Mechanical alloying and field assisted hot pressing of nanocrystalline B2-NiAl intermetallic compound

Abstract

Ordered B2-NiAl intermetallic compound powder was successfully synthesised by mechanical alloying after 20 h in an attritor mill, starting from elemental Ni and Al powders and without subsequent heat treatment. NiAl powder obtained was homogenous and had a nanocrystalline microstructure. It was consolidated by field assisted hot pressing (FAHP), in a novel configuration with a Gleeble 3800 thermomechanical simulator. The powder was also processed by hot isostatic pressing (HIP) in order to compare both methods. The consolidation was successful by both methods obtaining above 98% of NiAl theoretical density (5·86 g cm⁻³). The results showed that the consolidation process by FAHP technique is effective and uniform throughout the sample as indicated by homogenous hardness values, obtaining microstructure and properties similar to those obtained with HIP technique, with certain advantages over it. The achieved room temperature yield strength of 850 MPa and fracture strain 26–28% corresponds to the bulk values of NiAl intermetallic.

Keywords:

• NiAl intermetallic
• Mechanical alloying
• Field assisted hot pressing
• HIP

Acknowledgements

Funding of the Project NECTAR (PCIG10-GA-2011-303409) by the Marie Curie Actions Grant FP7-PEOPLE-2011-CIG program is gratefully acknowledged.