The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the...The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the grain boundaries were pinned by high-density nanosized Al_(3)(Yb,Zr)precipitates during extrusion deformation,consequently,the average grain size was significantly reduced from 232.7μm to 3.2μm.This grain refinement contributed substantially to the improvement in both strength and elongation.The ultimate tensile strength,yield strength,and elongation of the Yb/Zr modified alloy increased to 705.3 MPa,677.6 MPa,and 8.7%,respectively,representing enhancements of 16.2%,19.3%,and 112.2%compared to the unmodified alloy.Moreover,the distribution of MgZn_(2)phases along grain boundaries became more discontinuous in the Yb/Zr modified alloy,which effectively retarded the propagation of intergranular corrosion and improved the corrosion resistance.展开更多
Magneli phase titanium sub-oxide conductive ceramic Tin O2n-1 was used as the support for Pt due to its excellent resistance to electrochemical oxidation, and Pt/Tin O2n-1 composites were prepared by the impregnation-...Magneli phase titanium sub-oxide conductive ceramic Tin O2n-1 was used as the support for Pt due to its excellent resistance to electrochemical oxidation, and Pt/Tin O2n-1 composites were prepared by the impregnation-reduction method. The electrochemical stability of Tin O2n-1 was investigated and the results show almost no change in the redox region after oxidation for 20 h at 1.2 V(vs NHE) in 0.5 mol/L H2SO4 aqueous solution. The catalytic activity and stability of the Pt/Tin O2n-1 toward the oxygen reduction reaction(ORR) in 0.5 mol/L H2SO4 solution were investigated through the accelerated aging tests(AAT), and the morphology of the catalysts before and after the AAT was observed by transmission electron microscopy. At the potential of 0.55 V(vs SCE), the specific kinetic current density of the ORR on the Pt/Tin O2n-1 is about 1.5 times that of the Pt/C. The LSV curves for the Pt/C shift negatively obviously with the half-wave potential shifting about 0.02 V after 8000 cycles AAT, while no obvious change takes place for the LSV curves for the Pt/Tin O2n-1. The Pt particles supported on the carbon aggregate obviously, while the morphology of the Pt supported on Tin O2n-1 remains almost unchanged, which contributes to the electrochemical surface area loss of Pt/C being about 2times that of the Pt/Tin O2n-1. The superior catalytic stability of Pt/Tin O2n-1 toward the ORR could be attributed to the excellent stability of the Tin O2n-1 and the electronic interaction between the metals and the support.展开更多
The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-（0-1.0）%Pb （mass fraction） alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic a-Mg and Mg2Sn pha...The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-（0-1.0）%Pb （mass fraction） alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic a-Mg and Mg2Sn phase. The addition of Pb can refine the size of Mg2Sn phase and grain size, reduce the amount of Mg2Sn phase at grain or inter-dendrite boundaries and change the distribution of Mg2Sn phase. Pb exists in the Mg2Sn phase or dissolves in a-Mg matrix. The mechanical properties of the tested alloys at room temperature are improved with the addition of Pb. When the Pb content is over 0.5%, the mechanical properties are decreased gradually. The Mg-5%Sn-0.5%Pb shows the best ultimate tensile strength and elongation, 174 MPa and 14.3%, respectively. However, the compressive creep resistance of the Mg-Sn-Pb alloys is much lower than that of the Mg-Sn binary alloy at 175℃ with applied load of 55 MPa, which means that Pb has negative effects on the compressive creep resistance of the as-cast Mg-Sn alloys.展开更多
The precipitation behaviors of an A1-Cu-Li-Mn-Zr alloy at different ageing temperatures （120, 160 and 200 ~C） were investigated using Vickers hardness measurements and transmission electron microscopy （TEM） charac...The precipitation behaviors of an A1-Cu-Li-Mn-Zr alloy at different ageing temperatures （120, 160 and 200 ~C） were investigated using Vickers hardness measurements and transmission electron microscopy （TEM） characterization. Age hardening curves show an increase in precipitation kinetics with increasing ageing temperature. The results of TEM show that for the samples peak aged at 120 ~C, the amount of g＇ （A13Li）, GP zones/0＇ （A12Cu） and Z （A15Cu6Li2） phases is obviously higher than that of T1 （A12CuLi） precipitates; while the samples peak aged at 160 and 200 ~C are usually dominated by T1 phase with a minor fraction of GP zones/0＇ and g＇, and the Z phase almost does not form. In addition, quantitative analysis on the T1 platelets demonstrates that the samples peak aged at 200 ~C have larger plate diameter and smaller area fraction of T1, as compared to the samples peak aged at 160 ~C. Correspondingly, the possible reasons for such phenomena are discussed.展开更多
Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr ...Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr alloys were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope, X-ray diffraction and tensile test. The results show that the microstructure of as-cast Mg-6Al-2Sr alloy is composed of α-Mg, Mg_(17)Al_(12), Mg_(13)Al_(3)Sr and lamellar acicular Al_(4)Sr phase. After adding Sm element, granular block Al2Sm phase appears in the grain. With the increase of Sm content, the discontinuous long strip reticular Mg_(17)Al_(12)phase and the lamellar acicular Al4Sr phase gradually decrease, and the Al_(2)Sm phase increases and distributes more dispersedly, so the alloy microstructure is continuously refined. The average grain size of the alloys decreases at first and then increases with the increase of Sm content. When the Sm content is 1.5 wt%, the average grain size reaches the minimum value of 94.6 μm. With the increase of Sm content, the mechanical properties of the alloy at room temperature first increase and then decrease. When the Sm content is 1.5 wt%, the alloy has the best comprehensive mechanical properties at room temperature.展开更多
The effects of pyrolysis mode and pyrolysis parameters on Cl content in alumina were investigated, and the alumina products were characterized by XRD, SEM and ASAP. The experimental results indicate that the spray pyr...The effects of pyrolysis mode and pyrolysis parameters on Cl content in alumina were investigated, and the alumina products were characterized by XRD, SEM and ASAP. The experimental results indicate that the spray pyrolysis efficiency is higher than that of static pyrolysis process, and the reaction and evaporation process lead to a multi-plot state of the alumina products by spray pyrolysis. Aluminum phase starts to transform into γ-Al2O3 at spray pyrolysis temperature of 600 °C, which is about 200 °C lower than that of static pyrolysis process. The primary particle size of γ-Al2O3 product is 27.62 nm, and Cl content in alumina products is 0.38% at 800 °C for 20 min.展开更多
基金Project(51501228)supported by the National Natural Science Foundation of ChinaProject(202109)supported by the Open Sharing Fund for the Large-scale Instruments and Equipments of Central South University,China。
文摘The effects of Yb/Zr micro-alloying on the microstructure,mechanical properties,and corrosion resistance of an Al-Zn-Mg-Cu alloy were systematically investigated.Upon the addition of Yb/Zr to the Al-Zn-Mg-Cu alloy,the grain boundaries were pinned by high-density nanosized Al_(3)(Yb,Zr)precipitates during extrusion deformation,consequently,the average grain size was significantly reduced from 232.7μm to 3.2μm.This grain refinement contributed substantially to the improvement in both strength and elongation.The ultimate tensile strength,yield strength,and elongation of the Yb/Zr modified alloy increased to 705.3 MPa,677.6 MPa,and 8.7%,respectively,representing enhancements of 16.2%,19.3%,and 112.2%compared to the unmodified alloy.Moreover,the distribution of MgZn_(2)phases along grain boundaries became more discontinuous in the Yb/Zr modified alloy,which effectively retarded the propagation of intergranular corrosion and improved the corrosion resistance.
基金Project(21406273)supported by the National Natural Science Foundation of China
文摘Magneli phase titanium sub-oxide conductive ceramic Tin O2n-1 was used as the support for Pt due to its excellent resistance to electrochemical oxidation, and Pt/Tin O2n-1 composites were prepared by the impregnation-reduction method. The electrochemical stability of Tin O2n-1 was investigated and the results show almost no change in the redox region after oxidation for 20 h at 1.2 V(vs NHE) in 0.5 mol/L H2SO4 aqueous solution. The catalytic activity and stability of the Pt/Tin O2n-1 toward the oxygen reduction reaction(ORR) in 0.5 mol/L H2SO4 solution were investigated through the accelerated aging tests(AAT), and the morphology of the catalysts before and after the AAT was observed by transmission electron microscopy. At the potential of 0.55 V(vs SCE), the specific kinetic current density of the ORR on the Pt/Tin O2n-1 is about 1.5 times that of the Pt/C. The LSV curves for the Pt/C shift negatively obviously with the half-wave potential shifting about 0.02 V after 8000 cycles AAT, while no obvious change takes place for the LSV curves for the Pt/Tin O2n-1. The Pt particles supported on the carbon aggregate obviously, while the morphology of the Pt supported on Tin O2n-1 remains almost unchanged, which contributes to the electrochemical surface area loss of Pt/C being about 2times that of the Pt/Tin O2n-1. The superior catalytic stability of Pt/Tin O2n-1 toward the ORR could be attributed to the excellent stability of the Tin O2n-1 and the electronic interaction between the metals and the support.
基金Project(03GG009-007-4) supported by the Key Program of Science and Technology Bureau of Sichuan Province, China
文摘The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-（0-1.0）%Pb （mass fraction） alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic a-Mg and Mg2Sn phase. The addition of Pb can refine the size of Mg2Sn phase and grain size, reduce the amount of Mg2Sn phase at grain or inter-dendrite boundaries and change the distribution of Mg2Sn phase. Pb exists in the Mg2Sn phase or dissolves in a-Mg matrix. The mechanical properties of the tested alloys at room temperature are improved with the addition of Pb. When the Pb content is over 0.5%, the mechanical properties are decreased gradually. The Mg-5%Sn-0.5%Pb shows the best ultimate tensile strength and elongation, 174 MPa and 14.3%, respectively. However, the compressive creep resistance of the Mg-Sn-Pb alloys is much lower than that of the Mg-Sn binary alloy at 175℃ with applied load of 55 MPa, which means that Pb has negative effects on the compressive creep resistance of the as-cast Mg-Sn alloys.
基金Project（2016YFB0300901） supported by the National Key R＆D Program of China Project（51421001） supported by the National Natural Science Foundation of China Project（2018CDJDCL0019） supported by the Fundamental Research Funds for the Central Universities, China
文摘The precipitation behaviors of an A1-Cu-Li-Mn-Zr alloy at different ageing temperatures （120, 160 and 200 ~C） were investigated using Vickers hardness measurements and transmission electron microscopy （TEM） characterization. Age hardening curves show an increase in precipitation kinetics with increasing ageing temperature. The results of TEM show that for the samples peak aged at 120 ~C, the amount of g＇ （A13Li）, GP zones/0＇ （A12Cu） and Z （A15Cu6Li2） phases is obviously higher than that of T1 （A12CuLi） precipitates; while the samples peak aged at 160 and 200 ~C are usually dominated by T1 phase with a minor fraction of GP zones/0＇ and g＇, and the Z phase almost does not form. In addition, quantitative analysis on the T1 platelets demonstrates that the samples peak aged at 200 ~C have larger plate diameter and smaller area fraction of T1, as compared to the samples peak aged at 160 ~C. Correspondingly, the possible reasons for such phenomena are discussed.
基金Project(51975167) supported by the National Natural Science Foundation,China。
文摘Mg-6Al-2Sr alloys with different Sm contents(0%, 0.5%, 1%, 1.5%, 2%, mass fraction) were prepared by melting and casting method. The effects of Sm on the microstructure and mechanical properties of as-cast Mg-6Al-2Sr alloys were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer, transmission electron microscope, X-ray diffraction and tensile test. The results show that the microstructure of as-cast Mg-6Al-2Sr alloy is composed of α-Mg, Mg_(17)Al_(12), Mg_(13)Al_(3)Sr and lamellar acicular Al_(4)Sr phase. After adding Sm element, granular block Al2Sm phase appears in the grain. With the increase of Sm content, the discontinuous long strip reticular Mg_(17)Al_(12)phase and the lamellar acicular Al4Sr phase gradually decrease, and the Al_(2)Sm phase increases and distributes more dispersedly, so the alloy microstructure is continuously refined. The average grain size of the alloys decreases at first and then increases with the increase of Sm content. When the Sm content is 1.5 wt%, the average grain size reaches the minimum value of 94.6 μm. With the increase of Sm content, the mechanical properties of the alloy at room temperature first increase and then decrease. When the Sm content is 1.5 wt%, the alloy has the best comprehensive mechanical properties at room temperature.
基金Projects(U1202274,51004033,51204040)supported by the National Natural Science Foundation of ChinaProject(2012AA062303)supported by the National High Technology Research and Development Program of China+2 种基金Project(2012BAE01B02)supported by the National Science and Technology Support Program of ChinaProject(L2014096)supported by the Education Department of Liaoning Province,ChinaProject(N130702001)supported by the Fundamental Research Funds for the Central Universities,China
文摘The effects of pyrolysis mode and pyrolysis parameters on Cl content in alumina were investigated, and the alumina products were characterized by XRD, SEM and ASAP. The experimental results indicate that the spray pyrolysis efficiency is higher than that of static pyrolysis process, and the reaction and evaporation process lead to a multi-plot state of the alumina products by spray pyrolysis. Aluminum phase starts to transform into γ-Al2O3 at spray pyrolysis temperature of 600 °C, which is about 200 °C lower than that of static pyrolysis process. The primary particle size of γ-Al2O3 product is 27.62 nm, and Cl content in alumina products is 0.38% at 800 °C for 20 min.
