A detailed observation on the successive stress-induced martensitic transformations in Cu-Al-Ni alloy single crystals has been carried out to clarify ambiguous problems left in a previous work (Acta Met., 21 (1979), 585). As a result, the structural change associated with two stage transformation pseudoelasticity above Af has been revealed to differ depending upon the temperature range. In the temperature range between Af and Tc, (a critical temperature), distinct β1→β1' and β1'→α1' transformations successively take place on loading, and distinct α1 '→β1' and β1'→β1 reverse transformations do on unloading. In the temperature range above Tc, the transformation behavior of loading is the same as that in the temperature range between Af and Tc. However, on unloading, when the loading has been stopped on the halfway of the second stage, the β1'→β1 and continuous α1'→β1'→β1 transformations successively take place. On the other hand, when the loading has been continued until the β1'→α1' transformation is completed, the associated stress-strain curve on unloading has clearly showed one stage of the continuous α1'→β'1→β1 reverse transformations. On the basis of these observations, the previous interpretation for the unloading process of stress-strain curves above Tc has been corrected, and the critical stress vs temperature diagram has been replotted.
(Received March 29, 1985)
Keywords: martensitic transformation, successive stress-induced transformation, transformation pseudoelasticity, two stage pseudoelasticity, transformation stress, phase diagram in temperature-stress coordinates, copper-aluminum-nickel alloy
* This paper is a supplement to the paper published in Acta Met., 21 (1979), 585.
** Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihoga-oka, Ibaraki, Osaka 567, Japan.
*** Institute of Materials Science, The University of Tsukuba, Sakuramura, Niiharigun, Ibaraki 305, Japan.