Ti3Si(Al)C2-based ceramics fabricated by reactive melt infiltration with Al70Si30 alloy

Dense Ti₃Si(Al)C₂-based ceramics were synthesized using reactive melt infiltration (RMI) of Al₇₀Si₃₀ alloy into the porous TiC preforms. The effects of the infiltration temperature on the microstructure and mechanical properties of the synthesized composites were investigated. All the composites infiltrated at different temperatures were composed of Ti₃Si(Al)C₂, TiC, SiC, Ti(Al, Si)₃ and Al. With the increase of infiltration temperature from 1050 °C to 1500 °C, the Ti₃Si(Al)C₂ content increased to 52 vol.% and the TiC content decreased to 15 vol.%, and the Vickers hardness, flexural strength and fracture toughness of Ti₃Si(Al)C₂-based composite reached to 9.95 GPa, 328 MPa and 4.8 MPa m^1/2, respectively.     

Superior bending and impact properties of SiC matrix composites infiltrated with an aluminium alloy

A simple process based on melt infiltration was used to modify a silicon carbide (SiC) ceramic and thus improve its mechanical properties. SiC ceramics infiltrated with an Al alloy for 2 h, 4 h, 6 h, and 8 h exhibited outstanding mechanical performance. The three-point bending strength, four-point bending strength, and impact toughness of the SiC ceramics increased by 125–135%, 170–180%, and 140%, respectively, after infiltration with the Al alloy at 900 °C for 4–6 h. The maximum three-point bending strength, four-point bending strength, and impact toughness achieved were 430 MPa, 360 MPa, and 3.5 kJ/m², respectively. Analysis of the processing conditions and microstructure demonstrated that the molten Al alloy effectively infiltrated the gaps between the SiC particles, forming a compact structure with the particles, and some of the Al phases reacted with Si to form Al-Si eutectic phases. Moreover, the results showed that a reaction layer is present on the surface of the SiC sample, which mainly contains the Ti₃SiC₂ phase. Both complete infiltration with the Al alloy and the formation of the Ti₃SiC₂ phase contributed to the improvement of the mechanical properties.     

Ultra-high temperature ceramic coating for carbon/carbon composites against ablation above 2000 K

To improve the ablation resistance of carbon/carbon composites at the temperature above 2000 K, a ZrB₂-SiC-ZrC ultra-high temperature ceramic coating was prepared by combination of supersonic atmosphere plasma spray (SAPS) and reaction melt infiltration. The micro-holes in ZrB₂-Si-ZrC coating prepared by SAPS were effectively filled and the compactness and interface compatibility between the coating and C/C composites was improved through the reaction melt infiltration process. The ultra-high temperature ceramic coating exhibited good ablation resistance under oxyacetylene torch ablation above 2000 K. After ablation for 120 s, the mass and linear ablation rates of the ZrB₂-SiC-ZrC coated C/C samples were only ?0.016 × 10^?3 g/s and 1.30 µm/s, respectively. Good ablation resistance of the ultra-high temperature ceramic coating is mainly attributed to the dense coating structure and the improvement of interface compatibility between the coating and C/C composites.     

Microstructure and mechanical properties of BN-Si3N4 and AlON joints brazed with Ag-Cu-Ti filler alloy

AlON was successfully brazed to BN-Si₃N₄ using a Ag-Cu-Ti filler alloy. SEM, TEM and XRD studies revealed that a TiN + TiB₂ + Ti₅Si₃ reaction layer formed adjacent to the BN-Si₃N₄ while a (Cu,Al)₃Ti₃O layer formed adjacent to the AlON. In addition, Ag-Cu eutectic, Cu(s,s) and AlCu₂Ti were observed in the brazing filler. The effect of brazing temperature on the microstructure and mechanical properties of the joints was investigated. As the brazing temperature increased, the reaction layers became thicker, while the thickness of the brazing seam decreased. Meanwhile, the amount and the size of AlCu₂Ti intermetallic compounds decreased. The shear strength of the joints first increased and then dropped with increasing the brazing temperature. A joint with a maximum strength of 94 MPa was obtained when it was brazed at 850 °C for 15 min.     

High temperature interfacial phase stability of a Mo/Ti3SiC2 laminated composite

A Mo/Ti₃SiC₂ laminated composite is prepared by spark plasma sintering at 1300 °C under a pressure of 50 MPa. Al powder is used as sintering aid to assist the formation of Ti₃SiC₂. The fabricated composites were annealed at 800, 1000 and 1150 °C under vacuum for 5, 10, 20 and 40 h to study the composite's interfacial phase stability at high temperature. Three interfacial layers, namely Mo₂C layer, AlMoSi layer and Ti₅Si₃ solid solution layer are formed during sintering. Experimental results show that the Mo/Ti₃SiC₂ layered composite prepared in this study has good interfacial phase stability up to at least 1000 °C and the growth of the interfacial layer does not show strong dependence on annealing time. However, after being exposed to 1150 °C for 10 h, cracks formed at the interface.     

Microtopography and mechanical properties of vacuum hot pressing Al/B4C composites

Al/B₄C composites with various volume contents of B₄C (5%, 10%, 15%, 20%, and 25%) reinforcing the Al matrix, have been fabricated by vacuum hot press sintering at 680 °C, with a soaking time of 90 min and external pressure of 30 MPa. Mechanical properties, phase composition, and microstructure of the Al/B₄C composites are discussed to reveal the physical properties of the composites. Field emission transmission electron microscopy and selected area electron diffraction have been employed to verify the interior structure and crystal growth direction, respectively. The Vickers hardness, fracture strength, tensile strength, and maximum force attained the optimal values of 108.45 ± 4.02 HV, 585.70 ± 23.26 MPa, 196.18 ± 2.48 MPa, and 4.44 ± 0.17 kN, respectively, for 25 vol% B₄C/Al composites. The static compression strength increased before the 15 vol% B₄C addition and then decreased, acquiring the highest value of 292.15 ± 2.09 MPa for 15 vol% B₄C/Al composites. In general, the relative density and ductility of these composites consistently increased, with an increase in the volume content of Al, achieving a maximum of 99.22% and 54.63 ± 7.34%, respectively, for 5 vol% B₄C/Al composites.     

Microstructure and mechanical strength of transient liquid phase bonded Ti3SiC2 joints using Al interlayer

Based on the structure characteristic of Ti₃SiC₂ and the easy formation of Ti₃Si_1−xAl_xC₂ solid solution, a transient liquid phase (TLP) bonding method was used for bonding layered ternary Ti₃SiC₂ ceramic via Al interlayer. Joining was performed at 1100–1500 °C for 120 min under a 5 MPa load in Ar atmosphere. SEM and XRD analyses revealed that Ti₃Si(Al)C₂ solid solution rather than intermetallic compounds formed at the interface. The mechanism of bonding is attributed to aluminum diffusing into the Ti₃SiC₂. The strength of joints was evaluated by three point bending test. The maximum flexural strength reaches a value of 263 ± 16 MPa, which is about 65% of that of Ti₃SiC₂; for the sample prepared under the joining condition of 1500 °C for 120 min under 5 MPa. This flexural strength of the joint is sustained up to 1000 °C.     

Dependence of the microstructure and properties of TiC/Ti3SiC2 composites on extra C addition

TiC/Ti₃SiC₂ composites were synthesized with Ti/Si/C and Al (in which extra C addition ranges from 0 to 25 wt.%) as starting powders by hot-pressed sintering method at 1400 °C under 30 MPa. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate the phase composition and the fracture surface. The results reveal that with the increase of extra C addition, the content of Ti₃SiC₂ phase decreases while the content of TiC phase increases. Graphite phase is detected in the samples with extra C addition of 20 wt.% and 25 wt.%. The bending strength decreases from 554.81 MPa to 57.44 MPa due to the decrease of the densification and Ti₃SiC₂ phase content. The electrical conductivity falls from 42,474.52 s/cm to 1524.95 s/cm, resulting from lower Ti₃SiC₂ phase content and higher contact resistance.     

Fabrication and electromagnetic interference shielding effectiveness of Ti3Si(Al)C2 modified Al2O3/SiC composites

A dense alumina fiber reinforced silicon carbide matrix composites (Al₂O₃/SiC) modified with Ti₃Si(Al)C₂ were prepared by a joint process of chemical vapor infiltration, slurry infiltration and reactive melt infiltration. The conductive Ti₃Si(Al)C₂ phase introduced into the matrix modified the microstructure of Al₂O₃/SiC. The refined microstructure was composed of conductive phase, semiconductive phase and insulating phase, which led to admirable electromagnetic shielding properties. Electromagnetic interference shielding effectiveness (EMI SE) of Al₂O₃/SiC and Ti₃Si(Al)C₂ modified Al₂O₃/SiC were investigated over the frequency range of 8.2–12.4 GHz. The EMI SE of Al₂O₃/SiC-Ti₃Si(Al)C₂ exhibited a significant increase from 27.6 to 42.1 dB compared with that of Al₂O₃/SiC. The reflection and absorption shielding effectiveness increased simultaneously with the increase of the electrical conductivity.     

Microstructure and mechanical properties of Ti3SiC2/3Y-TZP composites by spark plasma sintering

Ti₃SiC₂/3Y-TZP (3 mol% Yttria-stabilized tetragonal zirconia polycrystal) composites were fabricated by spark plasma sintering (SPS). The effect of Ti₃SiC₂ content on room-temperature mechanical properties and microstructures of the composites were investigated. The Vickers hardness and bending strength of the composites decreased with the increasing of Ti₃SiC₂ content whereas the fracture toughness increased. The maximum fracture toughness of 9.88 MPa m^1/2 was achieved for the composite with 50 vol.% Ti₃SiC₂. The improvement of the fracture toughness is owing to the crack deflection, crack bridging, the transformation toughening effects.     

Enhancing copper infiltration into alumina using spark plasma sintering to achieve high performance Al2O3/Cu composites

Al₂O₃/Cu (with 30 wt% of Cu) composites were prepared using a combined liquid infiltration and spark plasma sintering (SPS) method using pre-processed composite powders. Crystalline structures, morphology and physical/mechanical properties of the sintered composites were studied and compared with those obtained from similar composites prepared using a standard liquid infiltration process without any external pressure. Results showed that densities of the Al₂O₃/Cu composites prepared without applying pressure were quite low. Whereas the composites sintered using the SPS (with a high pressure during sintering in 10 min) showed dense structures, and Cu phases were homogenously infiltrated and dispersed with a network from inside the Al₂O₃ skeleton structures. Fracture toughness of Al₂O₃/Cu composites prepared without using external pressure (with a sintering time of 1.5 h) was 4.2 MPa m^1/2, whereas that using the SPS process was 6.5 MPa m^1/2. These toughness readings were increased by 18% and 82%, respectively, compared with that of pure alumina. Hardness, density and electrical resistivity of the samples prepared without pressure were 693 HV, 82.5% and 0.01 Ω m, whereas those using the SPS process were 842 HV, 99.1%, 0.002 Ω m, respectively. The enhancement in these properties using the SPS process are mainly due to the efficient pressurized infiltration of Cu phases into the network of Al₂O₃ skeleton structures, and also due to high intensity discharge plasma which produces fully densified composites in a short time.     

Microstructure and properties of dense Tyranno-ZMI SiC/SiC containing Ti3Si(Al)C2 with plastic deformation toughening mechanism

In this paper, Ti₃Si(Al)C₂ was introduced into dense SiC/SiC to improve the mechanical and electromagnetic interference (EMI) shielding properties. In order to reveal the effect of Ti₃Si(Al)C₂, dense SiC/SiC-Ti₃Si(Al)C₂ and dense SiC/SiC without Ti₃Si(Al)C₂ were fabricated. Owing to the plastic deformation toughening mechanism of Ti₃Si(Al)C₂, SiC/SiC-Ti₃Si(Al)C₂ performs a new damage mode characterized by matrix/matrix (m/m) debonding. High interfacial shear strength (IFSS) due to large thermal residual stress (TRS) is weakened by m/m debonding. This new mode also brings high effective volume fraction of loading fibers and long path of crack propagation. Hence SiC/SiC-Ti₃Si(Al)C₂ exhibits higher flexural strength (503 MPa) and fracture toughness (23.7 MPa · m^1/2) than the dense SiC/SiC without Ti₃Si(Al)C₂. In addition, dense SiC/SiC-Ti₃Si(Al)C₂ shows excellent electromagnetic interference shielding effectiveness (EMI SE, 43.0 dB) in X-band, revealing great potential as thermo-structural and functional material.     

Effect of SiCp multimodal distribution on pitting behavior of Al/SiCp composites prepared by reactive infiltration

The effect of coated-SiC_p multimodal-size-distribution on the pitting behavior of Al/SiC_p composites was investigated. α-SiC powders (10, 54, 86, and 146 μm) were properly mixed and coated with silica to produce porous preforms with 0.6 volume fraction of the reinforcement with monomodal, bimodal, trimodal, and cuatrimodal size distribution. The preforms were infiltrated with the alloy Al–13 Mg–1.8Si (wt.%) in argon followed by nitrogen at 1100 ºC for 60 min. The composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) before and after cyclic polarization measurements in 0.1 M NaCl de-aerated solutions. Results show that whereas corrosion and passivation potentials are not influenced with increase in SiC_p particle size distribution, favorably, the susceptibility to pitting corrosion decreases. This beneficial effect is ascribed to the smaller area of the alloy matrix exposed to the chloride solution with augment in particle size distribution, substantially when going from monomodal to bimodal SiC_p particle size distribution.     

Infiltration behavior of Cu and Ti fillers into Ti2AlC/Ti3AlC2 composites during tungsten inert gas (TIG)brazing

Herein we study the infiltration behavior of Ti and Cu fillers into a Ti₂AlC/Ti₃AlC₂MAX phase composites using a TIG-brazing process. The microstructures of the interfaces were investigated by scanning electron microscopy and energy dispersive spectrometry. When Ti₂AlC/Ti₃AlC₂ comes into contact with molten Ti, it starts decomposing into TiC_x, a Ti-richandTi₃AlC; when in contact with molten Cu, the resulting phases are Ti₂Al(Cu)C, Cu(Al), AlCu₂Ti and TiC. In the presence of Cu at approximately 1630 °C, a defective Ti₂Al(Cu)C phase was formed having a P63/mmc structure. Ti₃AlC₂ MAX phase was completely decomposed in presence of Cu or Ti filler-materials. The decomposition of Ti₂AlC to Ti₃AlC₂ was observed in the heat-affected zone of the composite. Notably, no cracks were observed during TIG-brazing of Ti₂AlC/Ti₃AlC₂ composite with Ti or Cu filler materials.     

Near‐Net‐Shape Fabrication of Ti3SiC2‐based Ceramics by Three‐Dimensional Printing

This paper focuses on the preparation of near‐net‐shaped dense Ti₃SiC₂‐based materials via an indirect three‐dimensional printing (3D printing) and postreactive melt infiltration (RMI) processes. TiC preforms with bimodal pore size distribution were fabricated through 3D printing, followed by the infiltration of Si melt and Al–Si alloy (Al₄₀Si₆₀ and Al₇₀Si₃₀). Dense composites with density of ~4.1 g/cm³ were obtained after the infiltration. No volume shrinkage was obtained after the reactive infiltration with Al–Si alloy. The participation of Al during the infiltration process promoted the formation of Ti₃SiC₂. The as‐fabricated Ti₃SiC₂‐based materials showed enhanced mechanical and electromagnetic interference shielding properties.     

Wetting of AgCu-Ti filler on porous Si3N4 ceramic and brazing of the ceramic to TiAl alloy

The effect of Ti content on the wettability of AgCu-Ti filler on porous Si₃N₄ ceramic was studied by the sessile drop method. AgCu-2 wt% Ti filler alloy showed a minimum contact angle of 14.6° on porous Si₃N₄ ceramic during the isothermal wetting process. The mechanism of AgCu-Ti filler wetting on porous Si₃N₄ ceramic is clarified in this paper. Porous Si₃N₄ ceramic was brazed to TiAl alloy using AgCu-xTi (x = 0, 2 wt%, 4 wt%, 6 wt%, 8 wt%) filler alloy at 880 °C for 10 min. The effect of Ti content on the interfacial microstructure and mechanical properties of porous-Si₃N₄/AgCu-xTi/TiAl joints are studied. The typical interfacial microstructure of p-Si₃N₄/AgCu-Ti/TiAl joint is p-Si₃N₄/penetration layer (Ag(s,s)+Si₃N₄+TiN+Ti₅Si₃)/Ag(s,s)+Cu(s,s)+TiCu/AlCu₂Ti/TiAl. The maximum shearing strength of the brazed joint was 14.17 MPa and fracture that occurred during the shearing test propagated in the porous Si₃N₄ ceramic substrate for the formation of the penetration layer.     

High compressive strength in nacre-inspired Al−7Si−5Cu/Al2O3–ZrO2 composites at room and elevated temperatures by regulating interfacial reaction

Al−7Si−5Cu/Al₂O₃−ZrO₂ composites with nacre-like structures were prepared via ice-templating and gas pressure infiltration techniques. The composites were subsequently heat-treated at 850 °C for 0, 30, 60, 90 and 120 min to regulate the interfacial reaction between Al and ZrO₂. The yield of larger (Al_1−m, Si_m)₃Zr and ZrSi₂ phases increased with longer dwell times. The compressive strength initially increased and then decreased. The highest strength was observed in composites treated for 60 min and reached 1600±40, 1261±30 and 1033±22 MPa at temperatures of 20, 150 and 300 °C, respectively. These values increased by 30−40% as compared to those of the non-treated counterparts and were 2-, 5- and 12-fold more than those of the matrix alloy, respectively, which is demonstrative of the material's excellent load-bearing capacity, particularly at elevated temperatures.     

Facile synthesis of Ti3SiC2 powder by high energy ball-milling and vacuum pressureless heat-treating process from Ti–TiC–SiC–Al powder mixtures

In this article, Ti/TiC/SiC/Al powder mixtures with molar ratios of 4:1:2:0.2 were high energy ball-milled, compacted, and heated in vacuum with various schedules, in order to reveal the effects of temperature, soaking time, thickness of the compacts, and carbon content on the purity of the sintered compacts. X-ray diffraction and scanning electron microscopy were employed to investigate the phase purity, particle size and morphology of the synthesized samples. It was found that the Ti₃SiC₂ content nearly reached 100 wt.% on the surface layer of the sintered compacts prepared in the temperature range from 1350 °C to 1400 °C for 1 h. Powder containing 91 wt.% Ti₃SiC₂ was successfully synthesized by heating 6 mm green compacts of 4Ti/1TiC/2SiC/0.2Al at 1380 °C for 1 h in vacuum. The excessive carbon content failed to improve the purity of Ti₃SiC₂ powder. TiC phase was the main impurity in the formation process of Ti₃SiC₂.     

Fabrication of Ti3SiC2-based composites via three-dimensional printing: Influence of processing on the final properties

In this work the influence of the processing routes on the microstructure and properties of Ti₃SiC₂-based composites was investigated. The three main processing steps are (i) three-dimensional printing of Ti₃SiC₂ powder blended with dextrin, (ii) pressing of printed samples (uniaxial or cold isostatic pressing), and (iii) sintering of pressed samples at 1600 °C for 2 h. The Ti₃SiC₂-based composites were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Young's Modulus and flexural strength were measured to examine the mechanical properties. Porosity, density, shrinkage, and mass change were measured at each processing step. Those samples uniaxially pressed at 726 MPa presented the highest density, shrinkage, and mass change. However, microstructural morphologies were crack-free and homogeneous for cold isostatic pressed Ti₃SiC₂-based composites as compared to uniaxially pressed samples. The highest values for Young's Modulus (~300 GPa) and flexural strength (~3 GPa) were observed with uniaxially pressed Ti₃SiC₂-based composites.     

Tribological behavior of Ti3SiC2 and Ti3SiC2/Pb composites sliding against Ni-based alloys at elevated temperatures

The Ti₃SiC₂ and Ti₃SiC₂/Pb composites were tested under dry sliding conditions against Ni-based alloys (Inconel 718) at elevated temperatures up to 800 °C using a pin-on-disk tribometer. Detailed tribo-chemical changes of Pb on sliding surface were discussed. It was found that the tribological behavior were insensitive to the temperature from 25 °C (RT) to 600 °C (friction coefficient ≈0.61–0.72, wear rate ≈10⁻³ mm³ N m⁻¹). An amount of Pb in the composites played a key role in lubricating with the temperature below 800 °C. The friction coefficient (≈0.22) and wear rate (≈10⁻⁷ mm³ N m⁻¹) at elevated temperatures were both decreased by the added PbO. The wear mechanisms of Ti₃SiC₂/Pb-Inconel 718 tribo-pair at elevated temperatures were believed to be the combined effect of abrasive wear and tribo-oxidation wear. During the sliding, two oxidization reactions proceed, 2Pb+O₂=2PbO (below 600 °C) and 6PbO+O₂=2Pb₃O₄ (800 °C). The friction coefficient and wear rate of the composites were reduced due to the self-lubricating effect of the tribo-oxidation products.