Magnesium alloys have gained increasing interest in the past years due to their potential as implant materials. This interest is based on the fact that magnesium and its alloys are degradable during their time of service in the human body. Moreover magnesium alloys offer a property profile that is very close or even similar to that of human bone. The chemical composition triggers the resulting microstructure and features of degradation. In addition the entire manufacturing route is having an 2 influence on the morphology of the microstructure after processing. Therefore composition and manufacturing route have to be chosen carefully with regard to the requirements of an application. This paper will discuss the influence of composition and heat treatments on microstructure, mechanical properties and corrosion behaviour of cast Mg-Gd alloys. Recommendations will be given for the design of future degradable magnesium based implant materials.

The development of secondary magnesium alloys requires a completely different concept compared with standard alloys which obtain their corrosion resistance by reducing the levels of impurities below certain alloy and process depending limits. The present approach suitable for Mg-Al based cast and wrought alloys uses a new concept replacing the ß-phase by τ-phase, which is able to incorporate more impurities while being electrochemically less detrimental to the matrix. The overall experimental effort correlating composition, microstructure and corrosion resistance was reduced by using thermodynamic calculations to optimise the alloy composition. The outcome is a new, more impurity tolerant alloy class with a composition between the standard AZ and ZC systems having sufficient ductility and corrosion properties comparable to the high purity standard alloys.

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With the development of new heat resistant magnesium alloys, the automotive industry has introduced several parts to the drive train. The rising number of large magnesium components will result in a higher quantity of automotive post consumer scrap. It was the aim of this work to find a reasonable alloy system for the recycling of these magnesium drive train components. A matrix of potential recycling alloys based on the magnesium alloy AM50 was prepared via permanent mould casting. The materials were investigated via tensile testing, creep tests and salt spray tests. Three alloys were selected for processing via high pressure die casting and the tests were repeated on the new materials. A promising system for recycling has been isolated and will be investigated more deeply for the influence of impurities. magnesium recycling, end-of-life vehicles, recycling alloy, post consumer scrap

The increasing use of magnesium castings for automotive components and the number of newly developed alloys raise the question of suitable recycling processes. Remelting offers a high potential of energy saving and thereby improves the live cycle balance of magnesium components. Effective recycling processes are likely to involve the mixing of different alloys but little is known about the interaction of alloying elements. In order to approach this issue, the influence of strontium, silicon and calcium on phase formation and mechanical properties of magnesium alloy AM50 has been investigated.After strontium addition, X-ray diffraction demonstrated the formation of the Al 4 Sr-and the Mg 17 Sr 2 -phase.However, after simultaneous alloying with strontium, silicon and calcium the ternary Zintl-phase Compared to the two strontium-containing phases, precipitates of the ternary Zintl-phase exhibit a rather compact morphology. This results in a higher elongation-at-fracture under tensile stress.

The increasing use of heat resistant magnesium alloys for automotive applications is expected to influence the chemical composition of upcoming post consumer scrap. Therefore it would be useful to define alloys that resemble the future composition of the material. For this purpose a matrix of potential recycling systems has been set up. AM50 was used as a base material to which decisive amounts of strontium, silicon and calcium were added. The basic heat resistant alloy systems AJ, AS, and AX have been investigated closely. This work deals with combinations of the three above mentioned elements. Some essential observations shall be presented concerning the development of the microstructure and its influence on the materials properties. For combined additions of strontium, silicon and calcium the formation of a new ternary phase has been observed. The compound has a positive influence on the fracture elongation and the corrosion rate in the salt spray test.

Six alloys were prepared by high pressure die casting in order to develop a magnesium secondary alloy system for mixed post-consumer scrap. The alloys were investigated with regard to intermetallic phases, grain structures, mechanical properties and performance in the salt spray test. The results are discussed in relation to the characteristics of the high pressure die casting process. The effect of contamination by copper and compensation for this effect by the addition of zinc 1 were thoroughly investigated for the most promising alloy. It is evident that the alloying elements strontium, silicon and calcium are incorporated in the ternary Zintl phase Sr 6.33 Mg 16.67 Si 13 , while aluminium, zinc, copper and magnesium form the tauphases Mg 32 (Al x ,Cu 1-x) 49 and Mg 32 (Al,Zn) 49. The two tau-phases can merge due to isomorphism. Mg 32 (Al,Zn) 49 ensures improved corrosion resistance after the addition of copper.

Magnesium applications for structural components in the automotive industry are constantly rising. This is based on the recent development of new alloys, new fabrication processes, and the ambition of car manufacturers to reduce the vehicles weight and CO2 emissions according to the EU and US policy [1, 2]. A rising quantity of magnesium per vehicle leads to a rising quantity of scrap which needs to be recycled according to the European Directive on end-of life vehicles [3]. So far post consumer scrap has not been used for structural parts. But since the metal is still expensive compared to aluminium or steel, and remelting saves more than 90 % of the energy for primary production, magnesium recycling will significantly contribute to cost savings. In comparison to steel or aluminium a recycling cycle for magnesium has not yet been established. Concerning post consumer scrap it is likely that many vehicles will end up in the shredder fraction or at least will be mixed up instead of being dismantled and separated according to their alloy. Thus it is reasonable to define secondary alloys which allow the use of post consumer scrap for structural applications. Creep resistant alloys have the potential of a broad application concerning the weight of the components and therefore a secondary alloy would be reasonable. The aim of this work is to examine a row of AM50-based alloys, modified with additions of Sr, Ca, and Si due to the importance of these elements to increase creep resistance and their usage in modern magnesium alloys. The corrosion properties as well as the mechanical properties and microstructures are investigated in the as-cast and annealed condition. Salt spray tests (using 5 % NaCl) and electrochemical corrosion methods are applied to investigate the corrosion properties which are then compared to the unmodified AM50. Tensile and compression tests at temperatures ranging from 20 °C to 200 °C are applied to investigate the mechanical properties.