Processing of CP-Ti by high-pressure torsion and the effect of surface modification using a post-HPT laser treatment

Abstract

Commercial purity titanium (CP-Ti) was processed by high-pressure torsion (HPT) with various numbers of turns (N = 1, 10 and 20). The hardness of the CP-Ti increased with an increasing number of HPT turns due to grain refinement. Tensile testing showed that the HPT-processed 10 turns sample had low ductility and high strength but the ductility may be improved through post-HPT short-term annealing at carefully selected temperatures. Some HPT-processed samples were laser surface-treated with different laser powers and scanning speeds. The surface roughness of the laser-textured samples increased with increasing laser power and led to a lower contact angle which signifies an increased hydrophilicity. After a holding time of 13 days, the samples underwent a hydrophilic-to-hydrophobic transformation as the contact angle increased to as much as 129 o. It is concluded that laser surface texture processes are capable of controlling the hydrophilic / hydrophobic properties of ultra-fine grained CP-Ti.

Microstructural Evolution and Mechanical Properties of Ultrafine‐Grained Ti Fabricated by Cryorolling and Subsequent Annealing

“…[38] In addition, the tensile stresses of the samples drop during annealing for both the cryorolled and RTR-processed sheets and the rate of decrease is higher for the samples subjected to RTR. The engineering failure strains of the cryorolled sheets change slightly during annealing from 250 to 350 C. This is similar to HPT-processed nanocrystalline CP Ti during annealing where the engineering strength is reduced significantly, whereas the failure engineering strain changes only slightly with increasing annealing temperatures from 200 to 700 C. [39] Generally, the grain size determines the mechanical properties of UFG CP Ti and it was shown earlier that the strength of UFG Ti directly follows the Hall-Petch relationship. [10] Inspection of Figure 4 shows that the grain size of samples subjected to cryorolling and annealing is smaller than after RTR and annealing.…”

“…This is similar to HPT‐processed nanocrystalline CP Ti during annealing where the engineering strength is reduced significantly, whereas the failure engineering strain changes only slightly with increasing annealing temperatures from 200 to 700 °C. [ 39 ]…”

Nanostructured Bulk Titanium with Enhanced Properties—Strategies and Prospects for Dental Applications

“…[19,20] Multistage SPD is used to obtain ultrafine-grained (UFG) or even nanostructured Ti products. Equal channel angular pressing (ECAP), [21] high-pressure torsion (HPT), [22,23] and hydrostatic extrusion (HE) [24,25] are commonly used methods to refine grains in CP-Ti. Recent years have seen great progress in those deformation techniques as well as in the characterization of UFG/nano Ti products, especially for biomedical applications (Figure 1).…”

Advanced Materials for Mechanical Engineering: Ultrafine‐Grained Alloys with Multilayer Coatings

“…Similar results showing an improvement of tribological properties and wear resistance in samples of nanostructured grade 2 Ti with a TiN coating were demonstrated in other reports. [ 19,22 ]…”

“…[ 15–18 ] The formation of a UFG structure in the material of a part may have a significant effect on the physicochemical and mechanical properties of a modified layer or coating. [ 19–22 ] Thus, as a result of such a combined treatment, the service properties may be generally enhanced, whereas this same result cannot be achieved using only metal nanostructuring or surface modification. Such a synergetic approach to the enhancement of performance properties opens prospects for designing structural materials for parts that will operate in extremely severe environments.…”