الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Although zinc (Zn) is one of the elements with the greatest potential for biodegradable uses, pure Zn does not have the ideal mechanical or degrading properties for orthopedic applications. Pure Zn and two hypoeutectic Zn-Mg alloys, with 0.68 and 1.89 wt.% Mg content, were prepared via casting and conventional extrusion at 200 ºC with a reduction ratio of 16:1. The mechanical performance (strengths and elongations) was discussed in terms of the microstructural features (grain size distribution and second phase and twining formation), and texture. Zn-0.68Mg alloy exhibited a satisfactory combination of strength and ductility with an ultimate tensile strength (UTS) of 414.5 ± 17.6 MPa, yield tensile strength (YTS0.2%) of 325.9 ± 8.7 MPa and a uniform elongation to failure (Ef) of 16.3 ± 2.7%. The synergy between strength and ductility achieved by the Zn-0.68Mg alloy was as a consequence of low extrusion temperature and moderate extrusion ratio which resulted in a partial dynamic recrystallization and subsequently the development of a bimodal grain structure with weakening in the fiber basal texture and the arising of the pyramidal <c+a> texture. Compared to Zn-0.68Mg, pure Zn comprised very large grains which resulted in relatively low strength and ductility while Zn-1.89Mg alloy witnessed an uneven distribution in the secondary phase which resulted in a slightly higher strength and much lower Ef. The governing mechanisms of strength and ductility of pure and alloyed Zn were studied through detailed investigations analysis using the Scanning Electron Microscope (SEM) with Electron Backscatter Diffraction (EBSD). Furthermore, a poly methyl methacrylate (PMMA) layer of a few micrometers thick coat was applied on the alloys by the ”grafting-from” technique to decrease the alloys’ in-vitro biodegradation rate. The potentio-dynamic corrosion test stated that the corrosion current density decreases from 4.5E-04 (naked Zn-0.68Mg alloy) to 9.4E-06 mA/cm2 (PMMA coated alloy). The static immersion test confirmed the positive effect of PMMA grafting on the biodegradation of the alloy as the corrosion rate decreases from 0.43 to 0.25 mm/y after 720 h of immersion. Such performance of the PMMA grafted alloy was the motivation to design a 66% porous structure resembling the orthopedic scaffolds and examine its mechanical and corrosion properties. The porous structure exhibited a yield compressive strength of about 32 MPa and a corrosion rate of 1.24 mm/y when immersed in SBF for 720 h, this corrosion rate decreased to 0.49 mm/y after PMMA coating. The aim of the current work is to study the mechanism through which the microstructure and PMMA grafting could enhance the performance of biodegradable Zn-Mg alloy.