Titanium is a transition metal. It is present in several minerals including rutile and ilmenite, which are well dispersed over the Earth's crust. Even though titanium is as strong as some steels, its density is only half of that of steel. Titanium is broadly used in a number of fields, including aerospace, power generation, automotive, chemical and petrochemical, sporting goods, dental and medical industries. The large variety of applications is due to its desirable properties, mainly the relative high strength combined with low density and enhanced corrosion resistance. This chapter discusses the applications of titanium and its alloys in the medical field.
Metallurgical Aspects
IntroductionAmong the metallic materials, titanium and its alloys are considered the most suitable materials in medical applications because they satisfy the property requirements better than any other competing materials, such as stainless steels, CrCo alloys, commercially pure (CP) Nb and CP Ta [1][2][3][4][5][6]. In terms of biomedical applications, the properties of interest are biocompatibility, corrosion behavior, mechanical behavior, ability to be processed, and availability [7][8][9].Titanium may be considered as being a relatively new engineering material. It was discovered much later than the other commonly used metals, its commercial application started in the late 1940s, mainly as structural material. Its usage as implant material began in the 1960s [10]. Despite the fact that titanium exhibits superior corrosion resistance and tissue acceptance when compared with stainless M.J. Jackson (&) Kansas State University, Salina, KS, USA e-mail: jacksonmj04@yahoo.com [11]. To overcome such restrictions, CP titanium was substituted by titanium alloys, particularly, the classic grade 5, i.e., Ti-6Al-4V alloy. The Ti-6Al-4V α + β-type alloy, the most worldwide utilized titanium alloy, was initially developed for aerospace applications [12,13]. Although this type of alloy is considered a good material for surgically implanted parts, recent studies have found that vanadium may react with the tissue of the human body [2]. In addition, aluminum may be related with neurological disorders and Alzheimer's disease [2]. To overcome the potential vanadium toxicity, two new vanadium-free α + β-type alloys were developed in the 1980s. Vanadium, a β-stabilizer element, was replaced by niobium and iron, leading to Ti-6Al-7Nb and Ti-5Al-2.5Fe (α + β)-type alloys [4,6,14]. While both alloys show mechanical and metallurgical behavior comparable to those of Ti-6Al-4V, a disadvantage is that they all contain aluminum in their compositions.In recent years, several studies have shown that the elastic behavior of α + β-type alloys is not fully suitable for orthopedic applications [15][16][17][18]. A number of studies suggest that unsatisfactory load transfer from the implant device to the neighboring bone may result in its degradation [9]. Also, numerical analyses of hip implants using finite element method indicate that the use of biomaterials wi...
