The research of Ludwig Schultz has covered many aspects of advanced materials, particularly related to superconductivity and magnetism.  This talk will cover some recent work on metallic glasses, focusing on aspects that overlap with Ludwig’s interests.

Metallic glasses remain a particularly active research topic within research on advanced metallic materials. They have unique combinations of properties, and some individual properties that are best in class.  We will assess which are the most active research directions [1].  One of these is the search for new metallic-glass-forming compositions, now reinvigorated by machine-learning approaches [2].

Another particularly active research area follows from the realization that the properties of a metallic glass can be greatly varied even at fixed composition.  Most attention has been paid to ‘rejuvenation’, that is, raising the energy of the glass.  We survey the methods of thermomechanical processing used to achieve rejuvenation, ranging from treatments within the elastic limit [3,4] to plastic flow under compression [5].  The beneficial effects of rejuvenation can be great:  enabling bulk metallic glasses to show strain-hardening rather than strain-softening; [5]; increases in impact toughness of nearly a factor of three; and reversing the effects of annealing-induced embrittlement. 

That last effect is potentially important for Fe-based metallic glasses.  These show excellent soft-magnetic properties, and are of high and increasing importance in the energy transition.  To optimize their magnetic properties, however, they must be annealed, and they become brittle to an extent that significantly hinders fabrication of components.  If that embrittlement can be fully solved, that will greatly the more widespread use of metallic glasses in what is already their most important application area.