Metallic glasses are materials composed of metal components but lack long-range order. The latter renders metallic glasses unique in mechanical properties such as high hardness combined with high elastic limit. Since they exhibit also a low ductility caused by a very localized plastic deformation it is one of the challenging aims to fully understand the structure-property relationship in order to find ways and processes for improvements. It could be shown that rejuvenation of the disordered atomic structure to a higher energy state can impact the mechanical properties of the processed materials considerably. In order to obtain and control the rejuvenated amorphous structure different routes can be successful e.g. by irradiation or thermomechanical processing. In this lecture I will focus on recent results obtained by electron irradiation and severe plastic deformation. In the case of electron irradiation amorphous thin TiAl films were processed during in-situ TEM tensile straining, whereas CuZr based metallic glasses were rejuvenated as a bulk material via high-pressure torsion. To elucidate the correlation of the mechanical properties and structural state, various experimental methods including transmission electron microscopy, Synchrotron X-ray diffraction, nanoindentation, differential scanning calorimetry and atomic force microscopy were applied to characterize the processed samples. In addition, molecular dynamics simulations facilitate (i) to get deeper insights into the atomic structure and its changes during irradiation and deformation, and (ii) to improve our understanding in the structure-property relationship of amorphous materials.
Financial support by the Austrian Science Fund FWF: I1309 is acknowledged.
|Dr Christian Rentenberger
University of Vienna, Austria
After the seminar
(From left, Assoc. Prof. Matsuda, Dr Rentenberger, IROAST Director Hiyama)