Severe plastic deformation of a Ti-based nanocomposite alloy studied by nanoindentation

The mechanical properties of a Ti-based multicomponent alloy composed of micrometer-sized dendrites embedded in a nanostructured eutectic matrix have been studied before and after subjecting it to high-pressure torsion (HPT). HPT causes an increase of microstrains and a pronounced grain refinement in the different constituent phases, resulting in an enhancement of the overall hardness of the alloy. Nanoindentation experiments are used to probe the local hardening during HPT of each individual phase. The indentation-size effects and the applicability of the rule of mixtures of the constituent phases to extract the overall hardness of the composite are investigated. In the arc-melt state the dendrites are harder than the nanostructured eutectic matrix. Since HPT forces the material to plastically deform without fracture, the nanostructured eutectic matrix undergoes significant work hardening during HPT. The contribution of the local hardening of each phase to the overall mechanical response in the HPT alloy is discussed.