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With the rapid development of low-temperature fields such as deep space exploration，polar scientific research，low-temperature storage and transportation，the service conditions for low-temperature structural components are becoming increasingly stringent. Therefore，low-temperature materials have gradually become a research hotspot in the world. This article mainly summarizes the low-temperature performance and related mechanisms of common structural materials such as low-temperature steel，aluminum alloy，titanium alloy，aluminum matrix composites and resin matrix composites. The effects of different crystal structures，alloy types，alloying elements and other factors on the mechanical properties of structural materials such as low temperature strength，plasticity and toughness，and the mechanism of low temperature deformation，strengthening and toughening are concluded. The application and prospect of different grades of low-temperature structural materials in different fields at home and abroad are also briefly introduced. The future research prospect of low-temperature materials is put forward.

Nacre-inspired metal matrix composites have received much attention due to their excellent deformation coordination ability, which can achieve the synergy of strength and ductility. The preparation of nacre-like Al matrix composites by freeze casting has been a promising application, but the continuous ceramic-rich layer affects the corrosion resistance of the composites, facing complex corrosion problems during service. In this work, the microstructure and corrosion behavior of the nacre-inspired (TiBw-TiB2)/Al composites fabricated by freeze casting and squeeze casting were systematically studied. The results indicated that the Al layers and ceramic-rich layers had little change, about 35 μm and 31 μm, respectively, with an increasing ratio of the Ti/TiB2. Meanwhile, a high Ti/TiB2 ratio resulted in an increase in the Fe-Ti intermetallic phases, which was detrimental to the corrosion performance of the composites and was prone to pitting. The electrochemical test results showed that the 3Ti7TiB2 composite had the lowest corrosion current density (15.9 μA) and intergranular corrosion depth (231 μm), indicating that it had the best corrosion resistance, which can be attributable to its stable and dense passivation film. Two different corrosion phenomena during the intergranular corrosion test existed in the present nacre-inspired (TiBw-TiB2)/Al composites: intergranular corrosion in the Al matrix layer and pitting corrosion in the ceramic-rich layer. Among all the composites, the corrosion depth of the 3Ti7TiB2 composite was the smallest and significantly less than that of the 2024Al alloy. In addition, the continuous ceramic-rich layer acted as a corrosion channel during corrosion, significantly degrading the corrosion resistance of the nacre-like Al composites. [ABSTRACT FROM AUTHOR]

The distribution of reinforcements and interfacial bonding state with the metal matrix are crucial factors in achieving excellent comprehensive mechanical properties for aluminum (Al) matrix composites. Normally, after heat treatment, graphene nanosheets (GNSs)/Al composites experience a significant loss of strength. Here, better performance of GNS/Al was explored with a hybrid strategy by introducing 0.9 vol.% silicon carbide nanoparticles (SiCnp) into the composite. Pre-ball milling of Al powders and 0.9 vol.% SiCnp gained Al flakes that provided a large dispersion area for 3.0 vol.% GNS during the shift speed ball milling process, leading to uniformly dispersed GNS for both as-sintered and as-extruded (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al. High-temperature heat treatment at 600 °C for 60 min was performed on the as-extruded composite, giving rise to intragranular distribution of SiCnp due to recrystallization and grain growth of the Al matrix. Meanwhile, nanoscale Al4C3, which can act as an additional reinforcing nanoparticle, was generated because of an appropriate interfacial reaction between GNS and Al. The intragranular distribution of both nanoparticles improves the Al matrix continuity of composites and plays a key role in ensuring the plasticity of composites. As a result, the work hardening ability of the heat-treated hybrid (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al composite was well improved, and the tensile elongation increased by 42.7% with little loss of the strength. The present work provides a new strategy in achieving coordination on strength–plasticity of Al matrix composites. [ABSTRACT FROM AUTHOR]

Recent works have experimentally proven that metal matrix composites (MMCs) with network architecture present improved strength–ductility match. It is envisaged that the performance of architecturally designed composites is particularly sensitive to reinforcement strength. Here, reinforcing particles with various fracture strengths were introduced in numerical models of composites with network particle distribution. The results revealed that a low particle strength (1 GPa) led to early-stage failure and brittle fracture. Nevertheless, a high particle strength (5 GPa) delayed the failure behavior and led to ductile fracture at the SiC/Al–Al macro-interface areas. Therefore, the ultimate tensile strengths (UTS) of the network SiC/Al composites increased from 290 to 385 MPa, with rising particle strength from 1 to 5 GPa. Based on the composite property, different particle fracture threshold strengths existed for homogeneous (~2.7 GPa) and network (~3.7 GPa) composites. The higher threshold strength in network composites was related to the increased stress concentration induced by network architecture. Unfortunately, the real fracture strength of the commercial SiC particle is 1–2 GPa, implying that it is possible to select a high-strength particle necessary for efficient network architecture design. [ABSTRACT FROM AUTHOR]

For network architecture design, stress concentration sensitivity caused by particle shape may change, which is rarely studied. Here, the particle shape dependent stress concentration and its effect on the deformation, fracture, and mechanical properties were investigated. Three particle shapes including hexahedron, twenty-six face polyhedron, and sphere were utilized to generate different stress distribution states in the matrix. A numerical composite model showing network architecture (like grain boundary) was applied. A strong correlation between particle shape, stress concentration factor (R SiC ), and mechanical properties of network composite was built. The particle shape affected the load-bearing capability due to the stress concentration state generated at particle edges. Near the yield point, hexahedron particle wall parallel to the load direction (PaW) was more effective in carrying loads (∼1000 MPa) than that of twenty-six face polyhedron (750–1000 MPa) and sphere (600–1000 MPa) particles. In network composites reinforced by different shape particles, the main crack always initiated in perpendicular network walls (PeW), but propagated along different paths: in Al matrix for hexahedron particle, along macro-interface of SiC/Al–Al for twenty-six face polyhedron particle, and in PeW for sphere particle. Such crack propagation manners contributed to the different elongations of network composites by various particle shapes: sphere > twenty-six face polyhedron > hexahedron particles. Selection of round particle and adjustment of local volume fraction improved elongation with a sacrifice of modulus and strength. [ABSTRACT FROM AUTHOR]

A microstructure-based comprehensive finite element model, which incorporated the deformation/fracture of the matrix alloy, fracture of the particle and decohesion of interface, was built to predict the effects of particle size and shape on the plastic deformation and fracture behaviors in particle-reinforced metal matrix composites. The effect of particle size on the yield strength and work hardening rate of the matrix alloy was demonstrated. When the particle diameter is <10 µm, the fracture of the matrix alloy near the interface dominates the failure mechanism of the composite, whereas changed to particle fracture with particle diameter >10 µm. A cohesive zone model was also included in order to predict interfacial failure behavior. It was noted that SiC/Al interface exhibits a high interfacial bonding strength and the interfacial decohesion was caused by crack propagation from the particle to the interface. The simulation results are in good agreement with the experiment tensile test results in the SiCp/6061Al composite. [ABSTRACT FROM AUTHOR]

Abstract: 2024Al matrix composite reinforced with 1 wt.% carbon nanotubes (CNTs) was fabricated by cold isostatic pressing, followed hot extrusion techniques. The microstructure characteristics and the distribution of carbon nanotubes in the aluminum matrix were investigated. The mechanical properties of the composite were measured at room temperature. Experimental results showed that CNTs were distributed homogeneously in the composite, and the interfaces of Al–CNTs bonded well. The grain size of the matrix was as fine as 200 nm, and with a small amount of CNTs additions, the elastic modulus and the tensile strength were enhanced markedly over those of the 2024Al matrix fabricated under the same process. The reasons for the increments could be due to the extraordinary mechanical properties of CNTs, the bridging and pulling out role of CNTs in the Al matrix composite. [Copyright &y& Elsevier]