Characterisation of phase transformation in Ti50+xPd30Ni20-x alloys

Generally, a B2-B19 one-stage phase transformation exists in Ti50PdxNi50-x alloys when Pd content is higher than 20 at.%. However, in Ti rich Ti50+xPd30Ni20-x alloys, a B2-B19-B19' two-stage transformation can also take place. The alloys were firstly heated to high temperature of solid solutions, and then the one-stage transformation can be retained by subsequent furnace-cooling as well as the two-stage transformation by quenching. Annealing at lower temperature does not change the nature of the phase transformations. Differential scanning calorimetry (DSC), X-ray diffractometry (XRD), dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM) were used to ascertain the characteristics of the phase transformations. Discrepancies between the transformation elastic modulus of B2-B19 and B19-B19' have been found, a trough and a step can be employed for a description, respectively. The damping properties of the materials were also investigated, all the results provide valuable information for designs of intelligent materials and structures aimed for vibration control. (C) 2002 Published by Elsevier Science Ltd.