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    Effect of Relative Density on Microstructure, Corrosion Resistance and Mechanical Performance of Porous Ti-20Zr Alloys Fabricated by Powder Metallurgy
    (Springer Heidelberg, 2024) Karakurt, Eyyup Murat; Huang, Yan; Kaya, Mehmet; Demirtas, Huseyin; Acikgoz, Abuzer; Demircan, Gokhan
    The microstructure, corrosion resistance and mechanical properties of a binary Ti-20Zr (at. %) alloy with differing porosities were investigated. The alloys were produced following a standard powder metallurgy with sintering at 1200 degrees C for 4, 6, and 8 h. A space holder agent was used to obtain two ranges of relative density, i.e., 74.8-89.3% and 54.6-66.7%. Metallographic examinations were conducted by using optical microscopy and scanning electron microscopy. The confirmation of chemical composition was performed by energy dispersive spectrometry and elemental mapping analysis. Electron backscatter diffraction analysis was conducted to investigate microstructure morphology. Phase identifications were detected by X-ray diffraction. Uniaxial compressive tests were carried out and also potentiodynamic polarization was employed to understand the corrosion performances of the alloys. Experimental results showed that the pore size and pore connectivity were able to be controlled by the sintering time and a fixed amount of space holder agent. The phase constituents of the alloys were characterized as a mixture of predominant hcp alpha phase and some distorted hcp alpha ' phase. As foreseen, the ultimate compressive strength and elastic modulus of the alloys increased with increasing relative density. Results of corrosion resistance revealed adding space holder reduced the polarization resistance of Ti-20Zr (at. %) sintered for 6 h from 15.4 to 14.09 omega. However, volume fraction of general porosity did not affect the microstructure of the alloys. In conclusion, the relative density of the alloys achieved in this study played a crucial role on the mechanical properties and corrosion properties.
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    Microstructural, Biomechanical, and In Vitro Studies of Ti-Nb-Zr Alloys Fabricated by Powder Metallurgy
    (Mdpi, 2023) Karakurt, Eyyup Murat; Cetin, Yuksel; Incesu, Alper; Demirtas, Huseyin; Kaya, Mehmet; Yildizhan, Yasemin; Tosun, Merve
    This study investigated the microstructures, mechanical performances, corrosion resistances, and in vitro studies of porous Ti-xNb-10Zr (x: 10 and 20; at. %) alloys. The alloys were fabricated by powder metallurgy with two categories of porosities, i.e., 21-25% and 50-56%, respectively. The space holder technique was employed to generate the high porosities. Microstructural analysis was performed by using various methods including scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and x-ray diffraction. Corrosion resistance was assessed via electrochemical polarisation tests, while mechanical behavior was determined by uniaxial compressive tests. In vitro studies, such as cell viability and proliferation, adhesion potential, and genotoxicity, were examined by performing an MTT assay, fibronectin adsorption, and plasmid-DNA interaction assay. Experimental results showed that the alloys had a dual-phase microstructure composed of finely dispersed acicular hcp & alpha;-Ti needles in the bcc & beta;-Ti matrix. The ultimate compressive strength ranged from 1019 MPa to 767 MPa for alloys with 21-25% porosities and from 173 MPa to 78 MPa for alloys with 50-56% porosities. Noted that adding a space holder agent played a more critical role in the mechanical behaviors of the alloys compared to adding niobium. The pores were largely open and exhibited irregular shapes, with uniform size distribution, allowing for cell ingrowth. Histological analysis showed that the alloys studied met the biocompatibility criteria required for orthopaedic biomaterial use.