Search

Abstract Metal-hydrogen systems have attracted intense interest for diverse energy-related applications. However, metals usually reduce their ductility after hydrogenation. Here, we show that hydrogen can take the form of nano-sized ordered hydrides (NOH) homogeneously dispersed in a stable glassy shell, leading to remarkable enhancement in both strength and ductility. The yield strength is enhanced by 44% and the plastic strain is substantially improved from almost zero to over 70%, which is attributed to the created NOH and their interplay with the glassy shell. Moreover, the hydride-glass composite GdCoAlH possesses a giant magnetic entropy change (−ΔS M) of 18.7 J kg−1K−1 under a field change of 5 T, which is 105.5% larger than the hydrogen-free sample and is the largest value among amorphous alloys and related composites. The prominent ΔS M-ductility combination overcomes the bottlenecks of amorphous alloys as magnetic refrigerants. These results provide a promising strategy for property breakthrough of structural-functional alloys.

This investigation aims to improve the ductility of ultrahigh strength (>2 GPa) press hardening steels (PHS) by exploiting the heterogeneous carbon distribution in lath martensite. The proposed strategy is demonstrated in a medium carbon PHS with a lath martensite microstructure produced by quenching austenite. It is found that by enhancing auto-tempering, the solute carbon content in the coarse laths formed earlier during martensitic transformation can be reduced, leading to the softening and ductilizing of these laths. The softened coarse laths of small volume fraction provide significant improvement in the post-uniform elongation (PUE) without compromising the ultrahigh strength of lath martensite. The remarkable improvement in the PUE of ultrastrong lath martensite achieved by exploiting heterogeneous carbon distribution is expected to be instructive for the development of ultrahigh strength PHS with good ductility and fracture toughness.

Although there have been extensive studies on CoCrFeNi high entropy alloys (HEAs), they are still far from industrial applications due to their inferior strength. Based on the approach of interstitial atom strengthening which has been shown to be one of the effective ways to modify the properties of metallic materials, a series of (CoCrFeNi)100-xNx (x = 0, 0.25 and 0.50 at. %) HEAs were prepared in this study by selective laser melting (SLM). It was found that nitrogen addition in CoCrFeNi HEA can slightly refine the microstructure but did not change the preferred orientations after SLM. By increasing the nitrogen content in the matrix, the strength increases while the ductility is reduced. Also, the addition of nitrogen in CoCrFeNi HEA can decrease the stacking fault probability, leading to the increased stacking fault energy (SFE) in N-doped CoCrFeNi HEA. The increased strength in N-doped CoCrFeNi HEA samples mainly attributes to the solid solution strengthening of nitrogen, whereas the ductility loss results from the impediment on the formation of deformed twins induced by increased SFE. These results can provide a new strategy for designing high-strength N-doped HEAs.

Soft magnetic composites (SMCs) play a pivotal role in the development of high-frequency, miniaturization and complex forming of modern electronics. However, they usually suffer from a trade-off between high magnetization and good magnetic softness (high permeability and low core loss). In this work, utilizing the order modulation strategy, a critical state in a FeSiBCCr amorphous soft magnetic composite (ASMC), consisting of massive crystal-like orders (CLOs, ∼1 nm in size) with the feature of α -Fe, is designed. This critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex dots. Superior comprehensive soft magnetic properties at high frequency emerge in the ASMC, such as a high saturation magnetization ( M _s ) of 170 emu g ^−1 and effective permeability ( μ _e ) of 65 combined with a core loss ( P _cv ) as low as 70 mW cm ^−3 (0.01 T, 1 MHz). This study provides a new strategy for the development of high-frequency ASMCs, possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.

The effects of cryogenic thermal cycling (CTC) treatment on tensile plasticity and structure change of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 metallic glass (MG) ribbons were systematically investigated. Pronounced β-relaxation peaks locating at 643 and 693 K were observed after CTC treatment with diverse thermal temperatures. Specifically, the CTC treated samples exhibiting most remarkable β-relaxation showed tensile plastic strain of 5.2% at 643 K and 4% at 693 K, while the as-quenched sample only showed tensile plastic strain of 3% at 643 K and 2.1% at 693 K. The pronounced β-relaxation and enhanced tensile plasticity are considered to be originated from the increased structural heterogeneity. The separate β-relaxation peaks result from the different sizes/types of shear transformation zones induced by oscillatory (rejuvenation-relaxation) behavior during thermal cycling. Our results indicate that the CTC treatment has a significant impact on the energy states and structural heterogeneity, which makes it a powerful means to modify the mechanical properties of MGs.

Abstract Zr-based Bulk metallic glasses exhibit incredible corrosion resistance and glass forming ability, however, these properties need further enhancement to meet the practical use. In this study, Zr63Fe2.5Cu23Al11.5, a new type of Zr-based bulk metallic glass was fabricated. Potentiodynamic polarization techniques were used to measure the corrosion resistance of this alloy. Furthermore, crystallization behavior and kinetics of Zr63Fe2.5Cu23Al11.5 bulk metallic glass were investigated by using differential scanning calorimetry of non-isothermal model. Kissinger and Ozawa methods were used for calculating activation energies of crystallization and the mechanism of crystallization was analyzed by Johnson-Mehl-Avrami-Kolmogorow methods. The results suggest that this specified metallic glass system possesses a relatively high thermal stability and glass forming ability. Moreover, the crystallization procedure is mainly dominated by nucleation with an increasing rate. The study demonstrates that the slight composition adjustment of Zr–Fe–Cu–Al system bulk metallic glass can make a considerable contribution to higher glass forming and thermal stability as well as corrosion resistance.