Titanium

Titanium is a metal which is rarely used in the elemental form; titanium is often alloyed with vanadium and aluminium to increase strength and form high temperature corrosion resistant alloys. Titanium can form  oxides, nitrides and hydrides; titanium oxide and  titanium nitride have uses in a wide range of applications.  Titanium  dioxide, due to  its high stability and low toxicity is  frequently  used  as  a  paint  pigment  and used  in a  range  of  cosmetics.  Titanium  nitride,  due  to  its  high  stability  and  high  hardness  is  frequently  used  as  a  hard  wearing  coating  which  can  be  applied  to  a  range  of  abrasives  to  prolong  life and improve cutting performance.
The extraction and refining process for titanium is an energy intensive operation, hence a high proportion of the costs associated with titanium is based on the refining process as titanium chloride (one of the refined steps in the manufacture of titanium metal) is reduced using magnesium metal.
Although titanium is an incredibly stable metal at room temperature and even under a wide range of corrosive environments, at elevated temperatures titanium can be very reactive; for example for CP (commercial purity) titanium above ~800C titanium can dissolve it's own oxide! This is incredibly useful for diffusion bonding titanium components together. The process of diffusion bonding is a thermally driven process where atoms movement can move between two titanium components which results in a strong bond between components after cooling the components. The atmosphere around the diffusion bonding process for titanium is tightly controlled, normally a good vacuum to prevent nitrides, oxides or hydrides from forming. Another great property of titanium is the ability for superplastic forming at elevated temperatures, this is where titanium can be formed into shapes requiring a high degree of strain to form the final component. Since superplastic forming also relies of diffusion, for titanium it can be beneficial to have a small amount of amount of hydrogen present to favour the beta phase (which is one of the crystallographic phases for titanium) this beta phase allows for easier atom mobility and reduces the stress required for deformation. Once the deforming operation is complete, the hydrogen level is reduced using by vacuum at elevated temperature. If too much hydrogen is added then hydrogen embittlement can occur and during forming operations cracking occurs.