Feasibility Study of Compaction and Sintering of Commercially Pure Titanium using Friction Stir Processing

Abstract

Manufacturing of a component through powder metallurgy (PM) route involves at least three critical steps: powder blending, compaction, and sintering. Overall, the PM route takes 4 to 8 steps to get to the final product. Moreover, it requires a huge amount of capital investment to perform every step of the manufacturing process via PM route. Friction stir processing (FSP) is a derivative of friction stir welding which has emerged as a generic microstructural modification tool in last one decade. The aim of the current work was to explore the possibility of decreasing the number of steps required in the manufacturing of a product using the PM technique. Using the FSP method, the manufacturing process is reduced to two steps and the mechanical properties of the final product are significantly improved. In this study, commercially pure titanium (Ti) powder was used. The two-step process appeared extremely efficient and it involved: 1) constraining the Ti-powder in a die and using a punch to consolidate it in a final disk-like geometry, 2) next, the consolidated disk-shaped product was processed using FSP tool and methods. Initial mechanical characterization results show peak hardness of the FSP processed Ti-powder product to be approximately 436 HV0.3 with average hardness measured at about 251 HV. The electron backscattered diffraction of the FSP-assisted sintered region showed equiaxed grains with average grain size to be 440 ±254 nm. The initial result indicates FSP can be used as a manufacturing tool for consolidating powders in to bulk solid form.