Interfacial Reaction Products Research Articles

Investigation of interfacial reaction in SiC fiber reinforced Ti–43Al–9V composites

SiC fiber reinforced titanium aluminides matrix composites based on TiAl (Ti–43Al–9V) were fabricated by means of matrix-coated fiber method through hot isostatic pressing. Microstructure of the SiCf/Ti–43Al–9V interfacial reaction zone in the composites was identified by means of scanning electron microscopy and transmission electron microscopy. The results show that three types of reaction products TiC, Ti2AlC and (Ti,V)5(Si,Al)3 are formed between carbon coating of SiC fiber and the matrix. TiC is adjacent to the carbon coating of the SiC fiber, and (Ti,V)5(Si,Al)3 is close to the matrix. Ti2AlC layer exists as columnar grains between TiC and (Ti,V)5(Si,Al)3 layers. The TiC layer can be divided into fine-grained layer and coarse-grained layer. The fine-grained TiC layer contains amorphous carbon, and the coarse-grained TiC layer is separated from fine-grained TiC by an intermittent carbon layer. In addition, TiC particles are also formed between carbon coating and SiC. Furthermore, the formation mechanism of the interfacial reaction products was discussed.

Squeeze Infiltration Processing of Functionally Graded Aluminum–SiC Metal Ceramic Composites

The objective of the present work is on fabrication of functionally graded SiC/Al composite by direct squeeze infiltration of 6061 aluminum alloy using graded SiC porous preform prepared by inorganic porogen technique. Graded SiC preform is synthesized by varying the concentration of inorganic salt mixture and using Al as the binder. The microstructure analysis indicates the graded distribution of SiC particle and the melt has infiltrated completely throughout the preform to form functionally graded materials. The influence of preform and mold temperature, liquid metal superheat, squeeze pressure, and its rate of application plays major role on solidification microstructures and properties of the composites. The macro porous graded SiC preforms and the composites were characterized using SEM, optical microscopy, and XRD. The major interfacial reaction product is MgAl2O4 spinel which helps in formation of good interface bonding.

Effects of V2O5 addition on the corrosion resistance of andalusite-based low-cement castables with molten Al-alloy

Interfacial reactions between Al-alloy and andalusite low-cement castables (LCC) containing 5 wt% V2O5 were analyzed at 850 °C and 1160 °C using the Alcoa cup test. Interfacial reaction products and phases formed during heat treatment of the refractory samples were characterized using scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis. V2O5 addition resulted in the formation of glassy phases, which significantly improved the corrosion resistance. These phases were preferentially corroded by the alloy, due to their glassy nature. However, vanadium formed from reduction, formed intermetallic alloys (V–Al–Si–Mg), which formed an interfacial physical barrier to further alloy penetration.

Effect of Post-HPT Heat Treatment on the Mechanical Performance in Ti/Cu-Cr/S20C Clad Materials

In this study Ti/Cu-Cr/S20C were clad by High Press Torsioning(HPT) and the effect of post-HPT heat treatment on the interfacial reaction products and the mechanical performance in Ti/CuCr/S20C clad material were studied. No cracks were observed to be emanated from the corner of the indentation mark on the intremetallic compound layer at the Ti/Cu-Cr interface, suggesting those intermetallic compounds is not so brittle. The stress-strain curves exhibited three steps in as-HPTed clad samples and those heat-treated at 500°C for 1hr. Step-wise fracture occurred in the sequence of S20C, Cu-Cr and Ti with each fracture resulting in the sudden drop of the stress. The stress-strain curves exhibited two steps in clad metals annealed at 600°C for 1hr, with first step corresponding to the fracture of S20C plate and the second one corresponding to the concurrent fracture of Ti and Cu-Cr plates. Ti/Cu-Cr/S20C heat-treated at 600°C for 24hrs exhibited just one step final fracture, suggesting that the bonding strengths are high enough to resist the localized strain concentration at the interfaces.

The Research of β-SiCp/Al Electronic Packaging Composites Fabricated by Pressureless Infiltrating

The β-SiCp/Al electronic packaging composites with excellent performance were successfully fabricated by pressureless infiltration technology in air.The effects of alloying elements, infiltration temperature and time on infiltration process and application of -SiC were studied.The results show that by adding appropriate magnesium to aluminum matrix, a interface reaction between oxide films of SiC and magnesium occurs, and the interface reaction product MgAl2O4 is generated, the interface wettability of Al and SiC and pressureless infiltration are improved.The interface harmful phase Al4C3 can be inhibited by adding silicon to aluminum matrix.Identified 850°C for the best infiltration temperature, and the thickness with infiltration time and larger, infiltration rate is about 10mm/hour.Under the same parameter conditions, the thermal properties of β-SiCp/Al electronic packaging material are 4 ~ 6% higher than that of ɑ-SiCp/Al. The β-SiCp/Al electronic packaging materials with 66% SiC volume ratio has lower coefficiency of thermal expansion than those ɑ-SiCp/Al electronic packaging materials.And the thermal expansion coefficient and thermal conductivity of β-SiCp/Al electronic material can satisfy the requirements for electronic packaging materials.

Aluminum/diamond composites: A preparative method to characterize reactivity and selectivity at the interface

Reactivity at the interface in aluminum/diamond composites, which are excellent candidates for thermal management, has been identified to be determinant of their final properties. In this contribution a new preparative method consisting of electrochemical etching of the metal and spray cleaning, allows microstructural characterization of the interface. This methodology preserves interfacial reaction products and highlights the importance of a proper analysis of both fabrication parameters and sample preparation before any conclusion on reactive selectivity at the interface can be reached.

Microstructure and mechanical properties of SiCp/MgZnCa composites fabricated by stir casting

SiCp/MgZnCa composites with three volume fractions (5%, 10% and 15%) were successfully fabricated by stir casting. The particle distributions were fairly uniform in all composites, although most particles were segregated along grain boundaries in the micro-scale level. Interfacial reaction products were not observed at the interface between SiCp and matrix. SiCp affected the size and shape of the second phases as well as their distribution in the matrix. In the 5% composite, many large second phases were observed at the particle surfaces. As the particle content was increased up to 10%, large second phases were hardly observed at the SiCp surfaces. Moreover, the second phases mainly existed in the form of fine flake in the 10% and 15% composite, unlike the alloy and 5% composite in which the second phases were large. The effect of SiCp on the second phases significantly influenced the mechanical properties of the composites. Compared with the matrix alloy, 15% composites had good room temperature and high temperature mechanical properties.

Study on Reaction Products of B<sub>4</sub>C-CeB<sub>6</sub>/Al Composites

B4C-CeB6/Al composite was fabricated by pressureless infiltration technology. It is composed of the phases of Al, B4C, AlB2, Al3BC and CeB6, and Al4C3 is not found because of the existence of CeB6. It could identify that AlB2, CeB6, and Al3BC were formed as interfacial reaction products. Al3BC is formed on the interface of B4C and Al; therefore it connects the aluminum with the ceramic toughly. AlB2 as strip crystal is formed between B4C and Al, which has higher fracture toughness.CeB6 particles in B4C grain boundary are discovered by TEM, which caused intercrystalline rupture. Grain toughening and reinforcing, crack deflection, crack bridging is the main toughening and reinforcing mechanisms of B4C-CeB6/Al composites.

Microstructure and mechanical property evaluation of diffusion-bonded joints made between SAE 2205 steel and AISI 1035 steel

Microstructural and mechanical property evaluation of the joint region of direct diffusion-bonded joints made between duplex stainless steel SAE 2205 and medium-carbon steel AISI 1035 was studied for the samples processed at temperatures of 850, 900, 950 and 975°C, with holding time of 60 and 90-min and pressures of 20 and 30MPa. The energy dispersive X-ray analysis (EDAX) and X-ray diffraction analysis (XRD) confirmed the presence of interfacial reaction products, such as sigma phase and intermetallics at the interface. The shear strength of the samples processed at 975°C for 90min and at a pressure of 20MPa was 360.9MPa. Interestingly, the capability of the joint strength was not reduced as the result of formation of hard intermetallics because of diffusive and interfacial reactions.

C/Ti/Cu interfacial reaction in SiCf/Cu composites

Continuous SiC fiber reinforced copper matrix (SiCf/Cu) composites were prepared by fiber coating method, and Ti6Al4V interlayer was introduced as an interfacial modification coating to improve the interfacial bonding strength. The interfacial reaction characteristics were investigated by transmission electron microscopy (TEM). The results show that nearly all the titanium atoms reacted with the carbon coating of SiC fibers to form two layers of TiC. Also, a thin copper layer that is sandwiched between these two layers was detected. No Ti-Cu interfacial reaction product was observed. The formation process of the interfacial reaction along with its mechanism was discussed.

Interfacial Reaction of Alumina Ceramics to Mild Steel Braze Joint

Al2O3 is brazed with mild steel using 70Ag-27Cu-3Ti (wt.%) active filler alloy at 900°C for 5 min. The interfacial reaction products are analyzed with X-ray diffraction (XRD)．The interfacial phases are analyzed with EDAX. According to the experimental observations, the interfaces developed during brazing have been systematically characterized and the structure are separately Ti3Cu3O/Ti3Al+ TiMn+TiFe2 +Ag(s,s)+Cu(s,s)/TiC from alumina ceramics side to mild steel side.

Processing of surface-treated boron carbide-reinforced aluminum matrix composites by liquid–metal stir-casting technique

Boron carbide is one of the potential neutron-shielding materials and its use can be maximized for structural shielding application by dispersing it into metal matrixes such as aluminum. Dispersion of B4C and its interfacial stability is a major issue during its processing. This investigation is on the synthesis of B4C-reinforced 6061 aluminum matrix composite by liquid–metal stir-casting technique under optimized conditions after solving the issues related to the processing, and evaluation of the structural, mechanical, and interfacial characteristics. During processing of composites, pretreatment of B4C particles is necessary to improve its dispersion. However, higher preheating temperatures above 300°C lead to particle agglomeration in the matrix due to the formation of B2O3 phase during preheating. B2O3 is formed due to the surface oxidation of B4C particles above 300°C and this glassy phase leads to particle sintering and lump formation. Incorporation of particles preheated at 250°C has shown uniform distribution of particles in the composite. Interfacial characterization of the composite and the extracted B4C particles from the matrix has shown the presence of interfacial reaction products such as AlB2, Al3BC, AlB12, and AlB10.

Ce 0.8Gd 0.2O 2 modification on La 0.6Sr 0.4Co 0.2Fe 0.8O 3 cathode for improving a cell performance in intermediate temperature solid oxide fuel cells

To increase the cell performance of solid oxide fuel cells operated at intermediate temperature (600–800 °C), Ce 0.8Gd 0.2O 2 (GDC) was applied to the La 0.6Sr 0.4Co 0.2Fe 0.8O 3 (LSCF) cathode in electrode microstructure using sol–gel coating. We employed a GDC as a diffusion barrier layer on the yttria-stabilized zironia (YSZ) electrolyte to prevent the interlayer formation of SrZrO 3, which has poor ionic conductivity. This interfacial reaction product was hardly formed at the electrolyte–cathode interlayer after sintering the GDC layer resulting to reduce the cathode polarization resistance. Moreover, we use sol–gel method to coat GDC thin layer through the cathode pore wall surface to extend the triple phase boundary (TPB) area. The cathode polarization resistance also reduced due to the additional TPB area. For the single cell featuring LSCF cathode modified with GDC sol–gel coating, the maximum densities were 0.41 W/cm 2 and 0.89 W/cm 2 at 700 °C and 800 °C.

Effects of Different Calcium Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact with Molten Al-Alloy

An experimental study was conducted to investigate the interfacial phenomena between an Al alloy and andalusite low-cement castables (LCCs) containing fixed contents of barium compounds (BaO, BaSO4, and BaCO3) at 1123 K and 1433 K (850 °C and 1160 °C) using the Alcoa cup test. Interfacial reaction products and phases formed during heat treatment of the refractory samples were characterized using scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) and X-ray diffraction analysis (XRD). The addition of both BaO and BaSO4 led to a significant reduction of alloy penetration into the refractory. Hexa-celsian formation was observed in both these refractories, which drastically increased their corrosion resistance. Barite decomposition was observed at 1373 K (1100 °C) in the presence of alumina and silica, which was the precursor for hexa-celsian formation. Barium silicates were formed in all samples containing additives; however, this did not have any major influence on the corrosion resistance. Solidified eutectics of BaSi2 and α-BaAl2Si2 formed in all these samples, which acted as an interfacial barrier that prevented additional molten aluminum penetration; however, the positive effect of intermetallic formation was offset by glassy phase formation in samples containing BaCO3 as the additive.

Effect of Hot Extrusion on Interfacial Microstructure and Tensile Properties of SiC p/2009Al Composites Fabricated at Different Hot Pressing Temperatures

The effects of hot extrusion on the interfacial microstructures and tensile properties of 15 vol.% SiC(p)/2009Al composites fabricated at different hot pressing temperatures were investigated. After hot extrusion, the relative density of the composites increased, the SiC particle distribution became more uniform, and the SiC particles tended to align along the extrusion direction. Furthermore, the interface bonding was improved after hot extrusion; however, the extrusion exerted no obvious effect on the interfacial reaction products formed during sintering process. Tensile tests indicated that the mechanical properties of the composites were improved significantly after extrusion. Fractography revealed that the fracture mechanism of the extruded composites fabricated at the hot pressing temperatures below 540 degrees C was mainly the interfacial debonding. For the extruded composites fabricated at 560-600 degrees C, the fracture was the matrix ductile fracture and the SiC particle fracture. When the composites were hot pressed at or above 620 degrees C, after extrusion, the fracture mechanism of the composites was the matrix ductile fracture, the interface cracking and the SiC particle fracture.

Thermal properties of new copper matrix composite reinforced by β-eucryptite particulates

Cu matrix composites with different volume fraction of Ag coated β-eucryptite particulates were successfully fabricated by powder metallurgy method. Low thermal expansion coefficient and high thermal conductivity were attained simultaneously in the new Cu matrix composite. The microstructure of β-eucryptite–Cu composite was studied by scanning electron microscope and transmission electron microscope. The thermophysical properties of β-eucryptite–Cu composites were analysed by means of thermal dilatometer and diathermometer. No interfacial reaction products between β-eucryptite and Cu were found in the composite. The research indicates that β-eucryptite, which has a negative coefficient of thermal expansion, is a useful reinforcement, which can remarkably reduce the coefficient of thermal expansion of Cu matrix composite. The effects of volume fraction of β-eucryptite particulates on the thermal expansion coefficient and thermal conductivity of the composite were investigated.

Bulk nickel–carbon nanotube nanocomposites by laser deposition

Nickel–carbon nanotube (CNT) nanocomposites have been processed in a bulk form using a laser deposition technique, commercially known as the laser engineered net shaping (LENS) process. Mechanical milling of the powder feedstock consisting of nickel powders and CNTs before laser deposition has resulted in not only a more homogeneous distribution of the nanotubes in the nickel matrix, but also two distinct scales of reinforcements within the composite. The larger reinforcement scale consists of submicrometre to micrometre sized bundles of CNTs while the smaller scale consists of individual (or cluster of a few) CNTs within the nickel matrix. High resolution transmission electron microscopy studies indicate that the nickel/CNT interface is well bonded without the presence of any significant interfacial reaction product. The degree of disorder and defects in the CNT bundles in the nickel matrix varied as a function of bundle size as revealed by Raman spectroscopy results.

Interface Study of Short Mullite Fiber Reinforced Al-Cu-Si Alloy Composites

Short mullite fiber reinforced Al-Cu-Si alloy composites were produced by squeeze casting. The interfacial microstructure and microchemistry of the testing composites were studied by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and energy disperse spectrum (EDS) equipped with TEM, respectively. It is shown that chopped mullite fibers in the composites are polycrystalline in structure composed of many fine mullite crystal particles which are orthorhombic in structure with lattice constants of a = 0.749 nm, b = 0.927 nm and c = 0.581 nm based on electron diffraction (ED) analysis and high resolution transmission electron microscope (HRTEM). There are much denser dislocations in the near vicinity of both fiber/matrix interface and silicon/matrix interface. But interfacial reaction products at fiber/matrix interface in (3Al2O32SiO2)/Al-4.0Cu-5.0Si composites have not been observed yet.

Effect of Sc, Zr, and Ti on the interfacial reactions of the B4C/Al system

B4C plates were immersed in liquid aluminum alloyed with Sc, Zr, and Ti to investigate the interfacial reactions between B4C and liquid aluminum at 730 °C. The influences of alloying elements on the interfacial microstructure and reaction products in terms of individual and combined additions were examined using a scanning electron microscopy (SEM) and a transmission electron microscopy (TEM). Results reveal that all three elements react with B4C and form interfacial layers that act as a diffusion barrier to limit the decomposition of B4C in liquid aluminum. The interfacial reactions and the reaction products in each system are outlined. Moreover, by the combined addition of Sc, Zr, and Ti, most of the Ti is enriched at the interface, which not only offers appropriate protection of the B4C but also reduces the consumption of Sc and Zr at the interface.

Effect of Interfacial Reaction on High Temperature Properties of Fe-Cr-Si Fiber Reinforced AC8A Aluminum Composites

Metallic fibers (Fe-Cr-Si) with an excellent high temperature strength are expected to be use as a reinforced material of the engine piston head. However, the high reactivity of Al with most metals has disturbed the use of metallic fibers in aluminum composites until now. In this study, the influence of the reaction products at the fiber/matrix interface on high temperature properties of the composites was investigated by different solution treatment conditions. It is found that hardness and strength increase with an increase the solution treatment temperature (Tst). Reaction products (Al-Fe intermetallic compounds) resulting from solution treatments were formed along the fiber/matrix interface at 773 K or higher. The composites without interfacial reaction products (Tst=763 K) showed excellent rotating-bending fatigue life at 573 K. The fatigue crack propagation in this composite occurred at the necking region of the metal fiber because no cracks were observed in the interfacial reaction products.