction and multiplication of shear bands,thereby results in a brittle to ductile transition in Fe-based BMGs.This work provides new evidence on heterogeneity in plastic Fe-based BMGs from the aspects of atomic-scale structure,and provides new insight into the plastic deformation of Fe-based BMGs.

Excellent reusability of FeBC amorphous ribbons induced by progressive formation of through-pore structure during acid orange 7 degradation

The high-efficient degrading ability of Fe BC amorphous ribbons toward acid orange 7(AO7)via redox reactions is reported and compared with that of Fe PC amorphous ribbons.The time required for degrading50%of AO7 using Fe BC amorphous ribbons is only 1/3 of that using Fe PC amorphous ribbons.In the Fe BC amorphous matrix,galvanic cell structures are formed between the Fe-B and Fe-C bonds because of the large difference in their bonding strengths,which contributes to the low reaction activation energy and the high degrading efficiency of Fe BC amorphous ribbons.The extremely long service life of Fe BC amorphous ribbons comes from the progressive formation of 3 D porous nanosheet networks that allow more efficient mass transport and a larger specific surface area.The Fe BC amorphous ribbons show a satisfying degrading ability in not only acidic but also neutral and weak alkaline AO7 solutions.This work provides an effective and environmental-friendly material for degrading azo dyes.

Mechanical Properties and Phase Stability of WTaMoNbTi Refractory High-Entropy Alloy at Elevated Temperatures

High-temperature structural metals remain in high demand for aerospace aircraft,gas turbine engines,and nuclear power plants.Refractory high-entropy alloys(RHEAs)with superior mechanical properties at elevated temperatures are promising candidates for high-temperature structural materials.In this work,a WTaMoNbTi RHEA with adequate room temperature plasticity and considerable strength at 1600℃was fabricated by vacuum arc-melting.The room temperature fracture strain of the as-cast WTaMoNbTi RHEA was 7.8%,which was about 5.2 times that of the NbMoTaW alloy.The alloy exhibited a strong resistance to high-temperature softening,with a high yield strength of 173 MPa and compressive strength of 218 MPa at 1600℃.The WTaMoNbTi RHEA possessed excellent phase stability in the range of room temperature to 2000℃.The dendritic grains grew into equiaxed grains after compression test at 1600℃due to the dynamic recrystallization process at high temperature.This work presents a promising high-temperature structural material that can be applied at 1600℃.

Efficient rejuvenation of heterogeneous{[(Fe_(0.5)Co_(0.5))_(0.75)B_(0.2)Si_(0.05)]_(96)Nb_(4)}_(99.9)Cu_(0.1) bulk metallic glass upon cryogenic cycling treatment

The effects of cryogenic thermal cycling on deformation behaviour and structural variation of{[(Fe_(0.5)Co_(0.5))_(0.75)B_(0.2)Si_(0.05)]_(96)Nb_(4)}_(99.9)Cu_(0.1) bulk metallic glass(BMG)were studied and compared with Cufree[(Fe_(0.5)Co_(0.5))_(0.75)B_(0.2)Si_(0.05)]_(96)Nb_(4) BMG.After thermal-cycled treatment between 393 K and cryogenic temperature,the{[(Fe_(0.5)Co_(0.5))_(0.75)B_(0.2)Si_(0.05)]_(96)Nb_(4)}_(99.9)Cu_(0.1)BMG obtained a plastic strain of 7.4%combined with a high yield strength of 4350 MPa.The excellent soft magnetic properties were maintained after CTC treatment.The minor addition of Cu element results in an initial nano-sized heterogeneity in the matrix,which facilitates the rejuvenation process during thermal cycling,and brings to a low optimal thermal temperature of 393 K,making the{[(Fe_(0.5)Co_(0.5))_(0.75)B_(0.2)Si_(0.05)]_(96)Nb_(4)}_(99.9)Cu_(0.1) BMG more attractive in industrial application.During thermal cycling,the formation of more soft regions leads to the increase of structural heterogeneities,which is beneficial to the initiation of shear transition zones and the formation of multiple shear bands,and thus results in the enhancement of plasticity.This study links the subtle variation of specific structure with macroscopic mechanical properties,and provides a new insight of composition selection for cryogenic thermal cycling treatment.

A plastic FeNi-based bulk metallic glass and its deformation behavior

The strength and plasticity of Fe_(39)Ni_(39)B_(12.82)Si_(2.75)Nb_(2.3)P_(4.13)bulk metallic glass(BMG)are improved simultaneously by modulating atomic-scale structure through fluxing treatment.The compression strength increases from 3074 to 4220 MPa,and the plastic strain is enlarged from 10.7%to more than 50%.The increased mechanical properties of the fluxed Fe Ni BSi Nb P BMG originate from the optimization of atomic-scale structure.More icosahedral-like clusters(ILCs)and crystal-like clusters(CLCs)are found in this Fe Ni-based BMG with fluxing treatment,and the ILCs are usually surrounded by CLCs.Furthermore,phase separation and a sandwich-like heterogeneous structure of SB are also observed during deformation,indicating the multiscale deformation mechanism and a stable shear-band evolution.The unique"ILC surrounded by CLCs"structure and phase separation lead to a stable plastic deformation process with strong interactions of multiple shear bands,thereby the improved plasticity and strength.This work provides useful guidelines to develop strong and plastic Fe-based BMGs from a structural aspect.