Mechanical properties and corrosion resistance of the Ti-35Nb alloys applied as biomaterial / Propriedades mecanicas e de resistencia a corrosão de ligas Ti-35Nb a serem aplicadas como biomaterial

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Titanium alloys form the most versatile class of metallic materials used as biomaterials. Among them, one finds the ß ?type alloy, which must soon become the standard metallic materials for orthopedic applications. The aim of this work is to prepare and characterize a type ß ?titanium alloy containing 35 wt.% Nb. Samples of such alloy were rapidly and slowly cooled from the ß ?field temperatures. This work includes studies of microstructure stability, effects of heat treatment on the microstructure, evaluation of corrosion resistance and finally, analysis of fatigue resistance in non-aggressive and aggressive media. The results obtained allowed one to observe that microstructure of slowly cooled samples is formed by precipitates of ß ?and a phases in a ? ?matrix. Under rapid cooling, the microstructure consists of ß ?phase and a" martensite. Aging heat treatments resulted in the transformation of a" martensite into ß ?phase, followed by ? ?phase precipitation and hence, a ?phase nucleation. Mechanical testing showed that the elastic modulus and Vickers hardness of slowly cooled samples were significantly higher than that obtained in the case of the rapidly cooled samples. On the other hand, it was observed that slowly cooled samples showed higher tensile strength and lower ductility. Corrosion resistance testing led to the conclusion that both rapidly and slowly cooled samples have similar corrosion behavior, which allows one to conclude that cooling rate and consequently, the phases in the microstructure do not have a relevant influence on the corrosion resistance. Fatigue testing showed that both types of sample (rapidly and slowly cooled samples) have fatigue resistance lower than that of the Ti-6Al- 4V alloy. The rapidly cooled sample showed fatigue resistance higher than that of slowly cooled samples. The fatigue resistance measured in a NaCl (0,9% vol.) solution of both types of samples showed a slight tendency of reduction when compared to the same samples tested in nonaggressive medium

ASSUNTO(S)

metais - propriedades mecanicas mechanical behavior titanium alloys ligas de titanio microestrutura microstructure characterization metais - fadiga fatigue

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