Laser textured Ti-6Al-7Nb alloy for biomedical applications: An investigation of texturing parameters on surface properties.

Surface texturing with a laser beam is an effective method for engraving on the surface of biomaterials. The four laser texturing parameters (scan speed, frequency, fill spacing, and pulse width) having five different values were associated with five different scanning strategies (scan direction), and a total of 25 texturing conditions were tested on the Ti-6Al-7Nb alloy surface. The surface roughness and wettability of the textures created with a 20 W nanosecond fiber laser with a wavelength of 1064 nm on the surface of Ti-6Al-7Nb biocompatible alloy were investigated. Laser texturing parameters were analyzed according to the lowest surface roughness and a hydrophilic surface by creating L25 orthogonal arrays. The surface roughness values ranged between 2 and 26 µm. The lowest surface roughness with a value of 2.21 µm was achieved when the texture was processed with a frequency of 150 kHz, a fill spacing of 0.02 mm, a scan speed of 800 mm/s, a pulse width of 250 ns, and a cross-hatch strategy of 0°/90°. Considering the wettability test results, it was revealed that most of the textured surfaces have super hydrophilic and hydrophilic characteristics except the surface with a contact angle of 92.93°. The relevant surface was textured with 75 kHz frequency, 1000 mm/s scan speed, 0.05 mm fill spacing, 200 ns pulse width, and 45°/-45° cross-hatch strategy.

Mechanical, corrosion, nanotribological, and biocompatibility properties of equal channel angular pressed Ti-28Nb-35.4Zr alloys for biomedical applications.

This study systematically investigated the effect of equal channel angular pressing (ECAP) on the microstructure, mechanical, corrosion, nano-tribological properties and biocompatibility of a newly developed ß Ti-28Nb-35.4Zr (hereafter denoted TNZ) alloy. Results indicated that ECAP of the ß TNZ alloy refined its microstructure by forming ultrafine grains without causing stress-induced phase transformation, leading to formation of a single ß phase. The ECAP-processed TNZ alloy exhibited a compressive yield strength of 960 MPa, and high plastic deformation capacity without fracturing under compression loads. Potentiodynamic polarization tests revealed the higher tendency of ECAP-processed TNZ alloys to form passive oxide films on its surface, which exhibited a lower corrosion rate (0.44±0.07 µm/y) in Hanks' balanced salt solution compared to its as-cast counterpart (0.71±0.10 µm/y). Nanotribological testing also revealed higher resistance of the ECAP-processed TNZ alloy to abrasion, wear and scratching, when compared to its as-cast counterpart. Cytocompatibility and cell adhesion assessments of the ECAP-processed TNZ alloys showed a high viability (111%) of human osteoblast-like SaOS2 cells after 7 d of culturing. Moreover, the ECAP-processed TNZ alloy promoted adhesion and spreading of SaOS2 cells, which exhibited growth and proliferation on alloy surfaces. In summary, significantly enhanced mechanical, corrosion, and biological properties of ECAP-processed TNZ alloy advocate its suitability for load-bearing implant applications. STATEMENT OF SIGNIFICANCE: Equal channel angular pressing (ECAP) provides a unique combination of enhanced mechanical and functional properties of materials by optimizing their microstructures and phase transformations. This study investigated the mechanical, nano-tribological, corrosion, and biocompatibility properties of a newly developed ß Ti-28Nb-35.4Zr (TNZ) alloy processed via ECAP. Our findings indicated that ECAP of the ß TNZ alloy refined its microstructure by forming ultrafine grains without causing stress-induced phase transformation. Compared to its as-cast counterpart, ECAP-processed TNZ exhibited significantly enhanced compressive yield strength, plastic deformation capacity, hardness, wear, and corrosion properties. Moreover, in vitro cytocompatibility and cell adhesion studies revealed high cellular viabilities, growth and proliferation of osteoblast-like SaOS2 cells on the ECAP-processed TNZ alloy.

Effect of thermomechanical treatment on the mechanical and microstructural evolution of a ß-type Ti-40.7Zr-24.8Nb alloy.

In this study, the microstructural evolution and mechanical properties of a newly developed Ti-40.7Zr-24.8Nb (TZN) alloy after different thermomechanical processes were examined. As-cast TZN alloy plates were solution-treated at 890 °C for 1 h, after which the thickness of the alloy plates was reduced by cold rolling at reduction ratios of 20%, 56%, 76%, and 86%. Stress-induced α" formation, {332} <113> ß mechanical twinning, and kink band formation were observed in the cold-rolled TZN alloy samples. In the TZN sample after cold rolling at the 86% reduction ratio plus a recrystallization annealing at 890 °C for 1 h, the deformation products of a stress-induced α" phase, {332}<113> ß mechanical twinning, and kink bands disappeared, resulting in a fine, equiaxed single ß phase. The alloy samples exhibited elongation at rupture ranging from 7% to 20%, Young's modulus ranging from 63 to 72 GPa and tensile strength ranging from 753 to 1158 MPa. The TZN alloy sample after cold rolling and recrystallization annealing showed a yield strength of 803 MPa, a tensile strength of 848 MPa, an elongation at rupture of 20%, and an elastic admissible strain of 1.22%, along with the most ductile fractures during tensile testing.

An investigation of the mechanical and microstructural evolution of a TiNbZr alloy with varied ageing time.

Alloys comprised of the highly biocompatible elements titanium, niobium and zirconium have been a major focus in recent years in the field of metallic biomaterials. To contribute to the corpus of data in this field, the current paper presents results from a thorough microstructural and mechanical investigation of Ti-32Nb-6Zr subjected to a variety of ageing treatments. The presented alloy was stabilized to the higher temperature, body-centred cubic phase, showing only minimal precipitation on prolonged ageing, despite the presence of nanoscaled spinodal segregation arising from the Nb-Zr interaction. It further showed excellent mechanical properties, with tensile yield stresses as high as 820 MPa and Young's moduli as low as 53 GPa. This leads to the ratio of strength to modulus, also known as the admissible strain, reaching a maximum of 1.3% after 6 hours ageing. These results are further supported by similar measurements from nanoindentation analysis.

Deformation mechanism and mechanical properties of a thermomechanically processed ß Ti-28Nb-35.4Zr alloy.

The effects of thermomechanical treatment on the microstructure and mechanical properties of a newly developed ß titanium alloy, i.e., Ti-28Nb-35.4Zr (wt%, hereafter denoted Ti-Nb-Zr) were investigated. The as-cast Ti-Nb-Zr alloy was subjected to solution treatment at 890°C for 1h, after which its thickness was reduced by 20%, 56%, 76%, and 86% via cold rolling. Results indicated that annealing at 890°C for 1h after cold rolling at a thickness reduction ratio of 86% resulted in a phase transformation from the stress-induced α" and ω into ß, leading to a recrystallization of a uniform single ß phase. The recrystallized Ti-Nb-Zr alloy exhibited a tensile strength of 633MPa, Young's modulus of 63GPa, and elongation at rupture of 13%, respectively. The cold rolled specimens showed a higher Young's modulus than that of the recrystallized specimen due to the stress-induced ω phase. Transmission electron microscopy (TEM) analysis revealed that ω, α" and ß phases co-existed in the microstructure of the cold-rolled specimens. Electron backscatter diffraction analysis revealed that the deformation mechanisms during thermomechanical processing included kink bands, {332}<113> twins and shear bands; and the predominant deformation mechanism depended on the extent of CR deformation.

New Ti-Ta-Zr-Nb alloys with ultrahigh strength for potential orthopedic implant applications.

In this study, a new series of Ti-Ta-Zr-Nb alloys (Ti-38.3Ta-22Zr-8.1Nb, Ti-38.9Ta-25Zr-5Nb, Ti-39.5Ta-28Zr-2.5Nb, designated TTZN-1, TTZN-2, TTZN-3, respectively) with high elastic strain and high mechanical strength have been developed as alternatives to conventional orthopedic implant materials. The TTZN alloys have been designed using the electronic parameters of the alloying elements, combined with the approaches of the electron-to-atom ratio (e/a) and molybdenum equivalence (Moeq). X-ray diffraction analysis has revealed that all the TTZN alloys are comprised of a single ß phase, however, transmission electron microscopy observations revealed that ω and ß phases co-existed in the microstructure. The compression strains of the TTZN alloys range from 22% to 36% and the compression strength from 1787 to 1807MPa. The tensile Young's modulus, elastic strain and yield strength are 73.12 ± 4.43, 74.98 ± 2.19 and 76.62 ± 2.38 (GPa); 1.57 ± 0.27, 1.25 ± 0.27 and 1.29 ± 0.16 (%); and 1107.42 ± 144.68, 932.11 ± 195.22 and 953.58 ± 120.76MPa for TTZN-1, TTZN-2 and TTZN-3, respectively. Further, all the TTZN alloys exhibit excellent cytocompatibility as their cell adhesion density is higher than that of CP-Ti. This study demonstrates that these TTZN alloys can be anticipated to be promising candidate for orthopedic implant materials due to their high mechanical strength and high elastic strain.

Novel Ti-Ta-Hf-Zr alloys with promising mechanical properties for prospective stent applications.

Titanium alloys are receiving increasing research interest for the development of metallic stent materials due to their excellent biocompatibility, corrosion resistance, non-magnetism and radiopacity. In this study, a new series of Ti-Ta-Hf-Zr (TTHZ) alloys including Ti-37Ta-26Hf-13Zr, Ti-40Ta-22Hf-11.7Zr and Ti-45Ta-18.4Hf-10Zr (wt.%) were designed using the d-electron theory combined with electron to atom ratio (e/a) and molybdenum equivalence (Moeq) approaches. The microstructure of the TTHZ alloys were investigated using optical microscopy, XRD, SEM and TEM and the mechanical properties were tested using a Vickers micro-indenter, compression and tensile testing machines. The cytocompatibility of the alloys was assessed using osteoblast-like cells in vitro. The as-cast TTHZ alloys consisted of primarily ß and ω nanoparticles and their tensile strength, yield strength, Young's modulus and elastic admissible strain were measured as being between 1000.7-1172.8 MPa, 1000.7-1132.2 MPa, 71.7-79.1 GPa and 1.32-1.58%, respectively. The compressive yield strength of the as-cast alloys ranged from 1137.0 to 1158.0 MPa. The TTHZ alloys exhibited excellent cytocompatibility as indicated by their high cell viability ratios, which were close to that of CP-Ti. The TTHZ alloys can be anticipated to be promising metallic stent materials by virtue of the unique combination of extraordinarily high elastic admissible strain, high mechanical strength and excellent biocompatibility.

Development of Ti-Nb-Zr alloys with high elastic admissible strain for temporary orthopedic devices.

A new series of beta Ti-Nb-Zr (TNZ) alloys with considerable plastic deformation ability during compression test, high elastic admissible strain, and excellent cytocompatibility have been developed for removable bone tissue implant applications. TNZ alloys with nominal compositions of Ti-34Nb-25Zr, Ti-30Nb-32Zr, Ti-28Nb-35.4Zr and Ti-24.8Nb-40.7Zr (wt.% hereafter) were fabricated using the cold-crucible levitation technique, and the effects of alloying element content on their microstructures, mechanical properties (tensile strength, yield strength, compressive yield strength, Young's modulus, elastic energy, toughness, and micro-hardness), and cytocompatibilities were investigated and compared. Microstructural examinations revealed that the TNZ alloys consisted of ß phase. The alloy samples displayed excellent ductility with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, elongation at rupture, and elastic admissible strain were measured in the ranges of 704-839 MPa, 62-65 GPa, 9.9-14.8% and 1.08-1.31%, respectively. The tensile strength, Young's modulus and elongation at rupture of the Ti-34Nb-25Zr alloy were measured as 839 ± 31.8 MPa, 62 ± 3.6 GPa, and 14.8 ± 1.6%, respectively; this alloy exhibited the elastic admissible strain of approximately 1.31%. Cytocompatibility tests indicated that the cell viability ratios (CVR) of the alloys are greater than those of the control group; thus the TNZ alloys possess excellent cytocompatibility.