Orthorhombic lattice deformation of CuAlBe shape-memory single crystals under cyclic strain

X-ray diffraction experiments were carried out to prove that X-ray methods can be used to assess strain-induced fatigue in CuAlBe shape-memory alloys. The pseudoelastic fatigue behaviour of CuAlBe single crystals presents a strong decrease of the critical stress of the martensitic transformation. During the fatigue test, the austenitic lattice exhibits a lattice distortion. This lattice distortion evolves during the fatigue test: the austenitic cubic lattice (β₁) tends to transform gradually towards an orthorhombic one. Various hypotheses concerning this lattice distortion are proposed.