Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was foun...Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was found that thermoelastic martensitic transformation be-haviors could be observed from the samples sintered above 800 ℃ even with a short sintering time (5min),and the transformation tempera-tures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation.Although decreasing the sin-tering temperature and time to 700 ℃ and 5min could not protect defective MWCNTs from reacting with Ti,still-perfect MWCNTs re-mained in the specimens sintered at 900 ℃.This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.展开更多
In situ Al2O3np/Al-Al11Ce3 nanocomposite was successfully synthesized from Al-CeO2 system using a novel two-step processing method that combines liquid-state mechanical mixing（step-Ⅰ） and sonochemistry melt reactio...In situ Al2O3np/Al-Al11Ce3 nanocomposite was successfully synthesized from Al-CeO2 system using a novel two-step processing method that combines liquid-state mechanical mixing（step-Ⅰ） and sonochemistry melt reaction（step-Ⅱ）. The microstructural evolution and mechanical properties were investigated by optical microscopy（OM）, scanning electron microscopy（SEM）, transmission electron spectroscopy（TEM） and tensile tests, respectively. A good spatial distribution of CeO2 particles in the Al melt was achieved due to reactive wetting during step-Ⅰ, and the following formation of Al2O3 np during step-Ⅱ was attributed to the cavitation-accelerated interfacial reaction. The solidified microstructure comprised uniformly dispersed Al2O3 np in the matrix and ultrafine lamellar Al-Al11Ce3 at the grain boundaries. Such unique microstructure endowed Al2O3np/Al-Al11Ce3 nanocomposite with a good balance between tensile strength（175 MPa） and ductility（18.5%）. The strengthening mechanisms of the nanocomposite included grain refinement, Orowan strengthening and quench strengthening, among which Orowan strengthening contributed the most to the yield strength of the nanocomposite.展开更多
Al foam sandwich panel(AFS) with metallic bonding was fabricated by foaming a hotpressed three-layer composite with two steel facesheets and a melt route precursor as core. The melt route precursor was fabricated by d...Al foam sandwich panel(AFS) with metallic bonding was fabricated by foaming a hotpressed three-layer composite with two steel facesheets and a melt route precursor as core. The melt route precursor was fabricated by dispersing undecomposed blowing agent into molten Al, followed by solidification. Microstructures of the joints during fabrication process were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). Static three-point bending was conducted to evaluate joint quality of the AFS. It was found that a primary bonding was achieved by hot-pressing and significant diffusion layer of Fe-Al intermetallic compounds was sustained between steel and Al foam core by foaming. Damage modes of the AFS under three-point bending were dominated by indentation, plastic hinges, core shear and crack. Delamination between steel and foam was absent, implying that reliable metallic bonding was achieved. This method allows for producing large-scale AFS with steel facesheets.展开更多
基金financially supported by Natural Science Foundation of China (No.51071059 and No.50971052)the Fundamental Research Funds for the Central Universities (No.HIT.KLOF.2010005)
文摘Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was found that thermoelastic martensitic transformation be-haviors could be observed from the samples sintered above 800 ℃ even with a short sintering time (5min),and the transformation tempera-tures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation.Although decreasing the sin-tering temperature and time to 700 ℃ and 5min could not protect defective MWCNTs from reacting with Ti,still-perfect MWCNTs re-mained in the specimens sintered at 900 ℃.This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.
基金Project supported by the National Natural Science Foundation of China(51174098)Open Project of Key Laboratory for Ecological-Environment Materials of Jiangsu Province(EML201208)
文摘In situ Al2O3np/Al-Al11Ce3 nanocomposite was successfully synthesized from Al-CeO2 system using a novel two-step processing method that combines liquid-state mechanical mixing（step-Ⅰ） and sonochemistry melt reaction（step-Ⅱ）. The microstructural evolution and mechanical properties were investigated by optical microscopy（OM）, scanning electron microscopy（SEM）, transmission electron spectroscopy（TEM） and tensile tests, respectively. A good spatial distribution of CeO2 particles in the Al melt was achieved due to reactive wetting during step-Ⅰ, and the following formation of Al2O3 np during step-Ⅱ was attributed to the cavitation-accelerated interfacial reaction. The solidified microstructure comprised uniformly dispersed Al2O3 np in the matrix and ultrafine lamellar Al-Al11Ce3 at the grain boundaries. Such unique microstructure endowed Al2O3np/Al-Al11Ce3 nanocomposite with a good balance between tensile strength（175 MPa） and ductility（18.5%）. The strengthening mechanisms of the nanocomposite included grain refinement, Orowan strengthening and quench strengthening, among which Orowan strengthening contributed the most to the yield strength of the nanocomposite.
基金Funded by the National Natural Science Foundation of China(51174060 and 51301109)the Science and Technology Department of Liaoning Province of China(2013223004)the Fundamental Research Funds for the Central Universities(140203004)
文摘Al foam sandwich panel(AFS) with metallic bonding was fabricated by foaming a hotpressed three-layer composite with two steel facesheets and a melt route precursor as core. The melt route precursor was fabricated by dispersing undecomposed blowing agent into molten Al, followed by solidification. Microstructures of the joints during fabrication process were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). Static three-point bending was conducted to evaluate joint quality of the AFS. It was found that a primary bonding was achieved by hot-pressing and significant diffusion layer of Fe-Al intermetallic compounds was sustained between steel and Al foam core by foaming. Damage modes of the AFS under three-point bending were dominated by indentation, plastic hinges, core shear and crack. Delamination between steel and foam was absent, implying that reliable metallic bonding was achieved. This method allows for producing large-scale AFS with steel facesheets.
基金Natural Science of China(51201155)Natural Science of Shanxi Province(2012011019-1,2012011007-1)Chinese Education Ministry Foundation for Doctors(20101420120006)
