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In this paper, we were devoted to quantitatively analyzing the dimensional change of 2024Al alloy during the aging process. Types of precipitates have been defined and the corresponding volume fraction has been measured with Transmission Electron Microscopy (TEM) and Three-Dimensional Atom Probe Tomography (3D-APT). Guinier-Preston-Bagaryatsky (GPB) zone (0.86 vol.%) was found after aging for 8 h. GPB zone (0.17 vol.%) and S' phase (1.02 vol.%) was found after aging for 24 h. The reduced dimensional change was attributed to the reduction of matrix lattice parameter. Relative to the initial supersaturated solid solution state, the lattice strain of -2.79 × 10−5 and -5.16 × 10−5 was produced after 8 h and 24 h aging respectively. The difference of the lattice parameters between the precipitates and matrix was also considered. A model was established to quantitatively describe the relationship between the precipitation process and dimensional change of 2024Al alloy.

Mn3O4/Ni(OH)2 nanocomposites are simply synthesized by a hydrothermal reaction between MnCl2.4H2O, NiCl2.6H2O and NaOH at 200 °C. Compared with the individual Ni(OH)2 and Mn3O4 prepared under the same conditions, the Mn3O4/Ni(OH)2 composite hydrothermally treated for 5 h achieves excellent specific capacitance (707 F g−1 at 1 A g−1 in 1 M KOH electrolyte) and remarkable long-term cycling stability (retaining a capacitance retention of 89% after 2000 cycles at 2 A g−1). Meanwhile, the asymmetric supercapacitor constructed by the Mn3O4/Ni(OH)2 composite and active carbon delivers an energy density of 17.8 W h kg−1 at a power density of 162 W kg−1. The outstanding performance is attributable to the synergistic compositing effect of Mn3O4 and Ni(OH)2, yielding not only the mutual doping of Mn3+ in Ni(OH)2 and Ni2+ in Mn3O4 to improve the electronic conductivity of the Mn3O4/Ni(OH)2 composite but also the suitable mesoporous structure for electrolyte transfer. Thus the Mn3O4/Ni(OH)2 composites will be alternative candidates as practical electrode materials for pseudocapacitors.

Equivalent amount of B (BEq) can be used to evaluate the thermal neutron shielding property of materials. Based on the calculation of BEq, a novel boron carbide and gadolinium particles reinforced Al composite (15%B4C + 1%Gd)/Al was designed. The composite was successfully prepared by vacuum hot pressing method. The B4C particles and Gd phase were homogeneously distributed in the Al matrix. The Monte Carlo Particle transport program MCNP simulation and thermal neutron shielding tests demonstrated that the (15%B4C + 1%Gd)/Al composite definitely had an almost equivalent neutron shielding property as the 30%B4C/Al composite, which in turn proved the accuracy of the design. The macroscopic transmission cross section (Σ) of (15%B4C + 1%Gd)/Al composite was as high as 21.3 cm−1, which was better than that of 30%B4C/Al composite. Tension tests indicated that by decreasing B4C content, the elongation of the composite reached as much as 9%. The addition of Gd can replace a part of B4C content in the composite, which can increase the plasticity of the composite, and keep the neutron shielding property simultaneously. Keywords: B4C/Al, Gd, Neutron shielding property, Plasticity

The γ" phase and the γ′ phase are metastable precipitates in Cu-2.0 wt%Be alloy, which play a key role in strengthening the alloy. This paper mainly discusses the formation process, microstructure and strengthening mechanism of these two precipitates. The structure, quantity and size of precipitates in the alloy treated at different aging temperatures were analyzed by transmission electron microscopy (TEM). The strengthening mechanism of the γ" phase and the γ′ phase was analyzed by theoretical calculation. The results show that with the increase of aging temperature, the size of γ" phase changes slightly, but the density decreases significantly, while the size and density of γ′ phase increase with the increase of aging temperature. High resolution transmission electron microscopy (HRTEM) analysis shows that the γ" phase is semi coherent with the matrix, so it will be cut off by dislocations. The atoms in the γ′ phase are arranged perfectly, they can’t shear with dislocations, so they can be strengthened by the Orowan dislocation bypass mechanism. The strength mechanism of γ" phase is location shear mechanism and the strengthening mechanism of γ′ phase is Orowan bypass mechanism.

The micro-creep behavior of metal matrix composite for inertial instrumentation was studied in this work. The interface, defect state and precipitation behavior during micro-creep were focused. The strain-time and strain rate-time relationships for SiCp/2024Al were investigated in-depth. The stress exponent and activation energy were measured 3 and 34.0 kJ/mol, respectively. It was found that the dislocation viscous slip dominates micro-creep mechanism. Moreover, the influence of load on precipitation behavior and the evolution of micro-creep microstructure were also discussed.

High-temperature creep behavior of 45vol%-SiCp/2024Al was studied at 250–350 °C under 40–140 MPa. True stress exponent and activation energy were measured 8 and 227.7 kJ/mol, respectively. The feature substructure of SiCp/2024Al was the second phase Al2Cu dispersed at the interface. The evolution of microstructure and the reason for its high creep activation energy were both analyzed and discussed. θ′ phase and S′ phase underwent different evolution processes during creep. θ′ phase gradually transformed to θ phase and remain stable from the steady-state creep until creep rupture. High content of the interface facilitated the dispersion of Al2Cu. The relationship between true stress exponent and interface content as well as the key to high true stress exponent of high volume fraction particle reinforced aluminum matrix composite were also discussed. This research provided new perspectives and guidance for designing and fabricating composites with superior high-temperature creep properties.