Made available in DSpace on 2014-12-17T14:06:59Z (GMT). No. of bitstreams: 1 NarayannaMF_DISSERT.PDF: 4537293 bytes, checksum: 5d2c22b8b17b69adbe02ea6e28e15de6 (MD5) Previous issue date: 2011-07-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Microalloyed steels constitute a specific class of steel with low amount of carbon and microalloying elements such as Vanadium (V), Niobium (Nb) and Titanium (Ti). The development and application of microalloyed steels and steels in general are limited to the handling of powders with particles of submicron or nanometer dimensions. Therefore, this work presents an alternative in order to construction of microalloyed steels utilizing the deposition by magnetron sputtering technique as a microalloying element addiction in which Ti nanoparticles are dispersed in an iron matrix. The advantage of that technique in relation to the conventional metallurgical processes is the possibility of uniformly disperse the microalloying elements in the iron matrix. It was carried out deposition of Ti onto Fe powder in high CH4, H2, Ar plasma atmosphere, with two deposition times. After the deposition, the iron powder with nanoparticles of Ti dispersed distributed, were compacted and sintered at 1120 ? C in resistive furnace. Characterization techniques utilized in the samples of powder before and after deposition of Ti were Granulometry, Scanning Electron Microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (DRX). In the case of sintered samples, it was carried out characterization by SEM and Vickers Microhardness assays. The results show which the deposition technique by magnetron sputtering is practicable in the dispersion of particles in iron matrix. The EDX microanalysis detected higher percentages of Ti when the deposition were carried out with the inert gas and when the deposition process was carried out with reactive gas. The presence of titanium in iron matrix was also evidenced by the results of X-ray diffraction peaks that showed shifts in the network matrix. Given these results it can be said that the technique of magnetron sputtering deposition is feasible in the dispersion of nanoparticles of iron matrix in Ti. / Os a?os microligados constituem uma classe espec?fica de a?o com baixos teores de carbono e elementos microligantes, como: van?dio (V), ni?bio (Nb) e tit?nio (Ti). O desenvolvimento e aplica??o dos a?os microligados, e de a?os em geral, est?o limitados ? manipula??o dos p?s com part?culas de dimens?es submicrom?tricas ou mesmo nanom?tricas. Mediante isto, este trabalho apresenta uma t?cnica alternativa para a fabrica??o de a?os microligado empregando a deposi??o por magnetron sputtering, como fonte de adi??o de elemento microligante na forma de nanopart?culas de tit?nio dispersa em matriz de ferro. A vantagem dessa t?cnica em rela??o aos processos metal?rgicos convencionais ? a possibilidade de dispersar uniformemente o elemento microligante na matriz de ferro. Foram realizadas deposi??es de Ti sobre p? de ferro em atmosfera de CH4, H2, Ar, com dois tempos de deposi??o diferentes. Ap?s as deposi??es, o p? de ferro com nanopart?culas de Ti dispersamente distribu?das, foram compactados e sinterizados a 1120?C em forno resistivo. As t?cnicas de caracteriza??o utilizadas nas amostras de p? de ferro antes e ap?s a deposi??o de Ti foram granulometria, microscopia eletr?nica de varredura (MEV), energia dispersiva de raios X (EDX) e difra??o de raios X (DRX). Para as amostras sinterizadas utilizou-se a caracteriza??o por microscopia eletr?nica de varredura (MEV) e ensaio de microdureza Vickers. A microan?lise por EDX detectou percentuais maiores de Ti para as deposi??es em atmosfera de g?s inerte em rela??o ?s deposi??es em atmosfera de g?s reativo. A presen?a de tit?nio na matriz de ferro tamb?m foi evidenciada pelos resultados da difra??o de raios-X que apresentaram deslocamentos nos picos da rede da matriz. Diante desses resultados pode-se afirmar que a t?cnica de deposi??o por magnetron sputtering ? vi?vel na dispers?o de nanopart?culas de Ti em matriz de ferro.