Ti-6Al-4V is categorized as an alpha/beta titanium alloy. It's chemical make up is shown in Figure 1 below. Pure titanium has an HCP microstructure below 882 C this is known as the alpha phase of titanium. When the temperature is over 882 degrees Celsius the microstructure changes to a beta-phase BCC structure. When aluminum is alloyed with titanium it stabilizes the alpha phase of titanium, however vanadium stabilizes the beta-phase of titanium. Vanadium allows the beta phase to occur under the temperature of 882 C. The beta phase can be precipitated even further in samples of Ti-6Al4V with heat treatments. This is why it is categorized as an alpha/beta titanium alloy. The multi-phasic microstructure strengthens the material by resisting dislocation motion by adding strain and grain boundaries.
Figure 1: Chemical makeup of Ti-6Al-4V (reference 3)
Other applications of Ti-6Al-4V
Ti-6Al-4V has excellent mechanical properties which make it a great choice in many applications. It is used in aerospace engineering for structural frames and connections. It is also used in engines for fan blades and areas that aren't exposed to a high amount of heat. Its anti-corrosive properties make it ideal for marine applications. It is also sometimes used in sports equipment due to its high strength-to-weight ratio.