Study of superelastic behavior of CuAlBe Shape Memory Alloy by neutron diffraction

摘要

The aim of this work is to understand the evolutions of the β_1 metastable austenite phase of a CuAlBe Shape Memory Alloy at macroscopic and microscopic scales under mechanical solicitation by neutron diffraction. The tensile specimen, taken in the raw material is subjected to superelastic cycles at room temperature on SMARTS diffractometer. Before loading, the mater ial is fully austenitic. During loading, after elastic deformation of austenite, phase transformation starts, martensite variants appear. The material follows a law of pseudo elastic behavior. At the end of the first mechanical cycle after unloading, the macroscopic curve does not fully return into its original point. A macroscopic deformation is observed. The evolution of first order microdeformations during mechanical cycles shows a large deformation of {400} plane family. This deformation is linked to the presence of <001> partial fibber characterizing the crystallographic texture of the material after elaboration. The FWHM of the (400) diffraction peak is also largely increased during loading. This increase is the signature of the generation of stacking faults during the transformation of β_1 metastable austenite into β'_1 martensite.