Manipulation of microstructure and mechanical properties during dehydrogenation of hydrogen-sintered Ti–6Al–4V

Ti–6Al–4V parts produced using the powder metallurgy process known as hydrogen sintering and phase transformation (HSPT) have been shown to exhibit superior mechanical properties than those produced using traditional titanium powder metallurgy techniques. In this work, the dehydrogenation step of HSPT is investigated as an additional method to further manipulate the microstructure of Ti–6Al–4V. By varying the dehydrogenation temperature, several microstructural features can be controlled, such as α lathe & colony width and grain boundary α thickness. Furthermore, it is shown that the addition of hydrogen to Ti–6Al–4V greatly reduces the β transus temperature, which allows for super-transus processing to occur at reduced temperatures. This reduced β transus temperature also provides a method by which a graded microstructure can be formed, which consists of a coarse-grained core and a fine-grained shell.