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Aluminum matrix composites (AMCs) reinforced with graphene nanoplatelets (GNPs) were fabricated by using an accumulative roll-compositing (ARC) process. Microstructure, mechanical and electrical properties of the nanostructured AMCs were characterized. The results showed that small addition (0.2 vol% and 0.5 vol%) of GNPs can lead to a simultaneous increase in the tensile strength and ductility of the GNPs/Al nanocomposites, as compared with the same processed pure Al. With increasing GNPs content, the tensile strength of the GNPs/Al nanocomposites can be enhanced to 387 MPa with retained elongation of 15%. Meanwhile, the GNPs/Al nanocomposites exhibited a good electrical conductivity of 77.8%–86.1% that of annealed pure Al. The excellent properties (high strength, high ductility and high conductivity) of the GNPs/Al are associated with the particular ARC process, which facilitates the uniform dispersion of GNPs in the matrix and formation of ultrafine-grained Al matrix. The strengthening and toughening of the GNPs/Al nanocomposites were discussed considering different mechanisms and the unique effect of GNPs.

The present work investigates the thermal stability and mechanical properties of a Co–20Cr–15W–10Ni (wt%) alloy with a bimodal grain (BG) structure. The BG structure consisting of fine grains (FGs) and coarse grains (CGs) is thermally stable under high-temperature exposure treatments of 760 °C for 100 h and 870 °C for 100–1000 h. The size of both FGs and CGs remains no significant changes after thermal exposure treatments. The microstructural stability is associated with the slow kinetics of grain growth and the pinning of carbides. The thermal stability enables to maintain the BG structures, leading to the same mechanical properties as the sample without thermal exposure treatment. In particular, the BG alloy samples after thermal exposure treatment exhibit superior mechanical properties of both high strength and high ductility compared to the unimodal grain (UG) structured ones. The BG structure of the alloy samples after thermal exposure is capable of avoiding severe loss of ductility and retaining high strength. More specifically, the ductility of the BG alloy samples after thermal exposure treatments of 870 °C for 500–1000 h is ten times higher (44.6% vs. 3.5% and 52.6% vs. 5.0%) than that of the UG ones. The finding in the present work may give new insights into high-temperature applications of the Co–20Cr–15W–10Ni alloy and other metallic materials with a BG structure.

The influence of pre-strain on the formation of bimodal grain structures and tensile properties of a Co–20Cr–15W–10Ni alloy was investigated. The bimodal grain structures consist of fine grains (FGs; 2–3 μm in diameter) and coarse grains (CGs; 8–16 μm in diameter), which can be manipulated by changing the pre-strain (ɛ = 0.3–0.7) and annealing temperatures (1000–1100 °C). High pre-strain applied in the samples can intensify the plasticity heterogeneity through increasing the total dislocation density and the local volumes of high-density dislocations. This can essentially result in finer FGs, a higher FG volume fraction, and overall grain refinement in the samples after annealing. High-temperature essentially increases both the size and volume fraction of CGs, leading to an increase in the average grain size. The tensile test suggests that the bimodal grain structured samples exhibited both high strength and ductility, yield strengths of 621–877 MPa and ultimate tensile strengths of 1187–1367 MPa with uniform elongations of 55.0%–71.4%. The superior strength-ductility combination of the samples arises from the specific deformation mechanisms of the bimodal grain structures. The tensile properties strongly depend on the size ratio and volume fraction of FGs/CGs in addition to the average grain size in the bimodal grain structures. The grain structures can be modified via changing the pre-strain and annealing temperature.

In order to develop a new titanium alloy with a good combination of strength–ductility–toughness, a near-beta titanium alloy was designed based on the already widely used Ti-1023 alloy. To avoid beta fleck occurring in the microstructure, the new Ti–Al–Fe–V (Cr, Zr) alloy has been made through decreasing the content of Fe, based on molybdenum equivalency and Bo–Md molecular orbital method (a method for new alloy designing based on the molecular orbital calculating). After primary design computation, Ti–Al–Fe–V (Cr, Zr) alloy was optimized as Ti–3Al–4.5Cr–1Fe–4V–1Zr finally. The microstructure and tensile properties of this alloy subjected to several commonly used heat treatments were investigated. The results show that the tensile strength of the alloy after solution treated below the β-transus temperature comes between 850 and 1100 MPa, with elongation in the range of 12.5 %–17.0 %. In solution-treated and solution-aged samples, a low-temperature aging at 500 °C results in the precipitation of finer α phase. With the increase in aging temperature, the secondary α phase becomes coarser and decreases in amount. Thus, it will lead to the increase in tensile ductility, but reduction in strength. Eventually, after modulated aging treatment, the alloy can obtain high-strength level with acceptable ductility. The tensile strength of the alloy can achieve 1273 MPa, with an elongation of 11.0 %. At the same time, the fracture toughness (K IC) of the alloy achieves 83.8 MPa·m1/2. It is obvious that the newly designed alloy has achieved a good blend of strength–ductility–toughness.

A series of Ti–Al–V titanium alloy bars with nominal composition Ti–7Al–5V ELI, Ti–5Al–3V ELI, commercial Ti–6Al–4V ELI and commercial Ti–6Al–4V were prepared. These alloys were then heat treated to obtain bimodal or equiaxed microstructures with various contents of primary α phase. Dynamic compression properties of the alloys above were studied by split Hopkinson pressure bar system at strain rates from 2,000 to 4,000 s−1. The results show that Ti–6Al–4V alloy with equiaxed primary α (αp) volume fraction of 45 vol% or 67 vol% exhibits good dynamic properties with high dynamic strength and absorbed energy, as well as an acceptable dynamic plasticity. However, all the Ti53ELI specimens and Ti64ELI specimens with αp of 65 vol% were not fractured at a strain rate of 4,000 s−1. It appears that the undamaged specimens still have load-bearing capability. Dynamic strength of Ti–Al–V alloy can be improved as the contents of elements Al, V, Fe, and O increase, while dynamic strain is not sensitive to the composition in the appropriate range. The effects of primary alpha volume fraction on the dynamic properties are dependent on the compositions of Ti–Al–V alloys.