Avaliação do efeito da adição de Nb, Ta e Zr na estabilidade do composto Ti6Si2B

Abstract

According to numerous researches on alloys for structural applications at high temperatures, titanium alloys have a considerable space in relation to other alloys studied. The main field of application that encourages these studies is the aeronautics and aerospace industry, which seeks a continuous improvement in its materials to meet requirements requested in terms of aircraft performance and efficiency. Considering the behavior of the alloys currently used in the market, which operate in high performance in the stipulated temperature limits, new alloys have been studied to increase this range of operation that needs to expand. In this context, the Ti6Si2B phase has great potential for this application, but presentes a small single-phase region, which can be expanded and stabilized with the addition of elements in the Ti-Si-B ternary system. Thus, the present work evaluates the effect of the addition of Zr, Nb and Ta, varying the amount of Nb and Ta in 2 and 5%at., in the stability of the compound Ti6Si2B prepared by high energy ball milling and subsequent conventional sintering and spark plasma sintering (SPS). The X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techiniques were used to characterize the phases formed after high energy milling and subsequent conventional sintering and SPS. The effect of milling time was evidenced by the agglomeration of particles in the initial periods of milling and subsequent refinement of the powders in the time of 420 and 600 minutes of milling. The Ti5Si3 and TiB phases were formed during milling and the Ti6Si2B phase was identified by XRD at high milling times and after both sinterings. There was a prevalence of βTi, TiB and Ti5Si3 phases in the conventional sintering samples and of Ti5Si3 phase in the SPS samples. Iron contents between 7 and 10%at. were found in the conventional sintered samples and about 1 and 2%at. in the SPS samples.