Cryogenic Milling and Spark Plasma Sintering of Commercially Pure Ti and Metastable Beta Ti15Mo Alloy

Abstract

This contribution aims on reviewing what we have learnt about cryogenic milling and sintering of Ti based materials in the last five years. Gas atomized CP Ti powder and Ti15Mo alloy powder were cryogenically milled in liquid argon and subsequently sintered by SPS using various processing conditions.

Titanium remains ductile even at cryogenic temperatures (unless contaminated by nitrogen) and therefore powders are not significantly refined. On the other hand, each powder particle is severely deformed and cryogenic milling therefore resembles SPD methods for microstructure refinement.

UFG structure of powders was studied by transmission Kikuchi diffraction. Samples after sintering were thoroughly characterized.

UFG microstructure undergoes recovery and recrystallization during sintering with clear trade-off between remaining porosity and grain growth. Enhanced alpha phase precipitation was observed in the metastable Ti15Mo aloy.

Compact UFG Ti15Mo two-phase material is achievable by cryogenic milling and SPS.