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.

Preparation and Mechanical Properties of Misch Metal Based Bulk Metallic Glasses

The formation, thermal stability and mechanical properties of Misch metal （Mm）-based alloy bulk metallic glasses （BMGs） with composition of Mm55Al25Cu10Ni5Co5 were investigated by means of X-ray diffraction, differential scanning calorimetry, differential thermal analysis and compression test. The results indicate that the Mm-based BMGs exhibit a distinct glass transition and a wide supercooled liquid region Δ Tx（ 〉 60 K） before crystallization. The alloy can be fabricated into bulk glassy form of 3 mm in diameter by copper mold casting methods. Compared with the La55Al25Cu10 Ni5Co5 BMG, the Mm55Al25Cu10Ni5Co5 BMG shows higher compression fracture strength and lower cost. A new parameter γ and melting temperature Tl are closely correlated with the glass forming ability （GFA） of Mm-based alloys.

Mechanical properties and thermal conductivity of pristine and functionalized carbon nanotube reinforced metallic glass composites:A molecular dynamics approach

This work uses the molecular dynamics approach to study the effects of functionalization of carbon nanotubes(CNTs)on the mechanical properties of Cu64Zr36 metallic glass(MG).Three types of functional groups,carboxylic,vinyl and ester were used.The effect of CNT volume fraction(Vf)and the number of functional groups attached to CNT,on the mechanical properties and thermal conductivity of CNT-MG composites was analysed using Biovia Materials Studio.At lower values of Vf(from 0 to 5%),the percentage increase in Young’s modulus was approximately 66%.As the value of Vf was increased further(from 5 to 12%),the rate of increase in Young’s modulus was reduced to 16%.The thermal conductivity was found to increase from 1.52 W/mK at Vf?0%to 5.88 W/mK at Vf?12%,thus giving an increase of approximately 286%.Functionalization of SWCNT reduced the thermal conductivity of the SWCNT-MG composites.

Structural Origins for Enhanced Thermal Stability and Glass‑Forming Ability of Co–B Metallic Glasses with Y and Nb Addition

The effects of Y and Nb addition on thermal stability,glass-forming ability(GFA),and magnetic softness of Co75B25 metallic glass(MG)were comprehensively investigated.The experimental results indicated that the thermal stability,GFA,and magnetic softness of the studied MGs increase in the order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25).The structural origins of the improved properties were revealed by ab initio molecular dynamics(AIMD)simulations and density functional theory(DFT)calculations.Results showed that the B-centered prism units are the primary structure-forming units of the four MGs,connect through vertex-,edge-,and face-shared(VS,ES,and FS)atoms,and Co-centered units tend to connect with Co/B-centered units via the intercross-shared(IS)atoms.The addition of Y and Nb not only plays the role of connecting atoms but also enhances both bond strengths and the fractions of icosahedral-like units in increasing order Co_(75)B_(25)<Co_(73)Nb_(2)B_(25)<Co_(71.5)Y_(3.5)B_(25)<Co_(69.5)Y_(3.5)Nb_(2)B_(25),which is conducive to the enhancement of the structural stability,atomic packing density,and viscosity,thereby improving thermal stability and GFA.In addition,the improvement of structural stability and homogeneity leads to enhanced magnetic softness.

Formation,thermal stability and mechanical properties of Ti_(42.5)Zr_(7.5)Cu_(40)Ni_5Sn_5 bulk metallic glass

Ti42.5Zr7.5Cu40Ni5Sn5 bulk metallic glass with a critical diameter of 4 mm was fabri-cated by the conventional copper mould casting method. The supercooled liquid region ΔTx,reduced glass transition temperature Trg,γ parameter,and δparameter of the alloy were measured to be 63.9 K,0.561,0.393,and 1.400,respectively,im-plying that the alloy has an excellent glass-forming ability. The bulk metallic glass exhibits high compressive fracture strength of 2162 MPa with distinct plastic strain of 0.9%. The fracture surface consists mainly of vein-like patterns,typical of bulk glassy alloys.

Effect of Sn addition on the glass-forming ability and mechanical properties of Ni-Nb-Zr bulk metallic glasses

The effect of tin (Sn) addition on the glass forming ability (GFA) and mechanical properties of the Ni-Nb-Zr ternary alloy system has been studied. The addition of Sn improves the GFA; Ni61Nb35.5-xZr3.5Snx (in at.%) alloys with x=1 can be cast into amorphous samples at least 3 mm in diameter using a copper mold injection-casting method. The critical size for glass formation decreases to 2 mm when x=5 because Ni2SnZr phase precipitates readily. The addition of Sn is also effective in enhancing the stability of the supercooled liquid; a maximum supercooled liquid region of 48 K was attained for the Ni61Nb30.5Zr3.5Sn5 alloy. Compression tests reveal that the Ni61Nb33.5Zr3.5Sn2 alloy possesses the best mechanical properties,with yield strength～3180 MPa,fracture strength～3390 MPa and plastic strain ～1.3%. The fracture surfaces examined by scanning electron microscopy indicate that the alloys have a transition from ductility to brittleness in fracture behavior. The combination of high GFA,high thermal stability,high strength and compressive plasticity makes these alloys potentially attractive for engineering applications.

Effect of minor aluminium addition in Cu47Ti34Zr11Ni8 bulk metallic glasses

Cu47Ti34Zr11Ni8 and (Cu47Ti34Zr11Ni8)_ 99Al bulk metallic glass with size of 1mm×10mm×50mm were prepared by copper mold casting, and the influence of minor aluminium addition upon the alloy thermal stability and mechanical properties was studied. The results indicate that with the aluminium addition, the crystallizing behavior of the melt changes at the same cooling rate, and the crystallizing behavior of the glass changes at the same heating rate. The glass transition temperature(T_g), crystallization temperature(T_ x1), temperature interval of supercooled liquid region ΔT_x (=T_ x1-T_g) and reduced glass transition temperature (T_ rg) are proved to be changed from 672K, 734K, 62K and 0.578 to 681K, 729K, 48K and 0.590, respectively. Because of the addition of aluminium, three point-bending flexural strength and flexural modulus of the bulk glass are increased from 2350MPa and 102GPa to 2970MPa and 108GPa, respectively.

Strengthening bulk metallic glasses with minor alloying additions

Cu47Ti34Zr11Ni8, (Cu47Ti34Zr11Ni8)99Si and (Cu47Ti34Zr11Ni8)99Al bulk metallic glass were prepared by copper mold casting method, and the thermal stability, mechanical properties and microstrucrures of them were studied. With minor alloying of Si and Al additions, the glass transition temperature (Tg), crystallization temperature (Txl) and temperature interval of supercooled liquid region△Tx (=Txl-Tg) and reduced glass transition temperature (Trg) were proved to be changed from 672 K, 734 K, 62 K, 0.575 to 691 K, 752 K, 61 K, 0.592 and to 681 K, 729 K, 48 K, 0.590, respectively. The results indicate that the glass-forming ability (GFA) are improved with minor alloying additions. And the bulk glasses also exhibits high three point-bending flexural strength. Because of the additions of Si and Al, three point-bending flexural strength and flexural modulus of the bulk glass change from 2 350 MPa, 102 GPa to 3 260 MPa, 102 GPa and 2 970 MPa, 108GPa respectively. The obvious strengthening is due to the appearance of the medium-range ordered regions with a size of 2-5 nm under the high-resolution TEM image. The reason that the mixed amorphous and nanocrystalline phases caused by minor alloying of Si and Al additions, is that Si or Al is the third kind of elements, which are different from other constituting elements, and there are a strong bonding and atoms size effects between constituting elements, which cause the glass-forming ability (GFA) and the bulk metallic glasses strength improving.

Enhancement of glass-forming ability and thermal stability of a soft magnetic Co_(75)B_(25)metallic glass by micro-alloying Y and Nb

Soft magnetic Co-based Co-Y-Nb-B bulk metallic glasses(BMGs)without Fe have been developed by micro-alloying Y and Nb into a C075B25 alloy.First,addition of 3^at.%Y promotes the occurrence of glass transition and increases the supercooled liquid stability and magnetic softness.C0_(71.5)Y_(35)B_(25) metallic glass possesses a large supercooled liquid region(△T_(x))of 33 K and low coercivity(H_(c))of l.5 A/m.Subsequent alloying 2-4 at.% Nb into C0_(71.5)Y_(35)B_(25) alloy further enlarges △T_(x) to 50 K,lowers H_(c) to 0.9 A/m,and enables the formation of BMGs with a critical sample diameter up to 2.0 mm.The alloying Nb causes the formation of complex(Co,Nb,Y)_(23)B_(6) competing phase during crystallization and widens the melt undercooling during solidification,which improves the supercooled liquid stability and glass-forming ability,respectively.Co-Y-Nb-B BMGs also exhibit good soft magnetic and mechanical properties,i.e.,lowH_(c)of 0.9-1.2 A/m,relatively high saturation magnetic flux density of 0.36-0.57 T,high yielding strength of 3877-3930 MPa with plastic strain of 0.2%-0.3%,and high Vickers hardness of 1156-1201.The developed soft magnetic Co-based BMGs are promising for applications as structural and functional materials.

Effect of thermal cycling on the mechanical properties of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) alloy

The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated.The metallic glassy samples are sealed into quartz tubes under high vacuum condition,and liquid nitrogen together with electric furnace are used to control a periodical temperature variation between 196℃ and 150℃.The structure and properties of the tested samples for different thermal cycles have been examined by X-ray diffraction analysis,mechanical properties measurement and thermal analysis.It has been found that the structure and properties of the samples do not show a significant change even after 200 cycles,which suggests Zr41Ti14Cu12.5Ni10Be22.5 alloy as having potential in aerospace environment.

Recent progress in high-entropy metallic glasses

High-entropy metallic glass(HEMG)is a new type of metallic material with high-entropy alloy-like com-position and amorphous structure,which render HEMGs unusual glass formation behaviors and unique properties.In recent years,fast research progress has been witnessed on the HEMGs,and thus a sys-tematic review is required.In this review,we first introduce the concept of the HEMGs and summarize the developed HEMGs.Then,the glass-forming ability of the HEMGs is discussed,and the general rules are proposed.Focusing on the thermal stability of HEMGs,the effect of entropy on the energy states of HEMGs and the crystallization behavior of HEMGs are discussed.Finally,the mechanical,magnetic,cat-alytic and other properties of HEMGs are presented,and the advantages and disadvantages of HEMGs are shown.This review can function as a quick guideline for overviewing the HEMG field.

Effect of Ag addition on the thermal stability and glass-forming ability of Zr_(35)Ti_(30)Cu_(7.5)Be_(27.5) bulk metallic glass

The thermal stability and glass forming ability (GFA) of Zr35-xTi30Cu7.5Be27.5Agx (x = 0-10) alloys were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and ultrasonic techniques. We found that the addition of 1 at.% Ag can considerably enhance the GFA as indicated by an increase in the critical glass dimension from 15 mm in the Zr35Ti30Cu7.5Be27.5 alloy to 20 mm in the Zr34Ti30Cu7.5Be27.5Ag1 alloy. However, with the addition of more Ag the supercooled liquid region (△Tx) and y parameter (defined as Tx/(Tg+Tl)) drastically decreased from 155 K and 0.436 to 76 K and 0.363, respectively, resulting in a decrease in the GFA. Additionally, the elastic constant (the ratio of shear modulus to bulk modulus or Poisson's ratio) was also used as a gauge to evaluate the GFA in Zr35-xTi30Cu7.5Be27.5Agx alloys.

Fe−C micro-alloying effect on properties of Zr_(53)Al_(11.6)Ni_(11.7)Cu_(23.7)bulk metallic glass

(Zr_(53)Al_(11.6)Ni_(11.7)Cu_(23.7))_(1−x)(Fe_(77.1)C_(22.9))_(x)(x=0−2.2,at.%)bulk metallic glasses(BMGs)were prepared by copper mold suction casting method.Their glass forming ability and physical and chemical properties were systematically investigated.The glass forming ability is firstly improved with increasing x,and then decreased when x exceeds 0.44 at.%.Both glass transition temperature and crystallization temperature are increased,while the supercooled liquid region is narrowed,with Fe−C micro-alloying.The hardness,yielding and fracture strength,and plasticity firstly increase and then decrease when x reaches up to 1.32 at.%.The plasticity of the BMG(x=1.32 at.%)is six times that of the Fe-free and C-free BMG.In addition,by the Fe−C micro-alloying,the corrosion potential is slightly decreased,while the corrosion current density increases.The pitting corrosion becomes increasingly serious with the increase of Fe and C content.

Broadband 1.53 μm emission in Er^(3+)-doped Ga-Bi-Pb-Ge heavy metal oxide glasses

We investigated the thermal stability and spectroscopic properties of the 1.53 μm emission from ^4I13/2→^4I15/2 transition of Er^3＋ ions in Er^3＋/Yb^3＋-codoped Ga-Bi-Pb-Ge heavy metal oxide glass for use in broadband fiber amplifiers. It was noted that the addition of GeO2 effectively enhanced the thermal stability of the heavy metal oxide glass studied. The emission peak located at approximately 1530 nm with a full width at haft-maximum of approximately 58 nm. The measured lifetime and the calculated emission cross-section of this transition were -3.2 ms and -10.3×10^-21 cm^2, respectively. As a result, Ga-Bi-Pb-Ge heavy metal oxide glasses were assumed to be potential host material for the 1.53 μm broadband optical fiber amplifiers.

Tailoring mechanical heterogeneity,nanoscale creep deformation and optical properties of nanostructured Zr-based metallic glass

Metallic glasses are spatially heterogeneous at the nanometer scale.However,the effects of external excitation on their structural and mechanical heterogeneity and the correlation to their properties are still unresolved.Nanoindentation,atomic force microscopy(AFM) and high-resolution transmis sion elec tron micro scopy(HRTEM) were carried out to explore the effects of cryogenic thermal cycling(CTC) on mechanical/structural heterogeneity,nano sc ale creep deformation and optical properties of nano structured metallic glass thin films(MGTFs).The results indicate that CTC treatment alters the distribution fluctuations of hardness/modulus and energy dissipation and results in an increase-then-decrease variation in mechanical heterogeneity.By applying Maxwell-Voigt model,it can be shown that CTC treatment results in a remarkable activation of more defects with longer relaxation time in soft regions but has only a slight effect on defects in hard regions.In addition,CTC treatment increases the transition time from primary-state stage to steady-state stage during creep deformation.The enhanced optical reflectivity of the MGTFs after 15 thermal cycles can be attributed to increased aggregation of Cu and Ni elements.The results of this study shed new light on understanding mechanical/structural heterogeneity and its influence on nanoscale creep deformation and optical characteristics of nanostructured MGTFs,and facilitate the design of high-performance nanostructured MGTFs.

Ultrathin, flexible, and high-strength Ni/Cu/metallic glass/Cu/Ni composite with alternate magneto-electric structures for electromagnetic shielding

Electromagnetic interference(EMI)shielding materials with ultrathin,flexible,superior mechanical and thermal management properties are highly desirable for smart and wearable electronics.Here,ultrathin and flexible Ni/Cu/metallic glass/Cu/Ni(Ni/Cu/MG)multilayer composite with alternate magnetic and electrical structures was designed via facial electroless plating of Cu and Ni on an Fe-based metallic glass.The resultant 0.02 mm-thick Ni/Cu/MG composite displays a superior EMI shielding effectiveness(EMI SE)of 35 dB and a great EMI SE/t of 1750 dB/mm,which is greater than those of composites with monotonous multilayer or homogeneous structures.The improved EMI SE originates from the massive ohmic losses,the enhanced internal reflection/absorption,and the abundant interfacial polarization loss.Particularly,Ni/Cu/MG exhibits a high tensile strength of up to 1.2 GPa and outstanding mechanical stability,enabling the EMI SE remains unchanged after 10,000 times of bending.Moreover,Ni/Cu/MG has excellent Joule heating characteristics and thermal stability,which is very suitable for heating components of wearable hyperthermia devices.

Ni对Mg-Cu-Tb非晶合金形成及力学性能的影响

利用熔体铜模喷铸法制备出直径为3 mm的Mg65Cu25-xNixTb10(x=0,5,10)非晶合金。利用X射线衍射、差热分析、压缩实验分析和扫描电镜分析了添加Ni元素对Mg-Cu-Tb非晶合金形成能力及力学性能的影响。研究表明:随着Ni含量的增加,合金的玻璃转变温度Tg增大;开始结晶温度Tx降低;过冷液相区宽度ΔTx减小,约化玻璃转变温度Trg从0.562降至0.530,非晶形成能力逐渐降低。压缩实验结果表明:当Ni含量增加到5%时可以明显提高Mg-Cu-Tb-Ni非晶合金的断裂强度。

Nb对Zr基块体非晶合金热稳定性、非晶形成能力及机械性能的影响

利用水冷铜模铸造法成功制备了(Zr70Ni10Cu20)90-xNbxAl10(x=0,2,5,7)块体非晶合金,采用XRD,DSC 和DTA研究了Nb对该合金体系热稳定性和非晶合金形成能力(GFA)的影响.结果表明,适量Nb的添加可有效提高该合金的GFA和热稳定性.当Nb含量为x=2时,合金具有最宽的过冷液态区(△Tx=119 K)和最大的非晶形成能力(参数γ=Tx/(Tg+Tl=0.435).Nb的适量添加也有利于提高块体非晶合金的强度和塑性应变,其中x=2的块体非晶的抗压强度和断裂应变量分别达到1783 MPa和11.1%.

Zr含量对非晶合金非晶形成能力及力学性能的影响

采用铜模吸铸法制备出直径为3 mm的[Zr0.72+x(Cu0.59Ni0.41)0.28-x]88Al12(x=0,0.05,0.1)棒状非晶合金。通过X射线衍射(XRD)、差示扫描热量法(DSC)、微机控制电子式万能力学试验机和扫描电镜(SEM)研究其非晶形成能力与压缩力学性能的变化规律。结果表明:随着Zr含量的提高,合金的过冷液相区宽度ΔTx减小,热稳定性下降;约化玻璃转变温度Trg和参数γ均随着Zr含量的提高而下降,非晶形成能力下降;在x=0时,断裂强度、塑性应变和抗压强度均达到最大值,分别为1 531 MPa、14.61%和1 838 MPa;而在x=0.1时,塑性应变和抗压强度则分别达到最小值5.06%和1 495 MPa;试样的室温准静态压缩力学性能随Zr含量的增加而下降。

Er对ZrCuNiAl非晶合金结构、力学性能、热稳定性及非晶形成能力的影响

以(Zr_(0.6336)Cu_(0.1452)Ni_(0.1012)Al_(0.12))_(100-x)Er_x(x=0,0.5,1,1.5,2,2.5,3,原子分数,下同)系块体非晶合金为研究对象,通过改变微量元素Er的含量来研究Er对非晶合金的结构、力学性能、热稳定性及非晶形成能力的影响。结果表明:添加Er元素所制备出的试样都是完全非晶结构的合金。随着Er含量的增加,各试样的弹性模量呈现出先增大后减小,压缩塑性应变呈台阶式上升,x=0,x=0.5,x=1试样的塑性应变在4%的范围内波动;x=1.5,x=2,x=2.5试样的塑性应变在11%的范围内波动;x=3试样的塑性应变最高,其值为23.19%,弹性模量为37.76GPa,屈服强度为1604MPa,抗压强度为2068MPa,断裂强度为2060MPa;随着Er含量的增加,锆基非晶合金的热稳定性和非晶形成能力均先减小后增大。