Mg-based bulk metallic-glasses in the focus of materials science and engineering

Amorphization of Mg-based alloys was under focus of interest of materials scientists during last two decades and it remains to be attractive for many applied researchers now. Until the 1990s, very high cooling rates were required in order to avoid crystallization, leading to the availability of metallic glasses only as thin foils or ribbons. Today, due to improved chemical compositions, bulk metallic glasses (BMG) can be produced. They are regarded as a new family of promising materials due to their high specific strength. Among them, some Mg-TM-REM ternary alloys exhibit good glass-forming ability (GFA) combined with high strength-to-weight ratio. On the other hand, the achieved GFAs of the presently existing Mg-based amorphous-bearing systems do not permit use slow cooling to obtain BMGs. Therefore, remains the demand in relatively high cooling rate. Rapid-solidification technique combined with post-solidification consolidation/plastic forming permit to produce amorphous/nano-amorphous extruded bars with mechanical properties having engineering importance.

The present lecture focuses on several researches conducted in IIM, at which various Mg-based ternary alloys with predicted high glass-forming ability (GFA) have been obtained by melt-spinning in the form of nano/amorphous ribbons, which then were milled into powder and then compacted. The obtained ribbons as well as final extruded bars were characterized at various processing stages by means of SEM/EPMA, XRD, DSC and TEM. It was observed that the better material`s amorphization may be reached through better dissolution of the third (minor) element in a quasi-binary matrix formed of two major alloying elements.

The reasons for predicted high GFA of Mg-based BMGs as well as metallurgical aspects of amorphization/crystallization in the examined materials and consolidation mechanism will be discussed.