Study of the Influence of Plastic Deformation on Metastable Phases of CuAlBe Shape Memory Alloy by Neutron Diffraction

Abstract

This work aims to study by neutron diffraction the evolution of metastable phases of CuAlBe shape memory alloy after plastic deformation. Two samples were studied: the first one deformed by cold rolling at a reduction rate of 15% and the second, deformed by cold rolling at 15% followed by hot rolling at 200°C for a reduction rate of 30% respectively. Before plastic deformation, the material is fully austenitic at ambient temperature. Its crystallographic texture is mainly characterized by a <001> partial fibber. After deformation, this partial fibber disappears and the crystallographic texture is composed by isolated orientations. At higher reduction rates, the texture of austenitic phase remaining in the material is characterized by a <111> fibber. The rolling process modifies metastable phase quantities. After deformation at a reduction rate of 15%, the volume fraction of metastable austenite remaining is close to 8%. Plastic deformation also greatly modifies the characteristic transformation temperatures and enlarges the hysteresis. The material plastically deformed after hot rolling presents large variations of intensities of diffraction peaks belonging to martensite phase during a thermal cycle at low temperature. This effect is attributed to a reorganization of variants due to an evolution of crystallographic texture of martensite.