Papers by Keyword: TiB₂

Abstract: The demand for structural lightweight in a variety of industries, particularly the automobile industry, has driven the development of heat-free die-cast aluminum alloys with excellent properties. Utilizing lightweight materials, such as Al-Si alloys has several benefits, including higher overall performance in automobiles and other industries, increased heat resistance efficiency, decreased emissions, and reduced weight. The purpose of this study is to modify the microstructure and enhance the mechanical properties of high-pressure die-casting (HPDC) AlSi10MnMg foundry alloy by incorporation of TiB₂ and Sc without any heat treatment. The results showed that the HPDC process significantly refines the grain structure and AlSiMnFe intermetallic compounds, transforming the eutectic morphology from sharp to rounded, and 93% enhancement in elongation at the optimum content (0.018 wt.%) of TiB₂. While the hardness of the alloy was improved by 15.7% with the addition of 0.03wt.% TiB₂. TiB₂ incorporation refines the grain structure and AlSiMnFe phases, while depressing externally solidified crystals (ESCs). The HPDC process refines Al₃Sc phases as well as AlSiMnFe phases while increasing yield strength due to Al₃Sc strengthening effects. After 0.5wt.% Sc addition in 0.018wt.% TiB₂-AlSi10MnMg alloy, the YS, and EL reached the maximum of 196MPa and 9.93% respectively.

Abstract: Different Ta concentrations together with stochiometric grain refiner (Al-2.2Ti-1B) in Al-Si-Mg based alloys were investigated with the aim to elucidate grain refinement mechanisms. Post-solidification microstructure was characterised using optical microscopy and scanning electron microscopy (SEM), with a special focus on the Ta-rich layer (more likely to be Al₃Ta) on the basal planes (0001) of TiB₂. A significant grain refinement was observed by using the solute Ta together with stochiometric grain refiner (Al-2.2Ti-1B). In order to further elucidate the formation of Ta-rich layer on the basal planes (0001) of TiB₂, the Density Functional Theory (DFT) calculation were also performed to determine the interface energies of different interfaces and sandwich configurations, including Al (111), Al₃Ti (112) and Al₃Ta (112) at the interface of TiB₂ basal plane (0001). It was found that the interface energy for Ti-terminated TiB₂ at the interface throughout all configurations involved in this paper is lower than that for B-terminated TiB₂, indicating that Ti-terminated TiB₂ is more favourable. It was also found that the Al₃Ta configuration yields the same interface energies as the Al₃Ti configuration. Furthermore, the interface energy of the sandwich configuration also shows nearly identical values along the TiB₂ // Al₃Ti and TiB₂ // Al₃Ta interface energy, strongly indicating that the solute Ti can be fully replaced by the solute Ta.

Abstract: The TiB₂ reinforced Al-5Cu composites was manufactured by additive manufacturing with two kind of heat sources, i.e., cold metal transfer (CMT) and electron beam melting (EBM). The TiB₂ particles were in nano-sized with some submicron-sized particle clusters , and their morphologies were round and near round without sharp angles. It was found that the introduce of TiB₂ particles improved the mechanical properties of Al-5Cu alloy obviously. The results demonstrated that both the additive manufacturing methods of cold metal transfer (CMT) and electron beam melting (EBM) could improve the microstructure of the composites significantely. Compared with the traditional casting, Al-5Cu alloy the grain sizes of the TiB₂ reinforced Al-5Cu composites decreased from larger than 100 μm to 40 μm with CMT process and 25 μm with EBM process. The hardness of the TiB₂ reinforced Al-5Cu composites with EBM after heat treatment could be reached to 153 HV10. The refined grains and high hardness of the TiB₂ reinforced Al-5Cu composites with EBM additive manufacturing technique verified that AM technology is a promising way to optimize the microstructure and mechanical properties of Al-Cu composites.

Abstract: Titanium Boride (TiB₂) particles reinforced with aluminum alloy (AA 7075) composites were developed using the two-step stir casting method. TiB₂ with aluminium alloy was varied in 5, 10, 15 weight percentages (wt.%) . The mechanical properties of the composites were assessed through density, hardness, tensile and impact. Factography observations were also evaluated with Scanning Electron Microscopy (SEM) and phase identification of the composite was carried out through X-ray diffraction technique (XRD). The XRD pattern of alloy and composites revealed peaks of Al and TiB₂ particles and the intensity of TiB₂ particles increased with increase in wt. %. Compared to the base matrix, the density and hardness of composites increased with the wt. % of TiB₂. Addition of TiB₂ particles exhibited grain refinement, thereby improving the mechanical properties. Composite materials exhibited high load bearing capacity due to the strong bonding of TiB₂ and matrix material resulting in increased impact energy. The tensile strength of the composite increased with increasing wt. % of reinforcement. The failure in the composites observed were dimpled structure and ridges, voids, and cracks.

Abstract: The combination of heat treatment, addition of grain refiner and ECAP processing is used to improve mechanical properties and wear resistance of A356 Al alloys with 1.5 wt.% TiB₂. The alloys were grouped into as-cast and pre-ECAP annealing. The alloys were characterized with hardness and wear testing, optical microscopy and SEM. The ECAP processing was done through B_A route for 4 passes and it improved hardness, distribution of TiB₂ and Si particles in the aluminium matrix and increased wear resitance of pre-ECAP annealing specimen.

Abstract: The Ti₃SiC₂-TiB₂-TiC three-phase ceramics are prepared by Spark Plasma Sintering (SPS) method with Self-propagating High-temperature Synthesis (SHS) using Ti, Si, C andB₄C powders. The characterization of sintering product’s image and structure is analyzed by XRD and SEM. Most of TiB₂’s images are angular cuboid or short bar-shaped and most of TiC phase’s images are irregular spherical particles which are evenly embedded in Ti₃SiC₂ substrate and have a good combination interface with Ti₃SiC₂. In the composite ceramic SPS sintering process, sinter sample’s displacement along Z-axis goes through three stages of falling, balance and rising along with the change of heating temperature, which reflects the sample’s change rule between heated expansion force and pressure. Finally its machining performance is analyzed by wire cutting method and machining method. The Ti₃SiC₂-TiC-TiB₂ block composite ceramic proves to have a good machining performance.

Abstract: TiB₂p/Al-10Zn-1.7Mg-1.0Cu-0.12Zr composite was prepared by synthesis of in-situ Al-TiB₂ master alloy, high purity aluminum, pure zinc, pure magnesium, Al-50 wt% Cu and Al-4 wt% Zr master alloys. The mass fraction of TiB₂ particles was varied from 0% to 9.14%. SEM and TEM were applied to evaluate the microstructure and phase component. HB hardness test were carried out on hardness value of the matrix alloy and the composite. The results showed that TiB₂ particles uniformly distributed in the composite and well combined with the matrix alloy. The average grain size of the composites decreased from 110.35μm to 52.07μm when the TiB₂ particles is 4.47%, and the grain size changed slightly when TiB₂ content increased further. The hardness value of the composites which raised from 189HB to 206HB is superior to that of the matrix alloy. As the content of TiB₂ particles increased, HB hardness value also increased.

Abstract: Zirconium diboride (ZrB₂) is a material of particular interest because of the excellent and unique property combination of high melting point and high electrical and thermal conductivity. In this work, the effect of TiB₂ addition on pressureless sintering and hot pressing sintering of ZrB₂ was investigated. Four compositions were prepared with 0, 5, 10 and 20 wt% of TiB₂. First, ZrB₂ and TiB₂ powders were milled by planetary mill with SiC spheres at for 4 h and then they were wet mixed. Compacted samples were pressureless sintered at 2150 oC/1h and hot pressed at 1850 °C/30min with 20 MPa, both in Ar atmosphere. The added TiB₂ completely dissolved into the structure and formed a solid solution with ZrB₂. Addition of TiB₂ in ZrB₂ ceramic improved densification and hardness for both sintering process, but hot pressed samples exhibited better results.

Abstract: Aluminum nitride, AlN, and titanium diborite,TiB₂, are covalent-based ceramics with wide technological applications. However, sintering of these ceramics using conventional methods of high pressure requires not only elevated temperatures but also long processing time. This causes excessive grain growth, which impairs strength and hardness. In the present work, 70%AlN-30%TiB₂ ceramic composites were sintered to relatively higher density and hardness by means of the Spark Plasma Sintering (SPS) at temperatures in the interval from 1500 to 1900°C in order to improve the properties of both compounds and decrease the processing time. The SPS was applied for different sintering temperatures and the effects on density, hardness and surface structure were evaluated. Maximum values obtained for density and hardness were 98.8% of the theoretical value and 13.7 GPa, respectively.

Abstract: In this work, TiB₂-MoSi₂ composite coatings with various contents of MoSi₂ (20 vol. % and 40 vol. %, respectively) were fabricated on SiC coated C/C substrates by low pressure plasma spray (LPPS) technique. The microstructure and phase composition of the coatings were characterized. The ablation behaviors of the composite coatings were evaluated and compared with the pure TiB₂ coating using a plasma flame of about 2200°C. The results showed that MoSi₂ was uniformly distributed in the TiB₂ matrix. All the coatings kept intact after the ablation for 60s - 180s, indicating their excellent ablation resistance. The addition of MoSi₂ had great influence on the ablation behavior of the composite coatings. The TiB₂ coating gained mass after the ablation. The mass of the TM20 coating increased firstly (60s and 120s) and then decreased at 180 s. Mass loss was observed for the TM40 coating during the whole procedure of ablation test.