The role of slag in the process of continuous casting of steel (CCS) is reduced to the thermal and chemical insulation of the liquid steel surface, and additionally to refining. The ability to adsorb non-metallic inclusions flowing off from the crystallizer, mainly Al2O3, determines its physicochemical properties. As a result of adsorption and dissolution of inclusions tin he liquid layer the viscosity and thickness of mould flux change, which eventually affects the technological parameters and behavior of slag in the crystallizer. The influence of aluminum oxide on the viscosity of slag was empirically investigated with a structural viscosity model worked out by Nakamoto. The results of the simulation are presented in the form of plots. Authors observed a significant influence of Al2O3 on the slag viscosity, which suggests that this effect should be taken into account when selecting chemical composition of mould flux for definite types of steel. The results of calculations also show that the disturbances in casting caused by the use of the mould slag may be connected with the content of non-metallic inclusions in steel.
Ceramic injection moulding and gas pressure infiltration were employed for the manufacturing of alumina/AlSi10Mg composites. Porous ceramic preforms were prepared by mixing alumina powder with a multi-binder system and injection moulding of the powder polymer slurry. Then, the organic part was removed through a combination of solvent and thermal debinding, and the materials were finally sintered at different temperatures. The ceramic preforms manufactured in this way were infiltrated by an AlSi10Mg alloy. The microstructure and properties of the manufactured materials were examined using scanning electron microscopy, mercury porosimetry and bending strength testing. The results of transmission electron microscopy and scanning electron microscopy observations show that the fabricated composite materials are characterised by the percolation type of the microstructure and a lack of unfilled pores with good cohesion at the metal-ceramic interfaces. This is surprising considering that over 30% of the pores are smaller than 1 μm. The results show that the bending strength of the obtained composites decreased with increasing sintering temperature of the porous preforms.
The subject of the study was the production and characterization of three ceramic-metal graded composites, which differed in addition of the metallic phase. The following composites systems were investigated: Al2O3-Mo, Al2O3-Cu, Al2O3-W. Composites were produced by centrifugal slip casting method. This technique combines the classic casting of the slurry into porous molds with the action of centrifugal force. As a result, sleeve-shaped shapes with a metallic phase gradient were obtained. X-ray phase analysis have not revealed new phases in the produced composites. The type of metallic phase and its distribution in the ceramic matrix influenced the hardness of the produced composites.
Light weight, low density with high mechanical properties and corrosion resistance, aluminum is the most important material and is commonly used for high performance applications such as aerospace, military and especially automotive industries. The researchers who participate in these industries are working hard to further decrease the weight of end products according to legal boundaries of greenhouse gases. A lot of research was undertaken to produce thin sectioned aluminum parts with improved mechanical properties. Several alloying element addition were investigated. Yet, nowadays aluminum has not met these expectations. Thus, composite materials, particularly metal matrix composites, have taken aluminum’s place due to the enhancement of mechanical properties of aluminum alloys by reinforcements. This paper deals with the overview of the reinforcements such as SiC, Al2O3 and graphene. Graphene has recently attracted many researcher due to its superior elastic modulus, high fatigue strength and low density. It is foreseen and predicted that graphene will replace and outperform carbon nanotubes (CNT) in near future.
In this work, three ceramic composite coatings Al2O3-3TiO2 C, Al2O3-13TiO2 C, and Al2O3-13TiO2 N were plasma sprayed on steel substrates. They were deposited with two conventional powders differing the volume fraction of TiO2 and nanostructured powder. The mechanical and tribological properties of the coatings were investigated and compared. The increase in TiO2 content from 3 wt.% to 13 wt.% in the conventional feedstock improved the mechanical properties and abrasion resistance of coatings. However, the size of the used powder grains had a much stronger influence on the properties of deposited coatings than the content of the titania phase. The Al2O3-13TiO2 coating obtained from nanostructured powder revealed significantly better properties than that plasma sprayed using conventional powder, i.e. 22% higher microhardness, 19% lower friction coefficient, and over twice as good abrasive wear resistance. In turn, the Al2O3-13TiO2 conventional coating showed an increase in microhardness and abrasive wear resistance, 36% and 43%, respectively, and 6% higher coefficient of friction compared to the Al2O3-3TiO2 conventional coating.
The current study were performed in order to assess the fabrication possibility of the metal-ceramic composites based on nanocrystalline substrates. The influence of the variable time of the high energy ball-milling (10, 30 and 50 h) on the structure, pores morphology and microhardness of Ti/ZrO2 and Ti/Al2O3 compositions was studied. The X-ray diffraction analysis confirmed the composite formation for all milling times and sintering in the case of Ti/ZrO2 system. Decomposition of substrates during milling process of Ti/Al2O3 system was also observed. Additionally, the changes of lattice parameter as a function of milling time were studied. The morphology of powders and the microstructure of the sintered samples were observed by scanning electron microscopy (SEM). Also, analysis of microhardness and pores structure were performed.