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Go to Editorial ManagerAl2O3 is a major reinforcement in aluminum-based composites, which have been developing rapidly in recent years. The aim of this paper is to investigate the effect of alumina phases and amounts on the physical properties of fabricated Al-Al2O3 composite. Alpha micro and gamma nano of alumina with particle size of 30µm and 20 nm respectively reinforced aluminum matrix of 45 µm. The percentage of reinforcement material were in the range of (5, 10 and 15wt.%) fabricated by powder metallurgy technique. Specimens dimensions were a disc specimens with 11mm diameter and 5 mm thickness. The green density was achieved under compaction pressure of 500MPa, and then sintered under pressure less sintering at 500ºC in a vacuumed tube furnace for two hours Physical properties of the composite samples have been studied such as relative density, sintered density, porosity, microstructure characteristics, particles distribution, agglomeration, grain sizes and granularity accumulation distribution. It has been noticed that at the micro alumina phase, its relative densities are decreased when there is an increase in amount of micro alumina addition, on the contrary in case of nano composites, where the relative density are increasing along with the increase in nano alumina addition. At micro and nano composites, the produced relative densities are less than the pure aluminum relative density. Agglomeration are increasing with the increase in amount of reinforcement, while its more obvious with nano composite. Grain size reduced with the increase in amount of alumina in micro and nano composites, while, the obtained average grain size diameter is less in nano composite than in micro composites. It is obvious from the results that the variation in physical properties and microstructure of Al-Al2O3 composite are depends on both of alumina phases (size) and percentages. At 15wt.% of nano alumina higher relative density and lower porosity will be obtained.
Functionally graded materials were created using laser-directed energy deposition technology. This work examines how different mixing ratios of Stainless Steel 316L and Inconel 625 affect the relative density and porosity of these materials. Twelve samples were created using a constant laser power of 600 W, three different laser scan speeds (20, 25, and 30 mm/s), and four different SS316L/IN625 transition ratios (85%/15%, 60%/40%, 40%/60%, and 15%/85%). To determine the volumetric distribution across the compositional gradients, the porosity and relative density measurements were taken. Optical and scanning electron microscopy were used for microstructural analytical characterization to differentiate between compositional gradients in grain shape and phase distribution. The mechanical performance was examined using microhardness measures, namely the Vickers method. This study applied to prove the process parameters and compositional transformations to the resulting microstructural features and mechanical properties, providing insight into optimizing the laser-directed energy deposition-manufactured functionally graded materials for advanced performance. The best graded composition was found that gives the best overall performance based on experimental data.
This paper aim to study the effects of earth reinforcement on the stresses generated within a semicircular cross-section tunnel lining buried in sandy soil due to surface loading. The effect of position and number of reinforcement layers was studied. Also, the relative density of soil was investigated. The depth of soil above the tunnel crown was fixed to be three times the tunnel radius. Two relative densities for soil were used, 55.3% and 73.3%. One layer of reinforcement that was used located at distance equal to the radius or two times the radius above tunnel crown. Also, two layers of reinforcement were located at distance equal to radius and two times radius above the tunnel crown. The results show that the use of earth reinforcement will reduce the stresses generated in the tunnel lining due to application of surface loading.