The influence of grain size on the onset of the superelastic transformation in Ti-24Nb-4Sn-8Zr (wt%)

Superelastic Ti alloys have potential across a wide range of industrial sectors, but each application requires specifically tailored transformation behaviour. Composition is well known to influence transformation properties but for a given alloy, the effect of microstructural features, such as grain size, is far less clear. Within the literature, no consistent relationship between grain size and key parameters, such as the transformation stress, aSIM, exist. This lack of clarity is a major barrier to engineering uptake of these materials. Therefore, in the present work, the transformation behaviour of Ti-24Nb-4Sn-8Zr (wt%) from two different starting stocks has been studied, with grain sizes varied by changing solution heat treatment time. Irrespective of the material stock, aSIM was shown not to vary as a function of grain size. As such, this observation is believed to be a general effect, and as a result, microstructures can be tailored to improve other parameters such as yield stress, without altering the onset of transformation.