Coarse to Fine: The Role of Severe Plastic Deformation in Advancing Titanium-Based Medical Implants - A Comprehensive Review

This paper describes severe plastic deformation ( SPD) procedures, which are utilized to form an ultrafine-grained structure in metallic biomaterials. During the SPD process, a solid material sample is subjected to very high loads without a significant change in sample dimensions. In the present work, the high-pressure torsion (HPT) process, as one of the SPD techniques, which achieves a high degree of deformation and ensures refinement of the microstructure, will be discussed in more detail. Considering that grain size control is accepted as a method to obtain materials with desired characteristics, an overview of the properties of ultrafine-grained titanium-based biomaterials to be used in medicine is given. Moreover, particular attention is dedicated to the influences of HPT process parameters, primarily hydrostatic pressure, and number of revolutions during torsion, on the grain size and physical and mechanical characteristics (modulus of elasticity, microhardness, and tensile properties), corrosion resistance, and biocompatibility of the titanium-based biomaterials. A review of the literature indicates that titanium-based materials obtained by the SPD process show improved mechanical and physical properties without losing biocompatibility and corrosion resistance, which suggests that these methods of obtaining implants are something that should be further developed in the future.