Ausageing and ausforming of a copper based shape memory alloy with high transformation temperatures

The effect of ageing and ausforming on strength and transformation behaviou r of the alloy was investigated. Ageing starts above the reverse transforma tion temperature (A(f) = 139 degrees C). It is associated with the followin g processes: perfection of order, bainitic transformation, precipitation, A bove 550 degrees C re-solution and consequent homogenous betatisation start s. Ausforming consisted of plastic deformation in the range of the stable b eta phase: T-AF > 600 degrees C. Both ageing and ausforming lead to conside rable strengthening. Ageing below 400 degrees C raises, ausforming lowers t he transformation temperature. The various changes in microstructure were s tudied by light and transmission electron microscopy, the transformation te mperatures determined by DSC. The relations between microstructure and tran sformation behaviour are discussed.