Nonconventional production technologies for NiTi shape memory alloys

• Autor(es): Neves, Filipe ; Fernandes, F. M. Braz ; Martins, Isabel M. ; Correia, J. Brito ; Oliveira, M. ; Gaffet, E. ; Wang, T. Y. ; Lattemann, M. ; Suffner, J. ; Hahn, H.
• Data: 2009
• Identificador Persistente: http://hdl.handle.net/10400.9/702
• Origem: Repositório do LNEG
• Tipo de Documento: Documento de conferência
• Idioma: Inglês

Descrição

The development of new production technologies for NiTi Shape Memory Alloys (SMAs) is always challenging. Recently, we introduced two powder metallurgical (PM) processing routes involving mechanical activation of elemental powder mixtures and densification through extrusion or forging. Those processes were named Mechanically Activated Reactive Extrusion Synthesis (MARES) and Mechanically Activated Reactive FOrging Synthesis (MARFOS). Heat treatments were performed in order to adjust the B2-NiTi matrix composition, yielding a microstructure consisting of a homogeneous dispersion of Ni4Ti3 precipitates embedded in nanocrystalline B2-NiTi matrix. In the present study, we demonstrate the viability of those PM processes for producing NiTi SMAs. With insitu X-ray diffraction and differential scanning calorimetry it is shown that B2-NiTi matrix undergo a B2« R«B19 two-step phase transformation