Enhancement in age hardenability of sintered Ti–5Fe alloy by Zr addition processed by pulsed electric current sintering

ABSTRACT

The age-hardenable Ti–5Fe–5Zr (wt. %, 5Zr) alloy has been consolidated by pulsed electric current sintering, following a β solution treatment, and the results are compared with a Ti–5Fe (0Zr) alloy. The precipitation sequence measured at 640°C ageing is β + athermal ω → β + isothermal ω → β + α. At the peak hardness isothermal ω phase forms at 20 s of ageing. The Zr addition retards the precipitation kinetics of the α phase; as a result, the α phase nucleates at latest at 300 s ageing in the overaged state. Fe is partitioned into β, while it is depleted from the α phases. There is Zr enrichment near the α/β interface when the α phase precipitates due to a solute drag effect; the growth rate of the α phase in the 5Zr alloy is significantly reduced compared with that in the 0Zr alloy.

KEYWORDS:

• Word
• Ti
• sintering
• powder metallurgy
• Vickers hardness
• TEM

Acknowledgements

The authors acknowledge the facilities as well as the scientific and technical assistance of the Analysis and Instrumentation Center at Nagaoka University of Technology, Japan. In particular, we thank Associate Professor N. Saito of the Nagaoka University of Technology, Japan, for fruitful discussion. We also wish to thank Professor M. Nanko of the Nagaoka University of Technology, Japan, for the use of equipment.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Tomoyuki Homma http://orcid.org/0000-0003-1984-3270

Additional information

Funding

This work was in part supported by Grant-in-Aid for Scientific Research (C), 15K07100, 2015, Japan and the Sasakawa Scientific Research Grant, 2015 from The Japan Science Society.