Gas Pressure Infiltration Method Research Articles

Effect of Temperature on the Complex Modulus of Mg-Based Unidirectionally Aligned Carbon Fiber Composites.

Composite materials based on magnesium-lithium (MgLi) and magnesium-yttrium (MgY) matrices reinforced with unidirectional carbon fibers were prepared using the gas pressure infiltration method. Two types of carbon fibers were used, high-strength PAN-based T300 fibers and high-modulus pitch-based Granoc fibers. The PAN-based carbon fibers have an internal turbostratic structure composed of crystallites. The pitch-based carbon fibers have a longitudinally aligned graphite crystal structure. The internal carbon fiber structure is crucial in the context of the interfacial reaction with the alloying element. There are various mechanisms of bonding to carbon fibers in the case of magnesium-lithium and magnesium-yttrium alloys. This paper presents the use of the DMA method for the characterization of the role of alloying elements in the quality of interfacial bonding and the influence on the complex modulus at increasingly elevated temperatures (50-250 °C). The complex modulus values of the composites with T300 fibers were in the range of 118-136 GPa. The complex modulus values of the composites with Granoc fibers were in the range of 198-236 GPa. The damping capacity of magnesium-based unidirectionally aligned carbon fiber composites is related to the quality of the interfacial bonding.

Unveiling interfacial structure and improving thermal conductivity of Cu/diamond composites reinforced with Zr-coated diamond particles

To overcome the drawback of weak interface bonding in diamond particles reinforced Cu matrix (Cu/diamond) composites, we prepared the Cu/Zr-diamond composites via a gas pressure infiltration method with Zr coatings with thicknesses from 47 nm to 430 nm on diamond surfaces. The scanning transmission electron microscopy (STEM) and X-ray diffraction (XRD) analyses reveal that during preparation the gradual transformation of metallic Zr to ZrC occurs through the diffusion of C atoms, and the crystallographic orientation relationship between diamond and ZrC is characterized as (1¯11)diamond//(1¯11)ZrC and [110]diamond//[110]ZrC. The formed ZrC layer between diamond and Cu can bridge the large gap of acoustic impedance and greatly strengthen the interface bonding, and a maximal thermal conductivity of 735 W m−1 K−1 is achieved with the thickness of the interfacial ZrC layer of 50 nm (corresponding to Zr-coating thickness of 47 nm). However, with increasing the thickness of the interfacial ZrC layer, the composite thermal conductivity decreases attributed to the intrinsic low thermal conductivity of ZrC and the interface de-bonding with the large ZrC layer thickness. This study accurately establishes the relationship between interfacial structure and thermal conductivity and provides guidance for the interface design in Cu/diamond composites.

High volume fraction of copper coated graphite flake∖Nitrogen doped carbon fiber reinforced aluminum matrix composites

High volume fraction of carbon material reinforced aluminum matrix composites were developed by optimized vacuum gas pressure infiltration method, among which the reinforced materials are graphite flake and carbon fiber. To enhance the wettability between the reinforments and aluminum matrix, graphite flake was coated with a thin layer of copper by electroless plating and CF was doped with nitrogen, which proves to be effective and efficient. With the increase of reinforcements from 50 to 80 vol%, the flexural strength of the composites remains at practical level; the coefficients of thermal expansion decrease under the same temperature in direction parallel to basal planes of graphite flake; the thermal conductivity of the composites increase from 327 to 402 W/m K, adding up to relatively high comprehensive performances.

Investigation of wear and corrosion behavior of graphene nanoplatelet-coated B4C reinforced Al–Si matrix semi-ceramic hybrid composites

The present study aims to produce graphene nanoplatelet-coated B4C ceramic particle using semi-powder method and to investigate the effect of graphene nanoplatelets on wear and corrosion performance of Al–Si-based metal matrix hybrid composites. For this purpose, first graphene nanoplatelets at different ratios (0.25, 0.5, and 1 vol.%) were coated to the surfaces of B4C particles and then the Al–Si alloy was infiltrated into the reinforcements by gas pressure infiltration method. The characterization of graphene nanoplatelet-coated B4C powders and its composites was carried out by X-ray diffraction, differential scanning calorimetry, scanning electron microscope, and transmission electron microscope analysis. Tribological properties were investigated by reciprocating ball-on-flat method under three different loads (10–20–40 N) in a dry environment. The corrosion resistance was carried out with Tafel polarization method in 3.5% NaCl solution. Characterization results show that graphene coated on the B4C surface was successfully achieved by semi-powder method. After infiltration process, a new phase formation was not observed, but porosity increased with the increase of graphene content. When the boron carbide surface was coated with 0.5vol.% graphene, it was determined that the specific wear resistance increased by 55% and the corrosion resistance decreased by 12%.

The formation of atomic-level interfacial layer and its effect on thermal conductivity of W-coated diamond particles reinforced Al matrix composites

Diamond particles coated with a 45 nm-thick W layer were used to produce diamond particles reinforced Al matrix composites (Al/diamond(W)) by a gas pressure infiltration method. The results show that W atoms have diffused into Al matrix and replaced Al atoms during infiltration. As a result, a uniform 0.5 nm-thick Al5W interfacial layer is formed in the composite produced with 20 min infiltration time. The generation of the Al5W layer strengthens not only the interfacial bonding but also impedes the formation of hydrolysable Al4C3 phase. With increasing infiltration time from 10 to 60 min, the thermal conductivity increases from 520 to 620 W/m K, which manifests the influence of interfacial layer thickness on thermal properties of the Al/diamond(W) composite. The study provides a new strategy to modifying the interfacial structure of Al/diamond composites on the aspects of both enhancing the thermal conductivity and preventing the formation of hydrolysable Al4C3 phase.

High thermal conductivity of Cu-B/diamond composites prepared by gas pressure infiltration

A gas pressure infiltration method was used to prepare diamond particles reinforced Cu-B alloy matrix composites (Cu-xB/diamond, x = 0.3 and 1.0 wt%). The Raman spectroscopy and X-ray diffraction (XRD) analysis confirm the formation of boron carbide (B4C) at the Cu/diamond interface. The amount of interfacial boron carbide increases with increasing boron content in the Cu matrix. A high thermal conductivity of 868 W/mK and corresponding coefficient of thermal expansion of 5.3 × 10−6/K are obtained in the Cu-0.3 wt%B/diamond composite. When the boron content increases to 1.0 wt% B, the thermal conductivity decreases to 647 W/mK. It is found that boron carbide plays a critical role in improving the interfacial bonding and enhancing the thermal conductivity of the Cu-B/diamond composites; however, too much interfacial boron carbide will deteriorate the thermal conductivity of the composites.

Failure Behaviors of 2D-C<sub>f</sub>/Mg Composites Fabricated by Liquid-Solid Extrusion Following Vacuum Pressure Infiltration

Liquid-solid extrusion following vacuum pressure infiltration technique (LSEVI), which integrates melting, pouring, infiltration, and liquid-solid forming under high infiltration pressure, is a promising technique for the fabrication of metal matrix composite. LSEVI technology combines the advantages of both squeeze casting and gas pressure infiltration method. In this study, 2D carbon fiber reinforced AZ91D matrix composites (2D-Cf/Mg composites) were fabricated by LSEVI. Pyrolytic carbon (PyC) coating was deposited on surface of T700 carbon fiber by chemically vapour deposited (CVD) before fabrication. SEM observation indicated that the composites were well fabricated by LSEVI. The ultimate tensile strength of 2D-Cf/Mg composites fabricated by LSEVI was 390-410 MPa. Two kinds of failure behavior were found during tensile test: abrupt failure and progressive failure. The abrupt failure was characterized by a complete failure after the ultimate tensile strength (UTS) was reached. The progressive failure was a unique failure behavior with gradual damage after the UTS. In the case of progressive failure, the remaining strength after the UTS was 79% of the UTS. There was a remaining strength of 200 MPa under the strain of 0.1. Fracture surface morphology indicated that the remaining strength was attributed to the gradual breakage of the fiber bundles.

Effect of Metal Matrix Alloying on Mechanical Strength of Diamond Particle-Reinforced Aluminum Composites

Diamond particle-reinforced Al matrix (Al/diamond) composites were produced by a gas pressure infiltration method, where 0.5-4.0 wt.% Ti was added to Al matrix. An interfacial TiC layer of about 2 μm thickness was formed between Al and diamond at 4.0 wt.% Ti addition. The mechanical properties of the Al/diamond composites were enhanced by both the formation of interfacial layer and the strengthening of the matrix. The mechanical strength increased with increasing alloying Ti content, and a tensile strength of 153 MPa was obtained at 4.0 wt.% Ti addition. The tensile flow stress of the composites was found to be in broad agreement with the prediction of the Mori-Tanaka model. The effect of interfacial layer on mechanical properties provides guideline for the production of mechanically reliable Al/diamond composites.

Optimisation of high thermal conductivity Al/diamond composites produced by gas pressure infiltration by controlling infiltration temperature and pressure

In this study, Al/diamond composites were fabricated by the gas pressure infiltration method. The infiltration temperature and pressure were varied to study their influence on the interfacial microstructures and thermal conductivities of composites. The results show that the infiltration temperature and pressure dramatically affect the reaction between the Al matrix and the diamond particles. The appropriate conditions activate the reaction on the {111} faces of diamond which possesses a higher chemical stability than the {100} faces. The course of the reaction can lead to the structural and chemical modification of the interface, which strongly affects the thermal conductivity of the final composites. Using our optimised parameters of 800 degrees C and 0.8 MPa, a superior thermal conductivity above 760 W m(-1) K-1 was obtained. Controlling the fabrication parameters to optimise the reaction on the {100} and {111} faces can result in a superior Al/diamond material with greater thermal conductivity.

Thermophysical properties of SiC/Al composites with three dimensional interpenetrating network structure

Silicon carbide (SiC) reinforced aluminum composites with three dimensional interpenetrating network structure (3D-SiC/Al) were fabricated by the gas pressure infiltration method, and their thermophysical properties were investigated. The results show that the geometry of SiC reinforcement has a significant impact on the thermophysical properties of the composites. Continuous SiC reinforced aluminum composites (3D-SiC/Al) have higher thermal conductivities and lower coefficients of thermal expansion (CETs) than those of particulate SiC reinforced aluminum composites (SiCp /Al) with the same SiC volume fraction. The co-continuous structures of both the SiC reinforcement and the Al matrix in 3D-SiC/Al can be the reason behind this phenomena. As a result, when SiC volume fraction values were the same, 3D-SiC/Al composites will be more suitable for electronic packaging applications comparing with SiCp/Al composite.

Fabrication of Continuous Nickel-Coated Carbon Fiber Reinforced Aluminum Matrix Composites Using Low Gas Pressure Infiltration Method

Based on the principle of vacuum counter-pressure casting, a low gas pressure infiltration technology was developed to fabricate the Ni-coated carbon fiber reinforced A357 alloy composites. The soundness and microstructure of the as-cast composites were investigated. The results show the relative density increases with the increase of melt temperature, while it firstly increases and then declines as the fiber temperature and infiltration pressure increased. The enhancement of melt and fiber temperature can eliminate the incomplete infiltration defects and improve the uniformity of fiber distribution. The insufficient infiltration pressure leads to some micro-pores in the matrix alloy. However, the over high fiber temperature and infiltration pressure may result in the separation of nickel coating and the fiber aggregation respectively, both of which are responsible for the partial un-infiltrated or insufficient filling defects. The appropriate infiltration parameters identified in this study could provide a reference for inhibition of the hazard interfacial reactions by optimizing the low gas pressure infiltration process.

Manufacture studies and impact behaviour of light metal matrix composites reinforced by steel wires

Magnesium alloys play an important role in the development of light metal matrix composites. Magnesium based metal matrix composites reinforced by particles and fibres (especially carbon fibres) are successfully applied in various fields of automotive and aircraft industry. Equally high potential in large-batch production regarding to relatively low price and high strength is expected from MMC with wires made of iron-based alloys. However, their application is hampered by the absence of intermetallic phase between iron and magnesium and low solubility of iron in magnesium.This paper makes a contribution to the investigation of the effect of steel wires surface preparation and of optimised production methods to improve the quality and type of adhesion with selected industrial magnesium alloys. The Fe/Mg-MMC specimens with steel wires reinforcement were manufactured by the help of advanced gas pressure infiltration method (GPI) in a graphite mould at Institute of Lightweight Engineering and Polymer Technology (ILK) of TU Dresden. For the examination of the obtained composites the computer tomography (CT), SEM microscopy with EDX, strength tests and fracture surface inspection has been used.

The effect of the orientation of the basal plane on the mechanical loss in magnesium matrix composites studied by mechanical spectroscopy

In metal matrix composites, thermal stresses are relaxed by either interface debonding, crack propagation or dislocation motion. The present paper shows that in the case of a magnesium matrix, interface thermal stresses are relaxed by dislocation motion in the basal plane (0 0 1) of the hexagonal structure. Different specimens were processed by a gas pressure infiltration method and the metallic matrix was oriented with respect to the interface by the Bridgman technique. Mechanical spectroscopy experiments show that the damping as well as the evolution of the relative shear modulus depend strongly on the orientation of the basal plane. The results are in good agreement with the theoretical model. The calculations show that the orientation of the glide plane influences the coupling between the thermal stress and the applied mechanical stress.

Thermal stress relaxation in magnesium matrix composites studied by mechanical spectroscopy

AbstractThermal stress relaxation at the interfaces in magnesium matrix composites has been studied by mechanical spectroscopy. Two specimens were processed by a gas pressure infiltration method. In one sample, the metallic matrix was unidirectionally oriented with respect to the matrix‐reinforcement interface by a Bridgman technique, while the other was kept as infiltrated. The results show a strong dependence of the damping on the orientation of the matrix. The results are compared with a model of thermal stress relaxation by dislocation motion controlled by a solid friction mechanism. A fitting parameter proportional to the mobile dislocation density is obtained showing the entire evolution of the mobile dislocation density with respect to the temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Heat transport across the metal–diamond interface

Thermal conductivity of the aluminium–diamond (Al–diamond) composites, prepared by the gas pressure infiltration method, is measured by steady state technique. A detailed theoretical investigation on the heat conduction mechanism across the Al–diamond interface is presented. It was confirmed that both electrons and phonons actively take part in the flow of heat at the interface. In the Al side, electrons of Al couple with the phonons and carry the heat up to the interface. This electron–phonon pair which predominantly carries heat in the Al, breaks down at the Al–diamond interface. The coupling between phonons of both Al and diamond takes place at the interface which eventually leads the heat conduction across the interface to the diamond. The phonon–phonon coupling across the interface is discussed by scattering mediated acoustic mismatch model (SMAMM). It is shown that for Al–diamond composite, the implementation of the SMAMM yields an interface thermal resistance (ITR) value of 4.44 × 10 − 9 m 2K/W, which is in fairly good agreement with values derived from experimental thermal conductivity values of this composite implemented in the Hasselman–Johnson (HJ) mean field scheme.

Microstructure and tensile properties of 2014 Al alloy reinforced with continuous carbon fibers manufactured by gas pressure infiltration

Gas pressure infiltration method was used to prepare a composite consisting of unidirectional Ni-coated carbon fibers (Cf) in 2014 Al alloy matrix. The microstructure of the composite produced showed a full infiltration of molten aluminum alloy and evenly distributed fibers with a volume fraction of 30 vol%. Also, there was no sign of fiber clusters or residual porosity. The fiber–matrix interface was smooth with no discontinuities. Energy dispersive X-ray analysis (EDXA) results of the composite microstructure revealed no sign of significant reaction at the interface between the fibers and aluminum matrix alloy. Compared to the aluminum matrix alloy, the composite exhibited significant increases in modulus and ultimate tensile strength. However, the elongation to failure of the composite was considerably reduced. Moreover, the tensile modulus and ultimate tensile strength were in good agreement with the values predicted by the simple rule of mixture due to the strong interfacial bonding and absence of fiber strength degradation during composite preparation. SEM micrographs of the composite fracture surface showed that fracture took place mainly in the relatively weak aluminum alloy matrix, in comparison to the interfacial and fiber strengths, by void nucleation, growth, and shearing of the fibers.

Wear performance of 2014 Al alloy reinforced with continuous carbon fibers manufactured by gas pressure infiltration

Ni-coated continuous carbon fibers ( C f; 30 vol.%) were incorporated into 2014 Al Alloy by the gas pressure infiltration method. The sliding wear behavior of the 2014 Al–30 vol.% C f composite and 2014 Al matrix alloy was investigated using pin on ring wear test apparatus in the load range of 10–550 N and sliding speed of 0.65 ms −1. The results indicate that the incorporation of carbon fibers into 2014 Al alloy significantly improves the wear resistance, serves to suppress the transition to a severe wear rate regime and impedes the transition to a higher load (300 N) in comparison to the unreinforced alloy (100 N). Also, the composite exhibits a higher seizure resistance compared to the unreinforced alloy where the unreinforced alloy seized at load of 160 N and composite at load of 550 N. SEM micrographs and EDXA of the composite worn surface reveals that the surface is covered by graphite film, which prevents a metal-to-metal contact and acts as a solid lubricant, resulting in improvement in the wear and seizure resistance of the composite. Subsurface studies show that the carbon fibers tend to reduce the extent of plastic deformation in the subsurface region, thereby delaying the nucleation and propagation of subsurface microcracks.

Physical properties of graphite/aluminium composites produced by gas pressure infiltration method

Graphite/aluminium composites have been produced by means of gas pressure infiltration method. Two porous graphite preforms with a porosity of 10 and 13 vol%, respectively, have been infiltrated using either a commercially 99.85 pure aluminium or an AlSi7Mg alloy. Thermal expansion coefficient, electrical conductivity and flexural strength have been determined as a function of graphite preforms and metal matrices. To investigate the susceptibility of this composite system to thermal damage, specimens were thermally cycled between 60 and 300 °C up to 1020 cycles. Infiltrated graphites exhibited a significantly higher electrical conductivity (0.34–0.51 m/Ω mm 2) compared to porous graphite preforms depending on graphite type and metal matrix. Thermal cycling did not influence electrical conductivity. The coefficients of thermal expansion of the composites were at least three times lower than for monolithic aluminium. Thermal cycling has reduced these values even more, most likely due to stress relaxation processes. The infiltration of porous graphite preforms with AlSi7Mg alloy or Al99.85 has increased the flexural strength of the composites resulting in values up to 105 MPa. The decrease in mechanical strength due to thermal cycling was about 10%.