Materials Science. Non-Equilibrium Phase Transformations.
Vol. 7 (2021), Issue 3

Table of Contents

  • Improving the corrosion resistance of carbon steel cylindrical pipe by nano-materials coating, part -2

    pg(s) 79-84

    This part is a continuation of Part-1, which was studying the effect of anti-corrosion nano-materials coating using zinc (Zn) and cobalt (Co) on corrosion resistance and its relationship with mechanical properties. While, part 2 was on studying the linear stresses resistance after coating by using the same nanomaterials of paret-1 of carbon steel pipe and their relationship with chemical corrosion resistance using finite element analysis (FEA). The coating was tested with different thicknesses of nano-layers (300 μm, 600 μm, 900 μm, 10 μm) on a thick-walled cylindrical pipe subjected to a uniformly distributed internal pressure of 4 bars. The results showed that the value of linear normal stresses did not change when coating with 300 μm for both nano-coating materials. However, it was started to decrease slightly when covered with 600 μm of cobalt and continues to decrease with increasing the coating thickness. In addition, the results have shown that the overall improvement in linearized normal stresses and corrosion resistance due to cobalt coating can be about (66 %) higher in comparison with Zinc at 10 μm thickness of coating.

  • Impostation of an experimental design for studying the optimization of artificial aging process for the aluminium alloys

    pg(s) 85-88

    New area industry of Albania, in recent years, factories with closed cycle of production and processing of aluminium alloys are being targeted. In Albania about 25,000 tons of aluminum alloys per year are produced and there is a tendency to increase this production. This reality has encouraged us to undertake a number of studies with the primary objective for optimizing the parameters of the basic process of this industry. In this article we focus on the process of artificially aging aluminum alloys. From early and newer studies [2], the importance and delicacy of temperature-time parameters in the evolution of microstructure and in the mechanical properties of the final product are recognized and underlined. We have impost an experimental planning based on the Response Surface Method by choosing Central Composite Design to optimize the temperature and time parameters for the artificial aging with the object ive of maximizing the process indicator – mechanical properties, hardness in our case. The plan includes 13 tests with 5 replicas in the center of the experiment, built with the help of Design-Expert DX7 and DX13 software. The focus of our attention was the assesment of the design, analysis of residuals and diagnostic diagrams and forms of presentation of results: mathematical model, 3D response surface, isocontours and effects of interaction between factors. In the future works we will present the experimental results of the optimization of the artificial aging process for different aluminium alloys produced in Albania.

  • Nanosized ZnO and ZnO@zeolite composite prepared via sonication method

    pg(s) 89-92

    ZnO nanosized materials are well known for their photocatalytic and antibacterial properties. Their implication in water treatment and environmental protection, especially as a part of composite materials, has been an object of study of a great number of researchers working in the field. Zeolites are excellent candidates for support of composites preparation with semiconductor oxides since they are nonhazardous, non-expensive and naturally abundant materials. In order to synthesize nanosized ZnO with well-developed surface area and uniform size distribution in pristine form and supported on zeolite, we applied the method of precipitation assisted by sonicatio n. As prepared ZnO nanoparticles and the composite ZnO-zeolite were characterized by XRD, SEM and UV-Vis spectroscopy. The ZnO crystalized in wurtzite structure in both materials. The morphology of ZnO nanoparticles was affected by the zeolite framework, as in the composite the ZnO was formed in-situ at the presence of zeolite. The ultrasonic irradiation during the precipitation of Zn(OH)2 and aging of the reaction mixture causes activation of the zeolite surface and prevents the aggregation of ZnO particles. In result evenly distributed ZnO nanoparticles were obtained in the composite.

  • Electron Beam Melting and Refining of Copper

    pg(s) 93-95

    Experimental results for the quality of electron beam melting and refining of pyro-refined copper samples are analysed by an empirical model estimation approach. Investigation of the influence of the process parameters – melting power and time of refining on the removal efficiency of specific impurities, overall removal efficiency and material losses is performed.

  • Fabrication of the Porous Structures with Gradient Thickness of the Struts, by using FDM 3D Printing with Dynamically Changed Parameters during the Printing

    pg(s) 96-99

    This paper deals with 3D printing of porous, functionally graded structures by using Fused Deposition Modeling (FDM). We investigated the printing parameters that can allow printing with gradual infill and challenges associated with this method of printing. We fabricated polylactic acid (PLA) porous structures with variable infill by using FDM 3D printing. Set of the printing parameters for variable infill were investigated: gradient infill and gradient speed and the most successful case is shown. The significant influence of the printer hardware elements was noticed, among which, the worn gear tooth and inadequate extruder feed model can result in inability to print functionally graded lines.

  • Development and investigation of new special steel

    pg(s) 100-102

    New special high nitrogen steel used in arms industry is developed. The new steel and technology of its production are developed on the basis of the metallurgy under pressure. The mechanical properties by the results of the short -term strength and notchimpact strength tests are determined. The new steel has higher mechanical characteristics in comparison with conventional nitrogen free analogue. Non-destructive control is carried out. Dense structure without defects is established.

  • Technical requirements for the materials from which clothes for firefighters are made. Types of tests

    pg(s) 103-106

    The report examined the technical requirements for materials from which firefighters’ clothing is made and the types of testing of the materials from which the specialized protective equipment for the protection of firefighters, for neutralizing and elimin ating threats and their follow-up to incidents at critical infrastructure sites are made.

  • Physicochemical and technological researches of marls from the area of the village Lovets related to the production of the new “Yellow paving stones”

    pg(s) 107-109

    Due to force majeure circumstances, new researches of marls from the Alexandra deposit to the village of Lovets (Shumen region) were carried out to replace the marls from the village Svetlen (Targovishte region), which are part of a plastic mass for the production of large, fine-ceramic parts (yellow paving stones) from peturgical phases. Marls are characterized in terms of mineral and chemical composition. Their properties, characterizing them as a ceramic raw material, have been determined. Three test masses with a chemical composition similar to the one with the participation of marls from the village of Svetlen were developed. The test specimens are characterized in terms of sintering and strength characteristics. It has been established that the marls can be used to repla ce the marl from the village Svetlen in the composition of the plastic fine-ceramic masses for the production of yellow pavers.