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RISS 인기검색어
- 검색키워드
- 저자 : Jenei, P. (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Mechanical behavior and microstructure of compressed Ti foams synthesized via freeze casting
Jenei, P.,Choi, H.,Toth, A.,Choe, H.,Gubicza, J. Elsevier 2016 Journal of the mechanical behavior of biomedical m Vol.63 No.-
Pure Ti and Ti-5%W foams were prepared via freeze casting. The porosity and grain size of both the materials were 32-33% and 15-17@?m, respectively. The mechanical behavior of the foams was investigated by uniaxial compression up to a plastic strain of ~0.26. The Young@?s moduli of both foams were ~23GPa, which was in good agreement with the value expected from their porosity. The Young@?s moduli of the foams were similar to the elastic modulus of cortical bones, thereby eliminating the osteoporosis-causing stress-shielding effect. The addition of W increased the yield strength from ~196MPa to ~235MPa. The microstructure evolution in the grains during compression was studied using electron backscatter diffraction (EBSD) and X-ray line profile analysis (XLPA). After compression up to a plastic strain of ~0.26, the average dislocation densities increased to ~3.4x10<SUP>14</SUP>m<SUP>-2</SUP> and ~5.9x10<SUP>14</SUP>m<SUP>-2</SUP> in the Ti and Ti-W foams, respectively. The higher dislocation density in the Ti-W foam can be attributed to the pinning effect of the solute tungsten atoms on dislocations. The experimentally measured yield strength was in good agreement with the strength calculated from the dislocation density and porosity. This study demonstrated that the addition of W to Ti foam is beneficial for biomedical applications, because the compressive yield strength increased while its Young@?s modulus remained similar to that of cortical bones.
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Jenei, P.,Yoon, E.Y.,Gubicza, Jenő,Kim, Hyoung Seop,Lá,bá,r, J.L.,Ungá,r, Tamá,s Trans Tech Publications, Ltd. 2012 Materials science forum Vol.729 No.-
<P>Blends of Cu powders and 3 vol. % carbon nanotubes (CNTs), and an additional sample from pure Cu powder were consolidated by High Pressure Torsion (HPT) at room temperature (RT) and 373 K. The grain size, the lattice defect densities as well as the hardness of the pure and composite materials were determined. Due to the pinning effect of CNTs, the dislocation density is about three times larger, while the grain size is about half of that obtained in the sample consolidated from the pure Cu powder. The increase of the HPT-processing temperature from RT to 373 K resulted in only a slight increase of the grain size in the Cu-CNT composite while the dislocation density and the twin boundary frequency were reduced significantly. The flow stress obtained experimentally agrees well with the value calculated by the Taylor-formula indicating that the strength in both pure Cu and Cu-CNT composites is determined mainly by the interaction between dislocations. The addition of CNTs to Cu yields a significantly better thermal stability of the UFG matrix processed by HPT.</P>
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Jenei, P.,Yoon, E.Y.,Gubicza, J.,Kim, H.S.,Labar, J.L.,Ungar, T. Elsevier Sequoia 2011 Materials science & engineering. properties, micro Vol.528 No.13
Blends of Cu powders and 3vol.% carbon nanotubes (CNTs) were consolidated by High Pressure Torsion (HPT) at room temperature (RT) and 373K. The grain size, the lattice defect densities as well as the hardness of the composite samples were determined. It was found that the Cu-CNT composite processed at RT exhibited a half as large mean grain size and a three times higher dislocation density than those observed in the specimens either consolidated from pure Cu powder or processed from bulk Cu by HPT. The small grain size and the pinning effect of CNT fragments on dislocations led to significant twin boundary formation during HPT. The increase of the temperature of HPT-processing to 373K resulted in a slight increase of the grain size, and a strong decrease of the dislocation density and the twin boundary frequency in the composite. The correlation between the microstructural parameters and the flow stress calculated from the hardness was discussed.
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Gubicza, Jenő,Jenei, Pé,ter,Nam, Kyungju,Ká,dá,r, Csilla,Jo, Hyungyung,Choe, Heeman Elsevier 2018 Materials science & engineering. properties, micro Vol.725 No.-
<P><B>Abstract</B></P> <P>Experiments were conducted to study the compression behavior of Cu-Ni foams prepared using freeze casting. The struts of the foam samples were solid-solutioned with differing Cu/Ni ratios, after which the grain size in the struts was measured using scanning electron microscopy. The compression performance of the samples was studied in both parallel and perpendicular directions to the temperature gradient, and compared with model calculations. It was confirmed that alloying increased the yield strength of the struts. The experimentally determined yield strength and elastic modulus were compared with model calculations, which revealed that the elastic modulus of the foams was lower than the values calculated from the classical compression and Gibson-Ashby models due to variation in the thickness of the struts. It was also found that the alloying of Cu and Ni improved the mechanical performance of the alloy foams because the absorbed energy for the alloys was considerably higher than that for the pure foams.</P>
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