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.

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.

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.

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.

Liquid dynamics and glass formation of Gd_(55)Co_(20)Al_(25)metallic glass with minor Si addition

Liquid dynamics plays an essential role in glass formation.Here we observed a distinct change of liquid dynamics in Gd_(55)Co_(20)Al_(25)metallic glass induced by microalloying Si element.In the equilibrium melt,minor Si(0.5 at.%)addition leads to a more fragile liquid behavior and a smaller strength of liquid-liquid transition with the transition strength(F)decreasing from 0.76 to 0.35.However,in the supercooled liquid,Si-doped liquid exhibits a remarkable enhanced fragile-to-strong transition(FST),and the value of FST factor f increases sharply from 1.63 to 3.84,resulting in a stronger liquid behavior and more sluggish crystallization kinetics for Gd_(55)Co_(20)Al_(24.5)Si_(0.5)metallic glass.Moreover,minor Si addition promotes the formation of a crystal-like structure with a size of 1-2 nm.The interactions between the crystal-like structures and other local favored clusters frustrate the further growth of crystal-like phases,thus stabilizes the amorphous structure.As a result,the glass-forming ability(GFA)was largely improved.The critical diameter of Gd_(55)Co_(20)Al_(25)metallic glass increased from 2 to 7 mm with 0.5 at.%Si addition without deterioration of the magnetocaloric effect.This study provides valuable insight for understanding the distinct effect of microalloying on GFA of metallic glasses from the aspect of the evolution of the liquid.

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.

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.

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℃.

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.

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.