‘Age-hardened alloy’ based on bulk polycrystalline oxide ceramic

Abstract

We report here for the first time the development of ‘age-hardened/toughened’ ceramic alloy based on MgO in the bulk polycrystalline form. This route allows for the facile development of a ‘near-ideal’ microstructure characterized by the presence of nanosized and uniformly dispersed second-phase particles (MgFe₂O₄) within the matrix grains, as well as along the matrix grain boundaries, in a controlled manner. Furthermore, the intragranular second-phase particles are rendered coherent with the matrix (MgO). Development of such microstructural features for two-phase bulk polycrystalline ceramics is extremely challenging following the powder metallurgical route usually adopted for the development of bulk ceramic nanocomposites. Furthermore, unlike for the case of ceramic nanocomposites, the route adopted here does not necessitate the usage of nano-powder, pressure/electric field-assisted sintering techniques and inert/reducing atmosphere. The as-developed bulk polycrystalline MgO–MgFe₂O₄ alloys possess considerably improved hardness (by ~52%) and indentation toughness (by ~35%), as compared to phase pure MgO.

Keywords:

• age-hardened polycrystalline ceramics
• heat treatment
• microstructure
• mechanical properties

Acknowledgements

The authors thank the Department of Science and Technology (DST) [grant number SR/S3/ME/0019/2012], Government of India, and IRCC, IIT Bombay, for financial support and SAIF, IIT Bombay, for allowing the usage of SEM and TEM.