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An investigation was performed to evaluate the effect of vanadium (V) addition on the microstructure and the tensile behavior of Fe–27Mn–8Al-1.0C austenite lightweight steel after annealing and subsequently aging. The grain size of austenite in V-added steels was effectively refined and many nano-sized VC particles were observed in the austenite grains, compared to V-free steels, under annealed conditions. Subsequent aging promotes the precipitation of κ-carbide from the austenite matrix, and the dual-nanoprecipitation consisting of nano-sized VC and κ-carbide particles further improves the strength of the steel. Because of this, the current steels have good ductility (up to 41% total elongation) even when aged and high yield and ultimate tensile strengths of up to 1009 MPa and 1243 MPa, respectively. By examining the dislocation structure of the specimens during deformation, it was also possible to determine how precipitates affected the rate of strain hardening. As a result, the strain hardening rate of the V-added steel after aging is effectively improved at the initial deformation by the precipitation of VC particles, which compensates for the decrease in strain hardening rate due to shearable κ-carbide. This study provides a strategy to obtain an excellent combination of strength and ductility in lightweight steel by V microalloying and simple thermomechanical treatment.

In this work, five novel Ti- and TiZr-based high entropy bulk metallic glasses (HE-BMGs) with good glass forming ability (GFA) were developed, among which the (Ti37.31Zr22.75Be26.39Al4.55Cu9)94Ni6 alloy possesses the largest critical diameter of 9 mm. All developed HE-BMGs exhibit high yield strength and good compressive plasticity at room temperature. Especially, the (Ti37.31Zr22.75Be26.39Al4.55Cu9)94Co6 alloy with large GFA has suitable density and high specific strength (3.90 × 105 N m/kg), showing great potential in the aerospace sector. Moreover, the activation energies at characteristic temperatures of three HE-BMGs were obtained using the Kissinger method. The local Avrami exponents were calculated to analyze the crystallization mechanism of these HE-BMGs, revealing that the first crystallization process is mostly dominated by diffusion-controlled three-dimensional growth of pre-existing nuclei. In addition, all three HE-BMGs can be classified as “intermediate glasses” according to their fragility index values.

Bulk metallic glasses (BMGs) bear versatile advantages compared to traditional crystalline metallic materials. However, preparation of large size BMG components remains a great challenge due to the lack of understanding the casting dynamics of BMGs. The present work investigates the dynamics of the solidification process during casting of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 BMG by measuring the time-dependent temperature evolution and constructing distance–time curves showing the progress of solidification. The experimentally probed temperature evolution proves that a higher casting temperature causes a lower cooling rate and induces more pronounced nanocrystal phase formation in the final BMG casting. Thus, optimization of the casting temperature is crucial for casting BMG components. The solidification coefficient K of the studied Zr-based BMG in copper mold was determined. The solidification time can be calculated with model: τ=M2K2. The solidification of the Zr-based BMG occurs in a narrow transition layer region following a “layer-by-layer” solidification mode. This feature is vital for designing the casting process appropriately to avoid the formation of casting defects in BMG components. The present work sheds new light on the solidification mechanism of bulk glass-forming liquids and underlines the importance of optimizing the technology and processing conditions for fabrication of BMG components with practical applications.

The development of aerospace and military defense sectors has put forward higher requirements for the mechanical properties of metals under extreme conditions. Eutectic high entropy alloys (EHEAs) show a wide potential application in these fields due to their superior mechanical performances and good castability. Here, we systematically investigated the dynamic compressive properties and microstructural characteristics of the Al1.19Co2CrFeNi1.81 EHEA at room temperature (298 K) and liquid nitrogen temperature (77 K). The EHEA exhibits an excellent strength-plasticity combination, especially at the strain rate of 4300 s−1 at 77 K, showing a yield strength of 1365 MPa and a true plastic strain over 40%. The underlying deformation mechanisms were uncovered using transmission electron microscopy, revealing that the deformation mechanism is dominated by dislocation slip at 298 K. However, at 77 K, nanotwins together with dislocation slip dominate the plastic deformation. Meanwhile, profuse relatively stable structures are formed due to the interactions between stacking fault (SF)-SF, dislocation-twin boundary and nanotwin-nanotwin, which can effectively inhibit dislocation movement and contribute to a superior strain hardening ability. The adiabatic shear band forms in the late stage of dynamic deformation, and the fractographic observations show a transition from ductile to mixed ductile–brittle fracture mode with decreasing temperature.