In order to enhance the mechanical properties of the selective laser-melted(SLM) high-Mg content AlSiMg1.4 alloy,the Zr element was introduced.The influence of Zr alloying on the processability,microstructure,and mech...In order to enhance the mechanical properties of the selective laser-melted(SLM) high-Mg content AlSiMg1.4 alloy,the Zr element was introduced.The influence of Zr alloying on the processability,microstructure,and mechanical properties of the alloy was systematically investigated through performing microstructure analysis and tensile testing.It was demonstrated that the SLM-fabricated AlSiMg1.4-Zr alloy exhibited high process stability with a relative density of over 99.5% at various process parameters.Besides,the strong grain refinement induced by the primary Al3Zr particle during the melt solidification process simultaneously enhanced both the strength and plasticity of the alloy.The values for the yield strength,ultimate tensile strength,and elongation of the SLM-fabricated AlSiMg1.4-Zr were(343±3) MPa,(485±4) MPa,and(10.2±0.2)%,respectively,demonstrating good strengthplasticity synergy in comparison to the AlSiMg1.4 and other Al-Si-based alloys fabricated by SLM.展开更多
Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition technology in an additive-free Watts bath.The coating consists of massive equiaxial crystals with an average grain size of ab...Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition technology in an additive-free Watts bath.The coating consists of massive equiaxial crystals with an average grain size of about 24 nm and exhibits a（111） preferred orientation.The differential scanning calorimetry（DSC） analysis of nanocrystalline nickel demonstrates that the peak temperature of rapid grain growth is about 285.4 °C,and the peak temperature of grain growth towards equilibrium is around 431.5 °C.The isochronous annealing results reveal that abnormal grain growth behavior is not observed in nanocrystalline nickel without sulfur-containing.The thermal stability of the deposition was improved due to its initial microstructure of the as-deposited nickel and a certain amount of annealing nano-twins with low-energy,which reduces the driving force for grain growth.Consequently,the coating shows a low residual tensile stress of about 50 MPa and a high microhardness of HV 400 at the annealing temperature of 450 °C.展开更多
Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,ph...Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,physical and chemical properties of multi-doped cerium zirconium mixed oxides,a series of La and Y doped cerium zirconium mixed oxides(CZLYs)were synthesized via a co-precipitation method,and the physical and chemical properties of CZLYs were systemically characterized by XRD,N_(2) adsorption−desorption,TEM,XPS,oxygen storage capacity(OSC)and hydrogen temperature programmed reduction(H_(2)-TPR).The results show that co-precipitation temperature is an important parameter to influence the crystal size,oxygen storage capacity and thermal stability of CZLYs.When the co-precipitation temperature was 60℃,the best redox properties and thermal stability of CZLYs were obtained.After thermal treatment at 1100℃for 10 h,the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m^(2)/g and 497.7μmol/g,respectively.In addition,a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.展开更多
The grain growth and thermal stability of nanocrystalline Ni-TiO2composites were systematically investigated.Thenanocrystalline Ni-TiO2composites with different contents of TiO2were prepared via electroplating method ...The grain growth and thermal stability of nanocrystalline Ni-TiO2composites were systematically investigated.Thenanocrystalline Ni-TiO2composites with different contents of TiO2were prepared via electroplating method with the variation ofTiO2nano-particles concentration.The effect of TiO2content on the grain size,phase structure and microhardness was investigatedin detail.The corresponding grain growth and diffusion mechanisms during the heating process were also discussed.The optimalmicrohardness of HV50270was achieved for the composite with addition of20g/L TiO2nano-particles after annealing at400°C for90min.The calculation of the activation energy indicated that lattice diffusion dominated at high temperatures for thenanocrystalline Ni-TiO2composites.It was indicated that the increase of TiO2nano-particles content took effect on restricting thegrain growth at high temperatures by increasing the grain growth activation energy.展开更多
Thethermal stability and the kinetics of grain growth of nanocrystalline Mg-6Al-1Zn and Mg-6Al-1Zn-1Si alloys prepared via mechanical alloying were investigated. It started with elemental powders, using a variety of a...Thethermal stability and the kinetics of grain growth of nanocrystalline Mg-6Al-1Zn and Mg-6Al-1Zn-1Si alloys prepared via mechanical alloying were investigated. It started with elemental powders, using a variety of analytical techniques including differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and energy dispersive spectrometry. The kinetics of grain growth in isothermal annealing was investigated. The XRD results show that, although the grain sizes of both material systems increase as the annealing temperature rises, the Si-containing system displays a relatively smaller grain size, i.e., 60 nm compared with 72 nm in Mg-6Al-1Zn system, after being exposed to 350 ℃ for 1 h. The second-phase intermetallic particle Mg2Si formed during the isothermal annealing of Mg-6Al-1Zn-1Si system could influence not only the activation energy but also the exponent of kinetic equation. Higher hardness values obtained in the Si-containing system would be due to the formation of Mg2Si intermetallic phase.展开更多
基金supported by the National Natural Science Foundation of China (Nos.51801079, 52001140)。
文摘In order to enhance the mechanical properties of the selective laser-melted(SLM) high-Mg content AlSiMg1.4 alloy,the Zr element was introduced.The influence of Zr alloying on the processability,microstructure,and mechanical properties of the alloy was systematically investigated through performing microstructure analysis and tensile testing.It was demonstrated that the SLM-fabricated AlSiMg1.4-Zr alloy exhibited high process stability with a relative density of over 99.5% at various process parameters.Besides,the strong grain refinement induced by the primary Al3Zr particle during the melt solidification process simultaneously enhanced both the strength and plasticity of the alloy.The values for the yield strength,ultimate tensile strength,and elongation of the SLM-fabricated AlSiMg1.4-Zr were(343±3) MPa,(485±4) MPa,and(10.2±0.2)%,respectively,demonstrating good strengthplasticity synergy in comparison to the AlSiMg1.4 and other Al-Si-based alloys fabricated by SLM.
基金Project(51005244)supported by the National Natural Science Foundation of ChinaProject(2011CB013405)supported by the Basic Research Development Program of China
文摘Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition technology in an additive-free Watts bath.The coating consists of massive equiaxial crystals with an average grain size of about 24 nm and exhibits a（111） preferred orientation.The differential scanning calorimetry（DSC） analysis of nanocrystalline nickel demonstrates that the peak temperature of rapid grain growth is about 285.4 °C,and the peak temperature of grain growth towards equilibrium is around 431.5 °C.The isochronous annealing results reveal that abnormal grain growth behavior is not observed in nanocrystalline nickel without sulfur-containing.The thermal stability of the deposition was improved due to its initial microstructure of the as-deposited nickel and a certain amount of annealing nano-twins with low-energy,which reduces the driving force for grain growth.Consequently,the coating shows a low residual tensile stress of about 50 MPa and a high microhardness of HV 400 at the annealing temperature of 450 °C.
基金the Hebei Key Research and Development Program,China(No.20374202D)the Hebei High Level Talent Team Building,China(No.205A1104H).
文摘Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,physical and chemical properties of multi-doped cerium zirconium mixed oxides,a series of La and Y doped cerium zirconium mixed oxides(CZLYs)were synthesized via a co-precipitation method,and the physical and chemical properties of CZLYs were systemically characterized by XRD,N_(2) adsorption−desorption,TEM,XPS,oxygen storage capacity(OSC)and hydrogen temperature programmed reduction(H_(2)-TPR).The results show that co-precipitation temperature is an important parameter to influence the crystal size,oxygen storage capacity and thermal stability of CZLYs.When the co-precipitation temperature was 60℃,the best redox properties and thermal stability of CZLYs were obtained.After thermal treatment at 1100℃for 10 h,the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m^(2)/g and 497.7μmol/g,respectively.In addition,a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.
基金Project(51401024)supported by the National Natural Science Foundation of ChinaProject(20150942006)supported by Basic Research Program of Beijing Institute of Technology,China
文摘The grain growth and thermal stability of nanocrystalline Ni-TiO2composites were systematically investigated.Thenanocrystalline Ni-TiO2composites with different contents of TiO2were prepared via electroplating method with the variation ofTiO2nano-particles concentration.The effect of TiO2content on the grain size,phase structure and microhardness was investigatedin detail.The corresponding grain growth and diffusion mechanisms during the heating process were also discussed.The optimalmicrohardness of HV50270was achieved for the composite with addition of20g/L TiO2nano-particles after annealing at400°C for90min.The calculation of the activation energy indicated that lattice diffusion dominated at high temperatures for thenanocrystalline Ni-TiO2composites.It was indicated that the increase of TiO2nano-particles content took effect on restricting thegrain growth at high temperatures by increasing the grain growth activation energy.
文摘Thethermal stability and the kinetics of grain growth of nanocrystalline Mg-6Al-1Zn and Mg-6Al-1Zn-1Si alloys prepared via mechanical alloying were investigated. It started with elemental powders, using a variety of analytical techniques including differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and energy dispersive spectrometry. The kinetics of grain growth in isothermal annealing was investigated. The XRD results show that, although the grain sizes of both material systems increase as the annealing temperature rises, the Si-containing system displays a relatively smaller grain size, i.e., 60 nm compared with 72 nm in Mg-6Al-1Zn system, after being exposed to 350 ℃ for 1 h. The second-phase intermetallic particle Mg2Si formed during the isothermal annealing of Mg-6Al-1Zn-1Si system could influence not only the activation energy but also the exponent of kinetic equation. Higher hardness values obtained in the Si-containing system would be due to the formation of Mg2Si intermetallic phase.
