Compression, tension and high-velocity plate impact experiments were performed on a typical tough Zr_41.2Ti_13.8Cu₁₀Ni_12.5Be_22.5 (Vit 1) bulk metallic glass (BMG) over a wide range of strain rates from ∼10⁻⁴ to 10⁶ s⁻¹. Surprisingly, fine dimples and periodic corrugations on a nanoscale were also observed on dynamic mode I fracture surfaces of this tough Vit 1. Taking a broad overview of the fracture patterning of specimens, we proposed a criterion to assess whether the fracture of BMGs is essentially brittle or plastic. If the curvature radius of the crack tip is greater than the critical wavelength of meniscus instability [F. Spaepen, Acta Metall. 23 615 (1975); A.S. Argon and M. Salama, Mater. Sci. Eng. 23 219 (1976)], microscale vein patterns and nanoscale dimples appear on crack surfaces. However, in the opposite case, the local quasi-cleavage/separation through local atomic clusters with local softening in the background ahead of the crack tip dominates, producing nanoscale periodic corrugations. At the atomic cluster level, energy dissipation in fracture of BMGs is, therefore, determined by two competing elementary processes, viz. conventional shear transformation zones (STZs) and envisioned tension transformation zones (TTZs) ahead of the crack tip. Finally, the mechanism for the formation of nanoscale periodic corrugation is quantitatively discussed by applying the present energy dissipation mechanism.

In this work, we studied the shock response of two typical equiatomic high entropy alloys (HEAs) (i.e. FCC-structured CrMnFeCoNi alloy and BCC-structured NiCoFeCrAl alloy). The experimental results show that these two HEAs exhibit a relatively high Hugoniot elastic limit and high-phase transition threshold stress. We attribute this anomalous dynamic response of HEAs to their intrinsic chemically disordered structures. This work may provide new insight into shock compression behavior of HEAs. IMPACT STATEMENT This is the first work to demonstrate that high entropy alloys (HEAs) behave ‘super-stably’ under shock loading, which may provide new insight into shock compression behavior of HEAs. GRAPHICAL ABSTRACT

High-performance refractory alloys with ultrahigh strength and ductility are in demand for a wide range of critical applications, such as plasma-facing components. However, it remains challenging to increase the strength of these alloys without seriously compromising their tensile ductility. Here, we put forward a strategy to “defeat” this trade-off in tungsten refractory high-entropy alloys by stepwise controllable coherent nanoprecipitations (SCCPs). The coherent interfaces of SCCPs facilitate the dislocation transmission and relieve the stress concentrations that can lead to premature crack initiation. As a consequence, our alloy displays an ultrahigh strength of 2.15 GPa with a tensile ductility of 15% at ambient temperature, with a high yield strength of 1.05 GPa at 800 °C. The SCCPs design concept may afford a means to develop a wide range of ultrahigh-strength metallic materials by providing a pathway for alloy design.