Alloy Infiltration Research Articles

Hierarchical tungsten-copper composite reinforced by a concrete skeleton of particulate and fibrous tungsten with coherent Cr precipitates in the copper matrix

The substitution of a precipitation-hardenable alloy of Cu-0.5wt.%Cr for the widely adopted pure Cu has been proposed for infiltration into the pre-sintered concrete skeleton of particulate and fibrous W. By the reinforcement of a concrete skeleton of particulate and fibrous W along with coherent Cr precipitates in the Cu matrix, the composite exhibited superior comprehensive properties. Specifically, the proposed composite here exhibited a high tensile strength of 601.2 MPa improved by 22.7%, a low friction coefficient of 0.567 decreased by 27.3% and high electrical breakdown strength of 9.07 × 107 V/m increased by 101.5%. Notably, due to the precipitation of the coherent Cr particles to lower the solute content in the Cu matrix, the composite exhibited rather good electrical conductivity of 51.4%IACS. The proposed strategy by infiltration of precipitation-hardenable Cu-based alloys into the W skeleton here provides a new clue for the microstructure design and performance enhancement of novel WCu composites.

Liquid metal infiltration of silicon based alloys into porous carbonaceous materials. Part II: Experimental verification of modelling approaches by infiltration of Si-Zr alloy into idealized microchannels

In this work, the mechanisms leading to the pore closure in reactive melt infiltration (RMI) of carbon by pure silicon and a near eutectic Si-8 at-pct Zr alloy at 1500 and 1700 °C under vacuum were studied. Various geometrical configurations of microchannels were fabricated via laser ablation of glassy carbon plates. The micron size capillary channels allowed simplifying the complicated porosity distribution in the infiltration of powder or fibres based porous preform while keeping the physical dimensions in the range of where the physical phenomenon of pore closure takes place. The extent of infiltration was analysed by means of X-ray radiography. For RMI of pure Si, the widely accepted decrease in capillary radius by the formation of a solid state SiC layer by the reaction of liquid Si and C was observed, but did not lead to closure and it is hence not the infiltration limiting step in channels as small as 10 μm. However, in the case of the Si-Zr alloy infiltration, another mechanism of pore closure was observed, namely the precipitation of zirconium silicides at the infiltration front, due to Zr enrichment in the alloy by the continuous consumption of Si for the formation of SiC.

Liquid metal infiltration of silicon based alloys into porous carbonaceous materials. Part I: Modelling of channel filling and reaction phase formation

A relation for an adequate pore fraction needed to obtain residual Si and C free composites via reactive Si-X alloy infiltration is presented. The volume ratio of SiC and carbonaceous phase, the composition of the infiltrating liquid and the apparent density of the preform are used as design entities. The approach allows identifying combinations of these design entities leading to desirable microstructures, e.g. those free of residual silicon or free of excess graphite. The approach gives further access to important post infiltration characteristics like propensity of the various phases.An idealising mathematical model describing the reactive flow of Si-X alloy in a single micron sized capillary channel of carbon as well as in carbonaceous preforms is presented. The model is further expanded to evaluate the infiltration depth in porous carbonaceous preform for a given composition of Si-X alloy and infiltration temperature. The model is presented for both isothermal and non-isothermal cases.The analysis is formulated in general terms and is hence applicable to a large variety of Si-C-refractory metal systems of potential interest.

Microstructural characteristics, deformation behavior and mechanical properties of Inconel 718 treated by Te infiltration

Element Te has significant effect on the intergranular embrittlement of nickel-based alloys. This paper proposes a new alloy infiltration method to investigate the effect of Te infiltration on nickel-based superalloy Inconel 718. Micro-scratch test was performed to quantitatively assess the effect of Te infiltration on the mechanical properties of Inconel 718. Three-dimensional morphology of scratches was analyzed and the deformation behavior of treated samples was investigated. Te infiltration caused to the delamination phenomenon, where the material properties of each layer were different. The new intercrystalline phase (Cr3Te4) formated at the grain boundary was the main reason for weakening the properties of surface material. The stress reduction was larger than 50% in the infiltration zone. The failure mechanism was explained and the destructive effect of Te on Inconel 718 was utilized.

Hot-corrosion of refractory high-entropy ceramic matrix composites synthesized by alloy melt-infiltration

Carbon fiber-containing refractory high-entropy ceramic matrix composites (C/RHECs) were fabricated through a reaction with carbon powders, transition metal carbides, and Zr–Ti alloys as a novel heat resistant material used for components of hypersonic vehicles cruising at Mach 7–10. With the infiltration of alloys at 1750 °C into a composite preform containing carbon and carbide powders for 15 min, a high-entropy matrix was successfully formed in situ. Arc-jet tests were conducted in the temperature range of 1800–1900 °C. Results showed the formation of an oxidized region composed of complex oxides, such as (Zr, Hf)O2, (Nb, Ta)2(Zr, Hf)6O17, (Zr, Hf)TiO4, and Ti(Nb, Ta)2O7, with an average thickness of ~600 μm, under which an unoxidized region remained. The porous oxidized region resulted from the evolution of CO(g) during oxidation, while a dense oxide region formed as the outermost region. This indicates that the dense oxide region acted as a barrier to oxygen diffusion for the unoxidized region during oxidation.

Macroscopic rods from assembled colloidal particles of hydrothermally carbonized glucose and their use as templates for silicon carbide and tricopper silicide

Self-aggregated colloids can be used for the preparation of materials, and we studied long rod-like aggregates formed on the evaporation of water from dispersed particles of colloidal hydrochar. The monodispersed hydrochar particles (100–200 nm) were synthesized by the hydrothermal carbonization of glucose and purified through dialysis. During the synthesis they formed colloidal dispersions which were electrostatically stable at intermediate to high pH and at low ion strengths. On the evaporation of water, macroscopically large rods formed from the dispersions at intermediate pH conditions. The rods formed at the solid-water interface orthogonally oriented with respect to the drying direction. Pyrolysis rendered the rods highly porous without qualitatively affecting their shape. A Cu-Si alloy was reactively infiltrated into the in-situ pyrolyzed hydrochars and composites of tricopper silicide (Cu3Si)-silicon carbide (SiC)/carbon formed. During this process, the Si atoms reacted with the C atoms, which in turned caused the alloy to wet and further react with the carbon. The shape of the underlying carbon template was maintained during the reactions, and the formed composite preparation was subsequently calcined into a Cu3Si-SiC-based replica of the rod-like assemblies of carbon-based colloidal particles. Transmission and scanning electron microscopy, and X-ray diffraction were used to study the shape, composition, and structure of the formed solids. Further studies of materials prepared with reactive infiltration of alloys into self-aggregated and carbon-based solids can be justified from a perspective of colloidal science, as well as the explorative use of hydrochar prepared from real biomass, exploration of the compositional space in relation to the reactive infiltration, and applications of the materials in catalysis.

Experimental study and numerical simulation of infiltration of AlSi12 alloys into Si porous preforms with micro-computed tomography inspection characteristics

Experimental study and numerical simulation of infiltration of AlSi12 alloys into Si porous preforms with micro-computed tomography inspection characteristics

Kinetics of liquid metal infiltration in TiC-SiC or SiC porous compacts

TiSi2/SiC composites are promising materials for high temperature applications. The synthesis of these composites by metal infiltration is an interesting method that is not still mastered. This study aims at identifying the thermodynamic and kinetic processes involved during the synthesis of TiSi2/SiC composites by capillary infiltration of liquid silicon or Si-Ti molten alloys in porous compacts. Three cases were examined to produce dense TiSi2/SiC materials: 1) the infiltration of molten TiSi2 in pure SiC compacts at 1550 °C, 2) the reactive infiltration of the molten eutectic Ti0.16Si0.84 alloy in SiC + TiC compacts at 1380 °C, and 3) the reactive infiltration of pure liquid silicon in SiC + TiC compacts at 1450 °C. The effect of a TiC excess was considered for each reactive case. The infiltration kinetics and the filling percentage were measured from the monitoring of the weight gain increase. The decisive role played by thermodynamics on the infiltration progress is confirmed. It induces the dissolution and diffusion of Ti atoms from TiC which results in the presence of free silicon in the infiltrated areas. Excess content of TiC is not found favorable to the infiltration. This original study based on thermodynamic calculations and kinetic measurements at high temperatures provides decisive results for a complete understanding and improvements of the examined processes.

Effect of element Te on alterations of microstructure and mechanical property of nickel-based superalloy Inconel 718 through alloy infiltration

Alloying elements have significant effects on material physical and mechanical properties. The present work studies the effect of element Te on the alterations of microstructure and mechanical property of nickel-based superalloy Inconel 718. Te was diffused into the surface layer of treated samples with a new alloy infiltration method. The microstructure and element distribution within the modified layer were tested and quantitatively characterized with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The depth of infiltration layer presented an approximately linear relationship with the treating temperature range from 700 °C to 900 °C. Furthermore, the mechanical property of the modified layer was evaluated through nano-indentation experiments. The results show that the Te infiltration into the surface layer of Inconel 718 presents a gradient distribution from the outmost surface to the matrix, and it results in a substantial weakening of the modified layer. A gradual decrease in nano-hardness was detected from the surface to the matrix, and the nano-hardness value of infiltration layer was weakened by 31% for the Te infiltration treatment at 900 °C. The underlying weakening mechanism of Te on the superalloy Inconel 718 was revealed. Te element penetrates along the grain boundary leading to the formation of new intercrystalline phases. Consequently, the grain boundary is “opened” which causes the embrittlement of grain boundaries and weakening of the treated surface. This study can not only help to understand the influence of alloying elements on the variation of material properties, but also provide guidance for design of material compositions.

AlSi10Mg alloy infiltration into porous SiC structures manufactured by sponge replication

An AlSi10Mg aluminium casting alloy is infiltrated into porous silicon carbide (SIC) structures, and the microstructural, mechanical and physical properties of aluminium composites are investigated. Silicon carbide porous structures were formed by the polymeric template sponge replica method. Reticulated and open-pore polyurethane sponges with 45, 60 and 80 pores per inch were used for the polymeric replica application. The high-pressure die casting method was preferred to infiltrate the liquid aluminium alloy into porous ceramic structures. An AlSi10Mg aluminium casting alloy was used as the matrix alloy for the manufacturing of aluminium matrix composites. Molten aluminium alloy was pushed into the mould cavity for 5 s with 8 atm piston pressure. Microstructural, mechanical and physical properties of aluminium composites were examined, and the analyses of energy-dispersive spectrometry, X-ray diffraction and scanning electron microscopy and tensile test were performed for this. The experimental density of the non-reinforced sample was obtained as 2.62 g cm−3, while the composites were changed between 2.71 and 2.72 g cm−3 according to the pore structure. The highest tensile strength value was determined in aluminium composites with a pore density of 80 ppi reinforcement element with a value of 160 MPa.

Design of Lu2O3-reinforced Cf/SiC-ZrB2-ZrC ultra-high temperature ceramic matrix composites: Wetting and interfacial reactivity by ZrSi2 based alloys

The wettability and infiltration of molten ZrSi2 and ZrSi2-Lu2O3 alloys into Cf/SiC and B4C-infiltrated Cf/SiC composites were investigated to understand the interfacial interactions that occur during the development of Cf/SiC-ZrC and Cf/SiC-ZrB2-ZrC-Lu2O3 materials. A significant evaporation of Si from the liquid affected the wetting behaviour of the alloy when tested in a vacuum at 1670 °C. The better wetting and spreading of the alloy over the surface was observed for the composites with lower overall porosity (12 %). On the other hand, the formation of an outer dense layer, followed up by the uniform infiltrated region up to ∼ 1 mm was observed for the Cf/SiC with higher porosity (21 %). The infiltrated alloy reacted with SiC matrix to form ZrC or with B4C-infiltrated SiC matrix to form ZrB2-ZrC-SiC. The Lu2O3 particles were not wetted by the melt, and were pushed away of the reaction zone by the solidification front.

Reactive Infiltration and Microstructural Characteristics of Sn-V Active Solder Alloys on Porous Graphite.

In this work, the reactive wetting and infiltration behaviors of a newly designed Sn-V binary alloy were comprehensively explored on porous graphite for the first time. It was discovered that 0.5 wt.% addition of V can obviously improve the wettability of liquid Sn on porous graphite and the nominal V contents in Sn-V binary alloys has minor effects on the apparent contact angles wetted at 950 °C. Moreover, the V-containing Sn-V alloys were initiated to spread on porous graphite at ~650 °C and reached a quasi-equilibrium state at ~900 °C. Spreading kinetics of Sn-3V alloy on porous graphite well fitted in the classic product reaction controlled (PRC) model. However, our microstructural characterization demonstrated that, besides vanadium carbide formation, the adsorption of V element at the wetting three-phase contact line spontaneously contributed to the reactive spreading and infiltrating of Sn-V alloys on porous graphite. Meanwhile, the formation of continuous vanadium carbides could completely block the infiltration of Sn-V active solder alloy in porous graphite. Affected by the growth kinetics of vanadium carbides, the infiltration depth of Sn-V alloys in porous graphite decreased at increased isothermal wetting temperatures. This work is believed to provide implicative notions on the fabrication of graphite related materials and devices using novel V-containing bonding alloys.

Studies of the Joining-Relevant Interfacial Properties in the Si-Ti/C and Si-Ti/SiC Systems

Reactive melt infiltration of Si-based alloys into C preforms and SiC/C composites may be an affordable alternative route to fabricate highly performant lightweighting metal matrix and ceramic matrix composites (CMCs), as well as to obtain reliable and long-term stable joints. In order to optimize reactive infiltration process and to tailor the joint microstructures, the knowledge of interfacial phenomena including thermodynamics, kinetics and surface properties of involved phases (i.e., metals and ceramics) as well as wettability and reactivity occurring between dissimilar materials is of crucial importance. In the present work, the feasibility study of a novel brazing method using Si-Ti alloys as filler for SiCf/SiC is reported and supported by the analysis of microstructural evolution and interfacial phenomena observed during the joining process. Namely, the CMC joining was successfully obtained via the reactive infiltration approach. The results obtained were critically discussed and compared with the know-how coming from the previously carried out investigations on the wetting and reactivity of Si-Ti melts in contact with glassy-C and HIP-SiC substrates. In particular, the microstructural evolution of the Si-Ti/C and Si-Ti/SiC interfaces during wetting tests and at the joint of CMC parts was analyzed and related to the operating conditions.

Wetting behavior and reactivity of liquid Si-10Zr alloy in contact with glassy carbon

In designing advanced refractory composites for highly demanding applications, reactive infiltration of liquid Si-enriched Si-Zr alloys into C-or SiC-based preforms may be a viable cost-less manufacturing process.In such cases, in view to optimize liquid assisted processes such as reactive infiltration, fundamental investigations of the interfacial phenomena occurring when the liquid Si-Zr alloys are in contact with C and SiC substrates, are key steps.For this reason, aiming to ‘‘mimic’’ the conventional operating conditions imposed within a reactive infiltration process, the contact heating sessile drop method was applied to perform a basic study concerning the interaction phenomena taking place at the interface of Si-10% at Zr alloy/Glassy Carbon substrate under an Ar atmosphere. Specifically, the contact angle values as a function of time were measured in the temperature range of 1354–1500 °C.The final contact angle values decreased slightly with an increase in temperature.Moreover, at T = 1450 °C, the contact angle increased over a larger time interval before reaching its final value. The kinetics of SiC crystal growth at the interface and the related processing parameters such as temperature and time were carefully analysed. The growth of SiC crystals and their packaging phenomenon are time and temperature-dependent phenomena.

Design of refractory SiC/ZrSi2 composites: Wettability and spreading behavior of liquid Si-10Zr alloy in contact with SiC at high temperatures

Reactive infiltration of liquid Si-enriched alloys into C- or SiC-based preforms is a viable cost-less alternative to manufacture dense and highly performant SiC-based and MMC composites.In view to design and optimize liquid-assisted processes such as reactive infiltration, fundamental investigations on the interfacial phenomena occurring when the liquid Si-based alloys are in contact with C and SiC substrates, are crucial steps. In this context, targeted wettability studies may provide indications for predicting the key factors strongly influencing the reactive infiltration mechanisms, such as, unexpected interaction phenomena, etc. In particular, such preliminary experience may be helpful in finding the suitable set of operating conditions for fabricating tailored composites via reactive infiltration process.Aiming to “mimic’’ the conventional industrial processes for manufacturing SiC/ZrSi2 refractory composites, the sessile drop method was applied to study the interfacial phenomena occurring at Si-10 % atZr/SiC interfaces over the temperature range of T =1360 °C-1450 °C.

Calculation of Infiltration of AlSi12 Alloys into Si Porous Preforms with General and Modified Infiltration Equations

A high-resolution (~ 1 μm) three-dimensional (3D) X-ray micro-computed tomography (μ-CT) was used to nondestructively detect pore characteristics in silicon particle preforms with different starch contents (10%, 20% and 30%) and particle sizes (20, 50 and 90 μm). A pressure infiltration equipment was made to infiltrate the preforms. The preforms were infiltrated at constant temperature (800 °C) and pressure (400 kPa) with different pressure-applied times (3, 5, 8, 11 and 15 s). Since the discrepancy between the infiltration heights measured in the experiment and calculated with the general infiltration equation was found, a modified infiltration equation was proposed considering the pore characteristic parameters from 3D μ-CT. The results of the modified infiltration equation showed good agreement with the experiment.

Effect of Al–Mg Alloy Infiltration on Mechanical and Electrical Properties for Carbon/Carbon Composites

Under vacuum Al–Mg alloy, liquids were successfully infiltrated into carbon/carbon (C/C) composites at high temperatures. Then, the mechanical properties, the metallographics, the scanning electron microscope images, the transmission electron microscope images, the X-ray diffraction images, and the energy dispersive spectroscopy results of C/C–Al–Mg composites were analyzed. The result showed that the bending property of C/C–Al–Mg composites reached 183 MPa whereas that of C/C composites totaled 165 MPa. The compressive strength of C/C–Al–Mg measured 206 MPa whereas that of C/C composites amounted to 142 MPa. The flexural strength and compressive strengths of the steeped metal sliders measured 121 and 104 MPa, respectively. The alloy liquid infiltrated into the matrix by forming a “network conduction” structure which reduced the resistivity and improved the conductivity of the composites. The resistivity of C/C–Al–Mg totaled 1.63 µΩm whereas that of C/C was 3.56 μΩm. During infiltration, an excellent wettability was observed between Al and the carbon matrix due to the existence of Al4C3. The friction coefficients of C/C, the steeped metal slide, and C/Al–Mg were 0.152, 0.068, and 0.189, respectively. The properties of C/C–Al–Mg composites meet the performance requirements of locomotive pantograph sliders.

Microstructure and mechanical properties of Mo-ZrC-Cu composites synthesized by reactive melt infiltration of Zr-Cu melt into porous Mo2C preforms at 1300 °C

Mo-ZrC-Cu composites have been synthesized by reactive melt infiltration of Zr-Cu binary alloys into porous Mo2C preforms at 1300 °C for 10 min in argon. The influence of Zr content in the Zr-Cu infiltrator on microstructure and mechanical properties of Mo-ZrC-Cu composites are investigated. The as-synthesized composites consist of three major phases of Mo, ZrC and Cu, after a complete reaction of Mo2C(s) + Zr-Cu(l) → Mo(s) + ZrC(s) + Cu(l). Mo2Zr phase is formed when Zr content exceeds 50 at% in the Zr-Cu infiltrator. The formed ZrC grains have sizes less than 1 μm with Mo solid solute inside. Meanwhile, nanoscale zones enriched in Cu and C are also detected in ZrC grains. The angular ZrC particles and rounded Mo grains become larger with increasing Zr content in the Zr-Cu infiltrator. With decreasing Cu content from 43.5 to 31 vol% in Mo-ZrC-Cu composites, the elastic modulus and flexure strength increase from 146 to 156 GPa and from 542 to 569 MPa, respectively.

Biomorphic ceramics from wood-derived precursors

ABSTRACTMaterials development is driven by microstructural complexity and, in many cases, inspired by biological systems such as bones, shells and wood. In one approach, one selects the main microstructural features responsible for improved properties and design processes to obtain materials with such microstructures (continuous-fibre-reinforced ceramics, porous ceramics, fibrous ceramic monoliths, etc.). In a different approach, it is possible to use natural materials directly as microstructural templates. Biomorphic ceramics are produced from natural and renewable resources (wood or wood-derived products). A wide variety of SiC-based ceramics can be fabricated by infiltration of silicon or silicon alloys into cellulose-derived carbonaceous templates, providing a low-cost route to advanced ceramic materials with near-net shape potential and amenable to rapid prototyping. These materials have tailorable microstructure and properties, and behave like ceramic materials manufactured by advanced ceramic processing approaches. This review aims to be a comprehensive description of the development of bioSiC ceramics: from wood templates and their microstructure to potential applications of bioSiC materials.

Interfacial microstructure and improved wetting mechanism of SiO2f/SiO2 brazed with Nb by plasma treatment

Due to the poor wettability with AgCuTi and high residual stress, it is difficult to achieve high-strength brazed joint of SiO2f/SiO2 (quartz fiber reinforced silica) with metals. Herein, plasma treatment as an effective approach was conducted to modify the surface state of SiO2f/SiO2 for better wettability and high-strength brazed joints. Based on SEM, Raman, XPS and wetting experiment analysis, the mechanism of plasma treatment on the improved wettability of SiO2f/SiO2 with AgCuTi is proposed.Plasma treatment can coat thin carbon film and form C-Si bonding on the surface of SiO2f/SiO2, which both show good wettability with AgCuTi. Therefore, the contact angle was notably reduced from 131° to 45° with only 5min plasma treatment on the SiO2f/SiO2. Afterwards, the effect of plasma treating time on the interfacial microstructure and mechanical property of SiO2f/SiO2-Nb joints were investigated in detail. It was found that adjusting the plasma treating time can control the distance of brazing alloy infiltration. Further, the shear strength and the fracture morphologies were closely related with the distance of brazing alloy infiltration. The infiltration of AgCuTi at the SiO2f/SiO2 side can significantly increase the bonding areas and reduce residual stress, and thus enhance the mechanical properties of brazed joints.