Perspectives of scaling up of severe plastic deformation: a case of High Pressure Torsion Extrusion

A demand for cheap and simple methods of processing of nano crystalline materials attracted attention to metal forming techniques allowing introduction of large strains into metallic materials. Thanks t o that a new scientific field, "M ate rials by severe plastic deformation ", had been born and became an important segment of material science. High pressure torsion (HPT) is the most effective SPD method in respect of the microstructure refinement and processing costs. Despite attractive mechanical and physical properties demonstrated by HPT-processed materials, this technique cannot be used in industry due to a limited size of processed samples. To overcome this problem, a plenty of SPD methods, allowing processing of large-scale billets, was developed. However, none of them has found any application in industry, except a few cases, which are rather exceptions that confirm the rule. This overview is an attempt to analyze the reasons why industrial players remain reluctant t o use SPD in technological processes. For this purpose, the advantages and drawbacks of the High Pressure Torsion Extrusion method of SPD are regarded.