Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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2 resultados
Resultados da Pesquisa
- Influence of growth rate on the microstructure and mechanical behaviour of a NiAl-Mo eutectic alloy(2004-11-03) FERRANDINI, P.; BATISTA, W. W.; CARAM, R.The effect of the growth condition on the microstructure and mechanical behaviour of the NiAl-Mo eutectic alloy was investigated. Samples of the eutectic alloy were prepared using an arc furnace under argon atmosphere and then directionally solidified. The samples directionally solidified showed regular and aligned eutectic microstructure. Compression tests were performed at room temperature and 1173K. Vickers hardness was determined at several temperatures, from room temperature to 1150K. Mechanical properties of NiAl were also determined. Results showed that when the growth rate is gradually increased from 8 to 50mm/h the aligned microstructure presents higher fibre density, which leads to higher strength level at room temperature, while further increase in the growth rate causes the microstructure the loose regularity. NiAl presents a well defined mechanical behaviour transition, while the NiAl-Mo eutectic alloy softens almost linearly. The highest yield strength value of NiAl-Mo was found to be about 1200 and 300MPa at room temperature and 1173K, respectively. © 2004 Elsevier B.V. All rights reserved.
- Growth and morphological characterization of Al-Cr-Nb eutectic alloys(2005-10-27) SOUZA, S. A.; RIOS, C. T.; COELHO, A. A.; FERRANDINI, P. L.; GAMA, S.; CARAM, R.Directional solidification of eutectic alloys attracts considerable attention, when in situ composites are concerned. The eutectic alloys are regarded as presenting regular morphology (lamellar and fibrous structures). Besides, when directionally solidified they show high microstructure stability at high temperatures. This work reports a morphological study of an Al-Cr-Nb eutectic alloy. The solidification morphology of the alloys was studied both in the as-cast and in the directionally solidified conditions. The samples were first obtained in an arc furnace and then directionally solidified using Bridgman equipment. During the directional solidification process, the growth rates utilized varied from 5.0 to 30.0 mm/h. Optical (OM) and scanning electron microscopy (SEM) was used in order to determine the influence of the solidification conditions on the microstructure. The results obtained indicated that the eutectic transformation temperature is near 1347.9 °C with formation of Al3(Nb,Cr) and Cr(Al,Nb) phases. Also, it was noted that the Cr(Al,Nb) phase undergoes a polymorphic transformation (∼892.3 °C) forming the Al(Nb)Cr2 compound, followed by eutectoid decomposition Cr(Al,Nb) → Al(Nb)Cr2 + Al8Cr5. © 2005 Elsevier B.V. All rights reserved.