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Nano-indentation measurements were carried out on nitrided Fe-Cr alloys (1 and 3 wt% Cr) in order to determine local micro-mechanical properties. The method recently developed on nitrided 32CrMoV13 steel was applied to the Fe-Cr alloys. Evolution of micro-yield stress through the nitrided layer was correlated to microstructural parameters (volume fraction of CrN precipitates, diameter of precipitates, etc.) investigated and statistically analyzed by transmission electron microscopy (TEM). The results show that the mechanical behavior of the nitrided layer for both alloys studied can be described using the Orowan model of precipitation strengthening. 相似文献
996.
Toughness variation of non-notched poly(acrylonitrile-butadiene-styrene) (ABS) subjected to uniaxial fatigue loading was investigated. The experiments were conducted by applying fatigue loading to strip specimens first, from which dog-bone specimens were machined. The dog-bone specimens were tested to measure the strain for the on-set of fracture, named cracking strain here, thus to monitor the toughness change due to the fatigue loading.The test results showed that the fatigue loading caused the toughness drop in ABS, even before any visible crack was developed. Damage development and fracture behavior were then analyzed using scanning electron microscopy (SEM). The SEM analysis revealed that damage zones, not cracks, were initiated during the fatigue loading, and were the main cause of the toughness drop. Mechanisms for the damage initiation include matrix crazing and debonding of small rubber particles; however, large rubber particles remained intact. Based on the results, a deformation model is proposed for the damage zone initiation, which provides an explanation for the toughness change under the fatigue loading. 相似文献
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C. R. Foschini O. Treu Filho S. A. Juiz A. G. Souza J. B. L. Oliveira E. Longo E. R. Leite C. A. Paskocimas J. A. Varela 《Journal of Materials Science》2004,39(6):1935-1941
Reactive zirconia powder was synthesized by the complexation of zirconium metal from zirconium hydroxide using a solution of 8-hydroxiquinoline. The kinetics of zirconia crystallization was followed by X-ray diffraction, scanning electron microscopy and surface area measured by the nitrogen adsorption/desorption technique. The results indicated that zirconia with a surface area as high as 100 m2/g can be obtained by this method after calcination at 500°C. Zirconia presents three polymorphic phases (monoclinic, tetragonal and cubic), which are reversibly interconversible. The cluster model Zr4O8 and Zr4O7
+2 was used for a theoretical study of the stabilization process. The ab initio RHF method was employed with the Gaussian94 program and the total energies and the energy gap of the different phases were calculated and compared with the experimental energy gap. The theoretical results show good reproducibility of the energy gap for zirconia. 相似文献
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