[en] The resolution and the summing characteristics of an EXOGAM segmented Clover germanium detector has been studied for use it in γ spectroscopic experiments. The measurements have been performed with standard radioactive sources of ¹⁵²Eu, ¹³³Ba and β-delayed γ-rays from ¹⁷⁶Ir decay. The data analytic results, realized by software, are presented in this paper. (authors)

[en] The neutron deficient nuclide ¹⁷⁵Ir was produced by irradiation of ¹⁴⁶Nd with 210 MeV ³⁵Cl via a fusion-evaporation reaction channel. The reaction products were transported to a low-background location using a helium-jet recoil fast-moving tape-transport system for measurement. The experimental devices and data analysis method are introduced. Based on the decay-curve fitting of the β-delayed γ ray from ¹⁷⁵Ir, realized by the least-square method, a new long-lived isomeric state of ¹⁷⁵Ir is proposed and briefly discussed. (authors)

[en] Highlights: • CNT aspect ratio has only small effects on the strength of CNT/Al. • Reinforcement of CNT/Al is dominated by dispersion strengthening. • CNT addition within 0.5 wt% increases strength markedly without plasticity loss. • The calculated CNTs diameters are close to the experimental used ones. The effects of carbon nanotube aspect ratio (R) on mechanical properties of CNT/Al composites containing 0–2.0 wt% CNTs are studied. The optimum carbon nanotube (CNT) reinforced aluminum (Al) composites are fabricated at 580 °C for 1 h under 60 MPa, and subsequently hot extruded at 480 °C. CNT addition within 0.5 wt% can increase the strength significantly without plasticity loss, which overcomes the dilemma of strength and toughness. Strength and hardness increase significantly due to the uniformly distributed CNTs in Al matrix within a content of 1.0 wt%. Quantitatively fitting results also show that the main strengthening mechanism of CNT/Al composites should be dispersion strengthening rather than load transfer. The R, which is very crucial for load transfer theory, has only small effects on the mechanical properties of CNT/Al composites. The calculated CNTs diameters are close to the experimental used ones.

[en] To improve the dimensional stability of Al–Cu–Li–Sc–(Ag) alloys and identify the underlying micro-yield mechanism, the effects of silver (Ag) content (0, 0.2, 0.4, 0.6 and 0.8 wt%) on the microstructure, micro-yield behaviour and dimensional stability of Al–Cu–Li–Sc–(Ag) alloys were investigated by transmission electron microscopy (TEM), cyclic load–unload test and thermal cycle test. The results showed that increasing the Ag content promoted the precipitation of the T₁ and δ′ phases in the α–Al matrix and decreased their diameters, which resulted in the increase of the micro-yield strength and strain hardening rate of the Al–Cu–Li–Sc–(Ag) alloys. Because T₁ and δ′ precipitates can effectively pin the mobile dislocations and impede their movement, the critical resolved shear stress (CRSS) resulting from the pinning of mobile dislocations by T₁ and δ′ precipitates played a critical role in the micro-yield behavior. There existed a relation between σ _mys and τ _CRSS similar as that of macro-yield strength, σ _mys = α · τ _CRSS + σ ₀′. However, the low α value in the micro-yield stage compared with the macro-yield stage indicated that fewer activated slip systems would be enough to produce a residual strain of 1 × 10^–6 at the beginning of the micro-yield stage. The thermal cycle decreased the residual relative length (RRL) of the alloys and the stable RRL after the thermal cycle could serve as an indicator of the thermal dimensional stability of the alloys. Increasing the Ag content decreased the stable RRL of the Al–Cu–Li–Sc–(Ag) alloys and hence improved their thermal dimensional stability. (paper)

[en] One high-spin rotational band in neutron deficient odd-odd nucleus ¹⁷⁰Re has been identified and assigned to the πh_1/2 direct x νi_13/2 configuration through the ¹⁴²Nd (³²S, 1p3n γ) ¹⁷⁰Re reaction. The band is analyzed on the basis of the arguments of energy systematics, signature inversion systematics, intra-band B (M1)/B (E2) ratios, quasiparticle Routhians, dynamic moment of inertia and Total Routhian Surface (TRS) calculations. From detailed analyses on its structural properties, the configuration, spins and parity have been further assigned for this rotational band. (authors)

[en] Highlights: • NDs are uniformly dispersed in the matrix by a surface modification strategy. • NDs are intimately contacted with the matrix, forming stable, low-indexed interfaces. • A high tensile strength of 741.1 MPa was achieved for 0.8 vol% ND/2024Al composite. • The strengthening mechanisms of ND/2024Al composites are clarified. -- Abstract: Poor dispersion of nanodiamonds (NDs) is the bottleneck to exploit their intrinsically excellent properties in metal matrix composites (MMCs). In this study, a strategy of surface modification was developed to uniformly disperse ND particles into 2024 aluminum alloy. Microstructure observations showed that individual NDs are closely contacted with the matrix, forming reaction-free interfaces. Consequently, a high-strength 0.8 vol% ND/2024Al composite with an ultimate tensile strength of 741.0 MPa is developed. Theoretical and experimental measurements prove that the strength improvement of ND/2024Al composite is mainly attributed to the Orowan strengthening, thermal mismatch strengthening and grain refinement strengthening. This work demonstrates the effective application of NDs as a reinforcement for MMCs towards high-specific-strength materials.

[en] The effect of B/Ti mass ratio on grain refining of the low-titanium aluminum produced by electrolysis was investigated by adding AlB master alloy to the melt of the low-titanium aluminum. The results show that the addition of titanium by electrolysis is an effective way of grain refining of aluminum, and addition of boron to the melt of the low-titanium aluminum can further increase the grain refining efficiency. And the best grain refining efficiency is obtained when the B/Ti mass ratio is 1:10. However, when the B/Ti mass ratio is 1:2.22 (the stoichiometric value for TiB₂), the grain refining efficiency vanishes almost completely. It means that all of the solute titanium atoms in the melt of the low-titanium aluminum react with boron atoms that come from AlB master alloy to form TiB₂ particles, and TiB₂ particles have not grain refining ability. The grain refining efficiency seems to increase with addition of more boron to the melt after the B/Ti mass ratio exceeds 1:2.22. But the grain refining efficiency is very poor, and similar to that of pure Al refined by AlB master alloy. It further shows that TiB₂ particles do not participate in grain refining, and that the excess boron atoms in the melt also cannot turn TiB₂ particles into the effective nuclei for aluminum as the solute titanium atoms do

[en] The settlements and the grain refining action of TiB₂ particles in the melt of electrolytic low-titanium aluminum (ELTA) with Al-4B addition were investigated. The results show that numerous fine TiB₂ particles will be formed when Al-4B master alloy is added into the melt of ELTA at the Ti/B mass ratio of 5:1. Because of their fine sizes, though there are also TiB₂ particle settlements, there will still be more TiB₂ particles being suspended in the melt of the ELTA with Al-4B addition than in the melt of the pure Al with Al-5Ti-1B addition at a given Ti addition level. These fine TiB₂ particles, together with the titanium atoms left in the melt, will form more heterogeneous nucleation sites during solidification of the melt, improving the grain refining efficiency and the fading-resisting ability obviously. Comparing with the method of adding Al-5Ti-1B into pure Al, the present method has advantages in resulting in the formation of fine TiB₂ particles and preventing their settlements