Influence of Sc content on microstructure and stress corrosion cracking behavior of medium strength AI-Zn-Mg alloy have been investigated by optical microscopy, scanning electron microscopy, electron backscatter diffr...Influence of Sc content on microstructure and stress corrosion cracking behavior of medium strength AI-Zn-Mg alloy have been investigated by optical microscopy, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and slow strain rate test. The results indicate that the addition of Sc results in the formation of the quaternary coherent AI3(Sc, Zr, Ti) dispersoids during homogenization treatment, which will inhibit the dynamic recrystallization behavior. The number density ofAl3(Sc, Zr, Ti) particles increases with the increase of Sc content, and thus the recrystallization fraction of hot-extruded alloy is reduced and the peak strength in two-stage artificial aging sample is enhanced. At the same time, the wide of precipitation free zone is reduced, and the content of Zn and Mg in grain boundary particles and precipitation free zone is increased with the increase of Sc content. In peak-aged state, the 0.06 wt% Sc added alloy shows the better stress corrosion cracking resistance than the Sc-free alloy because of the reduction of recrystallization fraction and the interrupted distribution of grain boundary precipitates along grain boundary. However, the further addition of Sc to 0.11 wt% will result in the deterioration of stress corrosion cracking resistance due to the increase of electrochemical activity of grain boundary particles and precipitation free zone as well as hydrogen embrittlement.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.展开更多
Fusion weld is a portable and economical joining and repairing method of metals.However,weld cracks often occur during the fusion weld of Ni-base superalloys,which hinder the applications of fusion weld on this kind o...Fusion weld is a portable and economical joining and repairing method of metals.However,weld cracks often occur during the fusion weld of Ni-base superalloys,which hinder the applications of fusion weld on this kind of materials.In this work,the effects of microstructures of grain boundaries(GBs)of the prototype M951 superalloy on its weldability were investigated.The precipitated phases,the elemental segregations on GBs,and the morphologies of GBs can be largely altered by regulating the cooling rates of pre-weld heat treatments.With decreasing the cooling rate,chain-like M_(23)X_(6)phase precipitates along the GBs,accompanying segregations of B,and GBs becomes more serrated in morphology.During fusion weld,the engineered GBs in the M951 superalloy with a low cooling rate favor the formation of the continuous liquid films on GBs,which together with the serrated GB morphology significantly prevents the formation of weld cracks.Our findings imply that the weld-crack resistance of the superalloys can be ameliorated by engineering GBs.展开更多
A single-phase (Ni,Pt)Al coating with lean addition of Zr was prepared by co-electroplating of Pt-Zr com posite plating and subsequent gaseous alum inization treatm ents. Isotherm al and cyclic oxidation behavior of t...A single-phase (Ni,Pt)Al coating with lean addition of Zr was prepared by co-electroplating of Pt-Zr com posite plating and subsequent gaseous alum inization treatm ents. Isotherm al and cyclic oxidation behavior of the Zr-doped (Ni,Pt)Al coating sam ples was assessed at 1373K in static air in comparison with plain nickel alum inide (NiAl) and norm al (Ni,Pt)Al coatings. Results indicated th at Zr-doped (Ni,Pt)Al coating dem onstrated a lower oxidation rate constant and reduced tendency of oxide scale spallation as well as surface rumpling, in which the enhanced oxidation perform ance was m ainly attributed to the segregation of Zr at oxide scale grain boundaries and the im proved Young's modulus of the coating. Besides, the addition of Zr effectively delayed oxide phase transform ation of Al2O3 from θ phase to α phase in the early oxidation stage and coating degradation of β-NiAl to γ'-Ni3Al in the stable oxidation stage.展开更多
The synergistic eff ect of NaCl and SO2 on the atmospheric corrosion of zinc has been studied at equivalent total but different ratios of molar deposition rate under wet–dry cyclic conditions.The results show that th...The synergistic eff ect of NaCl and SO2 on the atmospheric corrosion of zinc has been studied at equivalent total but different ratios of molar deposition rate under wet–dry cyclic conditions.The results show that the corrosion rates,corrosion morphologies and the composition of the corrosion products are strongly infl uenced by the molar deposition rate ratio of NaCl and SO2(NaCl/SO2).The corrosivity of NaCl and SO2 toward zinc increases in order of SO2<1:3<3:1<NaCl<1:1.The corrosion morphology is patchy corrosion for Group 1:1,while it is pocking corrosion for the other four experimental groups.The corrosion product containing sulfur and chlorine detected on zinc is Gordaite(NaZn4SO4(OH)6Cl·6H2O),which has quite porous structure and was supposed to cause the patchy corrosion tendency of zinc in Group 1:1.In addition,soluble zinc corrosion products,which can inhibit the atmospheric corrosion process of zinc,were found on zinc samples in Groups 1:3 and SO2 and connected to the lower corrosion rates of zinc in these two groups.展开更多
Large size,high-density(99.97%)and well-organized Al2O3/Y3Al5O12(YAG)eutectic ceramics were prepared by the modified Bridgman method.The evolution of the three dimensional microstructure and micropores were investigat...Large size,high-density(99.97%)and well-organized Al2O3/Y3Al5O12(YAG)eutectic ceramics were prepared by the modified Bridgman method.The evolution of the three dimensional microstructure and micropores were investigated.The diameter of the micro-pores and the porosity decreased during directional solidification.The average equivalent diam eter of the micro-pores was 2.41μm in the well-prepared eutectic ceramics.Most of the pores(98.07%)were smaller than 4μm.These data are comparable to those prepared by the optical floating zone method.The as-grown eutectic ceramics were polycrystalline,but the interfaces were well-bonded and there were no amorphous phases in the microstructure.The misfits of the different crystallographic relationships were calculated,and the bottleneck of the single-crystal preparation was identified.These results could provide theoretical guidance for the preparation of large,single-crystal Al2O3/YAG eutectic ceramics by the modified Bridgman method.展开更多
In this work, the corrosion behavior of two differently oriented surfaces of an as-extruded Mg-3%Al- 1%Zn (AZ31) bar in a simulated body fluid of phosphate buffer saline (PBS) medium was investigated and compared,...In this work, the corrosion behavior of two differently oriented surfaces of an as-extruded Mg-3%Al- 1%Zn (AZ31) bar in a simulated body fluid of phosphate buffer saline (PBS) medium was investigated and compared, and the effect of crystallographic texture on corrosion resistance of the alloy was deeply described. The results showed that at the early stage of immersion, a layer of compact and flat film formed easily on surfaces of both oriented samples. With prolonged immersion time, the degradation of formed corrosive films started and their severity was quite sensitive to the composed crystallographic planes of sample surfaces. For the surface containing highly concentrated orientation of {10-10} and {11-20} prism planes, the degradation of formed corrosive film was quite slight and only occurred at some particular sites even after immersion for 48 h. Thus, the film could keep good corrosive protection to the under- neath substrate. However, for the surface containing [0002} basal planes, {10-10} and {11-20} prism planes, the degradation of corrosive production film occurred widely, resulting in further decrease in the corrosion resistance of immersed samples,展开更多
The application of wavy structures in stretchable electrochemical energy storage devices is reviewed. First, the mechanical anaJysis of wavy structures, specific to flexible electronics, is introduced. Second, stretch...The application of wavy structures in stretchable electrochemical energy storage devices is reviewed. First, the mechanical anaJysis of wavy structures, specific to flexible electronics, is introduced. Second, stretchable electrochemical energy storage devices with wavy structures are discussed. Finally, the present problems and challenges are reviewed, and possible directions for future research are outlined.展开更多
The structures of tungsten and tungsten carbide scaffolds play a key role in determining the properties of their infiltrated composites for multifunctional applications.However,it is challenging to construct and contr...The structures of tungsten and tungsten carbide scaffolds play a key role in determining the properties of their infiltrated composites for multifunctional applications.However,it is challenging to construct and control the architectures by means of self-assembly in W/WC systems because of their large densities.Here we present the development of unidirectionally porous architectures,with high porosities exceeding 65 vol.%,for W and WC scaffolds which in many respects reproduce the design motif of natural wood using a direct ice-templating technique.This was achieved by adjusting the viscosities of suspensions to retard sedimentation during freezing.The processing,structural characteristics and mechanical properties of the resulting scaffolds were investigated with the correlations between them explored.Quantitative relationships were established to describe their strengths based on the mechanics of cellular solids by taking into account both inter-and intra-lamellar pores.The fracture mechanisms were also identified,especially in light of the porosity.This study extends the effectiveness of the ice-templating technique for systems with large densities or particle sizes.It further provides preforms for developing new natureinspired multifunctional materials,as represented by W/WC-Cu composites.展开更多
基金supported by the State’s Key Project of Research and Development (Grant Nos. 2016YFB1200600, and 2016YFB1200504)the Strategic Priority Program of the Chinese Academy of Sciences (Grant No. XDB22000000)
文摘Influence of Sc content on microstructure and stress corrosion cracking behavior of medium strength AI-Zn-Mg alloy have been investigated by optical microscopy, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and slow strain rate test. The results indicate that the addition of Sc results in the formation of the quaternary coherent AI3(Sc, Zr, Ti) dispersoids during homogenization treatment, which will inhibit the dynamic recrystallization behavior. The number density ofAl3(Sc, Zr, Ti) particles increases with the increase of Sc content, and thus the recrystallization fraction of hot-extruded alloy is reduced and the peak strength in two-stage artificial aging sample is enhanced. At the same time, the wide of precipitation free zone is reduced, and the content of Zn and Mg in grain boundary particles and precipitation free zone is increased with the increase of Sc content. In peak-aged state, the 0.06 wt% Sc added alloy shows the better stress corrosion cracking resistance than the Sc-free alloy because of the reduction of recrystallization fraction and the interrupted distribution of grain boundary precipitates along grain boundary. However, the further addition of Sc to 0.11 wt% will result in the deterioration of stress corrosion cracking resistance due to the increase of electrochemical activity of grain boundary particles and precipitation free zone as well as hydrogen embrittlement.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
基金the National Natural Science Foundation of China(Nos.51971214,51771191 and 51801206)the Aeronautics Power Foundation of China(No.DLJJ1825)。
文摘Fusion weld is a portable and economical joining and repairing method of metals.However,weld cracks often occur during the fusion weld of Ni-base superalloys,which hinder the applications of fusion weld on this kind of materials.In this work,the effects of microstructures of grain boundaries(GBs)of the prototype M951 superalloy on its weldability were investigated.The precipitated phases,the elemental segregations on GBs,and the morphologies of GBs can be largely altered by regulating the cooling rates of pre-weld heat treatments.With decreasing the cooling rate,chain-like M_(23)X_(6)phase precipitates along the GBs,accompanying segregations of B,and GBs becomes more serrated in morphology.During fusion weld,the engineered GBs in the M951 superalloy with a low cooling rate favor the formation of the continuous liquid films on GBs,which together with the serrated GB morphology significantly prevents the formation of weld cracks.Our findings imply that the weld-crack resistance of the superalloys can be ameliorated by engineering GBs.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51,671,202 and 51,301,184)the Defence Industrial Technology Development Program (Grant No. JCKY2016404C001)sponsored by “Liaoning BaiQianWan Talents” Program
文摘A single-phase (Ni,Pt)Al coating with lean addition of Zr was prepared by co-electroplating of Pt-Zr com posite plating and subsequent gaseous alum inization treatm ents. Isotherm al and cyclic oxidation behavior of the Zr-doped (Ni,Pt)Al coating sam ples was assessed at 1373K in static air in comparison with plain nickel alum inide (NiAl) and norm al (Ni,Pt)Al coatings. Results indicated th at Zr-doped (Ni,Pt)Al coating dem onstrated a lower oxidation rate constant and reduced tendency of oxide scale spallation as well as surface rumpling, in which the enhanced oxidation perform ance was m ainly attributed to the segregation of Zr at oxide scale grain boundaries and the im proved Young's modulus of the coating. Besides, the addition of Zr effectively delayed oxide phase transform ation of Al2O3 from θ phase to α phase in the early oxidation stage and coating degradation of β-NiAl to γ'-Ni3Al in the stable oxidation stage.
基金supported by the National Science Fund of China under the Contract Nos. 51671197 and 51601199by Guangzhou Industry-university-research Collaborative Innovation Alliance Special Project under the Contract No. 201604046014
文摘The synergistic eff ect of NaCl and SO2 on the atmospheric corrosion of zinc has been studied at equivalent total but different ratios of molar deposition rate under wet–dry cyclic conditions.The results show that the corrosion rates,corrosion morphologies and the composition of the corrosion products are strongly infl uenced by the molar deposition rate ratio of NaCl and SO2(NaCl/SO2).The corrosivity of NaCl and SO2 toward zinc increases in order of SO2<1:3<3:1<NaCl<1:1.The corrosion morphology is patchy corrosion for Group 1:1,while it is pocking corrosion for the other four experimental groups.The corrosion product containing sulfur and chlorine detected on zinc is Gordaite(NaZn4SO4(OH)6Cl·6H2O),which has quite porous structure and was supposed to cause the patchy corrosion tendency of zinc in Group 1:1.In addition,soluble zinc corrosion products,which can inhibit the atmospheric corrosion process of zinc,were found on zinc samples in Groups 1:3 and SO2 and connected to the lower corrosion rates of zinc in these two groups.
基金financially supported by the National Natural Science Foundation of China (Nos. 51804252 and 51701156)the Equipment Pre-Research Foundation of China (Nos. 6140759040102 and 6140923040203)the Doctoral Starting Fund of Xi’an University of Technology (No. 101-451116013)
文摘Large size,high-density(99.97%)and well-organized Al2O3/Y3Al5O12(YAG)eutectic ceramics were prepared by the modified Bridgman method.The evolution of the three dimensional microstructure and micropores were investigated.The diameter of the micro-pores and the porosity decreased during directional solidification.The average equivalent diam eter of the micro-pores was 2.41μm in the well-prepared eutectic ceramics.Most of the pores(98.07%)were smaller than 4μm.These data are comparable to those prepared by the optical floating zone method.The as-grown eutectic ceramics were polycrystalline,but the interfaces were well-bonded and there were no amorphous phases in the microstructure.The misfits of the different crystallographic relationships were calculated,and the bottleneck of the single-crystal preparation was identified.These results could provide theoretical guidance for the preparation of large,single-crystal Al2O3/YAG eutectic ceramics by the modified Bridgman method.
基金supported by the National Natural Science Foundation of China under Grant Nos.51271183 and 51301172the National Basic Research Program of China(973 Program)under Grant No.2013CB632205+1 种基金the Innovation Fund of Institute of Metal Research(IMR)Chinese Academy of Sciences(CAS)
文摘In this work, the corrosion behavior of two differently oriented surfaces of an as-extruded Mg-3%Al- 1%Zn (AZ31) bar in a simulated body fluid of phosphate buffer saline (PBS) medium was investigated and compared, and the effect of crystallographic texture on corrosion resistance of the alloy was deeply described. The results showed that at the early stage of immersion, a layer of compact and flat film formed easily on surfaces of both oriented samples. With prolonged immersion time, the degradation of formed corrosive films started and their severity was quite sensitive to the composed crystallographic planes of sample surfaces. For the surface containing highly concentrated orientation of {10-10} and {11-20} prism planes, the degradation of formed corrosive film was quite slight and only occurred at some particular sites even after immersion for 48 h. Thus, the film could keep good corrosive protection to the under- neath substrate. However, for the surface containing [0002} basal planes, {10-10} and {11-20} prism planes, the degradation of corrosive production film occurred widely, resulting in further decrease in the corrosion resistance of immersed samples,
基金supported by the National Basic Research Program of China(Grant Nos.2011CB932604 and 2014CB932402)the National Natural Science Foundation of China(Grant Nos.51221264,51172242+1 种基金51525206,and U1401243)the Key Research Program of Chinese Academy of Sciences(Grant No.KGZDEW-T06)
文摘The application of wavy structures in stretchable electrochemical energy storage devices is reviewed. First, the mechanical anaJysis of wavy structures, specific to flexible electronics, is introduced. Second, stretchable electrochemical energy storage devices with wavy structures are discussed. Finally, the present problems and challenges are reviewed, and possible directions for future research are outlined.
基金the National Natural Science Foundation of China(Grant Nos.51871216 and 51501190)the Opening Project of Jiangsu Province Key Laboratory of High-end Structural Materials(Grant No.hsm1801)provided by the U.S.Air Force Office of Scientific Research,under MURI grant AFSOR-FA9550-15-1-0009 to the University of California Riverside through a subcontract to the University of California Berkeley。
文摘The structures of tungsten and tungsten carbide scaffolds play a key role in determining the properties of their infiltrated composites for multifunctional applications.However,it is challenging to construct and control the architectures by means of self-assembly in W/WC systems because of their large densities.Here we present the development of unidirectionally porous architectures,with high porosities exceeding 65 vol.%,for W and WC scaffolds which in many respects reproduce the design motif of natural wood using a direct ice-templating technique.This was achieved by adjusting the viscosities of suspensions to retard sedimentation during freezing.The processing,structural characteristics and mechanical properties of the resulting scaffolds were investigated with the correlations between them explored.Quantitative relationships were established to describe their strengths based on the mechanics of cellular solids by taking into account both inter-and intra-lamellar pores.The fracture mechanisms were also identified,especially in light of the porosity.This study extends the effectiveness of the ice-templating technique for systems with large densities or particle sizes.It further provides preforms for developing new natureinspired multifunctional materials,as represented by W/WC-Cu composites.