The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the...The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the addition of specific minor elements can greatly enhance the GFA of parent alloys,yet the underlying mechanism remains unclear.In this study,we use the ZrCuAl system as a model to explore how the addition of minor Al influences the crystallization rate by modulating the properties of the crystal-liquid interface,thereby affecting the GFA.The results reveal that the minor addition of Al significantly reduces the crystal growth rate,a phenomenon not governed by particle density fluctuations at the interface.The impact of minor element additions extends beyond a modest increase in crystal-unfavorable motifs in the bulk supercooled liquid.More importantly,it leads to a significant enrichment of these motifs at the crystal-supercooled liquid interface,forming a dense topological network of crystal-unfavorable structures that effectively prevent the growth of the crystalline interface and enhance GFA.Our results provide valuable insights for the design and development of high-performance metallic glasses.展开更多
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 ...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.展开更多
The glass forming ability （GFA） and thermodynamic properties of the La-AI-Cu-Co alloy system were investigated, and novel La-AI-Cu-Co bulk metallic glasses （BMGs） with a minimum critical diameter of 8 mm were fabr...The glass forming ability （GFA） and thermodynamic properties of the La-AI-Cu-Co alloy system were investigated, and novel La-AI-Cu-Co bulk metallic glasses （BMGs） with a minimum critical diameter of 8 mm were fabricated. The differing GFAs were examined from a thermodynamic viewpoint. The GFA of the La-A1-Cu-Co alloys was well-correlated with the supercooled liq- uid region, ATx, and the parameter, 7; but not with the reduced glass transition temperature, Trg. In addition, the La62Al14Cu14Co8 BMG exhibited a high GFA, low glass transition temperature of 412 K, and broad supercooled liquid region of 70 K. These novel BMGs, which were fabricated from low-cost raw materials, had the potential to be used in various applications. The GFA of the pre- sent alloys exhibited a dependence on the relative number of AlqEo and AI-Cu atomic pairs, i.e., on the AI：Co and AI：Cu ratios, which were -2.3 and 0.85, respectively.展开更多
Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) amorphous alloys were obtained by single-roller melt-spinning technique and the effect of Y addition on the glass forming ability(GFA), crystallization and micro-hardness of Mg-Ni ...Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) amorphous alloys were obtained by single-roller melt-spinning technique and the effect of Y addition on the glass forming ability(GFA), crystallization and micro-hardness of Mg-Ni alloys were studied. The results show that the GFA of Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) is improved successfully with the Y addition. The highest GFA appeares at x=6, while the reduced glass transition temperature (Trg) is 0.5225 and the supercooled liquid region(ΔTx) is 42.06 K; the position of the main diffraction halo is different for the alloys, and the maximum of the main diffraction halo of alloys with x=0, 1, 3 corresponds to the main peaks of a metastable fcc-Mg6Ni or fcc-Mg6Ni + Ni-Y intermetallic phases, and for the alloys with x=6, 10, it corresponds to Mg-Y and Ni-Y intermetallic phases; the micro-hardness of the alloys is improved with Y additions, and the highest micro-hardness is obtained at x=6 at.%, which is 960 MPa.展开更多
Fe-based metallic glasses(MGs)have shown great commercial values due to their excellent soft magnetic properties.Magnetism prediction with consideration of glass forming ability(GFA)is of great signifi-cance for devel...Fe-based metallic glasses(MGs)have shown great commercial values due to their excellent soft magnetic properties.Magnetism prediction with consideration of glass forming ability(GFA)is of great signifi-cance for developing novel functional Fe-based MGs.However,theories or models established based on condensed matter physics exhibit limited accuracy and some exceptions.In this work,based on 618 Fe-based MGs samples collected from published works,machine learning(ML)models were well trained to predict saturated magnetization(B_(s))of Fe-based MGs.GFA was treated as a feature using the experimental data of the supercooled liquid region(△T_(x)).Three ML algorithms,namely eXtreme gradient boosting(XGBoost),artificial neural networks(ANN)and random forest(RF),were studied.Through feature selection and hyperparameter tuning,XGBoost showed the best predictive performance on the randomly split test dataset with determination coefficient(R^(2))of 0.942,mean absolute percent error(MAPE)of 5.563%,and root mean squared error(RMSE)of 0.078 T.A variety of feature importance rankings derived by XGBoost models showed that T_(x) played an important role in the predictive performance of the models.This work showed the proposed ML method can simultaneously aggregate GFA and other features in ther-modynamics,kinetics and structures to predict the magnetic properties of Fe-based MGs with excellent accuracy.展开更多
The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA)are studied via molecular dynamics simulations.Pair distribution function and the largest...The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA)are studied via molecular dynamics simulations.Pair distribution function and the largest standard cluster(LSC)are adopted to characterize the local atomic structures in the(Zr_(50)Cu_(50))_(100-x)Al_(x)systems.The[12/555]icosahedra and their medium-range order(IMRO)play an important role in forming(Zr_(50)Cu_(50))_(100-x)Al_(x)metallic glasses(MGs).The fraction of[12/555],the number of IMRO,and the maximum size of IMRO in MGs increase significantly with increasing x.A tracking study further reveals that the configuration heredity of icosahedral clusters starts from supercooled liquids.No direct correlation exists between the GFA and the onset temperature of continuous or stated heredity.Instead,a larger hereditary supercooled degree of icosahedra matches with better GFA of Al-doped Zr_(50)Cu_(50)alloys.展开更多
The formation of bulk metallic glasses（BMGs） in the ternary Zr（56） Co（28-x）Al（16） and quaternary Zr（56） Co（28-x）CuxAl16（x=2, 4, 5, 6, 7, mole fraction, %） glassy alloys was investigated via the copper mo...The formation of bulk metallic glasses（BMGs） in the ternary Zr（56） Co（28-x）Al（16） and quaternary Zr（56） Co（28-x）CuxAl16（x=2, 4, 5, 6, 7, mole fraction, %） glassy alloys was investigated via the copper mold suction casting method. The main purpose of this work was to locate the optimal BMG-forming composition for the quaternary Zr Co（Cu）Al alloys and to improve the plasticity of the parent alloy. The X-ray diffractometry（XRD）, transmission electron microscopy（TEM） and differential scanning calorimetry（DSC） were used to investigate the glassy alloys structure and their glass forming ability（GFA）. In addition, the compression test, microhardness, nano-indentation and scanning electron microscopy（SEM） were utilized to discuss the possible mechanisms involved in the enhanced plasticity achievement. The highest GFA among Cu-containing alloys was found for the Zr（56） Co（22） Cu6 Al（16） alloy, which was similar to that of the base alloy. Furthermore, the plasticity of the base alloy increased significantly from 3.3% to 6% for the Zr（56） Co（22） Cu）6 Al（16） BMG. The variations in the plasticity and GFA of the alloys were discussed by considering the positive heat of mixing within Cu and Co elements.展开更多
Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out....Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out. The result reveals that after fluxing treatment the glass transition temperature of the as-prepared glassy ribbons is reduced while the initial crystallization tem- perature is enhanced. It results in that the supercooled liquid region (defined as the difference between the initial crystallization tem- perature and the glass transition temperature) of the glassy alloy treated with fluxing technology has been increased from 31 to 42 K. This shows that fluxing technique can enhance the glass forming ability (GFA) of the binary alloy and improve the thermal stability of supercooled liquid of the glassy alloy.展开更多
The influences of the addition of Ag on the glass forming ability (GFA) and corrosion behavior were investigated in the Mg-Ni-based alloy system by X-ray diffraction (XRD) and electrochemical polarization in 0.1 mol/L...The influences of the addition of Ag on the glass forming ability (GFA) and corrosion behavior were investigated in the Mg-Ni-based alloy system by X-ray diffraction (XRD) and electrochemical polarization in 0.1 mol/L NaOH solution.Results shows that the GFA of the Mg-Ni-based BMGs can be improved dramatically by the addition of an appropriate amount of Ag;and the addition element Ag can improve the corrosion resistance of Mg-Ni-based bulk metallic glass.The large difference in atomic size and large negative mixing enthalpy in alloy system can contribute to the high GFA.The addition element Ag improves the forming speed and the stability of the passive film,which is helpful to decrease the passivation current density and to improve the corrosion resistance of Mg-Ni-based bulk metallic glass.展开更多
The effects of microalloying of Ti and B on the glass formation of Cu60Pr30Ni10Al10-2xTixBx（x = 0, 0.05% （atom fraction）） amorphous alloys was investigated using differential scanning calorimetry （DSC） and X-ray...The effects of microalloying of Ti and B on the glass formation of Cu60Pr30Ni10Al10-2xTixBx（x = 0, 0.05% （atom fraction）） amorphous alloys was investigated using differential scanning calorimetry （DSC） and X-ray diffraction （XRD）. XRD analysis showed that mieroalloying with 0.05% Ti and 0.05% B improved the glass forming ability （GFA）. The smaller difference in the Gibbs free energy between the liquid and crystalline states at the glass transition temperature （△G1-X（Tg）） and the smaller thermodynamic fragility index （△Sf/Tm, where ASf is the entropy of fusion, and Tm is the melting temperature） after mieroalloying correlated with the higher GFA.展开更多
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 w...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.展开更多
The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying...The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth （RE） and transition metal （TM） elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.展开更多
The thermodynamic model of multicomponent chemical short range order (MCSRO) was established in order to evaluate the glass forming ability (GFA) of ternary alloys. Comprehensive numerical calculations using MSCRO sof...The thermodynamic model of multicomponent chemical short range order (MCSRO) was established in order to evaluate the glass forming ability (GFA) of ternary alloys. Comprehensive numerical calculations using MSCRO software were conducted to obtain the composition dependence of the MCSRO undercooling in Zr Ni Cu, Zr Si Cu and Pd Si Cu ternary systems. By the MCSRO undercooling principle, the composition range of Zr Ni Cu system with optimum GFA is determined to be 62.5 ～ 75 Zr, 5～ 20 Cu, 12.5 ～ 25 Ni ( n (Ni)/ n (Cu)=1～5). The TTT curves of Zr Ni Cu system were also calculated based on the MCSRO model. The critical cooling rates for Zr based alloy with deep MSCRO undercooling are estimated to be as low as 100?K/s, which is consistent with the practical cooling rate in the preparation of Zr based bulk metallic glass (BMG). The calculation also illustrates that the easy glass forming systems such as Pd based alloys exhibit an extraordinary deep MCSRO undercooling. It is shown that the thermodynamic model of MCSRO provides an effective method for the alloy designing of BMG.展开更多
The FePC-based bulk metallic glasses（BMGs）have been demonstrated to possess high plasticity and good soft magnetic properties.However,the relatively poor glass forming ability（GFA）and thermal stabilities limited t...The FePC-based bulk metallic glasses（BMGs）have been demonstrated to possess high plasticity and good soft magnetic properties.However,the relatively poor glass forming ability（GFA）and thermal stabilities limited their application in industries.The effects of microalloying with B in FePC-based BMGs on the GFA and thermal behaviors were systematically investigated.It was found that a small amount of B addition can dramatically enhance the GFA of FePC-based BMGs,which in turn leads to the critical maximum diameter up to 2 mm for full glass formation even using low cost raw materials.The underlying mechanism of the enhancement of GFA from the competing crystalline phase with amorphous phase,the average thermal expansion coefficient and dynamic viscosity were discussed in detail.展开更多
By a mean field theoretical computation,the equilibrium distributions of additional Ag and Al in the crystalline phase of CuZr-based alloys were determined to occupy the two sublattices of the B2 structure randomly.Wi...By a mean field theoretical computation,the equilibrium distributions of additional Ag and Al in the crystalline phase of CuZr-based alloys were determined to occupy the two sublattices of the B2 structure randomly.With the molecular dynamics technique,the effects of Ag and Al on the enthalpy difference（ΔH） between the supercooled melt and the crystalline phase were evaluated.The improved glass forming ability of Cu45Zr45Al10 and Cu45Zr45Ag10 can be attributed to their remarkably smaller ΔH than that of CuZr.The calculated diffusion coefficients are more sensitive to the atomic weight of the component atoms than to their interaction strength.As the component atom with the largest mass,the additional Ag increases the viscosity of the supercooled melt significantly and the experimentally stronger glass formation ability of Cu45Zr45Ag10 than Cu45Zr45Al10 can be well understood.展开更多
Zr-based Bulk metallic glasses exhibit incredible corrosion resistance and glass forming ability,however,these properties need further enhancement to meet the practical use.In this study,Zr63Fe2.5Cu23Al11.5,a new type...Zr-based Bulk metallic glasses exhibit incredible corrosion resistance and glass forming ability,however,these properties need further enhancement to meet the practical use.In this study,Zr63Fe2.5Cu23Al11.5,a new type of Zr-based bulk metallic glass was fabricated.Potentiodynamic polarization techniques were used to measure the corrosion resistance of this alloy.Furthermore,crystallization behavior and kinetics of Zr63Fe2.5Cu23Al11.5 bulk metallic glass were investigated by using differential scanning calorimetry of non-isothermal model.Kissinger and Ozawa methods were used for calculating activation energies of crystallization and the mechanism of crystallization was analyzed by Johnson-Mehl-Avrami-Kolmogorow methods.The results suggest that this specified metallic glass system possesses a relatively high thermal stability and glass forming ability.Moreover,the crystallization procedure is mainly dominated by nucleation with an increasing rate.The study demonstrates that the slight composition adjustment of Zr-Fe-Cu-Al system bulk metallic glass can make a considerable contribution to higher glass forming and thermal stability as well as corrosion resistance.展开更多
Co-X （X=Cr, Mo, W） magnetic thin films were prepared by using DC magnetron sputtering, and their structures were examined by using X-ray diffraction （XRD）. The amorphous forming ability （AFA） of the three alloy ...Co-X （X=Cr, Mo, W） magnetic thin films were prepared by using DC magnetron sputtering, and their structures were examined by using X-ray diffraction （XRD）. The amorphous forming ability （AFA） of the three alloy systems was discussed based on thermodynamic calculation and experiments. The results show that the Co-Mo thin films exhibit the largest AFA among them, and the Co-W thin films are conditiondependent amorphous while the Co-Cr thin films are hard to be amorphous, which is consistent with the thermodynamic calculation. The difference in AFA for the alloys of these three systems is finally ascribed to three main factors： differences in electronegativity, electron density and atomic size between Co and X elements.展开更多
Nd55-x Al10＋x Fe15 （x =0, 5, 10） bulk glass-forming alloys with distinct glass transition in differential scanning calorimetry （DSC） traces were obtained by suction casting, The glass forming ability （GFA） of t...Nd55-x Al10＋x Fe15 （x =0, 5, 10） bulk glass-forming alloys with distinct glass transition in differential scanning calorimetry （DSC） traces were obtained by suction casting, The glass forming ability （GFA） of the alloys was investigated. It was found that the reduced glass transition temperature （Trg） and the parameter γ of the alloys increased with the increasing concentration of Al. The glass formation enthalpy of the alloys was calculated based on Miedema＇s model, and it was suggested that the GFA of the alloys could be enhanced by the decrease of the glass formation enthalpy with Al additions.展开更多
The glass forming ability (GFA), microstructure and magnetic property in (Nd60Al10Ni10)Cu20-xFex (0≤ x≤ 20) alloys were investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), high re...The glass forming ability (GFA), microstructure and magnetic property in (Nd60Al10Ni10)Cu20-xFex (0≤ x≤ 20) alloys were investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), high resolution transmission electron mi- croscopy (HRTEM) and magnetic property measurement. It is shown that the GFA of the alloys decreases with Fe content. The sam- ples for bulk cylinders with x≤10 show a distinct endothermic peak in the DSC traces due to a glass transition in the range of 421-438 K. With further increasing Fe, the glass transition is masked by the crystallization. The microstructure of the Nd-based alloy can change progressively from full glassy state into composite state with nanocrystalline particles in the glassy matrix indicating the glass forming ability degrades with increasing Fe. The average size of nanocrystals increases with Fe and the distribution changes from homogenous to heterogeneous. The magnetic property varies from paramagnetic to hard magnetic when the Fe content increases up to about 4at% indicating that the magnetic property is related to the metastable phases.展开更多
La-and Nb-doped BaTi_(2)O_(5)(BT2)spherical glasses were prepared by a containerless aerodynamic levitation method and their glass-forming regions were established.It is found that La-doping on the Ba-site(network-mod...La-and Nb-doped BaTi_(2)O_(5)(BT2)spherical glasses were prepared by a containerless aerodynamic levitation method and their glass-forming regions were established.It is found that La-doping on the Ba-site(network-modifier)and Nb-doping on the Ti-site(network-former)show distinct difference in the glassforming region:less than 10%La can replace Ba whereas 40%Nb can incorporate into BT2 glass.The distinction in glass-forming ability induced by La-and Nb-doping is discussed mainly from the structural arrangement of the glass.Raman spectroscopy analysis shows that La-doping elongates the short Ti-O bonds in the distorted[TiO_(5)]polyhedra and thus relaxes the network.Nb-doping introduces[NbO_(6)]polyhedra into BT_(2) and there exists a critical doping level(20%),below which incorporation of Nb into BT_(2) relaxes the[TiOn]polyhedra by shortening the long Ti-O bond and above which[NbO_(6)]starts to participate in the network skeleton construction resulting in a dramatic change in the glass structure,which is supported by the dramatic change in the exothermic peak on the DTA curves.This work triggers the speculation that the network-modifiers in BT_(2) glass possess a very important role in the structure of network-former skeleton than those in glasses based on traditional network-former oxides such as SiO_(2),GeO_(2) and B_(2)O_(3),which may provide a useful strategy for modifying the properties of these novel glasses by chemical doping.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.T2325004 and 52161160330)the support from the Hong Kong Institute of Advanced Studies through the materials cluster project。
文摘The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the addition of specific minor elements can greatly enhance the GFA of parent alloys,yet the underlying mechanism remains unclear.In this study,we use the ZrCuAl system as a model to explore how the addition of minor Al influences the crystallization rate by modulating the properties of the crystal-liquid interface,thereby affecting the GFA.The results reveal that the minor addition of Al significantly reduces the crystal growth rate,a phenomenon not governed by particle density fluctuations at the interface.The impact of minor element additions extends beyond a modest increase in crystal-unfavorable motifs in the bulk supercooled liquid.More importantly,it leads to a significant enrichment of these motifs at the crystal-supercooled liquid interface,forming a dense topological network of crystal-unfavorable structures that effectively prevent the growth of the crystalline interface and enhance GFA.Our results provide valuable insights for the design and development of high-performance metallic glasses.
基金Project(50371016) supported by the National Natural Science Foundation of ChinaProject(50611130629) supported by the International Cooperation and Exchange of the National Natural Science Foundation of China
文摘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.
文摘The glass forming ability （GFA） and thermodynamic properties of the La-AI-Cu-Co alloy system were investigated, and novel La-AI-Cu-Co bulk metallic glasses （BMGs） with a minimum critical diameter of 8 mm were fabricated. The differing GFAs were examined from a thermodynamic viewpoint. The GFA of the La-A1-Cu-Co alloys was well-correlated with the supercooled liq- uid region, ATx, and the parameter, 7; but not with the reduced glass transition temperature, Trg. In addition, the La62Al14Cu14Co8 BMG exhibited a high GFA, low glass transition temperature of 412 K, and broad supercooled liquid region of 70 K. These novel BMGs, which were fabricated from low-cost raw materials, had the potential to be used in various applications. The GFA of the pre- sent alloys exhibited a dependence on the relative number of AlqEo and AI-Cu atomic pairs, i.e., on the AI：Co and AI：Cu ratios, which were -2.3 and 0.85, respectively.
基金supported by the Award Fund for Outstanding Young Scientist in Shandong Province, China (No. BS2011CL004)
文摘Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) amorphous alloys were obtained by single-roller melt-spinning technique and the effect of Y addition on the glass forming ability(GFA), crystallization and micro-hardness of Mg-Ni alloys were studied. The results show that the GFA of Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) is improved successfully with the Y addition. The highest GFA appeares at x=6, while the reduced glass transition temperature (Trg) is 0.5225 and the supercooled liquid region(ΔTx) is 42.06 K; the position of the main diffraction halo is different for the alloys, and the maximum of the main diffraction halo of alloys with x=0, 1, 3 corresponds to the main peaks of a metastable fcc-Mg6Ni or fcc-Mg6Ni + Ni-Y intermetallic phases, and for the alloys with x=6, 10, it corresponds to Mg-Y and Ni-Y intermetallic phases; the micro-hardness of the alloys is improved with Y additions, and the highest micro-hardness is obtained at x=6 at.%, which is 960 MPa.
基金financially supported by National Natural Science Foundation of China(No.21771017)the Fundamental Research Funds for the Central Universities。
文摘Fe-based metallic glasses(MGs)have shown great commercial values due to their excellent soft magnetic properties.Magnetism prediction with consideration of glass forming ability(GFA)is of great signifi-cance for developing novel functional Fe-based MGs.However,theories or models established based on condensed matter physics exhibit limited accuracy and some exceptions.In this work,based on 618 Fe-based MGs samples collected from published works,machine learning(ML)models were well trained to predict saturated magnetization(B_(s))of Fe-based MGs.GFA was treated as a feature using the experimental data of the supercooled liquid region(△T_(x)).Three ML algorithms,namely eXtreme gradient boosting(XGBoost),artificial neural networks(ANN)and random forest(RF),were studied.Through feature selection and hyperparameter tuning,XGBoost showed the best predictive performance on the randomly split test dataset with determination coefficient(R^(2))of 0.942,mean absolute percent error(MAPE)of 5.563%,and root mean squared error(RMSE)of 0.078 T.A variety of feature importance rankings derived by XGBoost models showed that T_(x) played an important role in the predictive performance of the models.This work showed the proposed ML method can simultaneously aggregate GFA and other features in ther-modynamics,kinetics and structures to predict the magnetic properties of Fe-based MGs with excellent accuracy.
基金the National Natural Science Foundation of China(Grant No.51701071)the Natural Science Foundation of Hunan Province,China(Grant Nos.2018JJ3100 and 2018JJ2078)the Project of the Hunan Educational Department,China(Grant No.19B122)。
文摘The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA)are studied via molecular dynamics simulations.Pair distribution function and the largest standard cluster(LSC)are adopted to characterize the local atomic structures in the(Zr_(50)Cu_(50))_(100-x)Al_(x)systems.The[12/555]icosahedra and their medium-range order(IMRO)play an important role in forming(Zr_(50)Cu_(50))_(100-x)Al_(x)metallic glasses(MGs).The fraction of[12/555],the number of IMRO,and the maximum size of IMRO in MGs increase significantly with increasing x.A tracking study further reveals that the configuration heredity of icosahedral clusters starts from supercooled liquids.No direct correlation exists between the GFA and the onset temperature of continuous or stated heredity.Instead,a larger hereditary supercooled degree of icosahedra matches with better GFA of Al-doped Zr_(50)Cu_(50)alloys.
基金Iran University of Science and Technology for the financial support
文摘The formation of bulk metallic glasses（BMGs） in the ternary Zr（56） Co（28-x）Al（16） and quaternary Zr（56） Co（28-x）CuxAl16（x=2, 4, 5, 6, 7, mole fraction, %） glassy alloys was investigated via the copper mold suction casting method. The main purpose of this work was to locate the optimal BMG-forming composition for the quaternary Zr Co（Cu）Al alloys and to improve the plasticity of the parent alloy. The X-ray diffractometry（XRD）, transmission electron microscopy（TEM） and differential scanning calorimetry（DSC） were used to investigate the glassy alloys structure and their glass forming ability（GFA）. In addition, the compression test, microhardness, nano-indentation and scanning electron microscopy（SEM） were utilized to discuss the possible mechanisms involved in the enhanced plasticity achievement. The highest GFA among Cu-containing alloys was found for the Zr（56） Co（22） Cu6 Al（16） alloy, which was similar to that of the base alloy. Furthermore, the plasticity of the base alloy increased significantly from 3.3% to 6% for the Zr（56） Co（22） Cu）6 Al（16） BMG. The variations in the plasticity and GFA of the alloys were discussed by considering the positive heat of mixing within Cu and Co elements.
基金This work was financially supported by the National Natural Science Foundation of China (No.50431030, 50671050)the Basic Science Research Foundation of Tsinghua University (No.091201107)the National Center for Nanoscience and Technology of China.
文摘Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out. The result reveals that after fluxing treatment the glass transition temperature of the as-prepared glassy ribbons is reduced while the initial crystallization tem- perature is enhanced. It results in that the supercooled liquid region (defined as the difference between the initial crystallization tem- perature and the glass transition temperature) of the glassy alloy treated with fluxing technology has been increased from 31 to 42 K. This shows that fluxing technique can enhance the glass forming ability (GFA) of the binary alloy and improve the thermal stability of supercooled liquid of the glassy alloy.
基金supported by the National Natural Science Foundation of China (Grant No. 50972066)
文摘The influences of the addition of Ag on the glass forming ability (GFA) and corrosion behavior were investigated in the Mg-Ni-based alloy system by X-ray diffraction (XRD) and electrochemical polarization in 0.1 mol/L NaOH solution.Results shows that the GFA of the Mg-Ni-based BMGs can be improved dramatically by the addition of an appropriate amount of Ag;and the addition element Ag can improve the corrosion resistance of Mg-Ni-based bulk metallic glass.The large difference in atomic size and large negative mixing enthalpy in alloy system can contribute to the high GFA.The addition element Ag improves the forming speed and the stability of the passive film,which is helpful to decrease the passivation current density and to improve the corrosion resistance of Mg-Ni-based bulk metallic glass.
基金Project supported by the National Natural Science Foundation of China (50471052)Natural Science Foundation of Shandong Province (Z2004F02)
文摘The effects of microalloying of Ti and B on the glass formation of Cu60Pr30Ni10Al10-2xTixBx（x = 0, 0.05% （atom fraction）） amorphous alloys was investigated using differential scanning calorimetry （DSC） and X-ray diffraction （XRD）. XRD analysis showed that mieroalloying with 0.05% Ti and 0.05% B improved the glass forming ability （GFA）. The smaller difference in the Gibbs free energy between the liquid and crystalline states at the glass transition temperature （△G1-X（Tg）） and the smaller thermodynamic fragility index （△Sf/Tm, where ASf is the entropy of fusion, and Tm is the melting temperature） after mieroalloying correlated with the higher GFA.
基金supported by the National Natural Science Foundation of China(No.51871237)the Natural Science Foundation of Jiangsu Province(No.BK20201282)Atom probe tomography research was conducted at the Inter-University 3D Atom Probe Tomography Unit of City University of Hong Kong supported by the CityU(No.9360161).
文摘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.
基金financial support obtained from the Science and Engineering Research Board,Department of Science & Technology,Government of India(SB/S3/ME/0044/2013)Sponsored Research and Industrial Consultancy,Indian Institute of Technology Kharagpur,India(GAF)
文摘The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth （RE） and transition metal （TM） elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.
文摘The thermodynamic model of multicomponent chemical short range order (MCSRO) was established in order to evaluate the glass forming ability (GFA) of ternary alloys. Comprehensive numerical calculations using MSCRO software were conducted to obtain the composition dependence of the MCSRO undercooling in Zr Ni Cu, Zr Si Cu and Pd Si Cu ternary systems. By the MCSRO undercooling principle, the composition range of Zr Ni Cu system with optimum GFA is determined to be 62.5 ～ 75 Zr, 5～ 20 Cu, 12.5 ～ 25 Ni ( n (Ni)/ n (Cu)=1～5). The TTT curves of Zr Ni Cu system were also calculated based on the MCSRO model. The critical cooling rates for Zr based alloy with deep MSCRO undercooling are estimated to be as low as 100?K/s, which is consistent with the practical cooling rate in the preparation of Zr based bulk metallic glass (BMG). The calculation also illustrates that the easy glass forming systems such as Pd based alloys exhibit an extraordinary deep MCSRO undercooling. It is shown that the thermodynamic model of MCSRO provides an effective method for the alloy designing of BMG.
基金financially supported by the National Natural Science Foundation of China(Nos.51301142and 51671162)China Postdoctoral Science Foundation(Nos.2015T80957and 2014M562279)+1 种基金Chongqing Research Program of Basic Research and Frontier Technology(No.cstc2015jcyjBX0107)the Fundamental Research Funds for the Central Universities(Nos.XDJK2015C064and XDJK2015C003)
文摘The FePC-based bulk metallic glasses（BMGs）have been demonstrated to possess high plasticity and good soft magnetic properties.However,the relatively poor glass forming ability（GFA）and thermal stabilities limited their application in industries.The effects of microalloying with B in FePC-based BMGs on the GFA and thermal behaviors were systematically investigated.It was found that a small amount of B addition can dramatically enhance the GFA of FePC-based BMGs,which in turn leads to the critical maximum diameter up to 2 mm for full glass formation even using low cost raw materials.The underlying mechanism of the enhancement of GFA from the competing crystalline phase with amorphous phase,the average thermal expansion coefficient and dynamic viscosity were discussed in detail.
文摘By a mean field theoretical computation,the equilibrium distributions of additional Ag and Al in the crystalline phase of CuZr-based alloys were determined to occupy the two sublattices of the B2 structure randomly.With the molecular dynamics technique,the effects of Ag and Al on the enthalpy difference（ΔH） between the supercooled melt and the crystalline phase were evaluated.The improved glass forming ability of Cu45Zr45Al10 and Cu45Zr45Ag10 can be attributed to their remarkably smaller ΔH than that of CuZr.The calculated diffusion coefficients are more sensitive to the atomic weight of the component atoms than to their interaction strength.As the component atom with the largest mass,the additional Ag increases the viscosity of the supercooled melt significantly and the experimentally stronger glass formation ability of Cu45Zr45Ag10 than Cu45Zr45Al10 can be well understood.
基金National Key R&D Program of China(Grant No.2017YFB0702404)National Natural Science Foundation of China(Grant Nos.51901212,51701192).
文摘Zr-based Bulk metallic glasses exhibit incredible corrosion resistance and glass forming ability,however,these properties need further enhancement to meet the practical use.In this study,Zr63Fe2.5Cu23Al11.5,a new type of Zr-based bulk metallic glass was fabricated.Potentiodynamic polarization techniques were used to measure the corrosion resistance of this alloy.Furthermore,crystallization behavior and kinetics of Zr63Fe2.5Cu23Al11.5 bulk metallic glass were investigated by using differential scanning calorimetry of non-isothermal model.Kissinger and Ozawa methods were used for calculating activation energies of crystallization and the mechanism of crystallization was analyzed by Johnson-Mehl-Avrami-Kolmogorow methods.The results suggest that this specified metallic glass system possesses a relatively high thermal stability and glass forming ability.Moreover,the crystallization procedure is mainly dominated by nucleation with an increasing rate.The study demonstrates that the slight composition adjustment of Zr-Fe-Cu-Al system bulk metallic glass can make a considerable contribution to higher glass forming and thermal stability as well as corrosion resistance.
基金supported by National Natural Science Foundation of China(No.50671020)Program for Changjiang Scholars and Innovative Research Team in University (No.IRT0713)
文摘Co-X （X=Cr, Mo, W） magnetic thin films were prepared by using DC magnetron sputtering, and their structures were examined by using X-ray diffraction （XRD）. The amorphous forming ability （AFA） of the three alloy systems was discussed based on thermodynamic calculation and experiments. The results show that the Co-Mo thin films exhibit the largest AFA among them, and the Co-W thin films are conditiondependent amorphous while the Co-Cr thin films are hard to be amorphous, which is consistent with the thermodynamic calculation. The difference in AFA for the alloys of these three systems is finally ascribed to three main factors： differences in electronegativity, electron density and atomic size between Co and X elements.
文摘Nd55-x Al10＋x Fe15 （x =0, 5, 10） bulk glass-forming alloys with distinct glass transition in differential scanning calorimetry （DSC） traces were obtained by suction casting, The glass forming ability （GFA） of the alloys was investigated. It was found that the reduced glass transition temperature （Trg） and the parameter γ of the alloys increased with the increasing concentration of Al. The glass formation enthalpy of the alloys was calculated based on Miedema＇s model, and it was suggested that the GFA of the alloys could be enhanced by the decrease of the glass formation enthalpy with Al additions.
文摘The glass forming ability (GFA), microstructure and magnetic property in (Nd60Al10Ni10)Cu20-xFex (0≤ x≤ 20) alloys were investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), high resolution transmission electron mi- croscopy (HRTEM) and magnetic property measurement. It is shown that the GFA of the alloys decreases with Fe content. The sam- ples for bulk cylinders with x≤10 show a distinct endothermic peak in the DSC traces due to a glass transition in the range of 421-438 K. With further increasing Fe, the glass transition is masked by the crystallization. The microstructure of the Nd-based alloy can change progressively from full glassy state into composite state with nanocrystalline particles in the glassy matrix indicating the glass forming ability degrades with increasing Fe. The average size of nanocrystals increases with Fe and the distribution changes from homogenous to heterogeneous. The magnetic property varies from paramagnetic to hard magnetic when the Fe content increases up to about 4at% indicating that the magnetic property is related to the metastable phases.
基金the National Natural Science Foundation of China(Nos.51971138,51727802 and 51821001)the National Natural Science Foundation of ChinaExcellent Young Scholars(No.51922068)+1 种基金the National Key Research and Development Program(No.2017YFA0403800)the Shanghai Pujiang Program(No.19PJ1404400)。
文摘La-and Nb-doped BaTi_(2)O_(5)(BT2)spherical glasses were prepared by a containerless aerodynamic levitation method and their glass-forming regions were established.It is found that La-doping on the Ba-site(network-modifier)and Nb-doping on the Ti-site(network-former)show distinct difference in the glassforming region:less than 10%La can replace Ba whereas 40%Nb can incorporate into BT2 glass.The distinction in glass-forming ability induced by La-and Nb-doping is discussed mainly from the structural arrangement of the glass.Raman spectroscopy analysis shows that La-doping elongates the short Ti-O bonds in the distorted[TiO_(5)]polyhedra and thus relaxes the network.Nb-doping introduces[NbO_(6)]polyhedra into BT_(2) and there exists a critical doping level(20%),below which incorporation of Nb into BT_(2) relaxes the[TiOn]polyhedra by shortening the long Ti-O bond and above which[NbO_(6)]starts to participate in the network skeleton construction resulting in a dramatic change in the glass structure,which is supported by the dramatic change in the exothermic peak on the DTA curves.This work triggers the speculation that the network-modifiers in BT_(2) glass possess a very important role in the structure of network-former skeleton than those in glasses based on traditional network-former oxides such as SiO_(2),GeO_(2) and B_(2)O_(3),which may provide a useful strategy for modifying the properties of these novel glasses by chemical doping.
