Materials Chemistry and Physics, Vol.173, 106-116, 2016
The effects of ball milling and the addition of blended elemental aluminium on the densification of TiH2 power
Powder production and sintering processes of titanium powder metallurgy are studied in order to reduce the cost of manufacturing titanium parts. The direct sintering of TiH2 simplifies powder processing and helps densification during sintering. The effects of ball milling have been shown to improve the dehydrogenation of TiH2, which during sintering, causes the earlier dissolution of the oxide layer surrounding the solid titanium particles, allowing solid diffusion to occur earlier. The combined effect of reduced particle size and increased dehydrogenation of ball milled TiH2 are studied here during sintering, in order to understand their roles during densification. TiH2 ball milled for various durations is vacuum hot press sintered at 700-900 degrees C. The density, microstructure and hardness of the fabricated titanium specimens are also studied. The effects of ball milled powder on the introduction of blended elemental aluminium are studied in comparison with a commercial titanium powder. The increase in ball milling duration of TiH2 powders to reduce particle size causes faster densification and dehydrogenation, with a finer uniform microstructure. When using fine ball milled powder with aluminium, the formation of Kir-kendall pores through the interaction of titanium and liquid aluminium is worsened. (C) 2016 Elsevier B.V. All rights reserved.