TiB2 Content Research Articles

Hot tearing susceptibility of TiB2-reinforced Al–5Cu matrix composite

This work investigated the hot tearing susceptibility of TiB2 reinforced Al–5Cu matrix composites. The results indicated that the hot tearing susceptibility of Al–5Cu alloy was significantly decreased when the TiB2 content was less than 3%. The improvement was attributed to the TiB2 particles promoted the grain refinement. The hot tearing susceptibility of TiB2-reinforced Al–5Cu matrix composite decreased first and then increased with the increase of TiB2 content. The 2TiB2/Al–5Cu composite had the smallest hot tearing susceptibility value. It could be ascribed to the refined grain and shortened solidification temperature range, which contributed to the hot tearing susceptibility decrease. Nevertheless, the 4TiB2/Al–5Cu and 6TiB2/Al–5Cu composites had more severe hot tearing susceptibility than others. The reason was that the enlarged solidification temperature range increased the solidification shrinkage strain, which was adverse to the hot tearing susceptibility improvement. Furthermore, the increase of TiB2 led to the formation of large particles agglomeration, which lowered the hot tearing initiation force and the feeding capacity of liquid metal.

Microstructure and Mechanical Properties of TiB-Ti/Ti-6Al-4V Composites Fabricated by Spark Plasma Sintering

TiB-Ti/Ti-6Al-4V composites were fabricated by spark plasma sintering (SPS) technique under a pressure of 50MPa, with sintering temperature of 1300 °C and heating rate of 100 °C /min. The effect of the TiB content in TiB-Ti composite layer on microstructures and mechanical properties of the TiB-Ti/Ti-6Al-4V composites were investigated. The results indicate that as an advanced welding method, SPS technique provided the excellent welding combination of TiB-Ti and Ti-6Al-4V. The relatively excellent mechanical properties of the joints, including the relative density of 98.6%, micro-hardness of 10.2GPa, fracture strength of 177MPa were achieved as TiB content in TiB-Ti composite layer reaches 50%.

Microstructure and Wear Resistance of Semisolid TiB2/7050 Composites Produced by Serpentine Tube Pouring Technique

TiB2/7050 (3, 6, and 9 wt%) composites slurries with globular were synthesized by in situ reaction and serpentine tube pouring techniques. The results showed that the semisolid 7050 alloy and 3, 6, and 9 wt%TiB2/7050 composites with average grain diameter of 28, 25, 20, and 19 µm and shape factor of 0.77, 0.83, 0.90, and 0.93, respectively, can be obtained at 660 °C pouring temperature. With increasing TiB2 content and curves number, the α-Al grain size was decreased. The composite melts have an effect of “self-stirring” when they flow through the serpentine tube, which is beneficial to make the primary nuclei with globular grains. Moreover, the wear resistance of TiB2/7050 composites improved obviously with increasing in situ TiB2 particles content and that the wear rate of 9 wt%TiB2/7050 composite was 79% lower than that of 7050 matrix alloy under 100 N applied load, 30 min sliding time, and 0.15 m/s sliding velocity.

Wear Properties of Metal Matrix Composite Al-Cu and Al-Cu-TiB<sub>2</sub>

Tensile and wear properties of aluminium (Al) based metal matrix composites (MMCs) was prepared by added titanium diboride (TiB2) with in-situ technique by salt route. The salts used in this research were potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4). Nanocomposite samples were prepared by casting technique associated with incorporating 3 and 6 wt.% of TiB2 into matrix of Al-6wt.%Cu. Instron and wear tests machine were used to characterize the tensile and wear Al-Cu alloys properties. Results showed that increase in TiB2 content gave the high properties of tensile and wear behavior. The study indicates that TiB2 particles have giving improvement the wear performance of the Al–6wt.%Cu alloy. For a constant load and sliding speed, the wear rate decreases as a function of amount of TiB2 in the composite. The wear rate decrease with increasing in wt.% TiB2 particles for the all loads applied. However, addition of TiB2 particle to the Al–6 wt%.Cu matrix has show the coefficient value of wear decreases regardless of applied load. Study of the wear surfaces both alloy and composites by optical microscope suggests that the improvement in wear resistance is mainly due to the formation of finer groove or debris by content of TiB2.

Corrosion behaviors, mechanical properties and microstructure of the steel matrix composites fabricated by HP–HT method

Steel-based composites with varying content of TiB2 were manufactured by HP–HT process. The main objective of the study was to determine the effect of sintering conditions and TiB2 content on the mechanical properties and corrosion behavior of steel–TiB2 composites. The corrosion resistance of the composites was examined in H2SO4 solution using two measurement techniques. The mechanical properties were determined in a compression test allowing also for the effect of elevated temperatures (600°C and 800°C).The results showed that both TiB2 content and sintering temperature affected the properties tested. The highest compressive strength was obtained in the composites with 8vol% TiB2. The corrosion properties of composites showed only insignificant variations. The microstructure was characterized by a homogeneous distribution of the TiB2 reinforcing phase.

Influence of TiB2 Addition on the Precipitation Kinetics in Al-7Si-0.3Mg In Situ TiB2 Composites

Precipitation behavior of the Al-7Si-0.3Mg/TiB2in situ composites was investigated using differential scanning calorimetry and transmission electron microscopy, and it was found that Si precipitation is accelerated with increase in TiB2 content. Non-isothermal kinetic analysis clearly showed a decrease in the precipitation kinetics of the overaged metastable precipitates in the Mg2Si precipitation sequence.

The influence of TiB2 content on microstructure and properties of W–30Cu composites prepared by electroless plating and powder metallurgy

W–30Cu composite materials with different concentrations of TiB2 particles ranging from 0 to 2wt.% were prepared by electroless plating with simplified pretreatment and powder metallurgy. The morphologies of W–30Cu composite powders, original TiB2 powders, W–30Cu/TiB2 composite powders were characterized using field emission scanning electron microscopy. X-ray diffraction analysis was used to characterize the phase of W–30Cu/TiB2 composite powders. Relative density, electrical conductivity, and hardness of the W–30Cu/TiB2 composites were examined. Results showed that uniform Cu-coated W composite powders were successfully synthesized by electroless plating with simplified pretreatment. The addition of TiB2 nanoparticles significantly affected the microstructure and properties of W–Cu composite materials. A good combination of the relative density, electrical conductivity, and hardness of the W–30Cu composite materials can be obtained with the incorporation of TiB2 additive at 0.25wt.%.

Mechanical properties and microstructure of Ti(C5N5)-TiB2-(W7Ti3)C composite cutting tool materials

Ti(C5,N5)-TiB2-(W7,Ti3)C composite ceramic cutting tool materials were prepared using the vacuum hot-pressed sintering technology. The effects of the sintering temperature and the heating rate on the mechanical properties and microstructure of different composite materials containing different contents of TiB2 were investigated. The sintering process of a higher temperature with a fast heating rate or a lower temperature with a slow heating rate was found to be beneficial to the mechanical properties of the composites. The better sintering temperature range for fabricating the composites was from 1585 to 1620 °C. The composite material with a content of 30 wt% TiB2 sintered at 1585 °C with either a heating rate of 90 or 50 °C/min had the prominent flexural strength. The composite with a content of 20 wt% TiB2 sintered at 1620 °C with a heating rate of 90 °C/min had the relatively better fracture toughness and hardness than that with a content of 30 wt% TiB2. The two core-rim microstructures were formed inside the TiB2 and Ti(C, N) grains, which further contributed to a compact microstructure and improved the mechanical properties of the composites. The optimum sintering temperature range for the formation of the core-rim microstructures was also from 1585 to 1620 °C.

Microstructure and properties of TiB2 particles reinforced Cu–Cr matrix composite

Copper–chromium matrix composites reinforced by TiB2 particles were prepared by in situ reaction between titanium and copper–boron alloy in the melt. The microstructures, mechanical, and electrical properties of the composite were investigated under as-cast and aging conditions. The results indicate that the TiB2 particles are formed by in situ reaction in matrix. The addition of TiB2 in composite reduces the segregation degree of Cr particles in matrix and inhibits the coarsening of Cr particles at high aging temperature. High hardness of Cu–Cr–TiB2 composite is achieved due to the multiple hardening mechanisms, which are in situ TiB2 particles hardening and precipitation hardening from Cr particles. The wear resistance of composite presents a dramatic improvement due to the formation of TiB2 particles, and TiB2 particles have significant effect on wear mechanism of Cu–Cr–TiB2 composite. The conductivity of composite is lower than that of Cu–Cr alloy, which is attributed to higher resistivity of TiB2 particles and the incremental interface scattering caused by TiB2 particles. But the composites with high TiB2 content still have considerable conductivity after aging.

Microstructure, mechanical properties and wear behaviour of Zn–Al–Cu–TiB2 in situ composites

Zn–Al–Cu–TiB2 (ZA27–TiB2) in situ composites were fabricated via reactions between molten aluminum and mixed halide salts (K2TiF6 and KBF4) at temperature of 875 °C. The microstructure, mechanical properties and wear behavior of the composites were investigated. Microstructure analysis shows that fine and clean TiB2 particles distribute uniformly through the matrix. The mechanical properties of the composites increase with the increase in TiB2 content. As TiB2 content increases to 5% (mass fraction), an improvement of HB 18 in hardness and 49 MPa in ultimate tensile strength (UTS) is achieved. The overall results reveal that the composites possess low friction coefficients and the wear rate is reduced from 5.9×10−3 to 1.3×10−3 mm3/m after incorporating 5% TiB2. Friction coefficient and worn surface analysis indicate that there is a change in the wear mechanism in the initial stage of wear test after introducing in situ TiB2 particles into the matrix.

Effect of (Ti:B) atomic ratio on mechanical properties of TiB2–Fe composites “in situ” fabricated via Self-propagating High-temperature Synthesis

The TiB2-based Fe–matrix cermets with titanium addition (literarily different Ti:B ratio) were fabricated from elemental powders “in situ” using the Self-propagating High-temperature Synthesis method (SHS) under high pressure. The effect of Ti:B ratio on microstructure and phase composition with particular focus on matrix phase were analyzed using X-ray diffraction (XRD) and Wavelength Dispersive Spectroscopy (WDS) for composites with intended 25 vol.% and 35 vol.% of Fe. Moreover, for composites with 35 vol.% of Fe bending strength and compressive strength were investigated. The compressive strength reached maximum value in material with Ti:B atomic ratio of 0.49, which possessed the highest TiB2 content and matrix phase consisting of Fe and Fe2B. However, modulus of rupture (MOR) test indicated that composite with titanium excess (Ti:B atomic ratio of 0.525) was characterized by the highest bending strength, due to successful elimination of Fe2B intermetallics.

Impact response of TiB2–TiB composites

TiB2–TiB composites with a TiB2 content that varied between 100 and 36 wt% were synthesized from TiB2 and Ti powder mixtures by the Spark Plasma Sintering (SPS) technique. The residual porosity, microstructure, phase composition and static mechanical properties of the composites (bending strength, hardness and fracture toughness) were determined using standard characterization techniques. The impact response of the composites has been studied in two series of planar impact experiments. In the first, the samples were shock loaded to an ultimate compressive stress of about 25 GPa in order to determine the materials Hugoniot elastic limit (HEL). In the second series, the composites were shock loaded by a modest, 3–4 GPa, compressive pulse with the purpose to define their spall strength.The experimental results show that both the static and the dynamic properties of the composites reflect their microstructure, residual porosity and phase composition, namely, the TiB2 fraction in the composites. Even a limited Ti addition (5 wt%) in the starting mixture allows to synthesize by an SPS process at a relatively low temperature (1550 °C), composites with elevated mechanical properties, in particular high hardness (∼2400 HV). The addition of 50 wt% of Ti (36 wt% of TiB2 in the composites) yields fully dense composites with a high fracture toughness (∼9.0 MPa m0.5). The wide range of the static and dynamic properties of the TiB2–TiB composites allows their tailor-design to specific applications.

Effects of Forming Conditions and TiC–TiB2 Contents on the Microstructures of Self-Propagating High-Temperature Synthesized NiAl–TiC–TiB2 Composites

The NiAl–TiC–TiB2 composites were processed by self-propagating high-temperature synthesis (SHS) method using raw powders of Ni, Al, Ti, B4C, TiC, and TiB2, and their microstructure and micro-hardness were investigated. The TiC–TiB2 in NiAl matrix, with contents from 10 to 30 wt%, emerged with the use of two methods: in situ formed and externally added. The results show that all final products are composed of three phases of NiAl, TiC, and TiB2. The microstructures of NiAl–TiC–TiB2 composites with in situ-formed TiC and TiB2 are fine, and all the three phases are distributed uniformly. The grains of NiAl matrix in the composites have been greatly refined, and the micro-hardness of NiAl increases from 381 HV100 to 779 HV100. However, the microstructures of NiAl–TiC–TiB2 composites with externally added TiC and TiB2 are coarse and inhomogeneous, with severe agglomeration of TiC and TiB2 particles. The samples containing externally added 30 wt% TiC–TiB2 attain the micro-hardness of 485 HV100. The microstructure evolution and fracture mode of the two kinds of NiAl–TiC–TiB2 composites are different.

Microstructure and mechanical properties of in-situ synthesized TiB whiskers reinforced titanium matrix composites by high-velocity compaction

High-velocity compaction (HVC) technology was applied to press titanium-based blended elemental powders containing boron sources of TiB2 and LaB6, and in-situ TiB whiskers reinforced titanium matrix composites (TMCs, TiB/Ti-4.5 Al-6.8 Mo-1.5 Fe) were successfully prepared after vacuum sintering at 1250°C for 3h. The effects of forming ability of the blended powders by HVC and TiB volume fraction (5–20%) on microstructure and mechanical properties of composites were studied. The results showed that the blended powders could be pressed by HVC into green compacts with relative density no less than 94%. While the hardness and brittleness of TMCs increased with increasing TiB content, the TMCs with 10% TiB had the maximum tensile strength of 1147MPa due to the combined effects of a relatively high relative density, a sufficient reinforcement of TiB and a homogeneous microstructure for this composition. The properties of the matrix alloy were also studied.

Effects of TiB2 content and alloy elements (Mg, Mo, V) on the compression properties of high-volume-fraction TiB2/Al composites

The compression yield strength and hardness of the TiB2/Al composites increase with the increase in the TiB2 content, while the fracture strain decreases, and the ultimate compression strength first increases and then decreases. The addition of Mg improves the ductility of the 50vol% TiB2/Al composite along with maintaining the ultimate compression strength. The fracture strain of the TiB2/Al–Mg composite increases from 8.18% to 10.68%. The addition of Mo significantly improves the compression yield strength and hardness of the composite while sacrificing the ductility. The compression yield strength and the hardness of the TiB2/Al–Mo composite are, respectively, 296MPa and 107.5Hv higher than that of the TiB2/Al composite, but the fracture strain decreases to 4.41%. With the addition of V, the TiB2/Al–V composite possesses the highest ultimate compression strength and relatively good ductility. The ultimate compression strength of the TiB2/Al–V composite is 218MPa higher than that of the TiB2/Al composite, and the fracture strain is 6.73%.

Effect of Ti Content on the Microstructure and Properties of TiC/TiB<sub>2</sub>-FeNiCr Composite Prepared by Thermite Reaction

TiC/TiB2-FeNiCr composite reinforced by TiC and TiB2 composite ceramic particles was successfully in-situ synthesized using thermite reaction. The effects of Ti content in the raw material on the microstructure and properties of the composite were studied. The microstructure was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The hardness, compressive strength and wear resistance were tested using the Vickers indentation method (HXZ-1000), mechanical testing machine (SANS5105) and the high temperature wear tester (HT-600), respectively. The results show that the composite is mainly consisted of TiC, TiB2, Cr7C3, α-FeNiCr and NiAl. The content of TiC and TiB2 is increased with the Ti content. The hardness and compressive strength of the composite is increased first and then decreased. They attain the maximum value at about 8.0wt%Ti. The hardness and the compressive strength of the composite are 1313.25HV and 2725.57MPa at 8.0% Ti. Also the wear resistance of the composite is good, and the weight wear loss at 8.0% Ti is nearly fifth of the mass loss of steel.

Numerical Simulation of Filling for 7075 Alloy and TiB<sub>2</sub>/7075 Composites Wheel Prepared by Low Pressure Die Casting

Based on the experimental and calculation results between the reinforcing particles content and thermal physical parameters, low pressure die casting of wheels was taken as an example to study the casting property of the 7075 alloy and TiB2/7075 composites. The influences of die temperature, pouring pressure, pouring temperature and TiB2 content on the filling of 7075 alloy and TiB2/7075 composites wheels are studied by numerical simulation. Shrinkage porosity appears both in the spoke and rim of the wheel. The shrinkage porosity of the 7075 alloy decreases from 2.089% to 1.622% with mold temperature increasing from 100°C to 400°C. The shrinkage porosity of wheel decreases from 1.630% to 1.598% and 1.583% in the composite with 3 and 6wt.% TiB2 particles. Besides, shrinkage porosities decrease with increasing pouring temperature.

Effect of TiB2 Particles on the Tribological Properties of Stainless Steel Matrix Composites

The AISI316L stainless steel composites reinforced with 2, 4, 6, and 8 vol% titanium diboride (TiB2) particles were sintered by the high pressure-high temperature method. Ball-on-disk method was carried out to study wear behavior of the composites. Tests were carried out at room temperature. The TiB2 particles improved the hardness and tribological properties of the composites. The friction coefficient of the composites decreased with the increasing content of TiB2. The reduction of the wear rate with the increasing of the content of TiB2 particles in the steel matrix was also observed. It is demonstrated that the friction coefficient of composites with the same content of TiB2 particles depend on the sintering conditions.

Microstructure and Sliding Wear Performance of Plasma-Sprayed TiB2-Ni Coating Deposited from Agglomerated and Sintered Powder

This work is aimed at developing a route for the deposition of TiB2-Ni cermet coating. The feedstock was firstly prepared by agglomeration and sintering, which was subsequently subjected to plasma spraying. The microstructures and the phase composition of the powder, as well as the sprayed coating were analyzed by scanning electron microscopy and x-ray diffraction. The microhardness (Hv) and the fracture toughness (KIC) of the coating were evaluated. A sliding wear test was also performed on the sprayed coating by SRV® tribo-tester using GCr15 steel as a counterpart. The results showed that the phase of sprayed TiB2-Ni coatings consisted of TiB2, Ni, and Ni20Ti3B6, whose amount varied depending on the powder calcination temperature and the TiB2 content in the powder. Both the hardness and the fracture toughness of the coating were also changed with different powders. The Ni20Ti3B6 brittle phase was the main factor affecting the fracture toughness of coating, which also had detrimental effect on the sliding wear performance. The 60TiB2-40Ni coating deposited from the powder calcined at 1250 °C had better sliding wear performance as it presented more dense structure, higher TiB2 content and less retained Ni20Ti3B6 phase in the coating.

Mechanical properties of in-situ TiB2/A356 composites

In the present work, the in-situ TiB2/A356 composites were successful synthesized through the salt–metal reaction route. The research was undertaken to study the mechanical properties of the A356 alloy reinforced with TiB2 particles at both as-cast state and T6 state. In two cases, the results showed the Young's modulus of composites was increased with increasing the TiB2 content up to 8.37% in volume fraction. The dependence of Young's modulus on the TiB2 particle content can be well rationalized by the Tsai-Halpin equation. Similarly, the yield strength of composites was improved with the increase of TiB2 particle content at both states. Using the modified shear lag model, the calculated yield strength can be well fitted with the experimental values at as-cast state, but not at T6 state. Further, a phenomenological model was proposed by accounting for TiB2 particulate strengthening mechanisms and microstructural features related coefficient in TiB2/A356 composites. The predictions of yield strength using this model are in good agreement with experimental data from both as-cast state and T6 state in this work and also reported in the literatures about in-situ TiB2/Al alloy composites.