Long-term thermal stability of a series of Zr-based metallic glasses with different oxygen contents below their glass transition temperatures was compared based on their deductive continuous-heating-transformation dia...Long-term thermal stability of a series of Zr-based metallic glasses with different oxygen contents below their glass transition temperatures was compared based on their deductive continuous-heating-transformation diagrams created by using the corollary of Kissinger analysis method. It is found that the influence of oxygen on the long-term thermal stability of Zr-based metallic glasses exhibits at lower temperature is different from that on their short-term thermal stability presented at higher temperature. For each kind of the Zr-based metallic glasses, there is a critical heating rate, φ , which corresponds to a critical c temperature, Tc. As heating rate is smaller than φ c and onset devitrification temperature is below Tc, the glass with higher oxygen content will have longer incubation period for onset devitrification. The values of φ c and Tc are related with the glasses’ reduced glass transition temperature Trg. The improving effect of oxygen impurity on the long-term thermal stability of Zr-based metallic glasses was discovered.展开更多
Bulk metallic glass Zr_52.5Ni_14.6Al_10Cu_17.9Ti_5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be ...Bulk metallic glass Zr_52.5Ni_14.6Al_10Cu_17.9Ti_5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively. By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM ), the predominant crystallized phase of Zr_2Ni0.67O0.33 distributed on glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr_2Ni_0.67O_0.33 and a small amount of ZrAl and Zr_2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr_2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr_2Ni_0.67O_0.33 is interface-controlled, but is diffusion-controlled to Zr_2Cu and ZrAl. With increasing annealing temperature up to 200 K above T_x, the nanometer grains became very fine because of the increase of nucleation rate for Zr_2Cu and ZrAl.展开更多
The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that par...The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that partial crystallization did not influence the reduced elastic modulus but increased the hardness, and then increased the scratch coefficient. The scratch coefficient increased linearly with increasing the hardness H but decreases when W>6.2GPa. Partial crystallization decreased evidently the wear depth, and when the load was large the wear depth decreased with increasing the hardness.展开更多
In this paper, glass transition and thermal stability of the Zr-AI-Cu-Ni metallic glasses were investigated by using electrical resistance measurement (ERM), DSC and X-ray diffraction techniques. The experimental resu...In this paper, glass transition and thermal stability of the Zr-AI-Cu-Ni metallic glasses were investigated by using electrical resistance measurement (ERM), DSC and X-ray diffraction techniques. The experimental results show that the ERM is capable of detecting the glass transition of the amorphous alloys and can help to distinguish the crystallization products of the Zr-AI-Cu-Ni metallic glasses owing to the difference of the electrical resistivity between the precipitation phases.展开更多
The metallic Zr65Ni25Ti10（mole fraction, %） glass has been fabricated by a single roller melt-spinning method. The glass forming ability（GFA） and thermal stability of the Zr65Ni25Ti10 melt-spun ribbons were invest...The metallic Zr65Ni25Ti10（mole fraction, %） glass has been fabricated by a single roller melt-spinning method. The glass forming ability（GFA） and thermal stability of the Zr65Ni25Ti10 melt-spun ribbons were investigated by using X-ray diffraction（XRD） and differential scanning calorimetry（DSC） in the mode of continuous heating. It is shown that the reduced glass transition temperature (Trg) is 0.506 and the supercooled liquid region （ΔTx） is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction（XRD） and transmission electronic microscope（TEM）. It is observed that the metastable FCC Zr2Ni（Fd3m, a=12.27 ） precipitated while annealing in the suppercooled region（615 K） and the stable BCT Zr2Ni（I4/mcm, a=6.499 , c=5.270 ） precipitated while annealing at higher temperature（673 K or 723 K）. The crystallines are on nanoscale, with grain size of 1530 nm. The reason for the precipitation of the different structural Zr2Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order（MCSRO）.展开更多
The unusual glass-forming ability（GFA） of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a ...The unusual glass-forming ability（GFA） of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr48Cu36Ag8Al8 alloy.High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature.The bulk metallic glass matrix composites were prepared by introducing extra Ta particles into the Zr48Cu36Ag8Al8 melt.The composites consist of Ta particles homogenously distributed in the Zr48Cu36Ag8Al8 metallic glass matrix.The optimum content of Ta powder is 10at%for the composite with the highest plasticity,which shows a plastic strain of 31%.展开更多
The crystallization process of metallic glass Zr_(65)Al_(7.5)Ni_(10)Gu_(17.5)(atom fraction in percent) were studied by transmission electron microscopy and X-ray diffraction.Two stages of crystallization process, whi...The crystallization process of metallic glass Zr_(65)Al_(7.5)Ni_(10)Gu_(17.5)(atom fraction in percent) were studied by transmission electron microscopy and X-ray diffraction.Two stages of crystallization process, which are indicated by the two exothermic peaks in thedifferential scanning calorimetry diagram, were studied separately. It is found that the phases inthe various stage of the crystallization are different. In the first stage, it consists mainly oftI-CuZr_2 and tP-Al_2Zr_3 phases, between which a definite orientation relationship is found. Whilein the second stage, in addition to the above phases, phase hP^2-Al_2NiZr_6 and phase hP^3-alpha-Zrappear, between which another orientation relationship is also found. At the same time, a comparisonis made based on the study of the phases exist in the arc-melted master ingot. The latticeparameters of the identified phases were determined and some interesting similarities were found.According to these similarities, all the phases were classified into two groups. The first is: oB,tI-CuZr_2 and hP^3-alpha-Zr; the other is: hP^2, tP-Al_2NiZr_3 and hP^1-Al_2NiZr_6. Therelationships between phases in these two groups were investigated and the probable reasons that mayresult in these relationships were discussed.展开更多
Antioxidation effects on Sm （Co, Cu, Fe, Zr）z-sintered magnets treated by different methods were studied through TGA and DTA. Microstructure of Sm（Co, Cu, Fe, Zr）z-sintered magnets was analyzed through SEM and EDS...Antioxidation effects on Sm （Co, Cu, Fe, Zr）z-sintered magnets treated by different methods were studied through TGA and DTA. Microstructure of Sm（Co, Cu, Fe, Zr）z-sintered magnets was analyzed through SEM and EDS. The results indicate that the antioxidation effect of the alloy powder treated in silane solution is better than that of the other methods. The alloy powders treated in stearic acid （SA） solution and polymethyl methacrylate （PMMA） solution can prevent powders from oxidation for a short period of time. Silane solution is not suitable for metal injection molding （MIM） because it severely damages the magnetic properties and microstructure of Sm（Co, Cu, Fe, Zr）z-sintered magnets. SA solution can not only prevent powders from oxidizing in MIM, but also does not damage magnetic properties and microstructure of Sm（Co, Cu, Fe, Zr）z magnets. The oxygen content of Sm（Co, Cu, Fe, Zr）z-sintered magnets by MIM is 3300μg·g^-1.展开更多
The crystallization kinetics of Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass has been studied by using DSC and XRD. The results show that two exothermal peaks are observed when the alloy is heated to 500?℃, ...The crystallization kinetics of Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass has been studied by using DSC and XRD. The results show that two exothermal peaks are observed when the alloy is heated to 500?℃, one peak results dominantly from the formation of Ti 2Ni ( α phase transition), the other peak is mainly due to the formation of Zr 2Cu ( β phase transition). At the beginning of the crystallization, the activation energy of the α phase is smaller, and it increases with increasing crystallized fraction ( x c). When x c increases to 90%, the crystallization activation energy shows the largest value (220?kJ/mol). The crystallization activation energy of the β phase remains about 227?kJ/mol, as it’s crystallized fraction is below 60%, and then it increases with increasing crystallized fraction, and shows the largest activation energy of 257?kJ/mol, as the x c is 65%.展开更多
In this paper, the vacuum brazing of Si3N4 ceramic was carried out with Ti40Zr25Ni15Cu20 amorphous filler metal. The interfacial microstructure was investigated by scanning electron microscopy （ SEM ）, energy disper...In this paper, the vacuum brazing of Si3N4 ceramic was carried out with Ti40Zr25Ni15Cu20 amorphous filler metal. The interfacial microstructure was investigated by scanning electron microscopy （ SEM ）, energy dispersive spectroscopy （EDS） etc. According to the analysis, the interface reaction layer was mode up of TiN abut on the ceramic and the Ti-Si, Zr-Si compounds. The influence of brazing temperature and holding time on the joint strength was also studied. The results shows that the joint strength first increased and then decreased with the increasing of holding time and brazing temperature. The joint strength was significantly affected by the thickness of the reaction layer. Under the same experimental conditions, the joint brazed with amorphous filler metal exhibits much higher strength compared with the one brazed with crystalline filler metal with the same composition. To achieve higher joint strength at relatively low temperature, it is favorable to use the amorphous filler metal than the crystalline filler metal.展开更多
基金Project(50671076) supported by the National Natural Science Foundation of China
文摘Long-term thermal stability of a series of Zr-based metallic glasses with different oxygen contents below their glass transition temperatures was compared based on their deductive continuous-heating-transformation diagrams created by using the corollary of Kissinger analysis method. It is found that the influence of oxygen on the long-term thermal stability of Zr-based metallic glasses exhibits at lower temperature is different from that on their short-term thermal stability presented at higher temperature. For each kind of the Zr-based metallic glasses, there is a critical heating rate, φ , which corresponds to a critical c temperature, Tc. As heating rate is smaller than φ c and onset devitrification temperature is below Tc, the glass with higher oxygen content will have longer incubation period for onset devitrification. The values of φ c and Tc are related with the glasses’ reduced glass transition temperature Trg. The improving effect of oxygen impurity on the long-term thermal stability of Zr-based metallic glasses was discovered.
文摘Bulk metallic glass Zr_52.5Ni_14.6Al_10Cu_17.9Ti_5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively. By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM ), the predominant crystallized phase of Zr_2Ni0.67O0.33 distributed on glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr_2Ni_0.67O_0.33 and a small amount of ZrAl and Zr_2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr_2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr_2Ni_0.67O_0.33 is interface-controlled, but is diffusion-controlled to Zr_2Cu and ZrAl. With increasing annealing temperature up to 200 K above T_x, the nanometer grains became very fine because of the increase of nucleation rate for Zr_2Cu and ZrAl.
基金support by the special funds for the major state basic research(2002AA331080).
文摘The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that partial crystallization did not influence the reduced elastic modulus but increased the hardness, and then increased the scratch coefficient. The scratch coefficient increased linearly with increasing the hardness H but decreases when W>6.2GPa. Partial crystallization decreased evidently the wear depth, and when the load was large the wear depth decreased with increasing the hardness.
基金The financial support from the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No.50271050) Prof. Li Y who provided the metallic glass samples are acknowledged.
文摘In this paper, glass transition and thermal stability of the Zr-AI-Cu-Ni metallic glasses were investigated by using electrical resistance measurement (ERM), DSC and X-ray diffraction techniques. The experimental results show that the ERM is capable of detecting the glass transition of the amorphous alloys and can help to distinguish the crystallization products of the Zr-AI-Cu-Ni metallic glasses owing to the difference of the electrical resistivity between the precipitation phases.
文摘The metallic Zr65Ni25Ti10（mole fraction, %） glass has been fabricated by a single roller melt-spinning method. The glass forming ability（GFA） and thermal stability of the Zr65Ni25Ti10 melt-spun ribbons were investigated by using X-ray diffraction（XRD） and differential scanning calorimetry（DSC） in the mode of continuous heating. It is shown that the reduced glass transition temperature (Trg) is 0.506 and the supercooled liquid region （ΔTx） is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction（XRD） and transmission electronic microscope（TEM）. It is observed that the metastable FCC Zr2Ni（Fd3m, a=12.27 ） precipitated while annealing in the suppercooled region（615 K） and the stable BCT Zr2Ni（I4/mcm, a=6.499 , c=5.270 ） precipitated while annealing at higher temperature（673 K or 723 K）. The crystallines are on nanoscale, with grain size of 1530 nm. The reason for the precipitation of the different structural Zr2Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order（MCSRO）.
基金supported by Grant-In-Aid for Scientific Research(C)(No.19560689)
文摘The unusual glass-forming ability（GFA） of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr48Cu36Ag8Al8 alloy.High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature.The bulk metallic glass matrix composites were prepared by introducing extra Ta particles into the Zr48Cu36Ag8Al8 melt.The composites consist of Ta particles homogenously distributed in the Zr48Cu36Ag8Al8 metallic glass matrix.The optimum content of Ta powder is 10at%for the composite with the highest plasticity,which shows a plastic strain of 31%.
文摘The crystallization process of metallic glass Zr_(65)Al_(7.5)Ni_(10)Gu_(17.5)(atom fraction in percent) were studied by transmission electron microscopy and X-ray diffraction.Two stages of crystallization process, which are indicated by the two exothermic peaks in thedifferential scanning calorimetry diagram, were studied separately. It is found that the phases inthe various stage of the crystallization are different. In the first stage, it consists mainly oftI-CuZr_2 and tP-Al_2Zr_3 phases, between which a definite orientation relationship is found. Whilein the second stage, in addition to the above phases, phase hP^2-Al_2NiZr_6 and phase hP^3-alpha-Zrappear, between which another orientation relationship is also found. At the same time, a comparisonis made based on the study of the phases exist in the arc-melted master ingot. The latticeparameters of the identified phases were determined and some interesting similarities were found.According to these similarities, all the phases were classified into two groups. The first is: oB,tI-CuZr_2 and hP^3-alpha-Zr; the other is: hP^2, tP-Al_2NiZr_3 and hP^1-Al_2NiZr_6. Therelationships between phases in these two groups were investigated and the probable reasons that mayresult in these relationships were discussed.
基金Project supported by Specialized Research Fundfor the Doctoral Programof Higher Education (20040008015)ProgramforNew Century Excellent Talents in University (NCET)
文摘Antioxidation effects on Sm （Co, Cu, Fe, Zr）z-sintered magnets treated by different methods were studied through TGA and DTA. Microstructure of Sm（Co, Cu, Fe, Zr）z-sintered magnets was analyzed through SEM and EDS. The results indicate that the antioxidation effect of the alloy powder treated in silane solution is better than that of the other methods. The alloy powders treated in stearic acid （SA） solution and polymethyl methacrylate （PMMA） solution can prevent powders from oxidation for a short period of time. Silane solution is not suitable for metal injection molding （MIM） because it severely damages the magnetic properties and microstructure of Sm（Co, Cu, Fe, Zr）z-sintered magnets. SA solution can not only prevent powders from oxidizing in MIM, but also does not damage magnetic properties and microstructure of Sm（Co, Cu, Fe, Zr）z magnets. The oxygen content of Sm（Co, Cu, Fe, Zr）z-sintered magnets by MIM is 3300μg·g^-1.
文摘The crystallization kinetics of Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass has been studied by using DSC and XRD. The results show that two exothermal peaks are observed when the alloy is heated to 500?℃, one peak results dominantly from the formation of Ti 2Ni ( α phase transition), the other peak is mainly due to the formation of Zr 2Cu ( β phase transition). At the beginning of the crystallization, the activation energy of the α phase is smaller, and it increases with increasing crystallized fraction ( x c). When x c increases to 90%, the crystallization activation energy shows the largest value (220?kJ/mol). The crystallization activation energy of the β phase remains about 227?kJ/mol, as it’s crystallized fraction is below 60%, and then it increases with increasing crystallized fraction, and shows the largest activation energy of 257?kJ/mol, as the x c is 65%.
基金Funded by National Natural Science Foundation of China （No. 50875117）.
文摘In this paper, the vacuum brazing of Si3N4 ceramic was carried out with Ti40Zr25Ni15Cu20 amorphous filler metal. The interfacial microstructure was investigated by scanning electron microscopy （ SEM ）, energy dispersive spectroscopy （EDS） etc. According to the analysis, the interface reaction layer was mode up of TiN abut on the ceramic and the Ti-Si, Zr-Si compounds. The influence of brazing temperature and holding time on the joint strength was also studied. The results shows that the joint strength first increased and then decreased with the increasing of holding time and brazing temperature. The joint strength was significantly affected by the thickness of the reaction layer. Under the same experimental conditions, the joint brazed with amorphous filler metal exhibits much higher strength compared with the one brazed with crystalline filler metal with the same composition. To achieve higher joint strength at relatively low temperature, it is favorable to use the amorphous filler metal than the crystalline filler metal.
