Papers by Keyword: Titanium Matrix Composites

Abstract: Titanium matrix composites (TMCs) have found extensive application in aerospace, biomedical, and military sectors due to their exceptional strength-to-weight ratio and wear resistance at ambient and elevated temperatures. Nevertheless, conventional production methods often face a compromise between cost and performance, thus limiting the suitability of this material for broad utilization in engineering contexts. Recent research findings indicate that the utilization of manufacturing techniques such as hydrogen assisted blended elemental powder metallurgy (HABEPM) with the incorporation of a double press-and-sinter option, as well as the sintering of powder blends that have been preliminarily activated through milling, can both serve as economically viable methods for the production of highly dense TMCs with satisfactory mechanical properties. Both methods guarantee the activation of sintering in powders, resulting in notable improvements in density and a more refined and uniform microstructure compared to porous and nonuniform composites obtained through traditional vacuum sintering of powder blends. This study provides novel insights into the design and production of cost-effective and environmentally friendly TMCs with determined mechanical properties.

Abstract: In this paper, TiB reinforced Ti-6Al-4V matrix composites were successfully fabricated using a spark plasma sintering, hot rolling and heat treating process. (Transformed β-Ti + secondary α-Ti) domains were formed in TiB/TMCs after heat treatment. The size of these domains increases from 2.5 μm to 4.6 μm with the increase of solution time. The aspect ratio of whiskers monotonously decreases along with the solution time extending. The highest ultimate tensile strength of 1332 MPa and yield-strength of 1315 MPa were achieved by (940 °C, 15min+ water-quenching+537 °C, 4h) TMC.

Abstract: Titanium alloy composites with titanium boride (TiB) discontinuous reinforcement have shown improved performance in terms of strength, stiffness, and hardness. Producing this composite through selective laser melting (SLM) can combine the advantages of freeform design with the ability to produce TiB reinforcement in-situ. In this study, SLM was used to consolidate a pre-alloyed Ti-6Al-4V (Ti64) and amorphous boron (B) powder mixture with the intent of producing 1.5wt% TiB reinforcement in a Ti64 matrix. The processing parameters of laser power and scanning speed were investigated for their effect on the density, microstructures, and hardness of the composite material. The results showed that the boron and Ti64 composite could achieve a density greater than 99.4%. Furthermore, it was found that processing parameters changed the microstructural features of the material. The higher the energy density employed the more homogenous the distribution of boron modified material. Macro features were also observed with laser paths being clearly evident in the subsurface microstructure. Micro-hardness testing and density measurement also showed a corresponding increase with increasing energy density. Maximum hardness of 392.4HV was achieved in the composite compared to 354.2HV in SLM fabricated Ti64.

Abstract: In this study, the titanium matrix composites (TiMCs) were fabricated by adding graphene nanoplatelets (GNPs). The dynamic compression test was carried out to study the effect of strain-rate and the GNPs content on dynamic mechanical properties of GNPs/Ti. Results show that the GNPs content (0wt%~0.8wt%) correspond to specific microstructure which affect the dynamic mechanical properties of the composites. Under high strain-rate (3500s^-1), the 0.4wt%GNPs/Ti has the highest dynamic stress (~1860MPa) and strain (~30%). The adiabatic shearing band (ASB) microstructure of GNPs/Ti with various GNPs content has been observed under 3500s^-1 strain-rate and the ASB microstructure evolution of 0.4wt%GNPs/Ti under different strain rate was investigated in particular.

Abstract: In the present work, in situ reinforced titanium composites (TMCs) synthesized using inductive hot pressing (iHP) are studied. The effects of B₄C phases and applied processing conditions, on the microstructure and properties of TMCs, are investigated. With the addition of B₄C particles, the microstructure of TMCs is refined and the strength is improved.Products of reactions which occur during the manufacturing process are analysed in detail. Microstructure observation illustrates, that B₄C survives - depending on the processing conditions. The reinforcing phases are homogeneously distributed in Ti matrix. Moreover, results of densification, mechanical properties and hardness measurements help to identify the most suitable processing conditions to produce this kind of TMCs.

Abstract: In this work, in-situ TiC reinforced Ti matrix composites (TMCs) have been fabricated via blending TiH₂ powder and multi-walled carbon nanotubes (CNTs) followed by thermomechanical consolidation of the TiH₂/CNTs powder mixture. The dehydrogenation, in situ reaction and consolidation occurred simultaneously and took less than 15 minutes in total. The effect of CNTs content (1 and 3 vol.% (0.56 and 1.69 wt.%)) on the evolution of microstructures and mechanical performances of the extruded samples has been investigated. The results showed that the extruded TMCs had a duplex microstructure consisting of coarse alpha titanium grains and ultrafine grained (UFG) regions, and the in-situ formed TiC particles had a near-spherical shape. The extruded sample with 1 vol.% (0.56 wt.%) CNTs reinforced exhibited a yield strength of 807.3 MPa, ultimate tensile strength of 1085.9 MPa and elongation to fracture of 3.3% at room temperature. The mechanism of microstructural evolution and material failure are discussed.e are discussed.

Abstract: High-speed grinding experiment of titanium matrix composites is carried out with cubic boron nitride (CBN) superabrasive wheels in this work. The heat transfer into the titanium matrix composites (TMCs) is discussed based on theoretical analysis. A calculation method of thermal ratio passing into the workpiece is represented. Results obtained show that high-speed grinding of PTMCs using vitrified CBN wheel has a greater thermal ratio passing into the workpiece than using electroplated CBN wheel. Moreover, a linear relationship is established between e_s and d_s^1/4a_p^-3/4v_w^-1/2.

Abstract: Titanium matrix composites (TMCs) were prepared by investment casting in a consumable arc skull casting furnace. The effects of B₄C additions on ambient-temperature and high-temperature tensile properties of TMCs were investigated. It has been found that with the addition of B₄C, the microstructure of TMCs was refined and the strength improved. The strength enhancement of the TMCs is ascribed to the combined effects of the second-phase strengthening, grain refinement strengthening and the solution strengthening. The grain refinement and solution strengthening effects play a main role in the yield strength enhancement of TMCs at ambient temperature, and the second-phase strengthening of TiB whiskers and TiC particles plays a more important role at high temperature.

Abstract: The weldability of in-situ titanium matrix composites (TMCs) was studied using the gas tungsten arc welding (GTAW). The effects of GTAW on the microstructure of fusion zone and heat-affected zone were discussed, and the changes of TiB whisker reinforcements in the welded joint were investigated by optical microscope (OM), scanning electron microscopy (SEM), XRD analysis and tension testing at room temperature. Research results show that the GTAW process is a suitable welding method for in-situ TMCs. Under reasonable welding parameters, the welded joints display goo weld seam formation, and TiB whiskers show distinctly smaller sizes and uniform distribution with a special network structure. The maximum tensile strength of welded joints can reach 92% of the base metal under optimum welding parameters.

Abstract: The investigations were focused on the thermochemical and mechanical properties for interface in continuous SiC fiber reinforced TC17 titanium alloy (nominal composition wt.% is Ti-5Al-2Sn-2Zr-4Mo-4Cr) matrix composites (SiC_f/Ti). Scanning electron microscope (SEM), transmission electron microscopy (TEM), and electron probe microanalyzer (EPMA) were applied to observe and analyze the interface reaction product at different heat treatment temperatures. In addition, the reaction rate as well as the relationship between the thickness of reaction layer and time was researched. The interfacial strength at different consolidation temperatures was obtained by means of push-out test, while erosion method was employed to measure the residual stress of composites under different consolidation parameters. The results demonstrate that the thickness of interface reaction layer and heat exposure time is accord with the relationship x=kt^1/2+x₀, and the interface strength is correlated with the thickness of interface reaction layer, which increases with the intensity of interface reaction. Through the comparison, we find that the inner residual stress of the sample consolidated at 940 °C is higher than that of 920 °C.