Mass transfer in Al/Ni system under high pressure torsion deformation

Severe plastic deformation (SPD) is a family of methods which permit tailoring the structure and properties of materials. High pressure torsion (HPT) is one of the common processes in this family. SPD leads both to the microstructure refinement and to various phase transformations in materials, e.g. the formation or decomposition of a supersaturated solid solution, dissolution of phases, synthesis of the low-temperature, high-temperature or high-pressure allotropic modifications, etc. We present in this talk the results of the microstructure evolution examination during the HPT deformation of the composite Ni-Al samples. The samples were assembled from six alternated layers of Ni and Al foils with the thickness of ca. 200 µm each. This “cake” was placed between two anvils in the HPT machine and deformed for five anvil´s revolution under a pressure of 5 GPa at room temperature. Samples were examined using X-ray diffraction and transmission electron microscopy. We observed that SPD caused the mass transfer between the layers in the sample. Formation of the Al- and Ni-based solid solutions and intermetallic phases was revealed.