Topologically designed Mg alloys for biomedical applications

The tasks of the present proposal aim at the development of particular Magnesium (Mg) alloys, which in general are used for light-materials applications in mobility areas, which in the present project, however, are to be mainly applied in biomedical areas. Magnesium has been selected as this material provides an outstanding application potential due its high strength/density ratio, and due to its extraordinarily high biological and environmental compatibility. This potential is to be exploited by topology - mediated multilevel structural design of Mg-alloys. The biomedical applications of this project comprise the development of Mg-alloys for implants and prostheses with tunable biodegradability, while the mechanical properties are to remain sufficiently high to ensure short-time and sustainable healing processes. For the development of such optimum Mg materials the project brings together Slowenian and Austrian scientists with both a high expertise throughout the topic and a spectrum of modern methods of alloy synthesis, of micro- and nanocrystallisation and of heat treatment. For the control of materials structures and of their mechanical properties, only state-of-the-art characterization techniques will be applied. The systematics of experimental investigations will be supported by ab-initio und multiscale computer simulations of the synthesis as well as of the structural materials modifications of the materials. The project results promise a significant progress in the design of new Mg-alloys, in the understanding of their biodegradation in various environments, as well as in the development of new technologies for the production of those alloys, as these open new perspectives in sustainable life management.

Different biodegradable Mg-solid-solution alloys (Mg5Zn0.3Ca, Mg5Zn, Mg0.3Ca, Mg5Zn0.15Ca, and Mg5Zn0.15Ca0.15Zr) with the potential for slight precipitation formation have been severely plastically deformed at different temperatures and specifically thermally aged, with the aim at achieving high strength-good ductility-low stiffness-low biocorrosion, with respect to their use as temporary implants in the human body. The results were as follows: (i) Strong enhancement of strength by up to a factor 2.5, and of fatigue strength by a factor 2 by low temperature processing & thermal treatment, but significant reductions of ductility were obtained down to 5% and less (ii) Moderate enhancement of strength by up to a factor 1.8 but still preserved ductility of about 15 %, increase of fatigue strength by 20% , all features by means of high temperature processing & thermal treatment None of these treatments (i), (ii) changed the low Young's modulus nor the low corrosion rates of the correspondingly selected initial alloys. Thus, at least with treatment (ii), a very effective way was found to significantly enhance both the strength and the ductility of Mg-alloys while the biomedically advantageous elastic and corrosion properties could be preserved. It should be noted that precipitation hardening - as the declared goal of this project - only contributed by about 20% to the enhancement of strength, while the increase from deformation induced dislocations and especially that from vacancy agglomerates almost achieved the 80% left.