Porous 2024Al-Al₃Zr composites were prepared by in situ and spatial scaffolding methods. As the Al₃Zr content increased from 5 wt.% to 30 wt.%, the binding of the powder in the pore wall increased and the defects in the composites decreased. The yield strength of the composites reached 28.11 MPa and the energy absorption capacity was 11.68 MJ/m³ at a Zr content of 20 wt.%, when the composites had the best compression and energy absorption performance. As the space scaffold content increased from 50% to 70%, the porosity of the composites then increased from 53.51% to 70.70%, but the apparent density gradually decreased from 1.46 g/cm³ to 0.92 g/cm³, leading to a gradual decrease in their compressive properties. In addition, by analysing the compression fracture morphology, the increase of Al₃Zr will reduce the stress concentration and hinder the crack growth, while too much Al₃Zr will lead to brittleness and reduce the performance.

Dual-scale (nano and micron) particle-reinforced TiB₂/6061Al matrix composites with different contents of TiB₂ were prepared using powder metallurgy, and then analyzed via microstructure observation and tests of microhardness, tensile properties, and friction and wear properties. The 6061Al powders’ particles changed from spherical to flaky after two rounds of high-energy ball milling, and the TiB₂ enhancer was embedded in or wrapped by the matrix particles after high-energy ball milling. Metallurgical bonding between TiB₂ particles and the matrix was achieved, and Al₃Ti was synthesized in situ during sintering. The hot-pressing process eliminated the internal defects of the composites, and the TiB₂ particles were diffusely distributed in the matrix. The best comprehensive mechanical properties (hardness and tensile strength) were achieved when the mass fraction of TiB₂ was 5% (1% micron + 4% nano); the hardness and tensile strength of the composites reached 131 HV and 221 MPa—79.5% and 93.9% higher than those of the pure matrix, respectively. The composites’ average coefficient of friction and volumetric wear rate were reduced. Composites with a TiB₂ mass fraction of 7% (3% micron + 4% nano) had the highest average coefficients of friction and the lowest volumetric wear rate of 0.402 and 0.216 mm³∙N⁻¹∙m⁻¹, respectively. It was observed that adhesion influences the friction mechanism, which transitions from adhesive wear with slight oxidative wear to abrasive wear.

Fast and accurate determination of effective bentonite content in used clay bonded sand is very important for selecting the correct mixing ratio and mixing process to obtain high-performance molding sand. Currently, the effective bentonite content is determined by testing the ethylene blue absorbed in used clay bonded sand, which is usually a manual operation with some disadvantages including complicated process, long testing time and low accuracy. A rapid automatic analyzer of the effective bentonite content in used clay bonded sand was developed based on image recognition technology. The instrument consists of auto stirring, auto liquid removal, auto titration, step-rotation and image acquisition components, and processor. The principle of the image recognition method is first to decompose the color images into three-channel gray images based on the photosensitive degree difference of the light blue and dark blue in the three channels of red, green and blue, then to make the gray values subtraction calculation and gray level transformation of the gray images, and finally, to extract the outer circle light blue halo and the inner circle blue spot and calculate their area ratio. The titration process can be judged to reach the end-point while the area ratio is higher than the setting value.

In this study, FSW experiments were conducted on a 4 mm-thick A380 aluminium alloy plate and 6061 aluminium alloy using four different needle lengths (2.5 mm, 2.8 mm, 3.0 mm, and 3.5 mm) of H13 steel. The experiments were conducted at the same welding parameters (1000 rpm and 120 mm/min) to explore the effects of different stirring needle lengths on the microstructures and properties of the FSW joints. The experimental results show that FSW joints with varying lengths of needles have a significant effect on the microstructures and properties of welded joints, and the tensile strength increases and then decreases with increases in the needle length. A 2.8 mm needle length can achieve the maximum tensile strength of 203 MPa, about 85.3% of the base material. Too long or too short a needle leads to a decrease in joint performance. Furthermore, different needle lengths have a significant influence on the flowability of the weld core zone, and a suitable needle length will lead to better flowability in the weld core zone. With increases in the needle length, the heat production also increases, and the area of the RS-HAZ will increase with the heat production. When the joints achieve appropriate heat production, the weld core zone will experience grain refinement. At the same time, the grain will grow in the RS-HAZ; the hardness cloud diagram shows that, in the RS-HAZ, the material properties are weaker, and the tensile specimens are mainly fractured in the RS-HAZ. Finally, the tensile specimens exhibit mixed fracture.

Carbonation technology offers a novel approach to enhance steel slag performance, where the compaction degree plays a pivotal role in optimizing the carbonation process. This study reveals that as the compaction degree increases, the peak temperature in the carbonation environment gradually decreases, and the intensity of the carbonation reaction weakens. Post-carbonating, the compressive strength initially increases before declining, peaking at a compaction degree of 60%. At this optimal compaction degree, the material achieves a compressive strength of 124.4 MPa and a CO₂ uptake of 14.5%. The analysis of pore size distribution and carbonation products reveals that steel slag compacts with lower compaction degrees exhibit larger internal pores, leading to dispersed and isolated carbonation products, which restrict performance improvement. Conversely, excessively high compaction degrees cause the premature blockage of gas diffusion pathways by calcium carbonate particles, which impede the carbonation process and degrade the mechanical performance. The moderate compaction of steel slag effectively prevents the early blockage of gas channels, and significantly facilitates the accumulation and bonding of carbonation products, thereby achieving the superior performance.