Metallurgy

In metallic liquids, the fragility is difficult to predict and measure. Here, the authors present the film inflation method, which reveals large fragility variations across Mg–Cu–Y, and introduce the crystallization complexity as additional contribution to glass forming ability.

Glass-to-glass transitions can help understanding the glass nature, but it remains difficult to tune metallic glasses into significantly different glass states. Here the authors demonstrate the high-entropy effects in glass-to-glass transitions of high-entropy metallic glasses.

Materials with controlled structural gradient have gained attention due to their unique combinations of properties. Here the authors report strategies to design controllable gradients in bulk metallic glasses, demonstrating extra plasticity and suppression of shear localization.

There is limited understanding of the Invar effect at atomic scale. Here the authors show that the Invar effect is not only a macroscopic effect, but also has a clear atomistic equivalent in the average distance of Fe–Fe pair as well as higher-order atomic shells composed of multiple atom species.

Common wisdom to improve ductility of bulk metallic glasses (BMGs) is to introduce local loose packing regions at the expense of strength. Here the authors enhance structural fluctuations of BMGs by introducing dense local packing regions, resulting in simultaneous increase of ductility and strength.

Here the authors study thermodynamic and dynamic glass transition of high entropy metallic glasses. Results show retarded α-relaxation and distinct crystallization resistance attributed to their sluggish diffusion and high-entropy mixing that is different from the traditional metallic glasses.

The competition between the formation of different phases and their kinetics need to be clearly understood to make materials with on-demand and multifaceted properties. Here, the authors reveal, by a combination of complementary in situ techniques, the mechanism of a Cu-Zr-Al metallic glass’s high propensity for metastable phase formation, which is partially through a kinetic mechanism of Al partitioning.

While metallic glasses are expected to have tunable structures, these have rarely been demonstrated. Here, the authors combine temperature and pressure to show a two-way structural tuning in rare earth-based metallic glasses beyond the nearest-neighbor atomic shells.

The coarsening of amorphous metallic nanoparticles remains poorly understood. Here, the authors combine high resolution microscopy and atomistic simulations to show the disordered structure of amorphous nanoparticles makes them coarsen faster than crystalline ones.

Thermal annealing of metallic glasses is known to cause a universal increase of the relaxation time with sample age. Here, however, the authors show how a mechanical stress disrupts this universal response, leading to highly non-monotonous structural dynamics with time.

Quantifying the complexity of glass formation is difficult because it usually requires cooling at enormous speeds. Here, the authors use fast differential scanning calorimetry to classify metallic glasses into two types, one with quenched-in nuclei and one without.

Producing nacre-like ceramics with a tough, non-polymeric matrix remains a challenge. Here, the authors use the reactive wetting of a zirconium-based bulk metallic glass to successfully infiltrate a porous alumina and create a composite with improved flexural strength and fracture toughness.

Conventional crystal growth models assume crystals grow into a structure-less liquid, even though liquid metals have shown evidence of structural ordering. Here, the authors show crystal growth can be influenced by the presence of thermodynamically unstable local structural order in the liquid.

Producing ultrastable metallic glasses has always been associated with substrates heated close to the glass transition temperature. Here, the authors show that reducing the deposition rate of the metallic glass on a cold substrate produces ultrastable metallic glasses with remarkably improved stability.

Iron-based bulk metallic glasses are remarkably plastic, but the origin of their plasticity remains challenging to isolate. Here, the authors use high resolution microscopy to show that nanocrystals are dispersed within the glass and form hard and soft zones that are responsible for enhancing ductility.

Understanding the fracture toughness of metallic glasses remains challenging. Here, the authors show that a fictive temperature controls an abrupt mechanical toughening transition in metallic glasses, and can explain the scatter in previously reported fracture toughness data.