Titanium is a transition metal which is found in the earth’s crust (Balazic et al, 2007). It is the fourth most abundant metal on earth and is found all over the world in volcanic and alluvial deposits. While ores such as rutile and ilmenite are plentiful, titanium reacts with nitrogen, hydrogen, and oxygen and is not easy to extract from its ore (Brunette et al, 2001). Extraction involves very expensive methods and a mere 5% of pure titanium is extracted from an ore usually (Brunette et al, 2001). The density of titanium is about half of that of steel though it is as strong as steel (Balazic et al, 2007).
Titanium is an allotropic element and can exist in three different forms in nature. The alpha form exists at room temperature and is a hexagonal crystal structure that is closely packed. The beta form exists when titanium in solid form is heated to a temperature above 883 C. it also exists when liquid titanium solidifies (Brunette et al, 2001).
Mixing titanium with other metals makes it possible to make alloys that are stable at room temperature in either the alpha or the beta form. Metals commonly used to make stable the alpha form include aluminum, tin, and oxygen. The beta form can be stabilized using metals like chromium, iron or vanadium. Using mixtures of both of these stabilizers leads to the production of alpha+beta titanium alloys (Brunette et al, 2001).
Titanium has used in many different fields including aerospace, power generation, automotive, chemical and petrochemical, sporting goods, dental and medical applications (Rack and Qaz, 2006. Sibum, 2003. Wang, 1996 from Balazic et al, 2007).
The commercial aspects of titanium were only exploited in the 1940s (Balazic et al, 2007). Starting in the 1960s, titanium was used as a material in medical implants (Balazic et al, 2007). Now, over 1000 tonnes or 2.2 million pounds of titanium are used in implants all over the world every year (The Titanium Information Group, 2003).
Titanium alloys have also been used in the medical industry and there are three main types of alloys which have been developed.