Al-Mg alloys are widely used as important engineering structural materials in aerospace engineering, transportation systems, and structural constructions due to their low density, high specific strength, corrosion resistance, welding capability, fatigue strength, and cost-effectiveness. However, the conventional Al-Mg alloys can no longer fully satisfy the demands of practical production due to difficulties caused by many defects. The high strength of Al-Mg alloys as non-heat treatment precipitation-strengthened alloys is achieved primarily by solid solution strengthening along with work hardening rather than precipitation strengthening. Therefore, severe plastic deformation (SPD) techniques can be often used to produce ultrafine-grained structures to fabricate ultra-high strength aluminum alloys. However, this approach often achieves the strengthening of material at the cost of reduced ductility. This paper comprehensively summarizes the various approaches of ultrafine/nanocrystalline materials for enhancing their plasticity, elaborates on the creation of a bimodal microstructure within the alloy, and discusses the formation of a nanotwin microstructure within the alloy and the incorporation of dispersed nanoparticles. The mechanisms underlying both the strengthening and toughening during large plastic deformation in aluminum alloys are summarized, and the future research direction of high-performance ultrafine crystalline and nanocrystalline Al-Mg aluminum alloys is prospected.

With the continuous development of the new energy vehicle industry, in order to further improve the safety and range of electric vehicles, vehicle lightweighting has been a key focus of major car companies. However, research on lightweighting and the impact protection effect of battery pack protective plates is lacking. The bottom protective plate of the battery pack in this study has a sandwich-type multi-layer structure, which is mainly composed of upper and lower glass-fiber-reinforced resin protective layers, steel plate impact resistant layers, and honeycomb buffer layers. In order to study the relationship between the impact damage response and material characteristics of the multi-material battery pack protective plate, a matrix experimental design was adopted in this study to obtain the energy absorption ratio of different material properties when the protective plate is subjected to impact damage. This work innovatively used a low-cost equivalent model method. During the drop hammer impact test, a 6061-T6 aluminum plate in direct contact with the lower part of the bottom guard plate test piece was used to simulate the deformation of the water-cooled plate in practical applications. High-strength aluminum honeycomb was arranged below the aluminum plate to simulate the deformation of the battery cell. This method provides a scientific quantitative standard for evaluating the impact resistance performance of the protective plate. The most preferred specimen in this work had a surface depression deformation of only 8.44 mm after being subjected to a 400 J high-energy impact, while the simulated water-cooled plate had a depression deformation of 4.07 mm. Among them, the high-strength steel plate played the main role in absorbing energy during the impact process, absorbing energy. It can account for about 34.3%, providing reference for further characterizing the impact resistance performance of the protective plate under different working conditions. At the same time, an equivalence analysis of the damage mode between the quasi-static indentation test and the dynamic drop hammer impact test was also conducted. Under the same conditions, the protective effect of the protective plate on impact damage was better than that of static pressure marks. From the perspective of energy absorption, the ratio coefficient of the two was about 1.2~1.3.

The passive safety performance of trains is important. To ensure passenger safety and avoid vehicle climbing and excessive deformation in a collision, anti-climbing energy absorption devices can be installed at the end of each vehicle. In this study, two new types of anti-climbing energy absorption structures—a five-section frame filled with a PU foam core (FSF-F) and a five-section frame filled with a honeycomb aluminum core (FSF-H)—were prepared. The mechanical properties of the FSF-F and FSF-H structures were compared using a dynamic loading test and a simulation. The results showed that the energy absorption performance of the FSF-H was better than that of the FSF-F. Combined with the actual working conditions of a train, the mechanical properties of FSF-H under an offset load were further studied. The results show that it has good energy absorption performance under an offset impact and can be used as an energy absorption device at the end of the train carriage.

This study examines the response of a composite material protection plate with an asymmetrical sandwich structure under low-velocity impact. The protection plate with an asymmetrical sandwich structure is constructed with materials such as polypropylene/glass fiber composites (PP/GFs), a steel plate, and a regular hexagonal honeycomb Al plate (Al honeycomb). The effects of the steel plate and Al honeycomb’s strength and thickness on the deformation behavior of the protection plate, as well as the influence of contact strength on the energy absorption of the Al honeycomb, were studied by combining models and experiments. A finite element model was established using Abaqus/Expliced software (2018), and the mechanical property parameters of each layer were simulated to analyze the greatest impact resistance of the protection plate. The experimental results show that the higher strength of the Al honeycomb can effectively improve the impact resistance of the protection plate. The energy absorption of the steel plate and the Al honeycomb accounted for 34.30% and 20.90%, respectively, and the damage area was more concentrated, making the protection plate more durable.