Recent developments in the application of the interdependence model of grain formation and refinement

The Interdependence model will be briefly reviewed and then applied to two different casting situations. One is the solidification of Mg–Al–Sm alloys to determine the optimum composition for achieving a fine as-cast grain size. Because the size range of the nucleant particles can be measured, the key factors describing the potency of the particle can be calculated providing a more complete description of the grain formation mechanisms operating for this alloy. This approach should be relevant for other Mg–Al–RE alloys. The other casting situation is where the melt of an AM60-AlN nanoparticle composite was treated ultrasonically producing a fine grain size on solidification. The limitations to grain size reduction by nanoparticles are discussed in terms of the Interdependence and Free Growth models

Ultrasound assisted casting of an AM60 based metal matrix nanocomposite, its properties, and recyclability

An AM60 magnesium alloy nanocomposite reinforced with 1 wt % of AlN nanoparticles was prepared using an ultrasound (US) assisted permanent-mould indirect-chill casting process. Ultrasonically generated cavitation and acoustic streaming promoted de-agglomeration of particle clusters and distributed the particles throughout the melt. Significant grain refinement due to nucleation on the AlN nanoparticles was accompanied by an exceptional improvement in properties: yield strength increased by 103%, ultimate tensile strength by 115%, and ductility by 140%. Although good grain refinement was observed, the large nucleation undercooling of 14 K limits further refinement because nucleation is prevented by the formation of a nucleation-free zone around each grain. To assess the industrial applicability and recyclability of the nanocomposite material in various casting processes, tests were performed to determine the effect of remelting on the microstructure. With each remelting, a small percentage of effective AlN nanoparticles was lost, and some grain growth was observed. However, even after the third remelting, excellent strength and ductility was retained. According to strengthening models, enhanced yield strength is mainly attributed to Hall-Petch strengthening caused by the refined grain size. A small additional contribution to strengthening is attributed to Orowan strengthening

Advanced metal matrix nanocomposites

10.3390/met9030330Metals9333

Microstructure, mechanical properties and creep of magnesium alloy Elektron21 reinforced with AlN nanoparticles by ultrasound-assisted

International audienc

The ExoMet project: EU/ESA research on high-performance light-metal alloys and nanocomposites

The performance of structural materials is commonly associated with such design parameters as strength and stiffness relative to their density; a recognized means to further enhance the weightsaving potential of low-density materials is thus to improve on their mechanical attributes. The European Community research project ExoMet that started in mid-2012 targets such highperformance aluminum- and magnesium-based materials by exploring novel grain refining and nanoparticle additions in conjunction with melt treatment by means of external fields (electromagnetic, ultrasonic, and mechanical). These external fields are to provide for an effective and efficient dispersion of the additions in the melt and their uniform distribution in the as-cast material. The consortium of 27 companies, universities, and research organizations from eleven countries integrates various scientific and technological disciplines as well as application areas—including automotive, aircraft, and space. This paper gives an overview of the project, including its scope for development and organization. In addition, exemplary results are presented on nanoparticle production and characterization, mixing patterns in metal melts, interface reactions between metal and particles, particle distribution in the as-cast composite materials, and mechanical properties of the as-cast composite materials. The application perspective is considered as well

Waste Mg-Al based alloys for hydrogen storage

Magnesium has been studied as a potential hydrogen storage material for several decades because of its relatively high hydrogen storage capacity, fast sorption kinetics (when doped with transition metal based additives), and abundance. This research aims to study the possibility to use waste magnesium alloys to produce good quality MgH2. The production costs of hydrogen storage materials is still one of the major barriers disabling scale up for mobile or stationary application. The recycling of magnesium-based waste to produce magnesium hydride will significantly contribute to the cost reduction of this material. This study focuses on the effect of different parameters such as the addition of graphite and/or Nb2O5 as well as the effect of milling time on the material hydrogenation/de-hydrogenation performances. In addition, morphology and microstructural features are also evaluated for all the investigated materials