Advanced structural materials 2011 (original) (raw)
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Molecules, 2021
Ti(C,N)-reinforced alumina-zirconia composites with different ratios of C to N in titanium carbonitride solid solutions, such as Ti(C0.3,N0.7) (C:N = 30:70) and Ti(C0.5,N0.5) (C:N = 50:50), were tested to improve their mechanical properties. Spark plasma sintering (SPS) with temperatures ranging from 1600 °C to 1675 °C and pressureless sintering (PS) with a higher temperature of 1720 °C were used to compare results. The following mechanical and physical properties were determined: Vickers hardness, Young’s modulus, apparent density, wear resistance, and fracture toughness. A composite with the addition of Ti(C0.5,N0.5)n nanopowder exhibited the highest Vickers hardness of over 19.0 GPa, and its fracture toughness was at 5.0 Mpa·m1/2. A composite with the Ti(C0.3,N0.7) phase was found to have lower values of Vickers hardness (by about 10%), friction coefficient, and specific wear rate of disc (Wsd) compared to the composite with the addition of Ti(C0.5,N0.5). The Vickers hardness val...
Mechanical properties of Al2O3\Ti composites fabricated by spark plasma sintering
Ceramics International, 2015
Al 2 O 3 \Ti composites presenting a range of metal to ceramic ratios were fabricated using SPS technology and subsequently characterized. A titanium hydride that decomposes in the 600-700 1C temperate range was used as the source of Ti. The composite densification process was initiated at 825 1C, and reached a maximum densification rate at 1150 1C. Microstructural analysis revealed the homogenous distribution of submicron-sized Al 2 O 3 grains and micron-sized Ti grains. Thus, the fine microstructure of the composites provided improvements in hardness, Young's moduli and flexure strengths. The composites displayed lower resistance to fracture than did pure alumina, with cracks largely propagating around the alumina grains, which indicates that the ceramic-metal interface is weak. Finally, the formation of a Ti-Al-O solid solution at the metal/ceramic interface was detected by scanning electron microscopy and X-ray diffraction.
Production and characterization of metastable Al2O3–TiO2 ceramic materials
Journal of Materials Science, 2007
Producing nanostructured materials through metastable phases is interesting in the field of ceramic materials. Metastable phases can be obtained by the Atmospheric Plasma Spray (APS) technique which, is a well-known technique to produce coatings. The initial powders are melted during the spraying obtaining a homogenized phase due to their solubility in the liquid state. Afterwards, the molten droplets are quenched in a cooled medium, producing the sought metastable phases. Finally, during material consolidation, the metastable structure evolves due to a dual structure. A suppression of the grain growth is produced as a consequence of the immiscibility of both phases in the solid state. Due to their small grain size and uniform structure, these nanostructured materials exhibit very interesting properties such as higher hardness and toughness. The aim of this research has been to produce nanostructured Al 2 O 3-TiO 2 ceramic powders through APS + quenching route, starting from commercially available micron-sized powders. A complete characterization of the obtained structures using XRD, SEM, FESEM and EDS has been carried out in the Thermal Spray Center (CPT) of the University of Barcelona.
The Effect of TiC Additives on Mechanical and Electrical Properties of Al2O3 Ceramic
Applied Sciences
In this study the influence of TiC content on the mechanical and electrical properties of Al2O3-TiC composites containing 30 and 40 vol.% TiC were investigated. The Vickers hardness and fracture toughness of the composites increased with the addition of TiC phase. The composite with 40 vol.% TiC showed the highest flexural strength (687 ± 39 MPa), fracture toughness (7.8 ± 0.4 MPa·m1/2) and hardness (22.3 ± 0.3 GPa) with a homogeneous distribution of the second phase within the ceramic matrix. Besides enhanced mechanical properties, it was found that ceramic composites with more than 30 vol.% TiC fabricated by the spark plasma sintering possess sufficient electrical conductivity for electrical discharge machining as well. Therefore, they do not limit the flexibility of the shape, and any intricate parts can be easily made with these composites which can be recommended for the production of cutting inserts in the tools for machining of superhard hardened steels, hard-to-machine mater...
Advanced Engineering Materials, 2010
The spalling resistance and the thermal shock behavior of ceramics in refractory applications are of a great importance during the advanced secondary metallurgy and continuous metal casting not only from the point of possible failure of steel making aggregates, but also under steel quality considerations due to possible refractory impurities. [1] High alumina containing materials are established refractories with high refractoriness under load as well as excellent corrosion resistance in steel/slag environments. In spite these excellent properties, due to their poor thermal shock performance they are commonly used in combination with carbon for functional components such as submerged entry nozzles, slide gates, etc. [2] The common basic principle and motivation to investigate the Al 2 O 3-TiO 2-ZrO 2 system in the afore cited and some other works, e.g., [3-5] is the microcrack formation and its contribution to both tailored thermal expansion behavior and thermal shock performance. The combination of Al 2 O 3 and TiO 2 leads to the formation of Al 2 TiO 5 that exhibits the highest R 1 thermal shock parameter according to Hasselman among all other ceramics. [6] Al 2 TiO 5 ceramics have a very low thermal expansion because of microcracks at grain boundaries induced by the high anisotropy along its three crystallographic axes. [7] However, pure Al 2 TiO 5 tends to decompose into Al 2 O 3 and TiO 2 at temperatures ranging from 800 to 1300 8C during cooling as a result of eutectic reactions. [8] The use of high-temperature neutron diffraction and differential thermal analysis has shown that the process of decomposition in metastable Al 2 TiO 5 is reversible and that reformation can occur readily when decomposed Al 2 TiO 5 is reheated above 1300 8C. [9] In the same contribution is further shown that decomposition of Al 2 TiO 5 during cooling below 1200 8C is governed by the temperature-dependent atomic diffusion rates. Following decomposition, the material no longer exhibits either a low thermal expansion coefficient or favorable thermal shock behavior. [10] The thermal durability of Al 2 TiO 5 can be improved by the formation of solid solutions with MgO, Fe 2 O 3 , or TiO 2 which are isomorphous with the mineral pseudobrookite. [11] Another source of stabilization is the limitation of microcracks, microcracks growth as well as grain growth by the addition of additives such as SiO 2 , ZrO 2 , ZrTiO 4 , or mullite most of which do not form a solid solution with Al 2 TiO 5 but rather restrain the tendency of Al 2 TiO 5 toward decomposition. [12] Especially during sintering of Al 2 TiO 5-ZrTiO 4 mixtures composite materials with high-temperature stability as well as low thermal coefficient can be produced due to in situ partial reactions. [13] Within the pseudoternary alumina-titania-zirconia system two basic compounds exist, namely aluminum titanate and zirconium titanate. [14] The zirconium titanate composition ranges from ZrTiO 4 over Zr 5 Ti 7 O 24 up to ZrTi 2 O 6 (Srilankite), that is, from zirconia titania ratio of 1:1 to 1:2. Complete solid solubility between the first two compounds appears. [15,16] Aluminum titanate occurs only in the form of Al 2 TiO 5. Depending on the temperature, the formation of either aluminum titanate or zirconium titanate is favored. Bonhomme-Coury et al. [17] stated that up to 1500 8C only zirconium titanate formation occurs. Wohlfromm et al. [18] concluded a
TiC-strengthened Al2O3 by powder tailoring and doping procedures
Materials Science and Engineering: A, 1993
High-carbide A1203/TiC composites have been fabricated without hot-pressing by different processing techniques. Transient liquid phase sintering with additions of Till 2 turned out to be the most promising of the doping procedures. The highest strength, (> 800 MPa), however, was measured when omitting all additives and using a tailored alumina raw material with narrow grain size distribution. The influence of the alumina grain size distribution on sintering and strength is discussed as being associated with the amount of grains and aggregates larger than 1/~m and with the mutual homogenization of oxide and carbide components. In contrast, the reduction of the median powder grain size plays a minor role only.
Analysis of alumina-based titanium carbide composites by laser-induced breakdown spectroscopy
In this work, alumina (Al2O3) containing different volume%of titanium carbide (TiC) ranging from 0 to 30 were consolidated by the novel spark plasma sintering. The spectroscopic analysis of the plasma generated by irradiation of laser Nd:YAG (k = 1,064 nm) on different concentrations of the composites in air atmospheric pressure was performed. The qualitative examination of the composites confirms the presence of aluminum, titanium, and carbon as major elements, while magnesium and sodium have been found as minor trace elements. Plasma parameters were estimated by assuming the LTE conditions for optically thin plasma. The electron density and temperature were evaluated by using the Stark broadening and intensity of selected aluminum emission lines, respectively. The addition of TiC to Al2O3 shows a linear behavior with plasma temperature corroborated by the calibration curve of Ti in the composites. The results suggest that calibration curve between plasma temperature and the composites can be used to estimate different concentrations of TiC in Al2O3 without analyzing the whole elements in the composites and thus opens up new applications of LIBS in ceramic industry.
Ballistic study of alumina ceramic-steel composite for structural applications
Journal of Ceramic Processing Research, 2020
The protection of security/military personnel and their structural facilities such as vehicles, aircraft and other security hardware continues to attract research attention as trade-off between weight and protection lingers. Ceramics are employed in lightweight armour system for its ballistic efficiency and weight advantage; meanwhile, it is comparatively expensive. This research examined the effectiveness of sintered alumina, developed from corundum, as a laminate component of ceramic-steel composite for structural armour applications. Both armour steel and medium carbon steel were separately impacted by 7.62 × 51 mm armour-piercing (AP) projectile before laminated with the prepared sintered ceramic in evaluating its ballistic resistance. The mechanical properties of the sintered ceramic compete favourably with the commercial CoorsTEK ® sintered ceramics. Subsequently, varying target configurations of the ceramic and medium carbon steel composites were studied and analyzed against the same projectile in accordance with NIJ Standard-0108.01. The composite structure, depending on the configuration, displays different forms of failure modes. The high-impact experimental study confirmed the protective capability of the sintered ceramic by its severity interaction against projectile and delay of projectile penetration when used as a laminate component plate.
Journal of Materials Engineering and Performance, 2020
In this work, two copper metal matrix composites (MMCs) reinforced with 20 wt.% of Ti(C,N) or Ti 2 AlN particles were studied. The reinforcement particles were synthesized by flash sintering under 2 bar nitrogen atmosphere causing an SHS reaction ignited by electrical current. This reaction led to produce TiC 0.7 N 0.3 solid solution for the MMC1 reinforcement and Ti 2 AlN, TiN, and Ti 3 Al titanium aluminide for the MMC2 reinforcement. Both MMCs were densified by liquid phase sintering. The structural characterization was performed by XRD analysis while the morphology and chemical element distribution of both MMCs were analyzed by SEM and EDS. The structure of the two MMCs was relatively dense and showed good wettability. The mechanical and tribological behavior of MMCs evaluated by nanoindentation and wear testing reveals that the addition of 20 wt.% of reinforcement considerably improves the properties of copper matrix. Indeed, the MMC1 proved to be 3 times harder and 10 times more wear-resistant than the MMC2 composite. Keywords mechanical and tribological properties, metal matrix composites (MMCs), nitrogen atmosphere, SHS, Ti(C,N), Ti 2 AlN
Materials Science and Engineering: A, 2020
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