Evolution of medium-range order and its correlation with magnetic nanodomains in Fe-Dy-B-Nb bulk metallic glasses

Fe-based metallic glasses are promising functional materials for advanced magnetism and sensor fields.Tailoring magnetic performance in amorphous materials requires a thorough knowledge of the correlation between structural disorder and magnetic order,which remains ambiguous.Two practical difficulties remain:the first is directly observing subtle magnetic structural changes on multiple scales,and the second is precisely regulating the various amorphous states.Here we propose a novel approach to tailor the amorphous structure through the liquid-liquid phase transition.In-situ synchrotron diffraction has unraveled a medium-range ordering process dominated by edge-sharing cluster connectivity during the liquid-liquid phase transition.Moreover,nanodomains with topological order have been found to exist in composition with liquid-liquid phase transition,manifesting as hexagonal patterns in small-angle neutron scattering profiles.The liquid-liquid phase transition can induce the nanodomains to be more locally ordered,generating stronger exchange interactions due to the reduced Fe–Fe bond length and the enhanced structural order,leading to the increment of saturation magnetization.Furthermore,the increased local heterogeneity at the medium-range scale enhances the magnetic anisotropy,promoting the permeability response under applied stress and leading to a better stress-impedance effect.These experimental results pave the way to tailor the magnetic structure and performance through the liquid-liquid phase transition.

Corrosion and in vitro cytocompatibility investigation on the designed Mg-Zn-Ag metallic glasses for biomedical application

In the present work,seven Mg-Zn-Ag alloys with the nominal composition of Mg_(96-x)Zn_(x)Ag_(4)(x=17,20,23,26,29,32,35 in at.%)were prepared by induction melting and single-roller melt-spinning.The X-ray diffraction(XRD)analyses indicate the metallic glasses with three composition of Mg_(73)Zn_(23)Ag_(4),Mg_(70)Zn_(26)Ag_(4),and Mg_(67)Zn_(29)Ag_(4)were obtained successfully.The differential scanning calorimetry(DSC)measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis.The maximum glass transition temperature(Trg)was found to be 0.525 with a composition close to Mg_(67)Zn_(29)Ag_(4),which results in the best glass-forming ability.Moreover,the immersion test in simulated body fluid(SBF)demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses.The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content.The sample Mg_(67)Zn_(29)Ag_(4)has the lowest corrosion rate of 0.19mm/yr,which could meet the clinical application requirement well.The in vitro cell experiments show that the Madin-Darby canine kidney(MDCK)cells cultured in sample Mg_(67)Zn_(29)Ag_(4)and its extraction medium have higher activity.However,the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma(RD)tumor cells.The present investigations on the glass-forming ability,corrosion behavior,cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.

Effect of overheating-induced minor addition on Zr-based metallic glasses

Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin responsible for the variation of properties remains poorly understood.In the present work,we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins.Specifically,we quenched the melt at different temperatures ranging from 1.1Tl to 1.5Tl(Tl is the liquidus temperature)to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating.We found that glass transition temperature,Tg,increases by as much as 36 K,and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5Tl.The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys.The incorporated oxygen and silicon can both enhance the interactions between atoms,which renders the cooperative rearrangements of atoms difficult,and thus enhances the kinetic stability of the MGs.

Magnetic and magnetocaloric effect of Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass

Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass exhibited excellent magnetic refrigeration material with a wide temperature range and high refrigeration capacity(RC)was reported.Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass was observed with typical spin glass behavior around 15.5 K.In addition,we find that the magnetic entropy change(-△S_(M))originates from the sample undergoing a ferromagnetic(FM)to paramagnetic(PM)transition around 20 K.Under a field change from 0 T to 7 T,the value of maximum magnetic entropy change(-△S_(M)^(max))reaches 12.5 J/kg·K,and the corresponding value of RC reaches 487.7 J/kg in the temperature range from 6 K to 60 K.The large RC and wide temperature range make the Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass be a promising material for application in magnetic refrigerators.

Structural color of metallic glass through picosecond laser

The alteration in surface color of metallic glasses(MGs)holds great significance in the context of microstructuredesign and commercial utility.It is essential to accurately describe the structures that are formed during the laser and colorseparation processes in order to develop practical laser coloring applications.Due to the high oxidation sensitivity of Labasedmetallic glass,it can broaden the color range but make it more complex.Structure coloring by laser processing on thesurface of La-based metallic glass can be conducted after thermoplastic forming.It is particularly important to clarify therole of structure and composition in the surface coloring process.The aim is to study the relationship between amorphoussurface structural color,surface geometry,and oxide formation by laser processing in metallic glasses.The findings revealedthat the periodic structure primarily determines the surface color at laser energy densities below 1.0 J/mm^(2).In contrast,thesurface color predominantly depends on the proportion of oxides that are formed when energy densities exceed 1.0 J/mm^(2).Consequently,this study provides a novel concept for the fundamental investigation of laser coloring and establishes a newavenue for practical application.

Effect of high-energy Ne ions irradiation on mechanical properties difference between Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5)metallic glass and crystalline W

In this paper,high-energy Ne ions were used to irradiate Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) metallic glass(MG)and crystalline W to investigate their difference in mechanical response after irradiation.The results showed that with the irradiation dose increased,the tensile micro-strain increased,nano-hardness increased from 7.11 GPa to 7.90 GPa and 8.62 GPa,Young’s modulus increased,and H3/E2 increased which indicating that the plastic deformability decreased in crystalline W.Under the same irradiation conditions,the Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG still maintained the amorphous structure and became more disordered despite the longer range and stronger displacement damage of Ne ions in Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG than in crystalline W.Unlike the irradiation hardening and embrittlement behavior of crystalline W,Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG showed the gradual decrease in hardness from 6.02 GPa to 5.89 GPa and 5.50 GPa,the decrease in modulus and the increase in plastic deformability with the increasing dose.Possibly,the irradiation softening and toughening phenomenon of Zr_(63.5)Cu_(23)Al_(9)Fe_(4.5) MG could provide new ideas for the design of nuclear materials.

Unveiling the early stage evolution of local atomic structures in the crystallization process of a metallic glass

The early stage evolution of local atomic structures in a multicomponent metallic glass during its crystallization process has been investigated via molecular dynamics simulation.It is found that the initial thermal stability and earliest stage evolution of the local atomic clusters show no strong correlation with their initial short-range orders,and this leads to an observation of a novel symmetry convergence phenomenon,which can be understood as an atomic structure manifestation of the ergodicity.Furthermore,in our system we have quantitatively proved that the crucial factor for the thermal stability against crystallization exhibited by the metallic glass is not the total amount of icosahedral clusters,but the degree of global connectivity among them.

Design and characterization of biodegradable Mg-Zn-Ag metallic glasses

In order to develop the Mg-Zn-Ag metallic glasses(MGs)for biodegradable implant applications,the glass formation ability(GFA)and biocompatibility of Mg-Zn-Ag alloys were investigated using a combination of the calculation of phase diagrams(CALPHAD)and experimental measurements.High GFA potentiality of two alloy series,specifically Mg_(96-x)Zn_xAg_(4)and Mg_(94-x)Zn_xAg_6(x=17,20,23,26,29,32,35),was predicted theoretically and then substantiated through experimental testing.X-ray diffraction(XRD)and differential scanning calorimetry(DSC)techniques were used to evaluate the crystallinity,GFA,and crystallization characteristics of these alloys.The results showed that compositions between Mg_(73)Zn_(23)Ag_(4)and Mg_(64)Zn_(32)Ag_(4)for Mg_(96-x)Zn_xAg_4,Mg_(66)Zn_(28)Ag_(6)and Mg_(63)Zn_(31)Ag_(6for)Mg_(94-x)Zn_xAg_(6)displayed a superior GFA.Notably,the GFA of the Mg_(96-x)Zn_xAg_(4)series was better than that of the Mg_(94-x)Zn_xAg_(6)series.Furthermore,the Mg_(70)Zn_(26)Ag_4,Mg_(74)Zn_(20)Ag_6,and Mg_(71)Zn_(23)Ag_(6)alloys showed acceptable corrosion rates,good cytocompatibility,and positive effects on cell proliferation.These characteristics make them suitable for applications in medical settings,potentially materials as biodegradable implants.

A group of ductile metallic glasses prepared by modifying local structure of icosahedral quasicrystals

Inspired by research into the association between icosahedral local orders and the plasticity of metallic glasses(MGs),beryllium(Be) is added to the icosahedral quasi-crystal forming alloy Zr40Ti40Ni20. In this way, bulk metallic glasses(BMGs) with favorable compressive plasticity are fabricated. Therein, the icosahedral quasi-crystalline phase is the main competing phase of amorphous phases and icosahedral local orders are the main local atomic motifs in amorphous phases.The alloys of(Zr40Ti40Ni20)76Be24and (Zr40Ti40Ni20)72Be28with their greater plastic strain capacity show similar characteristics to highly plastic amorphous systems: The serrated flow of compression curves always follows a near-exponential distribution. The primary and secondary shear bands intersect each other, bifurcate, and bend. Typical vein patterns are densely distributed on the fracture surfaces. The relaxation enthalpy of four MGs is linearly correlated with the plastic strain, that is, the greater the relaxation enthalpy, the larger the plastic strain.

Structural origin for composition-dependent nearest atomic distance in Cu–Zr metallic glass

We systematically investigate the structures of Cu–Zr metallic glass(MG) by varying the Cu concentration in classic molecular-dynamics simulation. From the pair distribution functions(PDFs), it is found that the nearest atomic distance between Zr atom and Zr atom increases significantly after adding Cu, which is related to the composition-dependent coordination behavior between Cu atom and Zr atom in the nearest neighbors. The portion of PDF related to the nearest connection is decomposed into the contributions from quadrilateral structure, pentagonal structure, hexagonal structure,and heptagonal bipyramid structure. Although the population of denser structures, i.e. 5-, 6-, and 7-number sharing ones,increases with Cu addition increasing, the connection distances between the central atoms in all these bipyramids increase for Zr–Zr pairs, leading to the expansion of Zr–Zr nearest atomic distance. These results unveil the effect of the interplay between chemical interaction and geometric packing on the atomic-level structure in Cu–Zr metallic glasses.

Fabrication, tribological and corrosion behaviors of detonation gun sprayed Fe-based metallic glass coating

A metallic glass coating with the composition of Fe51.33Cr14.9Mo25.67Y3.4C3.44B1.26 （mole fraction, %） on the Q235 stainless steel was developed by the detonation gun （D-gun） spraying process. The microstructure and the phase aggregate were analyzed by scanning electron microscopy and X-ray diffractometry, respectively. Microhardness, wear resistance and corrosion behavior were assessed using a Vickers microhardness tester, a ball-on-disk wear testing machine and the electrochemical measurement method, respectively. Microstructural studies show that the coatings possess a densely layered structure with the porosity less than 2.1%. The tribological behavior of the coatings examined under dry conditions shows that their relative wear resistance is five times higher than that of the substrate material. Both adhesive wear and abrasive wear contribute to the friction, but the former is the dominant wear mechanism of the metallic glass coatings. The coatings exhibit low passive current density and extremely wide passive region in 3.5% NaCl solution, thus indicating excellent corrosion resistance.

Casting effect on compressive brittleness of bulk metallic glass

An interesting phenomenon of cooling-rate induced brittleness in Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass （BMG） was reported. It was found that the as-cast BMG specimens exhibited a brittle-ductile transition when the larger specimens were machined into smaller specimens through removing the cast-softening surface layer by layer. After compression tests, the as-machined small specimens, owing to the absence of the cast-softening surface, displayed highly dense and intersecting shear bands, and extensive plastic deformation. This is in contrast to the catastrophic failure and low deformability in the as-cast large specimens. More free volume was detected in the smaller as-fractured specimens, by differential scanning calorimetry, which may be attributed to the occurrence of strain softening and increased plasticity. Compared with the relatively smooth fracture surface in the smaller specimens, the larger specimens showed more diverse features on the fracture surface due to their graded structures.

Effect of Ti on microstructure,mechanical and corrosion properties of (Zr_(0.55)Al_(0.1)Ni_(0.05)Cu_(0.3))_(100-x)Ti_x bulk metallic glasses

The（Zr_（0.55）Al_（0.1）Ni_（0.05）Cu_（0.3））_（100-x）Ti_x alloys were prepared using an in-situ suck-casting method in a copper mold. The effects of Ti addition on the microstructure, mechanical and corrosion properties of the（Zr_（0.55）Al_（0.1）Ni_（0.05）Cu_（0.3））_（100-x）Ti_x alloys were investigated by X-ray diffraction, scanning electron microscopy, compressive tests and corrosion tests. It has been found that the addition of Ti higher than 4%（mole fraction） causes the formation of many crystalline phases in the alloy. The alloys with 1%-3% Ti display an obvious yield stage on their compressive stress-strain curves. An appropriate addition of Ti can improve the strength and ductility of the alloys. All the alloys have high corrosion resistance in 1 mol/L Na OH solution, and are corroded in 1 mol/L HCl solution. However, the appropriate addition of Ti can significantly improve the corrosion resistance of the alloys in HCl solution.

Enhanced plasticity of Fe-based bulk metallic glass by tailoring microstructure

The room temperature compressive plasticity of Fe75MosP10Cs.3B1.7 bulk metallic glass （BMG） was improved from 0.5% to 1.8% by increasing the sample diameter from 1.5 mm to 2.0 mm. With increasing the sample diameter to 2.0 mm, a heterogeneous microstructure with in-situ formed a-Fe dendrite sparsely distributed in the amorphous matrix can be attained. This heterogeneous mierostructure is conceived to be highly responsible for the enhanced global plasticity in this marginal Fe-based BMG.

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%.

Effects of Y addition on structural and mechanical properties of CuZrAl bulk metallic glass

The effects of Y addition on the structural and mechanical properties of CuZrAl bulk metallic glass（BMG） were studied.The results show that the glass forming ability of CuZrAl system is improved by the addition of Y and the fracture strength decreases with Y addition due to the reduction of binding energy induced by Y.The fracture surface is dominated by vein-like patterns in Cu45Zr48Al7 bulk metallic glass,and changes to smooth regions in Cu46Zr42Al7Y5 BMG.TEM observation shows that Cu45Zr48Al7 BMG has a composite microstructure of nanocrystalline phases dispersed in amorphous matrix.However,the Cu46Zr42Al7Y5 BMG shows a fully amorphous structure.

Electrochemical corrosion properties of Zr- and Ti-based bulk metallic glasses

The corrosion behaviors of Ti-based and Zr-based amorphous alloys and their corresponding crystallized alloys were studied by electrochemical methods. It is found that the corrosion potentials of Zr-based amorphous alloy and its corresponding crystalline counterpart are both lower than those of the Ti-based amorphous alloy in the 1 mol/L H2SO4 solution. In the 3.5% NaCl solution,Zr-based crystallized alloy exhibits the lowest corrosion potential among the experimental samples. No passivation is observed in the corrosion process for the Zr-based crystalline alloy. However, Zr- and Ti-based amorphous alloys both exhibit passivation characteristics. EIS measurements indicate the amorphous alloys exhibit better corrosion resistance than the crystallized one in the NaCl solution. Surface analysis shows that both amorphous alloys in the NaCl solution are eroded by pitting corrosion. In the H2SO4 solution, all the alloys display similar behaviors and their surfaces can mostly keep intact except for some cracks on the corroded surface at local region.

Effect of minor Fe addition on glass forming ability and mechanical properties of Zr_(55)Al_(10)Ni_5Cu_(30) bulk metallic glass

A series of rod samples with diameter of 3 mm（Zr0.55Al0.10Ni0.05Cu0.30）100-xFex（x=0,1,2,3,4） were prepared by magnetic suspend melting and copper mold suction casting method.The effects of a small amount of Fe on glass forming ability（GFA） and mechanical properties of Zr55Al10Ni5Cu30 bulk metallic glass（BMG） were investigated.The results show that the addition of an appropriate amount（less than 3%,mole fraction） of Fe enhances GFA,as indicated by the increase in the reduced glass transition temperature Trg（=Tg/Tl） and the parameter γ（=Tx/（Tg＋Tl）） with increasing Fe content,and GFA gets deteriorated by further Fe addition（4%）.The addition of Fe also effectively improves the compressive plasticity and increases the compressive fracture strength in these Zr-based BMGs.Compressive tests on BMG sample with 3 mm in diameter and 6 mm in length reveal work-hardening and a certain plastic strain in the alloy containing 2% Fe.The BMG composite containing 4% Fe also exhibits a high fracture strength along with significant plasticity.

Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of Fe-Co-Ni-Cr-Mo-C-B-Y bulk metallic glasses

Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） metallic glasses were fabricated by copper mold casting method.The thermal stability and crystallization behavior of the metallic glass rods were investigated by differential scanning calorimetry and isothermal experiments.Hardness measurements for samples annealed at different temperatures for different time were carried out at room temperature by the Vickers hardness tester,and magnetic measurements were performed at different temperatures by the vibrating sample magnetometer.It is shown that the addition of Ni does not play a positive role for enlarging ΔTx and GFA from parameter γ（=Tx/（Tg＋Tl））,and it can,however,increase the activation energy in the initial stage of crystallization by changing the initial crystallization behavior.The minor addition of Ni can refine the crystal grain obtained from the full crystallization experiment.The primary crystallization causes the decrease of hardness in these alloys,and as the crystallization continues,the hardness in all samples increases instead due to the precipitation of carbide and boride.The annealing temperature has an obvious effect on magnetic properties of these alloys,and the minor addition of Ni can effectively prevent the alloy annealed at high temperature to transform from paramagnetic to ferromagnetic state.

Growth kinetics for intermetallic compound layer between molten In-Sn alloy and CuZr-based bulk metallic glass

The growth kinetics of intermetallic compound layer between molten In-Sn alloy and Cu40Zr44Al8Ag8 bulk metallic glass substrate was examined by solid state isothermal aging at the temperature range between 333 and 393 K.The aged samples were characterized by scanning electron microscopy and energy dispersive spectrometry.It is found that the intermetallic compound layer is composed of Zr,Cu and Sn.The layer growth of the intermetallic compound is mainly controlled by a diffusion mechanism over the temperature range and the value of the time exponent is approximately 0.5.The apparent activation energy for the growth of total intermetallic compound layers is 98.35 kJ /mol calculated by the Arrhenius equation.