Role of oxygen and nitrogen in mechanical alloying mechanism of Ni–Ti powder mixtures

Abstract

In this study, the critical milling behaviour of Ni–Ti powder mixtures was evaluated in relation to the effect of atmospheric gases, more specifically to oxygen and nitrogen. Within the experimental conditions used, it is shown that both gases play an important role in the alloying process and that not only oxygen gas reacts with the mechanically alloyed powders but also nitrogen. The most effective mixing occurred for the mixtures with the highest contaminant contents.

Keywords:

• NiTi
• Mechanical alloying
• Critical milling behaviour
• Powder processing
• Shape memory alloys

F. Neves was supported by an FCT/MCTES grant (grant no. SFRH/BPD/38354/2007). F. Neves and F. M. Braz Fernandes acknowledge the funding of CENIMAT by FCT/MCTES through the Strategic Project (project no. LA 25-2011–2012).

Notes

This paper is part of a special issue on ‘Euromat 2011: powder synthesis and processing for controlled microstructure’