Reactive Melt Infiltration Research Articles

Microstructure and Mechanical Properties of Ti-Cu-Based Materials Produced by Using Reactive Melt Infiltration and Liquid Phase Sintering Techniques

Microstructure and Mechanical Properties of Ti-Cu-Based Materials Produced by Using Reactive Melt Infiltration and Liquid Phase Sintering Techniques

A novel strategy for rapid fabrication of continuous carbon fiber reinforced (TiZrHfNbTa)C high-entropy ceramic composites: High-entropy alloy in-situ reactive melt infiltration

For the first time, dense continuous carbon fiber (Cf) reinforced (TiZrHfNbTa)C high-entropy ceramic (Cf/HEC) composites were rapidly prepared via in-situ reactive melt infiltration (RMI). A TiZrHfNbTa high-entropy alloy served as the cation source and carbon in Cf reinforced carbon matrix (Cf/C) preforms served as the anion source, and a (TiZrHfNbTa)C high-entropy ceramic phase with a near equimolar ratio was successfully formed. The results revealed that most of the TiZrHfNbTa high-entropy alloy reacted with the carbon matrix, and the harvested Cf/HEC composites exhibited an excellent bending strength (612.6 MPa) and low ablation rates. High reaction rates caused by ultra-high temperature and homogeneous distribution of elements in the high-entropy TiZrHfNbTa alloy significantly reduced the difference in reactivity with C among Ti, Zr, Hf, Nb, and Ta are considered to be the reasons for successful formation of (TiZrHfNbTa)C high-entropy ceramic with a near equimolar ratio in Cf/HEC composites.

Influence of graphitization treatment on microstructure and flexural strength of C/C-ZrC-SiC composites fabricated via reactive melt infiltration

C/C-ZrC-SiC composites were prepared by chemical vapor infiltration (CVI) and molten salt assisted reactive melt infiltration (RMI). The microstructure of low density and high density C/C composites without graphitization (LC/HC) and graphitization at 2000 °C (LCG/HCG) were compared. Moreover, the effects of graphitization of LC and HC on the microstructure and flexural strength of C/C-ZrC-SiC composites were investigated in detail. The composites prepared by infiltration of LC and LCG had lower flexural strength, 220.01 ± 21.18 MPa and 197.94 ± 19.05 MPa, respectively. However, the composites prepared by HC and HCG presented higher flexural strength, 308.76 ± 12.35 MPa and 289.62 ± 8.70 MPa, respectively. This was due to the phenomenon of fiber erosion in both LC and LCG during the RMI process. After graphitization, the flexural strength of C/C-ZrC-SiC composites prepared by RMI decreased, but the fracture behavior of the composites tends to be more mild. The decreased strength of the composites were caused by the increased matrix cracks, fiber damage in high temperature and the weak interfacial bonding. The improve of failure behavior of the composites was due to interface debonding between the fiber and matrix, and composites can consume the fracture energy through fiber pull-out.

Fabrication of SiCw/SiC–Si–Y composites and their resistance to water-oxygen corrosion at 1500 °C

The thermos-structural materials with high strength and high temperature water-oxygen corrosion resistance are urgently needed in aero-space fields. SiC whisker reinforced SiC matrix (SiCw/SiC) composites are the ideal candidate materials for their excellent mechanical properties and thermostability. However, the poor resistance to water-oxygen corrosion ability of SiC matrix limits their further application. In this work, a novel SiCw/SiC–Si–Y composites were first prepared by infiltrating silicon-yttrium (Si–Y) alloy into SiCw/C preform via reactive melt infiltration method. The as-obtained composites not only show the excellent mechanical properties (σF = 363 MPa, KⅠC = 9.14 MPa m1/2), and more importantly after water-oxygen corrosion of 20 h at such temperature as high as 1500 °C, the strength and toughness retention of the composites can reach 106.1% and 103.6%, respectively. The SiCw/SiC–Si–Y composites developed in this paper have a great potential as a new high-performance thermos-structural material for aero-space applications.

Microstructural tailoring, mechanical and thermal properties of SiC composites fabricated by selective laser sintering and reactive melt infiltration

Poor flowability of printable powders and long preparation cycles are the main challenges in selective laser sintering (SLS) of chopped carbon fiber reinforced silicon carbide composites (SiC composites) with complex structures. In this study, we develop an efficient and novel processing route in the fabrication of lightweight SiC composites via SLS of phenolic resin (PR) and C_f powders with the addition of α-SiC particles combined with one-step reactive melt infiltration (RMI). The effects of α-SiC addition on the microstructural evolution of the C_f/SiC/PR printed bodies, C_f/SiC/C green bodies, and derived SiC composites were investigated. The results indicate that the added α-SiC particles play an important role in enhancing the flowability of raw powders, reducing porosity, increasing the reliability of the C_f/SiC/C green bodies, and contributing to improving the microstructure homogeneity and mechanical properties of the SiC composites. The maximum density, flexural strength, and fracture toughness of the SiC composites are 2.749±0.006 g×cm⁻³, 266±5 MPa, and 3.30±0.06 MPa·m^1/2, respectively. The coefficient of thermal expansion (CTE) of the SiC composites is approximately 4.29×10⁻⁶ K⁻¹ from room temperature (RT) to 900 °C, and the thermal conductivity is in the range of 80.15-92.48 W·m⁻¹·K⁻¹ at RT. The high-temperature strength of the SiC composites increase to 287±18 MPa up to 1200 °C. This study provides a novel as well as a feasible tactic for the preparation of high-quality printable powders as well as lightweight, high strength, and high thermal conductivity SiC composites with complex structures by SLS and RMI.

Microstructure and Ablation Behavior of C/C-SiC-(ZrxHf1-x)C Composites Prepared by Reactive Melt Infiltration Method.

C/C-SiC-(ZrxHf1-x)C composites were prepared by the reactive melt infiltration method. The microstructure of the porous C/C skeleton and the C/C-SiC-(ZrxHf1-x)C composites, as well as the structural evolution and ablation behavior of the C/C-SiC-(ZrxHf1-x)C composites, were systematically investigated. The results show that the C/C-SiC-(ZrxHf1-x)C composites were mainly composed of carbon fiber, carbon matrix, SiC ceramic, (ZrxHf1-x)C and (ZrxHf1-x)Si2 solid solutions. The refinement of the pore structure is beneficial to promote the formation of (ZrxHf1-x)C ceramic. The C/C-SiC-(ZrxHf1-x)C composites exhibited outstanding ablation resistance under an air-plasma environment at around 2000 °C. After ablation for 60 s, CMC-1 appeared to possess the minimum mass and linear ablation rates of only 2.696 mg/s and -0.814 µm/s, respectively, which are lower than those of CMC-2 and CMC-3. During the ablation process, a Bi-liquid phase and a liquid-solid two-phase structure were formed on the ablation surface which could act as an oxygen diffusion barrier to retard further ablation, which is responsible for the excellent ablation resistance of the C/C-SiC-(ZrxHf1-x)C composites.

Melt/solid interaction and melt super-saturation effect on the microstructure asset of ultra-refractory composites prepared by reactive melting infiltration

The reactions occurring between a Zr2Cu melting phase and possible compounds intended for use in ultra-refractory ceramic matrix composite, i.e. SiC, TiB2 and ZrB2 are first explored through sessile drop tests, confirming a promising infiltration capability of the melt. Then, a multiphasic ultra-high temperature ceramic matrix composite was prepared by reactive melt infiltration (RMI), using a TiB2-coated carbon fiber preform infiltrated with Zr2Cu at 1500 °C which resulted in the precipitation of ZrB2 and ZrC sub-micrometric faceted grains and a general damage of both fiber and fiber coating, which were penetrated by the melt. Then, to decrease the RMI process temperature down to 1200 °C and limit the fiber damage degree, a second composite was prepared by introducing an additional ZrB2-B infiltration step. Although processing at 300 °C lower, notable alteration of the fiber occurred upon reaction with the Zr2Cu melt and developed a ZrC layer around them, but still allowing pull-out. In addition, the local B-rich environment promoted the development of a dual-phase microstructure within the matrix composed of new sub-micrometric grains and of larger ZrB2 grains, partially dissolved in the melt and re-precipitated acquiring a nano-sized lamellar eutectic structure. The combination of factors on multiple scale length, from the micro- of the fiber to the nano-of the lamella, seems to provide synergistic reinforcing phenomena and thus could be a valuable approach to develop materials for extreme environments.

Ablation behaviour of Csf/ZrB2-SiC composites fabricated by direct ink writing and reactive melt infiltration

Pitch-based short carbon fibres reinforced Csf/ZrB2-SiC composites were fabricated by direct ink writing of short carbon fibres, followed by slurry impregnation and reactive melt infiltration. Ablation behaviour of the Csf/ZrB2-SiC composite was studied by air plasma test. It is indicated that the skeleton of the oriented short carbon fibres provides heat diffusion channels. Consequently, temperatures at the ablation surface are as low as ∼1730 oC and ∼2000 oC respectively at 4 MW/m2 and 5 MW/m2. The composite presents outstanding ablation-resistant performance with a linear recession rate of ∼ − 0.04 µm/s and mass recession rate of ∼ − 3.40 mg/s at 4 MW/m2, ∼ − 0.17 µm/s and ∼ 3.58 mg/s at 5 MW/m2. It is revealed that the fibres area and matrix area of the composite present different ablation mechanisms. The fibres area is ablated severely, while the matrix area presents excellent ablation-resistance with continuous ZrO2-SiO2 protective layer.

Progress in preparation and ablation resistance of ultra-high-temperature ceramics modified C/C composites for extreme environment

Abstract Carbon/carbon (C/C) composites have received considerable attention for one of the most promising materials in thermal-structural applications owing to their low density, excellent mechanical strength at high temperature, and superior thermal shock resistance. However, C/C composites are susceptible to destructive oxidation in atmospheric environment at high temperature. Matrix modification by adding ultra-high-temperature ceramics (UHTCs) into carbon substrate has been proved to be a favorable route to achieve the improved ablation resistance of C/C composites. In this work, the main fabrication approaches of UHTCs-modified C/C composites were summarized, including chemical vapor infiltration/deposition, precursor infiltration and pyrolysis, reactive melt infiltration, and slurry infiltration, and the advantages and drawbacks of each process were also briefly analyzed. In addition, anti-ablation properties of UHTCs-modified C/C composites under different ablation tests with different shape specimens were introduced. Finally, some likely future challenges and research directions in the development and application of these materials were presented.

Ablation Mechanism of AlSiB-C/C Composites under an Oxy-Acetylene Torch

In order to improve the ablation resistance of C/C composites, an AlSiB alloy (mass ratio of Al/Si/B = 2:4:1) was used as a dissipative agent to fill the pores of a C/C composites matrix by reactive melt infiltration to prepare AlSiB-C/C composites. The microstructure evolution and ablation behavior of the obtained AlSiB-C/C composites (mass ratio of Al/Si/B = 2:4:1) under oxy-acetylene flame were investigated by SEM after ablating for 25 s, 50 s, 100 s and 150 s. At the beginning of the ablation process, thermal chemical erosion played a leading part. By using the heat-absorption effect of sweating and the sealing protection effect of the oxide layer, AlSiB-C/C composites significantly reduced the ablation surface temperature, and the linear ablation rate was 4.04 μm/s. With the process of ablation, thermal mechanical erosion tended to dominate. The specimen surface could not form a continuous covering of oxide film to slow down the flame scour, resulting in non-uniform ablation and further expansion of the ablation pit. The self-transpiration cooling behavior and the self-sealing of the ablation products of the dissipative agent played an important role in reducing the extent of thermal chemical erosion and preventing matrix ablation.

Laser ablation mechanism of ZrC-SiC-MoSi2 ternary ceramic modified C/C

C/C composites were prepared by chemical vapor infiltration (CVI), and then were subjected to Si, Zr, and MoSi2 reactive melt infiltration (RMI) to obtain C/C-SiC, C/C-SiC-ZrC, and C/C-SiC-ZrC-MoSi2 composites. The ablation behavior of these three composites was evaluated by high-energy CO2 laser irradiation. The surface temperature distribution of composite materials was simulated by finite element analysis. The results show that the ablation resistance mechanisms of the three materials are entirely different. The C/C-SiC-ZrC-MoSi2 composite showed the best ablation performance among them. It is attributed to the lower oxygen permeability and richer heat dissipation mechanism of the C/C-SiC-ZrC-MoSi2 composite within the total temperature threshold.

Stereolithography-based additive manufacturing of RB-SiC ceramics by a two-step sintering method

Digital light processing technology (DLP) is an effective method to manufacture ceramics with high precision. It is a big challenge to prepare SiC green body with high solid content by DLP method due to the limitation of high light-absorbance of SiC powder in stereolithograhy. Here, we present one novel route for DLP additive manufacturing of high-performance SiC ceramics by introducing low light-absorbance SiO 2 powders and a two-step sintering process including carbothermal reduction and reactive melt infiltration. As-prepared SiC ceramic exhibited higher flexural strength of 268.66 ± 10.19 MPa, compared with reported stereolithograhy-based SiC ceramics. This method demonstrates the potential of preparing SiC ceramic composites with high mechanical properties by stereolithography additive manufacturing.

Compression and thermophysical properties of carbon fiber-reinforced high textured pyrocarbon and SiC dual matrix composites

C/C–SiC composites with high textured pyrocarbon (HT PyC) were fabricated by isothermal chemical vapor infiltration and reactive melt infiltration. The evolution of HT PyC before and after heat treatment at 2100 °C as well as the internal defects of the composites, such as pores and cracks, were characterized. The compression and thermophysical properties of the C/C–SiC composites with 2100 °C heat-treated HT PyC (C–S-21) and C/C composites with 2100 °C heat-treated HT PyC (C–C-21) were studied. The results showed that the compression strength and modulus of C–S-21 were 323.19 ± 11.52 MPa and 4.49 ± 0.13 GPa, which were increased by 58.94% and 125.63%, respectively, compared with those of C–C-21 owing to the smaller number of pores and the higher modulus of SiC and Si, respectively. However, fewer pores and strong interfacial adhesion resulted in the brittle fracture of C–S-21. The thermal conductivity of C–S-21 was 73.56 W/(m·K) and 44.94 W/(m·K) in the XY and Z directions, respectively, which was attributed to the fewer defects and better orientation of the graphitized layer in HT PyC as well as the smaller number of pores.

Microstructure and flexural strength of C/HfC-ZrC-SiC composites prepared by reactive melt infiltration method

C/HfC-ZrC-SiC composites were fabricated via reactive melt infiltration (RMI) of the mixed HfSi2 and ZrSi2 alloys. The microstructure, infiltration behavior of the hybrid silicide alloys infiltrating C/C composites, and flexural strength of C/HfC-ZrC-SiC composites was studied. Inside composites, there were more Hf-rich (Hf, Zr)C phases distributed in the exterior region, while more SiC and Zr-rich (Zr, Hf)Si2 in the interior region. There was compositional segregation in (Hf, Zr)C, with the HfC content decreasing from the exterior region to interior region. The RMI process was performed at different temperatures to investigate the structural evolution, and a model for the reactive melt infiltration of the mixed HfSi2 and ZrSi2 alloys into C/C composites was established. Compared with C/HfC-SiC and C/ZrC-SiC prepared by same process, C/HfC-ZrC-SiC had the highest flexural strength of 247Mpa and 213Mpa after oxidation at 1200 ℃ for 15 min. Both the unoxidized and oxidized samples presented a pseudo-plastic fracture behavior.

Tuning ceramic content, mechanical and ablative properties of C/C–ZrC-ZrxCuy composites via using various C/C skeletons

C/C–ZrC-ZrxCuy composites were prepared by pressure-assisted reactive melt infiltration with Zr2Cu alloy as an infiltrator. The mechanical and ablation properties of C/C–ZrC-ZrxCuy composites were tuned by applying various C/C skeletons (1.28, 1.40, 1.58, and 1.73 g/cm3). When the C/C skeleton density increased from 1.28 to 1.73 g/cm3, the density of the composites decreased gradually. Additionally, due to the higher ceramic content, composites with low skeleton density (1.28, 1.40 g/cm3) exhibit a higher compressive and flexural strength. The fabricated composites with a skeleton density of 1.28 g/cm3 possess better mechanical properties and ablative properties at 2800 °C. After plasma flame ablation for 54 s, the linear and mass ablation rates of the composites are 33.70 ± 1.33 μm/s and 22.39 ± 2.99 mg/s, respectively.

Structure Evolution and Properties Modification for Reaction-Bonded Silicon Carbide.

Complex structure reaction-bonded silicon carbide (RB-SiC) can be prepared by reactive melt infiltration (RMI) and digital light processing (DLP). However, the strength and modulus of RB-SiC prepared by DLP are not sufficient, due to its low solid content (around 40 vol.%), compared with the traditional fabrication techniques (solid content > 60 vol.%). With this understanding, a new method to improve the properties of RB-SiC was proposed, by the impregnation of composite precursor into the porous preform. The composite precursor was composed of phenolic (PF) resin and furfuryl alcohol (FA). PF and FA were pyrolyzed at 1850 °C to obtain amorphous carbon and graphite into the porous preform, respectively. The effects of multiphase carbon on the microstructure and performance of RB-SiC was studied. When the mass ratio of PF to FA was 1/4, the solid content of RB-SiC increased from 40 vol.% to 68.6 vol.%. The strength, bulk density and modulus were 323.12 MPa, 2.94 g/cm3 and 348.83 Gpa, respectively. This method demonstrated that the reaction process between liquid Si and carbon could be controlled by the introduction of multiphase carbon into the porous preforms, which has the potential to regulate the microstructure and properties of RB-SiC prepared by additive manufacturing or other forming methods.

Effects of the La2O3 addition contents on the ablation performance of in-situ La-doped ZrC-SiC-ZrSi2 coating for C/C-ZrC-SiC composites

The C/C-ZrC-SiC composites coated by the La-doped ZrC-SiC-ZrSi2 coatings containing different La contents were fabricated by reactive melt infiltration (RMI) combined with gradient pack cementation in a one-step process. The composites' ablation behaviors under the oxyacetylene flame were comparatively studied. The effects of the La2O3 addition contents on the microstructure and phase composition evolution on the surface of the composites caused by ablation were investigated. The results indicated that the C/C-ZrC-SiC composites with an in-situ La-doped ZrC-SiC-ZrSi2 coating prepared by the mixed powders with 15 wt% La2O3 (15LZS) showed a better ablation performance. After ablation for 120 s, their mass and linear ablation rates were − 0.62 ± 0.15 mg/s and − 2.42 ± 0.24 μm/s, respectively. Such good ablation resistance should owe to appropriate La contents on the surface of the 15LZS. During ablation, the La elements could promote the formation of a dense oxide layer, which was composed of the m-ZrO2, t-ZrO2, and Zr0.9La0.1O1.95 phases. It could efficiently inhibit oxygen diffusion and endure the mechanical denudation of the oxyacetylene flame.

Comparative study of microstructure and ablation behaviour of C/C-HfC-SiC composites prepared under two different conditions

C/C-SiC-HfC composites were prepared using reactive melt infiltration (RMI) under a vacuum (noted as HS-V) and normal pressure (noted as HS-NP), separately. The distribution of the introduced SiC and HfC ceramics can be regulated by adjusting the RMI pressure. Different pressures of the environment at the high temperature stage led to the difference in volatilization of Si in the melt and the ratios of C and HfSi2 in unit volume on the surface of the sample, resulting in the different composition of the sample surface. A HfSi2-HfC-SiC mixed layer was formed on the surface of HS-NP, while HfC coating was formed on the surface of HS-V. HS-NP possessed better ablation performance than HS-V. After ablation for 120 s, its mass ablation rate decreased by 87.81%. The presence of HfSi2 improved the densification of HfO2 film, which made the ablation resistance of HS-NP better than HS-V. This work provides a guide for choosing an idea pressure condition during RMI to obtain C/C-SiC-HfC composites with high ablation resistance.

Additive Manufacturing of C/C-SiC Ceramic Matrix Composites by Automated Fiber Placement of Continuous Fiber Tow in Polymer with Pyrolysis and Reactive Silicon Melt Infiltration

An additive manufacturing process for fabricating ceramic matrix composites has been developed based on the C/C-SiC system. Automated fiber placement of the continuous carbon fibers in a polyether ether ketone matrix was performed to consolidate the carbon fibers into a printed preform. Pyrolysis was performed to convert the polymer matrix to porous carbon, and then Si was introduced by reactive melt infiltration to convert a portion of the carbon matrix to silicon carbide. The densities and microstructures were characterized after each step during the processing, and the mechanical properties were measured. The C/C-SiC composites exhibited a porosity of 10–20%, characteristic flexural strength of 234.91 MPa, and Weibull modulus of 3.21. The composites displayed toughness via a significant displacement to failure.

Structure evolution and ablative mechanism of C/C-ZrC-ZrxCuy composites with low porosity fabricated by pressure assisted reactive melt infiltration

C/C-ZrC-ZrxCuy composites were fabricated by pressure assisted reactive melt infiltration (PARMI). The infiltrated matrix contained three different ZrC-ZrxCuy regions due to the gradient distribution of carbon and Cu during PARMI, and the dimensions of ZrC particles decreased sequentially from matrix boundary to inside. During 30 s ablation, heat-absorbing effect of Cu-phase slowed down the increasement of surface temperature. After 60 s ablation, porous ZrO2 skeleton evolved to a protective integrated cover, including expanded large-scale infiltrator and network of curly whiskers. Thus, ablation rates of composites were reduced to − 1.7 ± 0.1 µm/s and 1.7 ± 0.1 mg/s, separately.