Corrosion and Tribocorrosion Behavior of Ti-40Nb and Ti-25Nb-5Fe Alloys Processed by Powder Metallurgy
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NTRODUCTION
TI and its alloys have attracted attention in biomedical field due to their good corrosion resistance, high biocompatibility, lower Young’s modulus as compared to stainless steel and CoCrMo, and superior mechanical properties. Although a-type commercially pure Ti (cp-Ti) and a + b-type Ti-6Al-4V alloy s are commonly employed for implants, they exhibit some clinical IHSAN C¸AHA and ALEXANDRA ALVES are with the CMEMS-UMinho - Center for MicroElectroMechanical Systems, Universidade do Minho, Azure´m, 4800-058 Guimara˜es, Portugal. Contact e-mail: [email protected]; CATERINA CHIRICO is with the Universidad Carlos III de Madrid, Avda. Universidad, 30, 28911 Legane´s, Spain; ANA PINTO is with the CMEMS-UMinho Center for MicroElectroMechanical Systems, Universidade do Minho and also with the Universidade do Minho, Dept. Eng. Mecaˆnica, Azure´m, 4800-058 Guimara˜es, Portugal; SOPHIA TSIPAS and ELENA GORDO are with the Universidad Carlos III de Madrid and also with the Instituto ‘‘A´lvaro Alonso Barba’’, 30, 28911 Legane´s, Madrid, Spain; FATIH TOPTAN is with the CMEMSUMinho - Center for MicroElectroMechanical Systems, Universidade do Minho and also with the Universidade do Minho, Dept. Eng. Mecaˆnica and also with the IBTN/Br Brazilan Branch of the Institute of Biomaterials, Tribocorrosion and Nanomedicine, 17033-360 Bauru, SP, Brazil. Manuscript submitted July 12, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
concerns. As reviewed by Niinomi and Nakai,[1] the Young’s modulus of cp-Ti and a + b-type Ti-6Al-4V alloy (~ 110 GPa) is much higher than that of bone (20 GPa for cortical bone), which leads to the stress-shielding effect caused by the mismatch in Young’s modulus between the implant and surrounding bone, eventually resulting in bone resorption and aseptic implant loosening. Moreover, as the most popular Ti alloy, Ti-6Al-4V alloy has raised concerns as a result of Al and V ion release that may cause adverse effects on tissues. For instance, Hallab et al.[2] reported that Al and V ions reduced proliferation, viability, and affected the morphology of human peri-implant cells (osteoblast, fibroblasts, and lymphocytes). Therefore, b-type Ti alloys have gained attention due to their composition having non-toxic and allergy free b stabilizer elements including Nb, Zr, Mo, Ta as reported by Okazaki et al.,[3] better corrosion resistance compared to cp-Ti as shown by Bai et al. for b-type Ti-45Nb alloy,[4] and also lower Young’s modulus as reviewed by Gepreel and Niinomi[5] for different b-type Ti alloys. Fang et al.[6] has recently reviewed powder metallurgy (P/M) of Ti and pointed the limitation on implant fabrication by melt-wrought techniques due to high cost, complex fabrication, and subsequent machining processes where P/M offers an attractive alternative to
enable near-net-shape processing with adjusted chemical composition, or even porosity, that is known to be favorable for biological response and for further reduction on Young’s modulus. According to a review by Niinomi et al.,[7,8] among the b-type Ti
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