Stress-induced martensitic transformations in a Cu-Al-Ni shape memory alloy studied by in situ transmission electron microscopy

摘要

Structural observations by transmission electron microscopy were performed and analyzed on in situ strained foils of a Cu-Al-Ni shape memory alloy. The experiments were carried out at room temperature. Two stress-induced transformation processes are described in this paper, (i) Transition between two variants of γ'_1 (2H) martensite. Both variants coexisted at low stresses. With increasing stress, one variant was replaced by the other one and appeared again during unloading, (ii) Transformation between β_1 (D0_3) austenite and β'_1 (18R) martensite. Nucleation and behaviour of the β'_1 needles under stress were followed.