The improvement in strength is usually accompanied by ductility loss in structural materials, which is a long-standing conflict referred as the strength-ductility trade-off. Here we present a heterogeneous-structures-architecting strategy, in which we design bulk high-entropy alloys with the largely-enhanced strength-ductility trade-off, possessing a yield strength of 711 MPa, a tensile strength of 928 MPa, and a uniform elongation of 30.3%. Such an enhancement of the strength-ductility trade-off is due to the microstructure comprised with a combination of the non-recrystallized and recrystallized grains arranged in complex heterogeneous structures with a characteristic dimension spanning from the submicron scale to the coarse-sized scale. The heterogeneous structures in the high-entropy alloy are produced by cold-rolling, followed by intermediate-temperature-annealing. Our results demonstrate that heterogeneous designs can be accomplished effectively by simple thermal treatments, which offer a design strategy towards a new generation of high-strength and high-ductility high-entropy alloys.

Stick-slip dynamics during nanoscratching is investigated for the Ni62Nb38 metallic glass. Detrended fluctuation analysis is introduced to explore the influence of loading force on the temporal scaling and stick-slip behavior. The self-similar characteristics and complexity in the temporal scale of the lateral force signal are investigated. A modified Cauchy class model is used for the stochastic stick-slip process, which connects the fractal dimension and the Hurst exponent and features the positive correlation process. The confidence intervals of the differential friction coefficient at different loading forces elucidate the inhomogeneous (and homogeneous) shear-branching processes during the nanoscratching process.

Changes in intermittent shear avalanches during plastic deformation of a Cu50Zr45Ti5 (atomic percent) alloy in response to variant structures including fully glassy phase and/or nanocrystal/glass binary phase are investigated. Second crystalline phases are introduced into the glassy-phase matrix of a Cu50Zr45Ti5 metallic glass to interfere with the shear-avalanche process, which can release the shear–strain concentration, and then tune the critically-dynamic behavior of the shear avalanche. By combining microstructural observations of the nanocrystals with the statistical analysis of the corresponding deformation behavior, we determine the statistic distribution of shear-avalanche sizes during plastic deformation, and established its dependence on the geometric distribution of nanocrystals. The scaling behavior of the distribution of shear-avalanche sizes follows a power–law relation accompanied by an exponentially-decaying scaling function in the pure metallic glass, and the metallic glass containing the small nanocrystals, which can be described by the mean-field theory. The large shear-avalanche events are dominated by structural tuning-parameters, i.e., the resistance of shear banding, and the size and volume fraction of the second crystalline phase in metallic glasses.

The origin of the deformation in metallic glasses is attributed to rearrangements of atoms in some structurally weak spots behaving as flow units, which are associated with free volumes. In the present study, Xe-ion beam is used to manipulate the free-volume fraction, and influence on the mechanical behavior of a Zr-based metallic glass. The irradiation at low dosages can change the structure by increasing the free volume, and by homogenising the distribution of free volume. The increase in the free-volume fraction is equivalent to the increase in the deformation temperature, thus resulting in the decrease in the yield strength. The analysis of stochastic strain burst size in the metallic glass irradiated at different dosages indicates that the strain burst depends on the yield strength and homogeneity of the glassy phase. The results of this study highlight the fact that the quantitative manipulation of the homogeneity and the amount of free volumes can be achieved through low-dose ion irradiation, which can modify the mechanical behavior of metallic glasses.

The high-entropy alloy coatings reinforced with nano oxides were synthesized by the atmospheric plasma spraying (APS). The crystal structure, microstructure, surface morphology, hardness and wear resistance properties of the CoCrFeNiAl and CoCrFeNiMo high-entropy alloy coatings are investigated. For CoCrFeNiAl high entropy coating (HEC) not only has high hardness (573 ± 19 Hv0.1) but also has good wear resistance [The coefficients of friction (COF) is 0.49 ± 0.04]. The transition of the wear mechanism obviously appears between the two HECs. The influences of the structure, composition and hardness on the tribological behavior of high-entropy alloy coatings were discussed in details. Graphical abstract Nano oxides enhanced high-entropy coatings (HECs) are successfully fabricated by atmospheric plasma spraying, which exhibit the highest hardness and the best wear resistance in HECs and high-entropy alloys.