Metallic glasses have aroused considerable interest in the past decades because they exhibit fascinating properties. First, this article briefly outlines the mechanical, thermal properties and application of the metal...Metallic glasses have aroused considerable interest in the past decades because they exhibit fascinating properties. First, this article briefly outlines the mechanical, thermal properties and application of the metallic glasses. In addition, we focus on the dynamic mechanical relaxation behaviors, i.e. main （α） and secondary （β） relaxations, in metallic glasses. The mechanical relaxation behaviors are connected to the mechanical properties and physical properties in glassy materials. The main relaxation in glassy materials is related to the glass transition phenomenon and viscous flow. On the other hand, the β relaxation is linked to many fundamental issues in metallic glasses. In these materials relaxation processes are directly related to the plastic deformation mechanism. The mechanical relaxations, particularly, the β relaxation provides an excellent opportunity to design metallic glasses with desired physical and mechanical properties. We demonstrate the universal characteristics of main relaxation in metallic glasses. The phenomenological models and the physical theories are introduced to describe the main relaxation in metallic glasses. In parallel, we show the dependence of the α. and β relaxations on the thermal treatments in metallic glasses. Finally, we analyze the correlation between the atomic mobility and the thermo-mechanical treatments in metallic glasses. On the one hand, the atomic mobility in metallic glasses is reduced by physical aging or crystallization. On the other hand, the atomic mobility in metallic glass is enhanced by deformation （i.e. compression and cold rolling）. Importantly, to analyze the atomic mobility in amorphous materials, a physical theory is introduced. This model invokes the concept of quasi-point defects, which correspond to the density fluctuations in the glassy materials.展开更多
Glasses-free three-dimensional(3D)displays are one of the game-changing technologies that will redefine the display industry in portable electronic devices.However,because of the limited resolution in state-of-the-art...Glasses-free three-dimensional(3D)displays are one of the game-changing technologies that will redefine the display industry in portable electronic devices.However,because of the limited resolution in state-of-the-art display panels,current 3D displays suffer from a critical trade-off among the spatial resolution,angular resolution,and viewing angle.Inspired by the so-called spatially variant resolution imaging found in vertebrate eyes,we propose 3D display with spatially variant information density.Stereoscopic experiences with smooth motion parallax are maintained at the central view,while the viewing angle is enlarged at the periphery view.It is enabled by a large-scale 2D-metagrating complex to manipulate dot/linear/rectangular hybrid shaped views.Furthermore,a video rate full-color 3D display with an unprecedented 160°horizontal viewing angle is demonstrated.With thin and light form factors,the proposed 3D system can be integrated with off-the-shelf purchased flat panels,making it promising for applications in portable electronics.展开更多
The thermal stability,glass-forming ability(GFA) and mechanical properties of Zr60Al15Ni25xTMx(TM = Cu,Fe and Co,x = 0-10) bulk metallic glasses(BMGs) were systematically investigated.Additional 5-10 at.% Cu greatly e...The thermal stability,glass-forming ability(GFA) and mechanical properties of Zr60Al15Ni25xTMx(TM = Cu,Fe and Co,x = 0-10) bulk metallic glasses(BMGs) were systematically investigated.Additional 5-10 at.% Cu greatly enhances the thermal stability and GFA of the base alloy.Zr60Al15Ni15Cu10 BMG exhibits the largest supercooled liquid region of 104 K and critical diameter of 18 mm.However,addition of 5-10 at.% Fe or Co decrease the thermal stability and GFA.In addition,the plasticity of the BMG can be improved by adding of Cu,while the strength is decreased slightly.Zr60Al15Ni20Cu5 BMG has the largest plastic strain of 5.5% with a yield stress of 1755 MPa and Young's modulus of 83 GPa.Addition of Co brings an increase of strength but a lower of plasticity,and additional Fe reduces the strength and plasticity simultaneously.展开更多
The effect of minor alloying on several bulk metallic glasses and high-entropy al-loys was studied. It was found that minor Nb addition can optimize the interface structure between the W fiber and the Zr-based bulk me...The effect of minor alloying on several bulk metallic glasses and high-entropy al-loys was studied. It was found that minor Nb addition can optimize the interface structure between the W fiber and the Zr-based bulk metallic glass in the compos-ites,and improve the mechanical properties. Minor Y addition can destabilize the crystalline phases by inducing lattice distortion as a result to improve the glass-forming ability,and the lattice distortion energy is closely related to the effi-ciency of space filling of the competing crystalline phases. A long-period ordered structure can precipitate in the Mg-based bulk metallic glass by yttrium alloying. For the high-entropy alloys,solid solution can be formed by alloying,and its me-chanical properties can be comparable to most of the bulk metallic glasses.展开更多
In this paper, effects of cryogenic thermal cycling on deformation behavior and thermal stability of the Zr46Cu46AI8 bulk metallic glass （BMG） were studied. The results show that with the increase of the number of c...In this paper, effects of cryogenic thermal cycling on deformation behavior and thermal stability of the Zr46Cu46AI8 bulk metallic glass （BMG） were studied. The results show that with the increase of the number of cryogenic thermal cycles （CTC）, thermal stability remains almost unchanged, while the plasticity is increased, indicating that the cryogenic thermal cyclic treatment is an effective way to improve plasticity of metallic glasses without distinctly deteriorating thermal stability. Our analysis suggests that the increase in the defect density resulted from the cryogenic thermal treatments are responsible for the plasticity increment. Variation of yield strength can be well interpreted from microstructural percolation which affected by both density and characteristic volume of the defect sites.展开更多
Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared wi...Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared with those of the respective ingots. An increasing Co content stabilises the B2 CuZr phase and leads to the precipitation of a ternary Cu-Zr-Co phase. The variation of the cooling rate affects the size of the B2 dendrites as well as the volume fraction and the morphology of the interdendritic phases. The mechanical properties were determined in compression and all alloys show a certain plastic deformability despite the presence of several binary and ternary intermetallic phases. The deformation mechanisms are discussed on the basis of the microstructures and the constituent phases.展开更多
The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission...The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission electron microscopy (HRTEM) techniques. We focused on the short-range order (SRO) and medium-range order (MRO) in the glassy structure. It is shown that there are icosahedral,FCC-and BCC-type SROs in the Zr-based metallic glasses. A structural model,characterized by imperfect ordered packing (IOP),was proposed based on the MD simulation and confirmed by the HRTEM observation. Furthermore,the evolution from IOP to nanocrystal during the crystallization of metallic glasses was also ex-plored. It is found that the growth from IOP to nanocrystal proceeds through three distinct stages: the formation of quasi-ordered structure with one-dimensional (1D) periodicity,then 2D periodicity,and finally the formation of 3D nanocrystals. It is also noted that these three growth steps are crosslinked.展开更多
To address the main stumbling-block of bulk metallic glasses （BMGs）, i.e., room temperature brittleness, designing BMG matrix composites has been attracted extensive attention. Up to date, BMG composites in various ...To address the main stumbling-block of bulk metallic glasses （BMGs）, i.e., room temperature brittleness, designing BMG matrix composites has been attracted extensive attention. Up to date, BMG composites in various alloy systems have been successfully developed by forming crystalline phases embedded in the amorphous matrix through either ex-situ or in-situ methods. In this paper, a brief review of our recent work in this topic will be presented and the novel approaches to improving composite formability and mechanical properties will also be highlighted. The main purpose of this manuscript is not to offer a comprehensive review of all the BMG composites, but instead focuses will be placed on illustrating recently developed advanced BMG composites including Fe-based BMG composite with no metalloids, AI-based BMG composite and BMG composites reinforced by the TRIP （transformation-induced plasticity） effects. The basic ideas and related mechanisms underlying the development of these novel BMG composites will be discussed.展开更多
Nd^3＋ doped CaO-Al2O-B2O3-CaF2 glasses were prepared by conventional melt-quenching technique,and their structural and thermal properties were studied.The amorphous nature of these samples was confirmed by X-ray diff...Nd^3＋ doped CaO-Al2O-B2O3-CaF2 glasses were prepared by conventional melt-quenching technique,and their structural and thermal properties were studied.The amorphous nature of these samples was confirmed by X-ray diffraction（XRD）.The measured density showed an increase with Nd2O3 doping,at the expense of CaO.Raman spectra presented changes with addition of Nd2O3,which indicated that the network structure of the glasses studied presented various borate groups,such as tetraborates,metaborates,ortho-borates and pyroborates units.The N4 values calculated from FTIR spectra revealed that incorporation of Nd2O3 into glass network converted the structural units from BO4 to BO3.From the analysis of DTA curves,we verified that Tg increased with the addition of Nd2O3;it was similar to the behavior caused by modifier oxides in the structure of borate glasses.Besides that,the calculated glass stability Tx–Tg for doped samples presented a decrease if compared to the undoped glass.Specific heat and thermal conductivity did not present significant changes with Nd2O3 concentration,up to 2.30 mol.%.The results of density,DTA,Raman and FTIR reinforced the idea that Nd2O3 acted as network modifier.展开更多
A group of Cu（Zr）-based bulk metallic glasses （BMGs） with critical diameter （De） in the 12 to 18 mm range have been obtained using copper mould casting. In the Cu-Zr-Y-Al quaternary system, a new record of Dc=14...A group of Cu（Zr）-based bulk metallic glasses （BMGs） with critical diameter （De） in the 12 to 18 mm range have been obtained using copper mould casting. In the Cu-Zr-Y-Al quaternary system, a new record of Dc=14 mm was established for Cu-based compositions, and 16 mm for compositions based on equi-atomic CuZr. Additional partial substitution of Hf for Zr further elevated the Dc to 18 mm at Cu42Zr43Hf1.5Y3.5Al10.展开更多
Various characterisation techniques were used to study the composition of the glass series 55-P<sub>2</sub>O<sub>5</sub>-2Cr<sub>2</sub>O<sub>3</sub>-(43-x) Na<sub>...Various characterisation techniques were used to study the composition of the glass series 55-P<sub>2</sub>O<sub>5</sub>-2Cr<sub>2</sub>O<sub>3</sub>-(43-x) Na<sub>2</sub>O-xPbO (with 8 ≤ x ≤ 38;mole %) in terms of chemical durability, IR spectroscopy and scanning electron microscopy (SEM). The change in the dissolution rate as a function of time when the studied glasses were kept submerged in distilled water at 90°C for 20 days showed an improvement in the chemical durability when Na<sub>2</sub>O content was substituted to PbO content. IR spectroscopy revealed a structural change from ultraphosphate groups to pyrophosphate, orthophosphate and probably ring metaphosphate groups. SEM revealed the existence of two phases: a vitreous phase and a crystalline phase. The presence of Cr<sub>2</sub>O<sub>3</sub>, even in small amounts, seems to play an important role in the formation of crystallites in the glass network. The improved chemical durability is attributed to the replacement of the easily hydrated Na-O-P and P-O-P bonds by covalent and resistant Pb-O-P bands. Both the increase in PbO content and in the Pb + Cr/P ratio causes an increase in the number of covalent Pb-O-P and Cr-O-P bonds, making the glass structure more rigid. The increase of the covalent Pb-O-P bands leads to a clear evolution of the structure and chemical resistance, caused by grain-boundary resistance as a result of glass crystallisation. The IR spectra indicate that the increase in PbO content favours the formation of isolated PO<sup>3-</sup>4</sub> orthophosphate groups at the expense of pyrophosphate groups. The radical change in the structure from ultraphosphate groups to pyrophosphate and orthophosphate groups seems to be the cause of the formation of crystallites. The existence of crystallites in these glasses results in a marked improvement in their chemical durability. However, when the crystallites exceed a certain limit, the equilibrium between the glass bath and these crystallites is no longer maintained;we notice, once, a dec展开更多
基金the Centre National de la Recherche Scientifique (CNRS) for providing the postdoctoral financial support
文摘Metallic glasses have aroused considerable interest in the past decades because they exhibit fascinating properties. First, this article briefly outlines the mechanical, thermal properties and application of the metallic glasses. In addition, we focus on the dynamic mechanical relaxation behaviors, i.e. main （α） and secondary （β） relaxations, in metallic glasses. The mechanical relaxation behaviors are connected to the mechanical properties and physical properties in glassy materials. The main relaxation in glassy materials is related to the glass transition phenomenon and viscous flow. On the other hand, the β relaxation is linked to many fundamental issues in metallic glasses. In these materials relaxation processes are directly related to the plastic deformation mechanism. The mechanical relaxations, particularly, the β relaxation provides an excellent opportunity to design metallic glasses with desired physical and mechanical properties. We demonstrate the universal characteristics of main relaxation in metallic glasses. The phenomenological models and the physical theories are introduced to describe the main relaxation in metallic glasses. In parallel, we show the dependence of the α. and β relaxations on the thermal treatments in metallic glasses. Finally, we analyze the correlation between the atomic mobility and the thermo-mechanical treatments in metallic glasses. On the one hand, the atomic mobility in metallic glasses is reduced by physical aging or crystallization. On the other hand, the atomic mobility in metallic glass is enhanced by deformation （i.e. compression and cold rolling）. Importantly, to analyze the atomic mobility in amorphous materials, a physical theory is introduced. This model invokes the concept of quasi-point defects, which correspond to the density fluctuations in the glassy materials.
基金This work was financially supported by the Natural Science Foundation of China(NSFC)(Nos.61975140 and 62075145)Leading Technology of Jiangsu Basic Research Plan(BK20192003)Suzhou Natural Science Foundation of China(SYG201930)。
文摘Glasses-free three-dimensional(3D)displays are one of the game-changing technologies that will redefine the display industry in portable electronic devices.However,because of the limited resolution in state-of-the-art display panels,current 3D displays suffer from a critical trade-off among the spatial resolution,angular resolution,and viewing angle.Inspired by the so-called spatially variant resolution imaging found in vertebrate eyes,we propose 3D display with spatially variant information density.Stereoscopic experiences with smooth motion parallax are maintained at the central view,while the viewing angle is enlarged at the periphery view.It is enabled by a large-scale 2D-metagrating complex to manipulate dot/linear/rectangular hybrid shaped views.Furthermore,a video rate full-color 3D display with an unprecedented 160°horizontal viewing angle is demonstrated.With thin and light form factors,the proposed 3D system can be integrated with off-the-shelf purchased flat panels,making it promising for applications in portable electronics.
基金supported by the Fundamental Research Funds for the Central Universities of China(Grant Nos.DUT11RC(3)70 and DUT11RC(3)29)the National Natural Science Foundation of China (Grant No.51171034)the China Postdoctoral Science Foundation (Grant No.2012M510802)
文摘The thermal stability,glass-forming ability(GFA) and mechanical properties of Zr60Al15Ni25xTMx(TM = Cu,Fe and Co,x = 0-10) bulk metallic glasses(BMGs) were systematically investigated.Additional 5-10 at.% Cu greatly enhances the thermal stability and GFA of the base alloy.Zr60Al15Ni15Cu10 BMG exhibits the largest supercooled liquid region of 104 K and critical diameter of 18 mm.However,addition of 5-10 at.% Fe or Co decrease the thermal stability and GFA.In addition,the plasticity of the BMG can be improved by adding of Cu,while the strength is decreased slightly.Zr60Al15Ni20Cu5 BMG has the largest plastic strain of 5.5% with a yield stress of 1755 MPa and Young's modulus of 83 GPa.Addition of Co brings an increase of strength but a lower of plasticity,and additional Fe reduces the strength and plasticity simultaneously.
文摘The effect of minor alloying on several bulk metallic glasses and high-entropy al-loys was studied. It was found that minor Nb addition can optimize the interface structure between the W fiber and the Zr-based bulk metallic glass in the compos-ites,and improve the mechanical properties. Minor Y addition can destabilize the crystalline phases by inducing lattice distortion as a result to improve the glass-forming ability,and the lattice distortion energy is closely related to the effi-ciency of space filling of the competing crystalline phases. A long-period ordered structure can precipitate in the Mg-based bulk metallic glass by yttrium alloying. For the high-entropy alloys,solid solution can be formed by alloying,and its me-chanical properties can be comparable to most of the bulk metallic glasses.
基金supported by the National Natural Science Foundation of China(51671018,11790293,51531001,51422101,51371003,and 51671021)111 Project(B07003)+3 种基金International S&T Cooperation Program of China(2015DFG52600)Program for Changjiang Scholars and Innovative Research Team in University of China(IRT_14R05)the Projects of SKLAMM-USTB(2016Z04,2016-09,2016Z-16)the financial support from the Top-Notch Young Talents Program and Fundamental Research Fund for the Central Universities(FRF-TP-15-004C1)
文摘In this paper, effects of cryogenic thermal cycling on deformation behavior and thermal stability of the Zr46Cu46AI8 bulk metallic glass （BMG） were studied. The results show that with the increase of the number of cryogenic thermal cycles （CTC）, thermal stability remains almost unchanged, while the plasticity is increased, indicating that the cryogenic thermal cyclic treatment is an effective way to improve plasticity of metallic glasses without distinctly deteriorating thermal stability. Our analysis suggests that the increase in the defect density resulted from the cryogenic thermal treatments are responsible for the plasticity increment. Variation of yield strength can be well interpreted from microstructural percolation which affected by both density and characteristic volume of the defect sites.
基金the financial support by CNPq, Brazil, and DAAD, Germany
文摘Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared with those of the respective ingots. An increasing Co content stabilises the B2 CuZr phase and leads to the precipitation of a ternary Cu-Zr-Co phase. The variation of the cooling rate affects the size of the B2 dendrites as well as the volume fraction and the morphology of the interdendritic phases. The mechanical properties were determined in compression and all alloys show a certain plastic deformability despite the presence of several binary and ternary intermetallic phases. The deformation mechanisms are discussed on the basis of the microstructures and the constituent phases.
基金the National Natural Science Foundation of China (Grant Nos. 50431030 and 50471097)the National Basic Research Program of China (Grant No. 2007CB613901)the Programme of Introducing Talents of Discipline to Universities (Grant No. B07003)
文摘The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission electron microscopy (HRTEM) techniques. We focused on the short-range order (SRO) and medium-range order (MRO) in the glassy structure. It is shown that there are icosahedral,FCC-and BCC-type SROs in the Zr-based metallic glasses. A structural model,characterized by imperfect ordered packing (IOP),was proposed based on the MD simulation and confirmed by the HRTEM observation. Furthermore,the evolution from IOP to nanocrystal during the crystallization of metallic glasses was also ex-plored. It is found that the growth from IOP to nanocrystal proceeds through three distinct stages: the formation of quasi-ordered structure with one-dimensional (1D) periodicity,then 2D periodicity,and finally the formation of 3D nanocrystals. It is also noted that these three growth steps are crosslinked.
基金supported in part by the National Natural Science Foundation of China (Nos. 51010001, 51371003, 51001009 and 51271212)111 Project (No. B07003)+2 种基金Program for Changjiang Scholars and Innovative Research Team in Universityfinancial support from the Fundamental Research Funds for the Central Universities (Nos. FRF-SD-12-005A and FRF-TP-11-005A)financial support from the Research Project of State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing (No. 2011Z-13)
文摘To address the main stumbling-block of bulk metallic glasses （BMGs）, i.e., room temperature brittleness, designing BMG matrix composites has been attracted extensive attention. Up to date, BMG composites in various alloy systems have been successfully developed by forming crystalline phases embedded in the amorphous matrix through either ex-situ or in-situ methods. In this paper, a brief review of our recent work in this topic will be presented and the novel approaches to improving composite formability and mechanical properties will also be highlighted. The main purpose of this manuscript is not to offer a comprehensive review of all the BMG composites, but instead focuses will be placed on illustrating recently developed advanced BMG composites including Fe-based BMG composite with no metalloids, AI-based BMG composite and BMG composites reinforced by the TRIP （transformation-induced plasticity） effects. The basic ideas and related mechanisms underlying the development of these novel BMG composites will be discussed.
基金Project supported by the Brazilian agencies CNPq,CAPES and FAPEMA
文摘Nd^3＋ doped CaO-Al2O-B2O3-CaF2 glasses were prepared by conventional melt-quenching technique,and their structural and thermal properties were studied.The amorphous nature of these samples was confirmed by X-ray diffraction（XRD）.The measured density showed an increase with Nd2O3 doping,at the expense of CaO.Raman spectra presented changes with addition of Nd2O3,which indicated that the network structure of the glasses studied presented various borate groups,such as tetraborates,metaborates,ortho-borates and pyroborates units.The N4 values calculated from FTIR spectra revealed that incorporation of Nd2O3 into glass network converted the structural units from BO4 to BO3.From the analysis of DTA curves,we verified that Tg increased with the addition of Nd2O3;it was similar to the behavior caused by modifier oxides in the structure of borate glasses.Besides that,the calculated glass stability Tx–Tg for doped samples presented a decrease if compared to the undoped glass.Specific heat and thermal conductivity did not present significant changes with Nd2O3 concentration,up to 2.30 mol.%.The results of density,DTA,Raman and FTIR reinforced the idea that Nd2O3 acted as network modifier.
基金supported by the National Natural Science Foundation of China under Grants Nos.50671105 and 50621091.
文摘A group of Cu（Zr）-based bulk metallic glasses （BMGs） with critical diameter （De） in the 12 to 18 mm range have been obtained using copper mould casting. In the Cu-Zr-Y-Al quaternary system, a new record of Dc=14 mm was established for Cu-based compositions, and 16 mm for compositions based on equi-atomic CuZr. Additional partial substitution of Hf for Zr further elevated the Dc to 18 mm at Cu42Zr43Hf1.5Y3.5Al10.
文摘Various characterisation techniques were used to study the composition of the glass series 55-P<sub>2</sub>O<sub>5</sub>-2Cr<sub>2</sub>O<sub>3</sub>-(43-x) Na<sub>2</sub>O-xPbO (with 8 ≤ x ≤ 38;mole %) in terms of chemical durability, IR spectroscopy and scanning electron microscopy (SEM). The change in the dissolution rate as a function of time when the studied glasses were kept submerged in distilled water at 90°C for 20 days showed an improvement in the chemical durability when Na<sub>2</sub>O content was substituted to PbO content. IR spectroscopy revealed a structural change from ultraphosphate groups to pyrophosphate, orthophosphate and probably ring metaphosphate groups. SEM revealed the existence of two phases: a vitreous phase and a crystalline phase. The presence of Cr<sub>2</sub>O<sub>3</sub>, even in small amounts, seems to play an important role in the formation of crystallites in the glass network. The improved chemical durability is attributed to the replacement of the easily hydrated Na-O-P and P-O-P bonds by covalent and resistant Pb-O-P bands. Both the increase in PbO content and in the Pb + Cr/P ratio causes an increase in the number of covalent Pb-O-P and Cr-O-P bonds, making the glass structure more rigid. The increase of the covalent Pb-O-P bands leads to a clear evolution of the structure and chemical resistance, caused by grain-boundary resistance as a result of glass crystallisation. The IR spectra indicate that the increase in PbO content favours the formation of isolated PO<sup>3-</sup>4</sub> orthophosphate groups at the expense of pyrophosphate groups. The radical change in the structure from ultraphosphate groups to pyrophosphate and orthophosphate groups seems to be the cause of the formation of crystallites. The existence of crystallites in these glasses results in a marked improvement in their chemical durability. However, when the crystallites exceed a certain limit, the equilibrium between the glass bath and these crystallites is no longer maintained;we notice, once, a dec
