Forming complex geometries using the casting process is a big challenge for bulk metallic glasses (BMGs), because of a lack of time of the window for shaping under the required high cooling rate. In this work, we open an approach named the “entire process vacuum high pressure die casting” (EPV-HPDC), which delivers the ability to fill die with molten metal in milliseconds, and create solidification under high pressure. Based on this process, various Zr-based BMGs were prepared by using industrial grade raw material. The results indicate that the EPV-HPDC process is feasible to produce a glassy structure for most Zr-based BMGs, with a size of 3 mm × 10 mm and with a high strength. In addition, it has been found that EPV-HPDC process allows complex industrial BMG parts, some of which are hard to be formed by any other metal processes, to be net shaped precisely. The BMG components prepared by the EVP-HPDC process possess the advantages of dimensional accuracy, efficiency, and cost compared with the ones formed by other methods. The EVP-HPDC process paves the way for the large-scale application of BMGs.

Recently, high-entropy alloy thin films (HEATFs) with nanocrystalline structures and high hardness were developed by magnetron sputtering technique and have exciting potential to make small structure devices and precision instruments with sizes ranging from nanometers to micrometers. However, the strength and deformation mechanisms are still unclear. In this work, nanocrystalline Al_0.3CoCrFeNi HEATFs with a thickness of ~4 μm were prepared. The microstructures of the thin films were comprehensively characterized, and the mechanical properties were systematically studied. It was found that the thin film was smooth, with a roughness of less than 5 nm. The chemical composition of the high entropy alloy thin film was homogeneous with a main single face-centered cubic (FCC) structure. Furthermore, it was observed that the hardness and the yield strength of the high-entropy alloy thin film was about three times that of the bulk samples, and the plastic deformation was inhomogeneous. Our results could provide an in-depth understanding of the mechanics and deformation mechanism for future design of nanocrystalline HEATFs with desired properties.

A new sintering method, namely ultrasonic assisted sintering (UAS), has been proposed using mechanical heat converted from high frequency motion between particles. Pure aluminum specimens with diameter of 5 mm and thickness of ~2 mm have been successfully sintered in two seconds. Based on the thermodynamic analysis, the underlying heating mechanism is quantitatively interpreted, which involves high-frequency interparticle friction and plastic deformation driven by ultrasonic squeezing. Consequently, temperature rises rapidly at a speed of about 300 K/s, and the maximum temperature reaches up to 0.9 times of melting point of the aluminum during UAS. The sintered specimens have a high density of dislocations, under the combined effects of dislocations and undulating stress field, volume diffusion coefficient for sintering increases by several orders of magnitude, therefore, rapid densification can be accomplished in seconds. In addition, the sintered aluminum has ultrahigh nanohardness (~1.13 GPa), which can be attributed to the hierarchical structure formed during UAS process.

Ni₃Al superlattice alloys with the L1₂ structure have garnered much attention due to their attractive high-temperature mechanical properties; however, their grain-boundary brittleness and low ductility in the ambient temperature range have greatly restricted their widespread application. In this study, we developed an L1₂ structure multicomponent Ni_46.5Co₂₄Fe₈Al_12.5Ti₉ (at. %) superlattice alloy that notably suppressed the room-temperature intergranular brittleness and exhibited a large tensile elongation of 17.1% ± 5.2% together with a high ultimate tensile strength of 1,080.2 ± 57.4 MPa. Multiple microstructural examinations reveal an L1₂ equiaxed-grain microstructure, with the presence of a minor B2 phase. Moreover, the co-segregation of Fe and Co atoms, and the associated reduction or elimination of the L1₂ chemical order at the grain-boundary regions were characterized, which were proved to be the root cause of the suppression of intergranular brittleness and the high tensile ductility. Further theoretical calculations show that alloying of Fe and Co to binary Ni₃Al reduced the ordering energy, which promoted intergranular segregation and associated disordering. This observation demonstrated that the elimination or reduction of interfacial chemical order is an effective ductilizing method for superlattice alloys.