Abstract
The phase and microstructure formation as well as mechanical properties of the rapidly solidified Mg67Ag33 (at. %) alloy were investigated. Owing to kinetic constraints effective during rapid cooling, the formation of equilibrium phases is suppressed. Instead, the microstructure is mainly composed of oversaturated hexagonal closest packed Mg-based dendrites surrounded by a mixture of phases, as probed by X-ray diffraction, electron microscopy and energy dispersive X-ray spectroscopy. A possible non-equilibrium phase diagram is suggested. Mainly because of the fine-grained dendritic and interdendritic microstructure, the material shows appreciable mechanical properties, such as a compressive yield strength and Young’s modulus of 245 ± 5 MPa and 63 ± 2 GPa, respectively. Due to this low Young’s modulus, the Mg67Ag33 alloy has potential for usage as biomaterial and challenges ahead, such as biomechanical compatibility, biodegradability and antibacterial properties are outlined.
Highlights
Mg and its alloys are known to be employed as structural materials for light-weight applications, due to their low density [1,2]
Mg-based alloys show low Young’s modulus close to that of bone and are potential candidates as load-bearing implant materials. Such biomaterials suffer from the formation of biofilms on their surface, due to colonialization of bacteria
A substantial fraction of Ag was alloyed to hcp Mg, since Ag has a distinct antibacterial effect entailing the significant reduction in biofilm-formation
Summary
Mg and its alloys are known to be employed as structural materials for light-weight applications, due to their low density [1,2]. Mg-based alloys show poor strength and plastic deformation, at low temperatures [3]. The reason behind this is the limited number of slip systems. Twinning is a further deformation mode extensively investigated and which entails low temperature anisotropy and strain hardening in Mg-based alloys, too [2,3,4]. Effective measures for improving their strength and, modulating their microstructure are diverse and encompass, for instance, processing at higher cooling rates to obtain finer grained microstructures or just by replacing rather adding further alloying elements [1,3,4,5]. Latter strategy can be described as alloy-design resulting in altered phase formation involving evolution of desired precipitations [6] and led to the development of a series of commercially employed alloys [7]
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