Highly ductile amorphous oxide at room temperature and high strain rate

Erkka J. Frankberg

The room temperature plasticity of ceramics is not considered possible as typically there are no active plasticity mechanism available. This is generally true for crystalline ceramics, but is not without exceptions. Already in 1950's Nobel laureate Percy Bridgman showed that under confined hydrostatic loading, even alpha alumina single crystals can be permanently deformed without fracture at room temperature. This led to the idea that it might be possible to also induce unconfined (bending, pulling, twisting) plastic deformation in a ceramic material. I begun studying this possibility 5 year ago and promising preliminary results led us to concentrate our studies on amorphous Al2O3 glass. We were expecting some plasticity in this structure, but the extent of plasticity totally surprised us. Moreover, although our experimental samples are microscopic, supercomputer simulations suggest that the viscous creep plasticity mechanism could extend to bulk glass materials. I will continue searching more glasses capable of plasticity at room temperature and our results will hopefully encourage others to study this phenomenon. If the phenomenon is found applicable on a larger scale, the discovery can very well change our perception on mechanical behavior of ceramic and glass materials. It is hard to imagine all the possible uses, but in general one could say that the applications for a ductile, ultra-high strength and light material are boundless in engineering. Glasses in particular have also functional properties ranging from dielectrics to tuned semiconductors coupled with visible light transparency, which adds to the range of possible applications to electronics and batteries.