Yttria catalyzed microstructural modifications in oxide dispersion strengthened V–4Cr–4Ti alloys synthesized by field assisted sintering technique

Abstract

The present work deals with synthesis, characterisation and elevated temperature mechanical property evaluation of V–4Cr–4Ti and oxide (yttria = 0.3, 0.6 and 0.9 at%) dispersion strengthened V–4Cr–4Ti alloy processed by mechanical alloying and field-assisted sintering, under optimal conditions. Microstructural parameters of both powder and sintered samples were deduced by X-ray diffraction (XRD) and further confirmed with high resolution transmission electron microscopy. Powder diffraction and electron microscopy study show that ball milling of starting elemental powders (V–4Cr–4Ti) with and without yttria addition has resulted in single phase α–V (V–4Cr–4Ti) alloy. Wherein, XRD and electron microscopy images of sintered samples have revealed phase separation (viz., Cr–V and Ti–V) and domain size reduction, with yttria addition. The reasons behind phase separation and domain size reduction with yttria addition during sintering are extensively discussed. Microhardness and high temperature compression tests were done on sintered samples. Yttria addition (0.3 and 0.6 at.%) increases the elevated temperature compressive strength and strain hardening exponent of α–V alloys. High temperature compression test of 0.9 at% yttria dispersed α–V alloy reveals a glassy behaviour.

Keywords:

• Vanadium alloy
• yttria
• ball milling
• field-assisted sintering
• interface
• off-stoichiometry

Acknowledgements

The authors would like to thank UGC-NRCM programme of Indian Institute of Science, Bengaluru and all the fellow students of Deformation Mechanics & Modelling Group, Materials Engineering, IISc for providing us the perfect platform to utilise and analyse the characterisation facilities.