In this study, the effect of cooling rates on microstructures and mechanical properties in a Al-bearing hot-rolled transformation-induced plasticity steel was investigated. The experiments were carried out using hot simulation machine and hot rolling mill, where the samples were cooled at different cooling rates. The results showed that with the increase in cooling rates, film-like retained austenite gradually disappeared and only blocky retained austenite was retained at higher cooling rates. The volume fraction of retained austenite was 9–11% at cooling rates of 0.05–1 °C/s and 4–6% at cooling rates of 5–10 °C/s. In addition, martensite/austenite island was observed because of the heterogeneous carbon distribution. The samples cooled at 0.05 °C/s and 0.5 °C/s exhibited excellent mechanical properties, with tensile strengths of 712 MPa and 726 MPa, total elongations of 42% and 36% and strength and ductility balances of 29.91 GPa% and 26.15 GPa%, respectively. During plastic deformation, the instantaneous work hardening exponent of the sample cooled at 0.05 °C/s increased continuously until it reached the maximum value, while the instantaneous work hardening exponent of the sample cooled at 0.5 °C/s remained stable.

The multiwalled carbon nanotubes thin-film-based electrode was fabricated by electrophoretic deposition and modified with copper (Cu) nanoparticles to fabricate Cu/CNTs nanocomposite sensor for nonenzymatic glucose detection. The expensive glassy carbon electrode was replaced by fluorine-doped tin oxide glass containing CNTs film to confine the Cu nanoparticles growth by electrodeposition through cyclic voltammetry (CV). The ultraviolet visible and X-ray diffraction analysis revealed the successful deposition of Cu nanoparticles on the CNTs-modified electrode. The atomic force microscopy images confirmed the morphology of electrodeposited Cu on CNTs film as uniformly dispersed particles. The electrocatalytic activity of electrode to the glucose oxidation was investigated in alkaline medium by CV and amperometric measurements. The fabricated sensor exhibited a fast response time of less than 5 s and the sensitivity of 314 μA mM⁻¹ cm⁻² with linear concentration range (0.02–3.0 mM) having detection limit 10.0 μM. Due to simple preparation of sensor, Cu/CNTs nanocomposite electrodes are a suitable candidate for reliable determination of glucose with good stability.

This paper discusses the tribological performance of the bearing steel GCr15 treated by an alternating magnetic field. The wear test results showed that the average of wear mass losses decreased by nearly 80% after the magnetic treatment, compared to those before the magnetic treatment. The micro-hardness and microstructures (i.e., grain size, carbide morphology and dislocation distribution) before and after the magnetic treatment were experimentally investigated, and the mechanism of the tribological performance improvement of the bearing steel GCr15 due to the magnetic treatment was then revealed based on the above results.

Nanocrystalline and amorphous Mg₂Ni-type (Mg₂₄Ni₁₀Cu₂)_100–xNd_x (x = 0, 5, 10, 15, 20) alloys were prepared by melt-spinning technology. The structures of as-cast and spun alloys were characterised by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Electrochemical performance of the alloy electrodes was measured using an automatic galvanostatic system. The electrochemical impedance spectra and Tafel polarisation curves of the alloy electrodes were plotted using an electrochemical work station. The hydrogen diffusion coefficients were calculated using the potential step method. Results indicate that all the as-cast alloys present a multiphase structure with Mg₂Ni type as the major phase with Mg₆Ni, Nd₅Mg₄₁ and NdNi as secondary phases. The secondary phases increased with the increasing Nd content. The as-spun Nd-free alloy exhibited nanocrystalline structure, whereas the as-spun Nd-doped alloys exhibited nanocrystalline and amorphous structures. These results suggest that adding Nd facilitates glass formation of Mg₂Ni-type alloys. Melt spinning and Nd addition improved alloy electrochemical performance, which includes discharge potential characteristics, discharge capacity, electrochemical cycle stability and high-rate discharge ability.

The microstructure and fracture toughness of weld metal under Ti-free and Ti-containing different fluxes were investigated in this study. It was found that the trace element Ti of flux in submerged arc welding produced significant influence on the fracture toughness. The addition of 60 ppm Ti induced the sharp increase in J_0.2 value from 232.78 to 364.08 kJ/m². Microstructure characterization revealed that a large number of oxide inclusions prompted the nucleation of acicular ferrites and refined grains, which improved the fracture toughness of Ti-containing weld metal greatly. Moreover, the crack propagation path was more tortuous and bifurcated due to the small amount of carbide precipitations along grain boundaries and blocky martensite–austenite islands for Ti-containing weld metal. Meanwhile, the large-angle grain boundaries caused crack deflection and increased the resistance of crack propagation compared to Ti-free weld metal.

The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using digital holography. The results indicate that solution chemistry has a significant effect on film breakdown and diffusion layer. The phase distribution changes at different applied potentials show that in the process of film breakdown, dissolution of metal ions from pitting is not remarkable in chloride-only solution, whereas dissolution of metal ions is significantly high in thiosulfate and chloride solution. Thiosulfate has a combined effect with chloride ions in passive film degradation.

A 0.2C-1.5Mn-1.5Si-0.6Cr-0.05Nb (wt%) steel is treated respectively by novel quenching-partitioning-tempering (Q-P-T) process and traditional quenching and tempering (Q&T) process for comparison. X-ray diffraction analysis indicates that Q-P-T steel has about 10% retained austenite, but Q&T steel hardly has one. With the increase of compression strain rate from 7 × 10² to 5 × 10³ s⁻¹, the flow stress of Q-P-T steel increases, which demonstrates the positive strain rate effect, but does not exist in Q&T steel. The characterization of scanning electron microscopy indicates that a large number of long, straight martensite laths in Q-P-T steel will bend or be destroyed by large compressive strain of 35% at 5 × 10³ s⁻¹. However, relative small compressive strain of about 5% at 7 × 10² s⁻¹ almost does not have any effect on the original lath morphology. The characterization of transmission electron microscopy further reveals the origin of the positive strain rate effect and the microstructural evolution during dynamic compressive deformation.

Electron irradiation effects on phase stability of the E (Al₁₈Cr₂Mg₃) phase have been investigated by high-angle annular dark-field scanning transmission electron microscopy and high-resolution transmission electron microscopy (HRTEM). The in situ HRTEM observations show that the Al₁₈Cr₂Mg₃ particles with different thickness undergo amorphization and dissolution under 300 keV electron irradiation at 25 °C. The results indicate that the intermetallic compound Al₁₈Cr₂Mg₃ is unstable under electron irradiation, and structural changes mainly depend on the thickness of particles. Amorphization in the thick particles is caused by a combination of chemical disordering and an increase in point defect concentration. Dissolution after amorphization in the thin particles is attributed to the diffusion of point defect towards the Al matrix.

The effect of Ca addition on the microstructure and impression creep properties of AS31 magnesium alloy was investigated in the current study. The results showed that the microstructure of AS31 alloy is composed of α(Mg) phase, massive Mg₁₇Al₁₂ and some Chinese script Mg₂Si compounds. Addition of 2 wt% Ca to AS31 alloy resulted in complete elimination of Mg₁₇Al₁₂ phase and formation of Al₂Ca compound. Ca improved the alloy’s creep properties especially at higher temperature. Improvement in the creep properties was attributed to the elimination of soft Mg₁₇Al₁₂ and formation of thermally stable Al₂Ca compound. According to the obtained stress exponent and creep activation energy, pipe diffusion climb-controlled creep was estimated as the dominant creep mechanism and Ca had no influence on the dominant mechanism.

The effect of sintering temperature on the densification mechanisms, microstructural evolution and mechanical properties of spark plasma sintered (SPS) compacts of a gas atomized Al-4.5 wt.%Cu alloy was investigated. The powder particles whose size varied between 10 to 500 µm was subjected to SPS at 400, 450 and 500 °C at a pressure of 30 MPa. The compact sintered at 500 °C exhibited fully dense microstructure which was characterized by a uniform distribution of the secondary phase, free of dendrites and micro-porosity. Microscopy and the SPS data reveal that the events such as particle rearrangement, localized deformation and bulk deformation appear to be the sequence of sintering mechanisms depending on the size range of powder particles used for consolidation. The compact sintered at 500 °C exhibited the highest hardness and compression strength since the microstructure was characterized by fine distribution of precipitates, large fraction of submicron grains and complete metallurgical bonding.