A study on the crystallization behavior of amorphous Ti50Ni25Cu25 shape memory ribbon by X-ray diffraction measurement

XRD spectra from the contact and free surfaces of amorphous Ti50Ni25Cu25 ribbon prepared by melt-spinning technique, crystallized, and aged at 500 degrees C for different times were collected for intensive investigation. A thin layer of textured grains with a thickness of 1 mu m formed at the contact surface, having {100}(B2) planes parallel to the ribbon surface during the crystallization process and resulting in an extraordinarily strong (200)(B2) diffraction peak from the contact surface. This textured layer was caused by the pre-arrangement of atoms with their easy growth < 100 >(Bcc) direction parallel to the maximum temperature gradient perpendicular to the contact surface during the melt-spinning process. On the other hand, equiaxed and randomly orientated grains of about 300 +/- 100 nm in size formed at the free surface. During the aging process, when aging time exceeded 15 min, precipitation of TiCu along {100}(B2) planes significantly distorted the B2 lattice and thus led to broadening, which decreased the intensity of (200)(B2) diffraction. Comparisons of experimental results with reported studies show that the texture developed in Ti50Ni25Cu25 ribbon is highly affected by the thickness and cooling rate.