Extreme Rejuvenation of a Metallic Glass

Metallic glasses (non-crystalline alloys) are of interest for their exceptional (sometimes record-breaking) property combinations, for example, high yield stress combined with high toughness.  Yet as the glasses relax (‘age’) into lower-energy states, they become more brittle.  There is much interest, therefore, in taking the glasses in the opposite direction, to higher-energy ‘rejuvenated’ states.  One method would be to form the glass at a higher quenching rate, but that is achievable only for ultra-thin sections.

This work shows that, by compression in a constrained geometry, a bulk sample of a metallic glass can be taken to a highly rejuvenated state that would be typical of a glass formed on cooling at 10¹⁰ K s^–1, 7 to 8 orders of magnitude higher than the cooling rate at which the sample actually formed.

Figure: Map of hardness measured on the cross-section of a notched cylindrical (4 mm diam.) sample of metallic glass compressed along the vertical cylinder axis.  The yellow region and those within are rejuvenated; the blue colour indicates the regions of extreme softening and rejuvenation.