Uniform strain high-pressure torsion (US-HPT): an approach to reduce strain gradients

Abstract

Based on the pioneering work of Erbel, we propose a simple modification of classical high-pressure torsion anvils that allows a strong reduction or even elimination of the inherent strain gradient in disk-shaped samples deformed by high-pressure torsion. This is realized by using an adapted anvil design, which entails a linearly varying depth of the anvil’s depression with the radius. In order to compare results of using the modified anvil design with classical flat anvils, a comparative study using high purity nickel was performed. The possible change in the strain gradient is assessed with hardness and microstructural investigations. The results prove that the strain gradient can be considerably reduced or even eliminated. The technical features of this technique, in the following termed as uniform strain high-pressure torsion (US-HPT), are presented with this feasibility study and practical limitations are discussed. Graphical abstract: (Figure presented.)