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.,
27 (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 β
1→β
1′ and β
1′→α
1′ transformations successively take place on loading, and distinct α
1′→β
1′ and β
1′→β
1 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 β
1′→β
1 and continuous α
1′→β
1′→β
1 transformations successively take place. On the other hand, when the loading has been continued until the β
1′→α
1′ transformation is completed, the associated stress-strain curve on unloading has clearly showed one stage of the continuous α
1′→β
1′→β
1 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.
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