Nondestructive characterization of the level of plastic deformation by thermoelectric power measurements in cold-rolled Ti-6Al-4V samples

This paper presents experimental data that illustrates the intrinsic sensitivity of the thermoelectric contact technique based on the Seebeck effect, in order to detect the presence of anisotropy due to plastic deformation produced by the manufacturing process of cold working at different degrees of reduction in thickness, namely 40, 60 and 80% in Ti-6Al-4V. In addition to the morphological anisotropy, the Ti-6Al-4V alloy also exhibits a substantial thermoelectric anisotropy due to the preferred alignment of the predominantly hexagonal grain structure. The results describe the behaviour of the thermoelectric power (TEP) coefficient with respect to the anisotropy and microstructure in a highly textured material, that presents both morphological and crystallographic texture. Ultrasonic measurements of shear wave velocity were also conducted in order to obtain a direct correlation between the presence of a significant anisotropy in the cold-rolled Ti-6Al-4V samples and the TEP measurements, before and after heat treatment (annealing). TEP measurements offer a means to assess the evolution of the level of plastic deformation, which allows for a better correlation between texture-induced anisotropy and the material's microstructural and properties. Of course, the TEP values depend on tile physical nature and degree of the imperfection that is to be characterized.