Hamid M. Mahan

The development of high-strength, low-weight composite materials has been a high-priority demand in the structural, aerospace, automotive, renewable energy, and sports equipment sectors. Micro-particle size Yttrium oxide (Y2O3) has been utilized to enhance the microstructure and mechanical characteristics of the 2024-Al alloy. The stir-casting technique is employed to prepare 2024-Al alloy and aluminum matrix composites (AMCs) with different Y2O3 weight fractions (1 %, 2 %, and 3 %). Scanning electron microscope ESM with EDS analysis and optical microscope imaging have been used to assess the development in the microstructure of AMCs. Furthermore, optical microscope images have been analyzed by using image processing software, ImageJ to evaluate development in microstructure grain size. Vickers' micro-hardness, tensile strength, elongation, and wear-resistant tests were conducted to assess the mechanical properties of AMCs. AMC image analysis results demonstrated a significant reduction in microstructure grain size. The highest reduction in grain size was recorded when adding 2 wt. % of Y2O3, which was approximately 22.5 % smaller than that of the plain alloy. Other mechanical test results demonstrated an increase in the hardness and tensile strength of AMCs compared with the plain alloy by approximately 58 % and 116 %, respectively, upon the addition of 2 wt. % of Y2O3, also tensile test shows increasing of AMCs elongation at failure point with increasing Y2O3 content, 132 % upon adding 3 wt. %. Finally, wear tests show a decrease in the AMC wear rate with an increasing Y2O3 weight fraction compared to the plain alloy.

Using aluminium metal matrix nanocomposites has recently gained increased attention in the industry due to their high strength and ductility. In this paper, TiO₂ nanoparticles in volume percentages of 5 wt. % were added to the AA2024 alloy using the stir casting method. Using a novel powder injection system, TiO₂ nanoparticles with an average particle size of 30 ± 5 nm was added to the matrix. The influence of TiO₂ content on the fatigue life before and after heat treatment was studied. The results showed the fatigue properties of AA2024 with TiO₂ nanoparticles increased after heat treatment. The optimum improvement in fatigue properties was obtained at 5 wt. % TiO₂ after heat treatment, with an improving fatigue life in 14.71% compared with sample based. This is due to an increased number of fine precipitates besides its uniformly distributed after heat treatment. The fatigue life of the composite materials with added nanoparticles was investigated using a finite element-based ANSYS workbench. There was a good match between what happened in the experiments and what happened to the numerical fatigue strength. For the composite materials, the difference between the experimental and numerical values of fatigue strength was not greater than 4% for the matrix. The results also, indicated that, after ageing, the precipitate-free zone at the inter-dendritic zone disappeared or became smaller. However, after adding 5 wt. % of titanium and, also, performing heat treatment, it is not possible to precipitate the Al₂CuMg precipitates, and, instead of it, the Al₃TiCu and Al₇TiCu phases precipitates have been formed.

An aluminum alloy, AA2024, was reinforced with different mass fractions of titanium dioxide nanoparticles (0%, 2.5%, 5% and 7.5%) by stir casting, this was followed by a solution treatment at 500°C for 3 h, quenching in water, and aging at 175°C for 3 h. The purpose was to investigate the effect of TiO2 nanoparticles on the microstructure and mechanical properties of the stir-cast aluminium alloy AA2024. Through ageing treatment, the effects of heat treatment conditions on the homogeneity of the impact toughness and microhardness of AA2024 with nanoparticles were studied. After heat treatment and ageing treatment, the hardness values and impact resistance in different positions of the composite aluminium are greatly improved compared to the unreviewed samples. Furthermore, the distribution of elements existed in the interior of the grain boundary, and the grain was homogeneous after heat treatment, which increased the intercrystallite hardness values. The results showed that 5 wt.% TiO2 was the optimum fraction to achieve the highest microhardness and impact resistance. Using the optimum content of TiO2 and heat treatment, the microhardness and impact resistance were significantly improved over the unreinforced aluminium matrix, specifically due to an increased number of fine precipitates that were uniformly distributed after the heat treatment.

This paper concerns developing the mechanical properties of unsaturated polyester. This work involves preparing a composite material and reinforcing it using river shell particles with volume fractures of (5%, 10%, 15%, 20%, 25%). The composite materials undergone mechanical tests with regard to hardness, tensile, and impact strength. The experimental results obtained show that the addition of river shell particles reduce the original tensile strength and impact strength up to 5% wt, while the hardness is increased with increasing addition of river shell particles percent.