Production of Ultrafine‑Grained Titanium with Suitable Properties for Dental Implant Applications by RS‑ECAP Process

Abstract

The only problem of pure titanium for dental implant applications is its low strength and failure under different loadings. Various studies have shown that the utilization of severe plastic deformation processes such as Equal Channel Angular Pressing (ECAP), through reducing the grain size of titanium, can improve not only its mechanical properties but also its corrosion resistance and biocompatibility. In this study, a reduced-scale ECAP process on pure titanium was performed to investigate the effects of scale reduction. An ECAP die was made with an internal diameter of d = 3 mm, and the tests were performed at 250 °C for several number of passes. It was found out that after 10 passes of reduced-scale ECAP, the grain size of CP Ti had strongly been reduced from 25 to 122 nm. This sharp reduction in grain size resulted in an increase in micro-hardness from 205.5 to 321.3 Hv. Moreover, Nano-hardness test results showed that after 10 passes, the hardness of titanium increased from 2461 to 3812 MPa, and simultaneously elastic modulus decreased from 108.1 to 94.8 GPa. Such reduction of elastic modulus of titanium for dental implant applications decreased stress-shielding and jaw bone damages. According to the results of this research, after RS-ECAP process the strength of titanium is greatly increased and its elastic modulus is reduced, which are desirable features for dental implant applications. Since dental implants are small in size, the reduced ECAP process (d = 3–5 mm) can produce titanium implants with improved properties.