Microstructure characterization and effect of thermal cycling and ageing on vanadium-doped Cu-Al-Ni-Mn high-temperature shape memory alloy

The effect of vanadium addition on the microstructure of Cu-Al-Ni-Mn high-temperature shape memory alloy (SMA) and its thermal cycling and ageing behaviour has been investigated. Using scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction analysis, the morphology, distribution and structure of secondary phase, induced by vanadium addition, have been identified. The effect of secondary phase on grain refining of Cu-Al-Ni-Mn has also been revealed. Differential scanning calorimetry measurement was used to investigate the effect of thermal cycling and ageing on the transformation temperature. It has been found that thermal cycling has a strong influence on the transformation temperature of the present Cu-Al-Ni-Mn-V high-temperature SMA. Ageing also caused an apparent change of the transformation temperature. It has been suggested that this was mainly due to the precipitation of secondary phase, because the sample was heated to a rather high temperature in both thermal cycling and the ageing process. The experiment showed that the transformation temperature could be maintained stable in the thermal cycling process by pre-ageing the sample at a suitable temperature. © 1998 Kluwer Academic Publishers.