Pressure Infiltration Method Research Articles

Effect of hot extrusion temperature on graphene nanoplatelets reinforced Al6061 composite fabricated by pressure infiltration method

In the present work, 0.6 wt% graphene nanoplatelets reinforced 6061Al (GNPs/6061Al) composite was prepared by pressure infiltration process and hot extruded (HE) at 420 °C∼500 °C in order to investigate the evolution of GNPs in different extrusion temperature, which has not been reported yet. The GNPs agglomeration were eliminated by extrusion and were arranged in an orientation. In the sample extruded at 420 °C, the dispersion effect was not significant and agglomeration of large-sized GNPs was still found. However, the agglomeration of the GNPs was eliminated when extruded at 450 °C, and waved structure, exfoliation and bend of GNPs were observed. While in the sample at 500 °C, interlayer sliding of GNPs and interfacial reaction product Al4C3, due to excessively high extrusion temperature, were detected. The composites extruded at 450 °C showed the highest yield strength and ultimate tensile strength of 389 MPa and 500 MPa, respectively, which increased 16.8% and 40.1% comparing with the unreinforced matrix. The present results indicate that the uniform dispersion of graphene is still one of the main challenges in Graphene/Al composites, while the deformation treatment provides the possibility of further dispersion of graphene.

Effect of interfacial microstructure on the mechanical properties of GNPs/Al composites

The interfacial bonding affects the performance of Graphene/Al matrix composites significantly. However, the relationship between interfacial structure and mechanical properties has not been fully understood yet. In the present work, the GNPs/Al composites were prepared by pressure infiltration method, and the interface structure of Graphene-Al2O3–Al and graphene-(Al4C3, Al2OC)–Al was prepared by addition of polydimethylsiloxane (PDMS) as process control agent (PCA). The tensile strength of the GNPs/Al composite material with Al2O3 interfacial bonding was 303 MPa, which was about 30% higher than that with Al4C3 and Al2OC interface. Moreover, calculated by first-principle, it has been found that the interfacial shear strength of the graphene-Al2O3–Al interface (378 MPa) was much higher than that of graphene-Al (37 MPa), graphene-Al4C3 (83 MPa) and graphene-Al2OC (66 MPa), which leads to the improved mechanical properties.

Ablation behavior of Al20Si/graphite composite nozzle-throats in a solid rocket motor environment

Small solid rocket motors (SRM) require low density, low ablation nozzle-throat materials. In the present study, Al20Si alloy was infiltrated into the porous graphite matrix to develop Al20Si/graphite composites by pressure infiltration method. The ablation behavior of the as-prepared composite was investigated in a small SRM testing system with an average pressure of 13.3 MPa and 5 wt% Al for 1.4 s. The results show that the linear ablation rate of the Al20Si/graphite throat decreased by 92% compared to that of the C/C composite throat. The increased anti-ablative properties are provided by Al20Si alloy fillers, which reduce the degree of thermochemical ablation of the graphite matrix through heat dissipation, oxygen dissipation, and thermal blockage. Furthermore, the Al4SiC4 generated from Al20Si alloy and graphite fills graphite pores, which contributes to the oxidation resistance of the composite.

Experimental study on secondary bearing mechanism of weakly cemented broken rock mass

In order to study the secondary bearing mechanism of weakly cemented broken surrounding rock, the surface of granite, limestone and mudstone broken rock samples were poured by cement slurry, and the weakly cemented rock mass was formed by static pressure infiltration method, and then an uniaxial loading test was carried out. The results show that the weakly cemented broken rock mass has a certain bearing capacity, but the bearing capacity is low, and the dispersion is high. The secondary bearing capacity of weakly cemented rock mass is affected by factors such as broken rock strength, rock particle size and rock gradation. The larger the rock particle size and strength are, the higher the secondary bearing capacity of the weakly cemented rock mass is. The average bearing capacity of the mudstone weak cementation specimen is 18.77 kN, and the residual bearing capacity is 1.46 kN, and a dispersion coefficient is 0.34. The average bearing capacity of granite is 343.65 kN, and the residual carrying capacity is 25.81 kN, and a dispersion coefficient is 0.11. The average bearing capacity of limestone is 367.22 kN, and the residual carrying capacity is 22.78 kN, and a dispersion coefficient is 0.3. After a certain grading, the average residual secondary bearing capacity of the weakly cemented rock mass is obviously improved, and the dispersion coefficient of peak bearing capacity is reduced. The grading scheme 1 has an average peak carrying capacity of 330.06 kN, a residual carrying capacity of 34.56 kN, and a dispersion coefficient is 0.07. The averaging scheme 2 has an average peak carrying capacity of 297.8 kN, a residual carrying capacity of 29.86 kN, and a dispersion coefficient is 0.14. The cementation regeneration mechanism of the broken rock mass mainly includes the cement-bonding effect of the cement slurry inside and on the broken rock mass. Under the loaded condition, the internal load-bearing network of the broken rock mass is the main mechanism for the secondary load of the broken rock mass, and the stability of the force-chain network is affected by the constraint. After the loss of the confinement, the force chain network fails, and the residual secondary bearing mechanism of the weakly cemented broken rock mass is transformed into the friction between the broken rock masses in the residual core rock pillar.

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.

Microstructure and mechanical property of the 2024Al matrix hybrid composite reinforced with recycled SiCp/2024Al composite particles

In the present work, the SiCp/2024Al composite chips have been recycled to be SiCp/2024Al composite particles (CPs for short) with average diameter of 900, 650 and 300 μm, which has been used as the reinforcement in the CP/2024Al hybrid composites prepared by pressure infiltration method. The CPs-Al interface was well bonded with an amorphous alumina interlayer. With the decrease of the dimension of the CPs from 900 to 300 μm, the tensile strength of the CP/2024Al hybrid composites was increased from 178 to 392 MPa, while the height difference of the LSCM profiles curves was decreased from 458 to 216 μm, and the length value of the LSCM profiles curves was increased from 1280 to 2184 μm, respectively. Based on the finite element analysis (FEA) simulation, the stress and strain concentration phenomenon of the CP/2024Al hybrid composites have been discussed. It has been found that the applied tensile stresses in the composites for the occurrence of debonding were increased with the decreased CPs size. Moreover, according to the Griffith's fracture criterion, the corresponding tensile strength of the composites with 300 μm CPs was 1.73 times of that with 900 μm CPs, which was close to the experimental results (2.15 times). It is suggested that the interfacial bonding strength should be improved to further increase the mechanical properties of the CP/2024Al hybrid composites.

Ballistic behavior and microstructure evolution of B4C/AA2024 composites

Abstract In this research, the ballistic behavior and microstructure evolution of 45vol% B4C/AA2024 composites produced by pressure infiltration method were studied. The ballistic behavior of composites was carried out using 7.62 mm armor-piercing incendiary (API). The results demonstrate that the 45vol% B4C/AA2024 composites has excellent ballistic performance and the protection coefficient reaches 3.6. The residual microstructure of composites after impact was mainly investigated by the transmission electron microscope (TEM). The results show that the residual microstructure of B4C particles mainly include dislocations, stacking faults, twins and poly-crystallization. For Al matrix, the residual microstructure is mainly the existence of large numbers of dislocations especially in the area near the sharp corner of B4C particles. In addition, inhomogeneous precipitates of AA2024 matrix were observed after impact.

Magnesium Matrix Composite with Open-Celled Glassy Carbon Foam Obtained Using the Infiltration Method

In this study, we present a new composite material that was developed using the pressure infiltration method. In this composite, carbon reinforcement in the form of an open-celled rectangular foam (Cof) was applied, and pure magnesium with two commercial magnesium cast alloys (AZ31, RZ5) was used as the matrix. We examined the microstructure (LM, SEM + EDS) of composites as well as the density, porosity, hardness, compressive strength, flexural strength and tribological properties in dry conditions. It was revealed that the chemical composition of the matrix had a significant impact on the macrostructure, microstructure and properties of the composite. The matrix with rare elements (RZ5) induced poor infiltration of Cof and physicochemical degradation of the reinforcement, while pure magnesium ensured good infiltration, a stable friction coefficient and low wear. For the AZ31 alloy, the effects of infiltration were good; however, an increase in the tribological properties was not observed. Compared with the as-cast matrix materials, the presence of carbon foam in both pure Mg and AZ31 alloy induced an increase in compressive strength and stiffness as well as a decrease in flexural strength. Furthermore, SEM examination of the fractured and wear surfaces microstructure showed structural effects’ dependence on the matrix composition.

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%.

Mechanical properties and biodegradation of porous Zn-1Al alloy scaffolds

Biodegradable porous Zn-1Al alloy scaffolds were fabricated by air pressure infiltration method (APIM) for biomedical applications. The grains of porous Zn-1Al alloy scaffold are significantly refined due to the addition of Al. Tiny (Al) solid solution particles uniformly disperse in the grains of Zn matrix. Under the combined effect of grain size reduction and (Al) solid solution particles dispersion strengthening, the compressive yield strength of the porous alloy scaffolds is improved remarkably. During immersion tests in simulated body fluid (SBF), the porous Zn-1Al alloy scaffold can effectively induce Ca-P precipitation. In addition, the porous alloy scaffold has a lower degradation rate than the porous pure Zn scaffold in SBF.

Thermal management applied laminar composites with SiC nanowires enhanced interface bonding strength and thermal conductivity.

Design and fabrication of oriented thermal management materials has great significance in meeting the requirements of high-power heat dissipation device applications. To synchronously improve the structure stability and thermal management performance, in this study, large-scale silicon carbide (SiC) nanowires were deposited on the graphite film (GF) surface to reinforce the aluminum-based laminar composites. Highly thermally conductive SiCnws-GF multiscale architecture reinforced Al laminar composites with enhanced interlayer bonding strength were achieved by an innovative pressure infiltration strategy. The embedding of the silicon carbide nanowires not only improved the thermal conductivity of the laminar composites but also enhanced the interface bonding strength between the Al matrix and the SiCnws-GF multiscale structure robustly. The interlaminar shear strength of the SiCnws-GF reinforced Al laminar composites was 134.1 MPa, which was 2.4 times the value of GF reinforced Al composites. The in-plane thermal conductivity of the best-performing SiCnws-GF reinforced Al laminar composites was 868.9 W (m K)-1, which was 16.9% higher than the value of the GF reinforced Al laminar composites. The outstanding interlaminar shear strength and superior thermal conductivity of the SiCnws-GF reinforced Al laminar composites revealed that a potential and competitive thermal management material was obtained.

Effect of ball milling time on graphene nanosheets reinforced Al6063 composite fabricated by pressure infiltration method

Evolution of graphene nanosheets (GNSs) during mechanical milling process was investigated to fabricate GNSs/Al nanocomposite by routes combined of pressure infiltration and hot extrusion. The structural integrity and dispersion homogeneity of GNSs together with the degree of interfacial reaction were systematically discussed. It was revealed that a moderate milling time existed for well dispersion and small quantities of Al4C3 (partial reaction bonding) via mechanical milling technique. A highest tensile strength of 276 MPa was obtained only with 0.3 wt% GNSs, which was 22.5% enhancement over the unreinforced Al matrix with the same preparation process and no decrease in elongation. Meanwhile, compared with reference Al, a great enhancement of electrical conductivity was achieved about 17.4%, which had not been reported previously. This study could provide new insights into the control factors of mechanical milling process for GNSs/Al composite and improve the interfacial bonding condition in situ during ball milling and subsequent densification processes to take full advantage of the extraordinary performance of graphene in metal matrix composites.

Fabrication and properties of porous Zn-Ag alloy scaffolds as biodegradable materials

Porous Zn-xAg binary alloy scaffolds (where x = 1.0 and 3.5 wt.%) with porosity of 59.1 ± 0.7% were successfully prepared as biodegradable biomedical implant materials using air pressure infiltration method (APIM) in this work. NaCl particles of around 100–400 μm in size were used as space holders. Their morphologies and structures, compressive mechanical properties, corrosion characterizations in simulated body fluid (SBF), and antibacterial ability were studied in detail. Scanning electron microscopy imaging shows that the grain sizes of porous Zn scaffolds are refined to some extent due to the addition of Ag element. The compressive plateau stresses at 3% strain for the porous Zn-3.5Ag, Zn-1Ag and Zn scaffolds with a porosity of 59.1 ± 0.7% are around 13.7 ± 0.2 MPa, 5.5 ± 0.2 MPa and 4.0 ± 0.3 MPa, respectively. The mean weight loss rate of porous Zn-Ag alloy scaffolds is about 1.1 mg/day during immersion tests, which is much less than the tolerable limit of Zn intake (40 mg/day). XRD results suggest that the corrosion products on the degraded surface consisted mainly of ZnO, Ca3(PO4)2 and Zn(OH)2. Antibacterial tests indicate that the antibacterial ability of the porous Zn-Ag scaffolds becomes higher and higher with the increase of Ag content.

Microstructure and tensile properties of 5083 Al matrix composites reinforced with graphene oxide and graphene nanoplates prepared by pressure infiltration method

In the present work, 5083Al matrix composites reinforced with graphene oxide (GO) and graphene nanoplates (GNPs) have been prepared by the pressure infiltration method. Regardless of the graphene types, no peaks of Al4C3 phase have been detected by the XRD analysis. However, needle-like Al4C3 phase has been observed in the GO/5083Al and the GNPs/5083Al composites, while the content of the Al4C3 phase in the GNPs/5083Al composite was much lower. Furthermore, the segregation of Mg element at the surface of the GNPs has been found in the GNPs/5083Al composite, implying the inhibition effect of Mg element on the formation of the Al4C3 phase. It has been found that the yield strength of the composites was slightly improved by the addition of the GO and GNPs, and the GNPs/5083Al composite demonstrated 14% increment in the tensile strength. Meanwhile, the pulling-out of the GO and GNPs have been observed.

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.

Mechanical and wear performances of aluminum/sintered-carbon composites produced by pressure infiltration for pantograph sliders

Novel aluminum/sintered-carbon (Al/SC) composites for pantograph sliders were produced by means of pressure infiltration method, in which five porosity sintered carbon preforms were pressure infiltrated using 6201 aluminum alloy. Meanwhile, the effects of aluminum alloy on the properties and microstructures of Al/SC composites were investigated. The interface phase of Al4C3 between Al alloy and sintered carbon was identified. The resultant Al/SC composites exhibited an excellent mechanical strength, even with the highest compressive strength value of 304.28MPa benefiting from the metal acting as a reinforcement phase. The tribological performance study shew that the friction coefficient of the Al/SC composite infiltrated by 7.17% volume fraction aluminum alloy reached a minimum in comparison to other volume fraction samples under 70N, and the Al/SC composite containing 26.92% volume fraction aluminum alloy under the low applied load of 20N presented a low friction coefficient. Although the wear behaviors of Al/SC composites containing various aluminum alloy volume were variant, the same wear mechanisms were involved, including adhesive, abrasive, fatigue and oxidative wear.

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.

Bonding strength and thermal shock resistance of glass coatings on anisotropic mullite fibrous ceramics

Mullite fibrous ceramics with a two-dimensional planar random structure was prepared via a pressure infiltration method. The in-plane and out-of-plane mechanical properties, thermal expansion coefficients and thermal conductivities were compared. MoSi2-borosilicate glass coatings were applied on two adjacent surfaces of the as-prepared mullite fibrous ceramics via an in-situ reaction method. The bonding strength and thermal shock resistance of the two coatings were compared. Results show that higher crosslinking degree and more fiber orientating in the planes resulted in the fact that the in-plane compressive and tensile strength of the ceramics were 4.6 times and 2.1 times higher than the out-of-planes values, respectively. The in-plane CTE (Coefficient of Thermal Expansion), thermal conductivity and permeability were also higher than the out-of-plane ones. The interface bonding strength of Coating B (coated perpendicular to the planes) was higher than that of Coating A (coated parallel to the planes), because of the better mechanical locking at the interface and the higher tensile strength of the substrate. Besides, Coating B presented a better thermal shock resistance because the CTE of the substrate parallel to Coating B was closer to the CTE of the coating, and the substrate was more complaint parallel to Coating B so that could absorb some of the thermal stress by deformation.

Microstructure and mechanical properties of graphene nanoplates reinforced pure Al matrix composites prepared by pressure infiltration method

In the present work, microstructure and mechanical behavior of the graphene nanoplates (GNPs) reinforced pure Al (GNPs/Al) composites prepared by the pressure infiltration method was investigated. No Al4C3 phase was detected in the composites, while GNPs have been well bonded with the Al matrix. It is suggested that the reaction between pure Al matrix and graphene could also be inhibited by using graphene with fewer defects. It has been found that the mechanical properties of the composites could be significantly improved by the addition of graphene. After addition of 0.54 wt% GNPs, the improvement of the yield and tensile strength before the extrusion was 116% and 45%, respectively. However, after the extrusion treatment, the corresponding increment of the yield and tensile strength was increased to 228% and 93%, respectively. Moreover, the fracture surface of the GNPs/Al composites before and after the extrusion treatment was mainly characterized by the lamellar structure with bridging of GNPs and the fine equiaxed structure with the pulling-out of the GNPs, respectively. Based on the modified shear-lag model, the strengthening mechanism of the GNPs/Al composites has been discussed, and the effect of GNPs and the extrusion treatment on the yield strength of the composites have been analyzed.

Impact Strength of Composite Materials Based on EN AC-44200 Matrix Reinforced with Al2O3 Particles

AbstractThe paper presents the results of research of impact strength of aluminum alloy EN AC-44200 based composite materials reinforced with alumina particles. The research was carried out applying the materials produced by the pressure infiltration method of ceramic preforms made of Al2O3particles of 3-6μm with the liquid EN AC-44200 Al alloy. The research was aimed at determining the composite resistance to dynamic loads, taking into account the volume of reinforcing particles (from 10 to 40% by volume) at an ambient of 23°C and at elevated temperatures to a maximum of 300°C. The results of this study were referred to the unreinforced matrix EN AC-44200 and to its hardness and tensile strength. Based on microscopic studies, an analysis and description of crack mechanics of the tested materials were performed. Structural analysis of a fracture surface, material structures under the crack surfaces of the matrix and cracking of the reinforcing particles were performed.