Manufacturing sectors, including automotive, aerospace, military, and aviation, are paying close attention to the increasing need for composite materials with better characteristics. Composite materials are significantly used in industry owing to their high-quality, low-cost materials with outstanding characteristics and low weight. Hence, aluminum-based materials are preferred over other traditional materials owing to their low cost, great wear resistance, and excellent strength-to-weight ratio. However, the mechanical characteristics and wear behavior of the Al-based materials can be further improved by using suitable reinforcing agents. The various reinforcing agents, including whiskers, particulates, continuous fibers, and discontinuous fibers, are widely used owing to enhanced tribological and mechanical behavior comparable to bare Al alloy. Further, the advancement in the overall characteristics of the composite material can be obtained by optimizing the process parameters of the processing approach and the amount and types of reinforcement. Amongst the various available techniques, stir casting is the most suitable technique for the manufacturing of composite material. The amount of reinforcement controls the porosity (%) of the composite, while the types of reinforcement identify the compatibility with Al alloy through improvement in the overall characteristics of the composites. Fly ash, SiC, TiC, Al₂O₃, TiO₂, B₄C, etc. are the most commonly used reinforcing agents in AMMCs (aluminum metal matrix composites). The current research emphasizes how different forms of reinforcement affect AMMCs and evaluates reinforcement influence on the mechanical and tribo characteristics of composite material.

This paper presents research of the impact toughness and hardness distribution in specific zones of a ‘single V’butt multiple-pass welded joints of the high-strength low-alloyed steels. Obtained values of the impact toughness are analyzed in correlation with a microstructure in specific zones of the welded joint, together with the micro hardness distribution found in the related zones. Based on the carried out analysis and results obtained in experiments, the applied technology of welding was evaluated. The original conclusions on influence of the selected welding procedure manual metal arc (MMA) for the root passes and metal active gas (MAG) for the filling and covering passes) on impact toughness of the high-strength low-alloyed steels are drawn. The paper also presents discussion on the valid standards and recommendations related to welding of those steels, from the aspect of applications in design of steel welded constructions.

An optimisation model for small datasets was applied to thixocasted/compocasted composites and hybrid composites with hypereutectic Al-18Si base alloys. Composites were produced with the addition of Al₂O₃ (36 µm/25 nm) or SiC (40 µm) particles. Based on the design of experiment, tribological tests were performed on the tribometer with block-on-disc contact geometry for normal loads of 100 and 200 N, a sliding speed of 0.5 m/s, and a sliding distance of 1000 m. For the prediction of the tribological behaviour of composites, artificial neural networks (ANNs) were used. Three inputs were considered for ANN training: type of reinforcement (base alloy, Al₂O₃ and SiC), amount of Al₂O₃ nano-reinforcement (0 and 0.5 wt.%), and load (100 and 200 N). Various ANNs were applied, and the best ANN for wear rate (WR), with an overall regression coefficient of 0.99484, was a network with architecture 3-15-1 and a logsig (logarithmic sigmoid) transfer function. For coefficient of friction (CoF), the best ANN was the one with architecture 3-6-1 and a tansig (hyperbolic tangent sigmoid) transfer function and had an overall regression coefficient of 0.93096. To investigate the potential of ANN for the prediction of two outputs simultaneously, an ANN was trained, and the best results were from network 3-5-2 with a logsig transfer function and overall regression coefficient of 0.99776, but the predicted values for CoF in this case did not show good correlation with experimental results. After the selection of the best ANNs, the Taguchi grey multi-response optimisation of WR and CoF was performed for the same combination of factors as the ANNs. For optimal WR and CoF, the combination of factors was as follows: composite with 3 wt.% Al₂O₃ micro-reinforcement, 0.5 wt.% Al₂O₃ nano-reinforcement, and a load of 100 N. The results show that developed ANN, the Taguchi method, and the Taguchi grey method can, with high reliability, be used for the optimisation of wear rate and coefficient of friction of hypereutectic Al-Si composites. Microstructural investigations of worn surfaces were performed, and the wear mechanism for all tested materials was light abrasion and adhesion. The findings from this research can contribute to the future development of hypereutectic Al-Si composites.

This paper presents results of comparison of two welding procedures’ influence on selected properties of the welded joints of high-strength low-alloyed steel (HSLA), specifically the impact toughness and the hardness distribution in the specific zones of “single V” butt multiple-pass welded joints. Based on results obtained from experiments, the two applied welding technologies were evaluated. They differ by the welding grove geometry and by the applied root pass welding procedure. Both procedures use MAG (Metal Active Gas) welding for execution of the filling and covering passes, while the root passes are executed by the MMA (Manual Metal Arc) procedure in the first case and by the MIG (Metal Inert Gas) procedure in the second. Experimentally obtained values of the fracture energy of the welded samples for both procedures were smaller than the values for the parent metal, which confirms the fact that welding causes degradation of the mechanical properties of HSLA steel; thus, any welding technology parameters must be so selected to mitigate this deficiency.