Papers by Keyword: Cryomilling

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Authors: Qing Hou, Run Hua Fan, Zi Dong Zhang, Ke Lan Yan, Chuan Bing Cheng, Min Chen, Kai Sun, Xu Ai Wang, Qian Qian Li
Abstract: In this paper, epoxy resin was used as matrix to prepare composite cryomilling at liquid nitrogen temperature in which the content of CNTs powder vary from 25 wt% to 40 wt%. The microstructure and dielectric properties of the composite were analyzed by SEM and RF impedance material analyzer. The result showed that permittivity of the composites turned negative after the CNTs reached certain content. The plasma oscillation of delocalized electrons in CNTs conductive networks causes negative permittivity phenomenon.
Authors: Pei Tao Xie, Run Hua Fan, Qing Hou, Feng Dang
Abstract: FeSiCr-epoxy composites consisting of different FeSiCr contents were prepared through the pressure molding after mixing by cryomilling at liquid nitrogen temperature. The electromagnetic properties including ac conductivity, permittivity, and permeability were investigated in detail. The results show that the frequency dispersions of ac conductivity followed the power law, indicating the hoping conduction behavior. The real permittivity of composites increased with the increase of FeSiCr contents, and the enhancement of permittivity may be attributed to the increase of the interface area between FeSiCr and epoxy, while Debye-like dielectric relaxations were observed, and the fitting analysis of Cole-Cole curve indicates a nonideal Debye relaxation. The frequency dispersions of permeability were also relaxation linetype, which is attributed to the domain wall displacement.
Authors: Byung Ahn, R. Mitra, A.M. Hodge, Enrique J. Lavernia, S.R. Nutt
Abstract: Al 5083 alloy powder was mechanically milled in liquid nitrogen to achieve a nanocrystalline (NC) structure having an average grain size of 50 nm with high thermal stability, and then consolidated by quasi-isostatic (QI) forging. The consolidation resulted in ultrafine grains (UFG) of about 250 nm, and the bulk material exhibited enhanced strength compared to conventionally processed Al 5083. The hardness of as-cryomilled powder and the UFG material was measured by nanoindentation using loading rates in the range of 50−50,000 /N/s, and results were compared with the conventional grain size alloy. Negative strain rate sensitivity was observed in the cryomilled NC powder and the forged UFG plate, while the conventional alloy was relatively strain rate insensitive.
Authors: Osman Ertörer, Troy D. Topping, Ying Li, Yong Hao Zhao, Wes Moss, Enrique J. Lavernia
Abstract: The room temperature tensile behavior of commercially pure titanium (CP-Ti), cryomilled under different conditions and forged quasi-isostatically into bulk form, was studied in detail. The results demonstrate that the ductility of cryomilled titanium can be improved, and that the mechanical properties can be tailored using three specific strategies: the use of liquid argon as cryomilling media, introduction of coarse grained regions, and low temperature heat treatment. Cryomilling in a liquid argon environment, which differs from the widely used nitrogen cryogenic environment, was found to have a particularly strong influence on ductility, as it prevents nitrogen embrittlement. The contribution of coarse grains and heat treatment to ductility are also introduced and discussed using a comparative approach.
Authors: Jason Milligan, Mathieu Brochu
Abstract: A strong push has been observed in the automotive industry to replace current components with high-performance and lightweight materials such as aluminum alloys. Novel monolithic materials such as bulk nanostructured materials, cannot always offer the best performance in hostile environments and often have high manufacturing costs. This has required the development and engineering of processes to allow nanostructured surface functionalization of conventional materials. This processing strategy, similar to the metal-ceramic joining approach, exploits the advantages of both materials while reducing overall manufacturing costs. Spark Plasma Sintering (SPS) will be evaluated as potential a method for manufacturing a nanostructured Al-Si cladding. This novel coating method has a significant advantage over traditional processes in that it forms metallurgical bonds at both the interface and throughout the deposited layer to produce a coating with isotropic properties. The objective of this work is to create a nanostructured eutectic Al-Si feedstock powder and simultaneously consolidate and clad the powder onto a forged aluminum substrate using Spark Plasma Sintering. Results show that after mechanical milling, the aluminum grain size was refined to 47nm. The results also show that SPS is capable of sintering the powder in extremely short sintering times while maintaining nanostructure, and that the heating rate has a large effect on increasing densification rates. Mechanical properties of the resultant coating were also investigated.
Authors: M. Ice, Rodolfo-Martín Rodriguez, D. Cheng, G. Kim, M. Trudeau, J. Terlecki, Enrique J. Lavernia
Authors: Xiu Hua Ma, Wei Min Wang, Hao Wang, Yu Cheng Wang, Zheng Yi Fu
Abstract: In this text, 5083 aluminum alloy was prepared with the method of the liquid nitrogen cryogenic milling (cryomilling). The microstructure,microstructural evolution and thermal stability of sample powder was investigated by XRD,SEM and DSC. The experimental results show that the particles size of 5083 aluminum alloy power during cryomilling was gradually reduced; milling time and milling speed are the main factors of affected alloy structure and performance, and high speed cryomilling could result in more uniform nanometer grains. The microstructure of the cryomilling 5083 aluminum alloy for 5 hours is micron-sized agglomerates with an average grain size of 45 nm.
Authors: Severino L. Urtiga Filho, Rodolfo-Martín Rodriguez, James C. Earthman, Enrique J. Lavernia
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