Influência da microestrutura e da anodização nas propriedades mecânicas, de superfície e corrosivas de ligas Ti-xNb-ySi para aplicações biomédicas

Abstract

This thesis aimed to evaluate the influence of niobium and silicon on Ti-xNb-ySi alloys (x = 15, 37 and y = 0; 0.35; 0.55% by mass), in relation to their microstructures, correlating them with mechanical properties, corrosion resistance, wettability, surface energy, roughness and bioactivity, before and after anodizing. Through X-ray diffractometry, the results showed the formation of a polyphase microstructure for the Ti-15Nb-xSi alloys with the presence of the α, β and α” phases, the latter being responsible for the greater hardness of the alloys in this group. On the other hand, increasing the niobium content to 37% provided a refined microstructure, mostly composed of the β phase, in addition to the α” phase, and lower hardness values attributed to the greater volume fraction of the β phase. For this alloy content, the addition of silicon considerably favored the reduction of the average grain size, in addition to contributing to the reduction of hardness. The polyphase microstructure associated with the addition of alloying elements also allowed the formation of irregular nanotubular layers in both alloying systems. However, the Ti-37Nb-0.35Si alloy, due to the greater stabilization of the β phase, presented regions with more organized nanotubes. Furthermore, all compositions examined hydrophilic surfaces and the formation of particles and agglomerates that intensified after anodization.. It is also noteworthy that the anodized alloys also showed a reduction in contact angle, an increase in surface energy and an increase in roughness. Finally, electrochemical tests showed that non-anodized 15% Nb group alloys had the best corrosion resistance.