DFG project Development of Fine-Grained Magnesium Alloys Using by qnq11541


									GKSS Forschungszentrum , Saturday, 11-Oct-2008 23:09:12 CEST

    DFG project: “Development of Fine-Grained Magnesium Alloys Using Nanoscale Grain Refiners”

DFG project: “Development of Fine-Grained Magnesium Alloys Using Nanoscale
Grain Refiners”
Prof. J. Estrin, Institute of Materials Research and Technology, Clausthal University of Technology

Dr. N. Hort, GKSS Forschungszentrum Geesthacht GmbH

Dr. H. Kaufmann, Leichtmetallkompetenzzentrum Ranshofen, Austria

There is currently great demand for lightweight engineering materials in order to meet the requirements of
industry and governments. This is essentially due to the need to reduce weight and thus cut fuel consumption
and pollutant emissions. This requires not only enhanced design guidelines and production processes but
also, and most important, use of lightweight materials including magnesium alloys. Today, the latter is
predominantly used in cast form, with the result that research is now focusing on enhancing the properties of
the cast alloys currently available and on extending their range. To be suitable for further processing such as
thixoforming, cast alloys must have a globular structure. At the same time, work is also being carried out on the
development of wrought alloys. Grain refinement provides advantages in terms of ductility, which is why
additives are necessary as grain refiners. Similarly, it has been shown that fine-grained magnesium alloys
produced in dead-mould and continuous casting have enhanced static and dynamic material properties. This
is because the fine grain hampers twinning, thereby reducing mechanical anisotropy and permitting ductile
forming at moderate temperatures. The aim of the current project is to develop fine-grained magnesium alloys
by alloying new nanoscale particles with conventional alloys such as AZ31, AZ91 and MEZ and then casting
them using casting processes with different cooling rates. To ensure that the nanoparticles are dispersed
throughout the molten metal, a precursor material with a high nanopowder content is added to the melt before
the material is cast. In this process, the particles in the new material function as a heterogeneous nucleation
agent. The precursor material consists of inert nanoparticles, which are wet with the corresponding
magnesium alloy by means of a mechanical process in which they are ground together with a metal matrix
micropowder. The current project is investigating whether these particles deliver not only the expected grain
refinement but also increase the degree of dispersion. In addition, the possibility of increasing creep resistance
by means of the dispersoid also present in the matrix grain boundaries will be studied and optimised. Finally,
the project will investigate the influence of the nanoparticles on castability and material characteristics,
including forming properties at low temperatures.

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