In situ fabrication of titanium carbide particulates-reinforced iron matrix composites

Titanium carbide (TiC) particulates-reinforced iron matrix composites were prepared by in situ fabrication method combining an infiltration casting with a subsequent heat treatment. The effects of different heat treatment times (0, 1, 6 and 11 h) at 1138 °C on the phase evolution, microstructural features, and properties of the composites were investigated. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microhardness and wear resistance tests. The XRD results showed that the composites consisted of graphite, α-iron and titanium carbide after heat treatment at 1138 °C for 11 h. The SEM observation revealed that the formed TiC particulates were homogenously distributed in the iron matrix. The average microhardness of the composite heat treated at 1138 °C for 6 h increased depending upon the region: 209 HV_0.1 (iron matrix) < 787 HV_0.1 (titanium wire) < 2667 HV_0.1 (composite region). After being heat treated at 1138 °C for 11 h, the composite indicated no considerable change in microhardness value, and the average microhardness of the composite region was about 2354 HV_0.1. The highest microhardness value obtained for the composite region was due to the formation of titanium carbide particulates as reinforcement phase within the iron matrix. Relative wear resistance was determined by a pin-on-disc wear test technique under different loads, and as a result, the composites containing higher volume fraction of hard titanium carbide particulates presented higher wear resistance compared with the unreinforced gray cast iron.     

Mechanical properties and damping capacity of SiCp/TiNif/Al composite with different volume fraction of SiC particle

SiC_p/TiNi_f/Al composite with 20 Vol.% TiNi fibers were fabricated by pressure infiltration method. The effect of volume fraction of SiC particle on the mechanical properties and damping capacity of the composite were studied. Four different volume fractions of SiC particle in the composite were 0%, 5%, 20% and 35% respectively. The microstructure and damping capacity of the composites was studied by SEM and DMA respectively. As the gliding of dislocation in the Al matrix was hindered by SiC particle, the yield strength and elastic modulus of the composites increased, while the elongation decreased with the increase in volume fraction of SiC particle. Furthermore, the damping capacity of the composites at room temperature was decreased when the mount of strain was more than 1 × 10⁻⁴. In the heating process, the damping peak at the temperature of 135 °C was attributed to the reverse martensitic transformation from B19′ to B2 in the TiNi fibers.     

A study of the effect of antimony content on damping capacity of ZA84 magnesium alloy

The effects of antimony content on damping capacity of as cast Mg–8Zn–4A1–0.3Mn magnesium alloy were investigated by using optical microscopy and dynamic mechanical analyzer, etc. The results indicated that the damping capacity of Mg–8Zn–4A1–0.3Mn magnesium alloy was reduced at the low temperatures (<80 °C) after adding antimony, but its damping capacity was improved at the higher temperatures (>80 °C). There exists a damping peak in both modified and unmodified alloys with different temperature, adding antimony postpones the emergence temperature of damping peak. The damping capacities of the modified alloys were decreased gradually with the increase of antimony content. In the present work, the best damping capacity was obtained from the modified alloy containing 0.1 wt.% antimony at the high temperatures.     

Production of TiC reinforced-aluminum composites with the addition of elemental carbon

TiC reinforced Al matrix composites were produced by the additions of elemental carbon to both Al + 4%Ti and Al + 5%Ti alloys. It is shown that the microstructure, phase composition as well as fracture behavior of the composites produced are controlled by the processing parameters, such as temperature, amount of excess carbon and duration. Composite microstructure subjected to 1300 °C for 15 min includes only TiC particles where the fracture occurs in a ductile manner whilst composites subjected to 1200 °C for 30 min contain Al₃Ti and TiC particles which show mixed mode of fracture behavior where Al₃Ti particles resulted in brittle fracture due to their coarser size.     

Investigation of microstructure,hardness and wear properties of Al–4.5 wt.% Cu–TiC nanocomposites produced by mechanical milling

The present work deals with studies on the manufacturing and investigation of mechanical and wear behavior of aluminum alloy matrix composites (AAMCs), produced using powder metallurgy technique of ball milled mixing in a high energy attritor and using a blend–press–sinter methodology. Matrix of pre-mechanical alloyed Al–4.5 wt.% Cu was used to which different fractions of nano and micron size TiC reinforcing particles (ranging from 0 to 10 wt.%) were added. The powders were mixed using a planetary ball mill. Consolidation was conducted by uniaxial pressing at 650 MPa. Sintering procedure was done at 400 °C for 90 min. The results indicated that as TiC particle size is reduced to nanometre scale and the TiC content is increased up to optimum levels, the hardness and wear resistance of the composite increase significantly, whereas relative density, grain size and distribution homogeneity decrease. Using micron size reinforcing particulates from 5% to 10 wt.%, results in a significant hardness reduction of the composite from 174 to 98 HVN. Microstructural characterization of the as-pressed samples revealed reasonably uniform distribution of TiC reinforcing particulates and presence of minimal porosity. The wear test disclosed that the wear resistance of all specimens increases with the addition of nano and micron size TiC particles (up to 5 wt.%). Scanning electron microscopic observation of the worn surfaces was conducted and the dominant wear mechanism was recognized as abrasive wear accompanied by some delamination wear mechanism.     

Structural and chemical characterization of precipitates in Al-2024/TiC composites

Structural characterizations based on transmission electron microscopy observations were carried out on as-fabricated and heat-treated Al-2024/TiC composites. These composites types reinforced with TiC particles were produced with a pressureless melt infiltration route at 1200 °C for 2 h under argon atmosphere. The composites were heat-treated at 530 °C during 150 min, cold-water quenched and subsequently artificial and natural aged at 190 °C for 12 h in an argon environment and at room temperature for 96 h, respectively. Different precipitate types were obtained and they were identified as CuAl₂, Al₃Ti, Ti₃AlC and Ti₃Al. Most of the precipitates were found to be uniformly distributed in the matrix and some regions show precipitates which have a cubic morphology (Ti₃Cu). High-resolution electron microscopy images were partially used for the characterization of the precipitates in these composites.     

Damping characteristics of carbon nanotube reinforced aluminum composite

A multi-walled carbon nanotube (MWNTs) reinforced 2024Al composite was successfully fabricated by a procedure of mixing 2024Al powders and CNTs, cold isostatic press and hot extrusion. The damping behaviors of the composite were investigated with frequency of 0.5, 1.0, 5.0, 10, 30 Hz, at a temperature of 25–400 °C. The experimental results show that the frequency significantly affects the damping capacity of the composite when the temperature is above 230 °C; meanwhile, the damping capacity of the composite with a frequency of 0.5 Hz reaches 975 × 10^− 3, and the storage modulus is 82.3 GPa when the temperature is 400 °C, which shows that CNTs are a promising reinforcement for metal matrix composites to obtain high damping capabilities at an elevated temperature without sacrificing the mechanical strength and stiffness of a metal matrix.     

Nanocrystalline matrix TiC–Al3Ti and TiC–Al3Ti–Al composites produced by reactive hot-pressing of milled powders

Mechanically alloyed nanocrystalline TiC powder was short-term milled with 40 vol.% of Al powder. The powders mixture was consolidated at 1200 °C under the pressure of 4.8 GPa for 15 s and at 1000 °C under the pressure of 7.7 GPa for 180 s. The bulk materials were characterised by X-ray diffraction, light and scanning electron microscopy, energy dispersive spectroscopy, hardness, density and open porosity measurements. During the consolidation a reaction between TiC and Al occurred, yielding an Al₃Ti intermetallic. The microstructure of the produced composites consists of TiC areas surrounded by lamellae-like regions of Al₃Ti intermetallic (after consolidation at 1200 °C) or Al₃Ti and Al (after consolidation at 1000 °C). The mean crystallite size of TiC is 38 nm. The hardness of the TiC–Al₃Ti and TiC–Al₃Ti–Al composites is 13.28 GPa (1354 HV1) and 10.22 GPa (1041 HV1) respectively. The produced composites possess relatively high hardness and low density. The results obtained confirmed satisfactory quality of the consolidation with keeping a nanocrystalline structure of TiC.     

Microstructure and mechanical properties of an Al–TiC metal matrix composite obtained by reactive synthesis

A metal matrix composite has been obtained by a novel synthesis route, reacting Al₃Ti and graphite at 1000 °C for about 1 min after ball-milling and compaction. The resulting composite is made of an aluminium matrix reinforced by nanometer sized TiC particles (average diameter 70 nm). The average TiC/Al ratio is 34.6 wt.% (22.3 vol.%). The microstructure consists of an intimate mixture of two domains, an unreinforced domain made of the Al solid solution with a low TiC reinforcement content, and a reinforced domain. This composite exhibits uncommon mechanical properties with regard to previous micrometer sized Al–TiC composites and to its high reinforcement volume fraction, with a Young’s modulus of ∼110 GPa, an ultimate tensile strength of about 500 MPa and a maximum elongation of 6%.     

Fabrication of in situ TiC locally reinforced manganese steel matrix composite via combustion synthesis during casting

In situ TiC particulates locally reinforced manganese (Mn) steel matrix composite was successfully fabricated via combustion synthesis of (Fe,Ti)–C system during casting. XRD results reveal that the phases of the composites consist of TiC, α-Fe and austenite. Microstructure of the locally reinforced manganese (Mn) steel matrix composite consists of three separate regions, i.e. a TiC particulate-reinforced region, a transition region, a steel matrix region. TiC particles in the reinforced region, having fine size of 2 μm, are distributed uniformly. The hardness and wear resistance of the TiC particulates locally reinforced composites are much higher than those of quenched Mn13 steel. Furthermore, the microstructure formation mechanism of the composite was discussed.     

A developed method for producing in situ TiC/Al composites by using quick preheating treatment and ultrasonic vibration

Quick preheating treatment of Al–Ti–C was introduced in the fabrication of in situ TiC/Al metal matrix composites in our research. Al–Ti–C pellets were preheated in the furnace at 750 °C, in which the pure aluminum was melted. After adding the preheated pellets into the molten aluminum, the thermal explosion reaction of Al–Ti–C took place in a short time. In situ TiC particles synthesized in the pure molten aluminum were spherical in morphology and most of which were smaller than 1 μm in size. The synthesizing temperature of in situ TiC/Al composites was decreased significantly by using the quick preheating treatment, at least 150 °C lower than those used in the conventional methods. In addition, high-intensity ultrasonic vibration was applied into the melt to disperse TiC particle-reinforcement into the matrix and degas the melt as well. In situ TiC particles were distributed uniformly in the matrix, and the porosity in the composites was below 1% due to the effect of ultrasonic vibration. Furthermore, the microhardness test indicated that a homogeneous microstructure of in situ TiC/Al composite was obtained.     

Tribological behavior of Ni3Al matrix self-lubricating composites containing WS2, Ag and hBN tested from room temperature to 800 °C

Ni₃Al matrix self-lubricating composites (NMSC) containing varied amounts of WS₂, Ag and hBN (WAh) with weight ratio of 1:1:1 were fabricated by in situ technique using spark plasma sintering. The friction and wear properties of NMSC against the commercial Si₃N₄ ceramic ball at the load of 10 N and sliding speed of 0.234 m/s for 80 min from room temperature to 800 °C were investigated. The results showed that the tribological properties of NMSC strongly depended on the addition content of WAh. Moreover, NMSC with 15 wt.% WAh and 5 wt.% TiC exhibited the relatively lower friction coefficients and the less wear rates from RT to 800 °C. The excellent tribological behavior of NMSC with 15 wt.% WAh and 5 wt.% TiC was attributed to the synergetic action of composite lubricants of WAh and reinforced phase of TiC.     

Microstructure,mechanical property,bio-corrosion and cytotoxicity evaluations of Mg/HA composites

Mg/HA (10 wt.%, 20 wt.% and 30 wt.%) composites were prepared by pure magnesium and hydroxyapatite (HA) powders using powder metallurgy (PM) method. The microstructure, mechanical property, corrosion and cytotoxicity of these Mg/HA composites were studied, with the bulk pure magnesium as control. The results showed that the main constitutional phases of Mg/HA composites were simply α-Mg and HA. The HA particulates distributed uniformly in Mg matrix for Mg/10HA composite, and few HA clustering occasionally spread over the Mg/20HA composite, whereas severe agglomeration of HA particulates could be seen for Mg/30HA composite. The yield tensile strength of Mg/10HA composite increased compared with that of the as-extruded bulk pure magnesium, yet the yield tensile strength, ultimate tensile strength and ductility of Mg/HA composites decreased with the further increase of HA content. The corrosion rate of Mg/HA composites increased with the increment of HA content. The cytotoxicity tests indicated that Mg/10HA extract showed no toxicity to L-929 cells, whereas Mg/20HA and Mg/30HA composite extracts induced significantly reduced cell viability.     

Thermal shock behavior of nano-sized SiC particulate reinforced AlON composites

Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8 wt% SiC–AlON composites over a temperature range between 175 °C and 275 °C. The residual strength and Young's modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC–AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200 °C in the monolithic AlON to 225 °C in the SiC–AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC–AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge-like characteristics, crack deflection, and crack branching in the SiC–AlON composites.     

Characterization of hot deformation behavior of a new Ni–Cr–Co based P/M superalloy

The hot deformation behavior of a new Ni–Cr–Co based P/M superalloy was studied in the temperature range of 950–1150 °C and strain rate range of 0.0003–1 s^? 1 using hot compression tests. It was characterized by true stress–true strain curves, constitutive equation, strain rate sensitivity m contour maps, power dissipation η maps and hot processing maps. The microstructural validation of processing maps was also done. The results show that the flow stress decreases with increasing temperature and decreasing strain rate. The hot deformation apparent activation energy of the Ni–Cr–Co based P/M superalloy at peak stress is 805 kJ/mol. The m and η contour maps are similar, and the values of m and η in the peak zones increase with increasing strain. When the strain is 0.5, a domain with its peak η of 40% and peak m of 25% occurs at 1050 °C and 0.0003 s^? 1, which corresponds to dynamic recrystallization and can be as an optimum condition for good workability.     

Hot deformation behavior and workability characteristics of bimodal size SiCp/AZ91 magnesium matrix composite with processing map

The hot deformation behavior of (0.2 um 1.5 vol.% + 10 um8.5 vol.%) bimodal size SiCp/AZ91 magnesium matrix composite fabricated by stir casting was investigated at the temperature of 270–420 °C and strain rate of 0.001–1 S⁻¹. The flow stress at the strain of 0.5 was used for kinetic analysis. Results indicate that dislocation climb is likely to be the main deformation mechanism responsible for the present composite. By evaluating the efficiencies of power dissipation and instability parameters, the processing maps are developed to optimize the hot working processing. Two domains of dynamic recrystallization are found in the processing map. One exists at the temperature of 270–370 °C and strain rate of 0.001–0.01 s⁻¹ with maximum dissipation efficiency of 38%; the other exists at 420 °C and 0.01 s⁻¹ with peak dissipation efficiency of 24%. The instability region of flow behavior can also be recognized at the temperature of 270–320 °C and the strain rate of 0.1–1 s⁻¹. The characteristic microstructures predicted from the processing map agree well with the result of microstructure observations.     

Comparison of electrochemical performances of LiFePO4/C composite materials by two preparation routes

This study reports on the preparation of LiFePO₄/C composite materials prepared by the hydrothermal and sol–gel processes for comparison. The synthesis condition on the hydrothermal process was performed at 170 °C for 19 h. The polystyrene (PS) polymer was used as a carbon source; the PS was added at a range of 0–5 wt.%. The temperature of the post-thermal process was set at 750–850 °C. The citric acid (denoted as CA) was used as the reducing agent and the carbon source in the sol–gel process. The temperatures of the sintering process were set at a range of 650–850 °C. The optimal sintering temperature was at 850 °C for 12 h in the hydrothermal process; the optimal carbon residue content was approximately 3.20 wt.%. It was revealed that the highest discharge capacity of LiFePO₄/C composites by the hydrothermal process at 0.1 C is 163 mAh g^?1. The optimal sintering temperature was found to be at 750 °C for the sol–gel process. The highest carbon content was approximately 11.94 wt.% as the molar ratio of CA is 1.0. The highest discharge capacity of LiFePO₄/C composites by the sol–gel process at 0.1 C was approximately 130.35 mAh g^?1.     

Effect of (α + β) heat treatment on microstructure and mechanical properties of (TiB + TiC)/Ti–B20 matrix composite

For the first stage, a metastable β titanium alloy, Ti–3.5Al–5Mo–4V–2Cr–2Sn–2Zr–1Fe reinforced with trace amounts of TiB whiskers and TiC particles was fabricated by vacuum arc melting process and hot forging followed by heat treatment at 780 °C/740 °C, then by aging at 500 °C, 550 °C, 570 °C and 600 °C. For the second stage, the unreinforced titanium alloy was also fabricated by the same process. The microstructural characteristics were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Traces of TiB whiskers and TiC particles (2.2 vol.%) with a volume ratio of 2:3 synthesized in situ exerted a hybrid reinforcing effect on the β titanium alloy. The reinforcements were uniformly distributed in the matrix and the elastic modulus was improved about 25 GPa. Ultimate tensile strength and yield strength achieves about 1625 MPa and 1500MPa respectively, with ductility at 7% when the aging temperature is 500 °C. The ductility of (TiB + TiC)/(Ti–3.5Al–5Mo–4 V–2Cr–2Sn–2Zr–1Fe) matrix composite could be enhanced by increasing the aging temperatures. After 780 °C followed by aging at 570 °C, excellent strength and plasticity properties were obtained (ultimate tensile strength of matrix alloy is 1350 MPa with elongation of 18% and ultimate tensile strength of composite is 1500 MPa with elongation of 13%).     

Effect of strain rate on the dynamic compressive mechanical behaviors of rock material subjected to high temperatures

Strain rate is not only an important measure to characterize the deformation property, but also an important parameter to analyze the dynamic mechanical properties of rock materials. In this paper, by using the SHPB test system improved with high temperature device, the dynamic compressive tests of sandstone at seven temperatures in the range of room temperature to 1000 °C and five impact velocities in the range of 11.0–15.0 m/s were conducted. Investigations were carried out on the influences of strain rate on dynamic compressive mechanical behaviors of sandstone. The results of the study indicate that the enhancement effects of strain rates on dynamic compressive strength, peak strain, energy absorption ratio of sandstone under high temperatures still exist. However, the increase ratios of dynamic compressive strength, peak strain, and energy absorption ratio of rock under high temperature compared to room temperature have no obvious strain rate effects. The temperatures at which the strain rates affect dynamic compressive strength and peak strain most, are 800, and 1000 °C, respectively. The temperatures at which the strain rates affect dynamic compressive strength and peak strain weakest, are 1000 °C, and room temperature, respectively. At 200 and 800 °C, the strain rate effect on energy absorption ratio are most significant, while at 1000 °C, it is weakest. There are no obvious strain rate effects on elastic modulus and increase ratio of elastic modulus under high temperatures. According to test results, the relationship formula of strain rate with high temperature and impact load was derived by internalizing fitting parameters. Compared with the strain rate effect at room temperature condition, essential differences have occurred in the strain rate effect of rock material under the influence of high temperature.     

Microstructure and mechanical properties of in situ TiC and Nd2O3 particles reinforced Ti–4.5 wt.%Si alloy composites

(TiC + Nd₂O₃)/Ti–4.5 wt.%Si composites were in situ synthesized by a non-consumable arc-melting technology. The phases in the composites were identified by X-ray diffraction. Microstructures of the composites were observed by optical microscope and scanning electron microscope. The composite contains four phases: TiC, Nd₂O₃, Ti₅Si₃ and Ti. The TiC and Nd₂O₃ particles with dendritic and near-equiaxed shapes are well distributed in Ti–4.5 wt.%Si alloy matrix, and the fine Nd₂O₃ particles exist in the network Ti + Ti₅Si₃ eutectic cells and Ti matrix of the composites. The hardness and compressive strength of the composites are markedly higher than that of Ti–4.5 wt.%Si alloy. When the TiC content is fixed as 10 wt.% in the composites, the hardness is enhanced as the Nd₂O₃ content increases from 8 wt.% to 13 wt.%, but the compressive strength peaks at the Nd₂O₃ content of 8 wt.%.