13 - Spark plasma sintering and hot pressing of titanium and titanium alloys

Abstract

Spark plasma sintering (SPS) and hot pressing (HP) are both advanced powder consolidation techniques. They are both effective in producing pore-free preforms of titanium and titanium alloys from powder, compared to pressureless sintering. This chapter deals with the SPS and HP of commercially pure titanium (CP-Ti) powder and prealloyed (PA) Ti-6Al-4V (wt%) powder and elemental and master alloy (EMA) powder mixtures of Ti-6Al-4V. In particular, the densification behavior, densification mechanism, microstructure evolution, impurity pickup, and mechanical properties are discussed. It is concluded that powder particle deformation is responsible for densification by both SPS and HP, and no difference has been observed in the fabrication of CP-Ti by SPS and HP. However, SPS leads to much faster solute homogenization in the fabrication of Ti-6Al-4V from EMA powder mixtures than does HP due to the Joule heat generated during SPS. This is the main advantage of SPS over HP identified. Achieving solute homogenization is critical to the fabrication of a titanium alloy containing slow diffusers.