Effect of parent phase ageing on CuZnAl shape memory alloys with Mn and Zr addition

The effect of parent phase ageing on CuZnAl and CuZnAlMnZr shape memory alloys was studied. It was found that re-ordering took place during parent phase ageing for the CuZnAl alloy. When the ageing temperature reached 200°C, bainite started to precipitate and further ageing resulted in decomposition to the equilibrium phases. The consequence was a drastic drop in shape memory capacity and the decrease of transformation temperatures by solute depletion. With the Mn and Zr addition, bainitic precipitation and decomposition were also found. However, the re-ordering phenomenon was not significant when the ageing temperature was below 200°C where there was no change in shape memory capacity. © 1998 Elsevier Science B.V.