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For the development of a lightweight, high-strength, and oxidation-resistant steel matrix composite, titanium carbide (TiC) reinforced SUS431 metal matrix composites (MMCs) were proposed in this study. TiC–SUS431 composite, which is 25.5% lighter than SUS431, was successfully fabricated by a liquid pressing infiltration (LPI) process. The TiC particles are homogenously distributed in the SUS431 matrix without apparent pores or impurities. Effect of TiC particle size on the anti-oxidation properties of the composites was also investigated in the research. The mass gain of the tested TiC(1 μm)–SUS431 composite, held at 700 °C for 50 h in an air environment, decreased by about 90% compared to that of the TiC(3 μm)–SUS431 composite, which indicates improved oxidation resistance originating from the formation of a thermally stable thin Ti oxides on the composite.

We successfully fabricated a controllable intragranular pore containing hydroxyapatite (HA) by the combination of an electric current assisted sintering and pre-heat treatment process. The microstructure and mechanical properties of the sintered HA bulk with and without intragranular pores were investigated in this study. Fully densified HA fabricated by the combination of an electric assisted sintering and pre-heat treatment process showed extremely superior mechanical properties. Meanwhile, hierarchically structured porous HA consisting of nanosized intragranular pores without macropores in the grain boundary showed dramatically decreased elastic modulus by different fracture mechanism compared with fully densified HA.

The corrosion properties of Fe-Cr-Mn-C-N high interstitial austenitic stainless cast steels were investigated for down-hole application in sour environments. The two cast alloys contained 0.66% and 0.71% of total nitrogen and carbon. The corrosion properties of the alloys that were solution-treated and fast-cooled were directly responsible for high corrosion resistance in NaCl solution, including resistance to pitting corrosion resulting from a better distribution of chromium chemical compound in the high interstitial stainless cast steel. However, the sour corrosion resistance of the alloys decreased with the fast cooling rate, which can be attributed to the increased amount of ferrite containing Fe2+, which causes iron sulfide precipitate formation in H2S.

Oxidation resistance of TiC–SKD11 composite has been improved through SiC/TiB2 based hybrid coating by a simple air spray process and subsequent transition to dense and stable phases in oxidation environment. As a result of the oxidation test at 700 °C for up to 50 h, the coated TiC–SKD11 composite exhibited excellent oxidation resistance characteristics compared with the uncoated TiC–SKD11 composite, and also compared to SUS431 and 17-4PH. The formation of a thermally stable, volume-expanded SiO2 and TiO2 coating layer with the aid of B2O3 by phase transition of TiB2/SiC based hybrid coating under oxidation atmosphere is the origin of the improved anti-oxidation ability of the TiC–SKD11 composite.

A 7075 Al alloy matrix composite reinforced with SiC particulates (SiCps) whose sizes were 10 and 30 μm, i.e., a bimodal Al–SiCp composite, was made by a liquid pressing process, and its quasi-static and dynamic compressive properties were evaluated by using a universal testing machine and a split Hopkinson pressure bar, respectively. Mg–Si-, Al–Fe-, and Cu-rich intermetallic compounds existed inside the Al matrix, but might not deteriorate compressive properties because of their low volume fraction (about 2.6%) which was much lower than that of SiCp. The dynamic compressive strength was higher than the quasi-static strength, and was higher in the specimen tested at 2800 s−1 than in the specimen tested at 1400 s−1 according to the strain-rate hardening. For explaining the strain data, the blocking extent of crack propagation by the Al matrix was quantitatively examined. The melting of Al matrix occurred by adiabatic heating was favorable for the improvement in compressive strain because it favorably worked for activating the shear band formation and for blocking the crack propagation, thereby leading to the excellent compressive strain (10.9–11.6%) as well as maximum compressive strength (1057–1147 MPa). Thus, the present bimodal 7075 Al–SiCp composite provides a promise for new applications to high-performance armor plates.

In order to explore the possibility of using carbon nanotube (CNT) to introduce and control the temperature coefficient of resistance (TCR) of metal matrix composite, relatively thick and short multi-walled CNTs (MWCNTs) were introduced in the metal matrix with in-situ formation of chromium carbide (Cr7C3) at the CNT/copper (Cu) interface. We demonstrate that incompatible properties such as electrical conductivity and TCR can be achieved simultaneously by introducing MWCNTs in the Cu matrix, with control of the interfacial resistivity using the MWCNT/Cr7C3–Cu system. High electrical conductivity of 94.66 IACS and low TCR of 1,451 10–6 °C−1 are achieved in the 5 vol.% MWCNT–CuCr composite. In-situ formation of Cr7C3 nanostructures at the MWCNT/Cu interface by reaction of diffused Cr atoms and amorphous carbon of MWCNTs would assist in improving the electrical properties of the MWCNT–CuCr composites.

Titanium carbide (TiC) reinforced tool steel matrix composites were successfully fabricated by a liquid pressing infiltration process and research was subsequently conducted to investigate the composites’ oxidation resistance. The mass gain of the tested TiC–SKD11 composite held at 700 °C for 50 h in an air environment decreased by about 60%, versus that of the SKD11, which indicates improved oxidation resistance. Improved oxidation resistance of the TiC–SKD11 composite originates from uniformly reinforced TiC, with a phase transition to thermodynamically stable, volume-expanded TiO 2 .

The anisotropy of the Nd2Fe14B powder is originated during the creation of a fine Fe2B lamellar structure in the disproportionation step. The aspect ratio (A/R) of Fe2B structure increased from 3.37 ± 1.5 to 6.69 ± 3.2 during phase decomposition for 0 ~ 60 min at 820 ◦ C (P H2 = 10 kPa). The Fe2B having high A/R ratio recombined Nd2Fe14B, which is close to the single domain, and the magnetic properties are also improved with increasing A/R ratio.

Novel structures of TiC/TiAl2/carbon nanofiber (CNF) hybrid reinforcements with attached magnesium oxide (MgO) particles were successfully fabricated in the matrix of the Mg alloy AZ91 (Mg 9 wt%, Al 1 wt%, Zn) composite. This was done using a novel liquid pressing process, coupled with in situ reactions between titanium dioxide (TiO2)-coated CNFs and the Mg alloy. Homogeneously dispersed hybrid reinforcement with strong interfacial bonding through TiC/TiAl2, led to dramatic improvement in the mechanical properties of AZ91 alloys, with the assistance of an anchoring effect by MgO particles chemically attached to the coating layer.

In this study, A356 Al alloy composites reinforced with SiC particulates (SiC p ), whose SiC p volume fraction was quite high (about 56 vol%) for a candidate surface material of multi-layered armors, were fabricated by a liquid pressing process, and their dynamic compressive properties were investigated by using a split Hopkinson pressure bar. Defects such as misinfiltration or pores were eliminated, but about 2 vol% of eutectic Si particles and about 3 vol% of Fe-Al intermetallic compound particles were contained in the Al matrix. According to the dynamic compressive test results, dynamic compressive strength and strain were much higher than quasi-static ones because of strain-rate hardening effect and existence of molten Al matrix formed by adiabatic heating. The as-cast composite showed the best combination of dynamic strength and strain, together with the highest dynamic toughness, because the crack propagation was effectively blocked by the molten Al matrix and deformation band formation, while the T6-heat-treated composite showed the lowest compressive strain in spite of the highest strength. These findings suggested that the present Al-SiC p composites could be reliably applied to armors because the dynamic toughness or resistance to fracture was much higher under the dynamic loading than under the quasi-static loading.

A combined analysis has been performed for the penetration of a long-rod into MMC/Ceramic layered armour systems with several shot test and a series of simulations. Metal Matrix Composites (MMCs) can be a potential candidate for military applications due to the light weight. The length to diameter (L/D) ratio of the penetrator is 10.6. Two types of MMC plate have been fabricated by a liquid pressing method; A356/45%vol.SiC with a uniform distribution of SiC particle and Al7075/45%vol.B4Cp with B4C particle. The mechanical properties were measured with the high-speed split Hopkinson bar test, hardness test and compression test. The popular Simplified Johnson-Cook model was adopted to represent the material characteristics for FEM simulations. Based on the depth of penetration (DOP) by simulation and high-speed shot test, the performance evaluation of the MMC applied armour system has been made by comparing with the conventional semi-infinite mild steel target. The results show that placing ceramic front layer provides a certain gain in protection, and that placing another ductile front layer provides a further gain. The application of MMC is found to be attractive. Whether SiC or B4C is best deserves more delicate shot tests.

In this study, high volume fraction B4C reinforced Al matrix composites were fabricated with a liquid pressing process. Microstructural analysis by scanning electron microscope and a transmission electron microscopy shows a uniform distribution of the B4C reinforcement in the matrix, without any defects such as pore and unwanted reaction products. The compressive strength and wear properties of the Al7075 matrix and the composite were compared at room temperature, 100, 200, and 300 &deg, C, respectively. The B4C reinforced composite showed a very high ultimate compression strength (UCS) over 1.4 GPa at room temperature. The UCS gradually decreased as the temperature was increased, and the UCS of the composite at 300 &deg, C was about one third of the UCS of the composite at room temperature. The fractography of the compressive test specimen revealed that the fracture mechanism of the composites was the brittle fracture mode at room temperature during the compression test. However, at the elevated temperature, AMCs had a mixed mode of a brittle and ductile fracture mechanism under the compressive load. The composite produced by a liquid pressing process also showed superior wear resistance compared with the Al matrix. The result of the wear test indicates that the wear loss of the Al matrix at 300 &deg, C was two times higher than that of the AMCs, which is attributed to the formation of a mechanically mixed layer (MML) in the composites at the high temperature.

Carbon-doped TiZrN nanocomposite coatings were investigated for phase formation and wear behavior. They were prepared by laser carburization using carbon paste, and the thermal energy of the pulsed laser was limited to the range of 20 to 50%. X-ray photoelectron spectroscopy analysis revealed that the ratio of carbide (TiC, ZrC) increased as the thermal energy of the laser increased. The sp2/sp3 ratio increased by approximately 16% when the laser thermal energy was raised from 30 to 40%, and the formation of amorphous carbon was confirmed in the carbon-doped TiZrN coatings. As a result of microstructural analysis, the carbon-doped TiZrN nanocomposite was formed by an increase of hybrid bonds in expanded localized carbon clusters. Wear resistance was evaluated using a ball-on-disc tester, which showed that the friction coefficient decreased from 0.74 to 0.11 and the wear rate decreased from 7.63 × 10−6 mm3 (Nm)−1 to 1.26 × 10−6 mm3 (Nm)−1. In particular, the friction coefficient and wear rate improved by 71 and 66%, respectively, owing to the formation of carbon-doped TiZrN nanocomposite with amorphous carbon while the thermal energy was increased from 30 to 40%.

In this study, different volume fractions of silicon-carbide-reinforced AA2024 matrix composites were successfully fabricated using stir-casting (SC) and die-casting (DC) processes. The microstructural difference and physical properties of the composites during the manufacturing process were investigated in detail. The microstructural analysis found that the composite produced by the SC process had some reinforcement clusters and pores, however, defects and clusters significantly decreased after the DC process. In particular, the degree of reinforcement dispersion was quantitatively analyzed and compared before and after the DC process using the dispersion-analysis method. As a result of quantitative evaluation, the degree of dispersion was improved 2.5, 4.6, and 4.0 times with 3 vol.%, 6 vol.%, and 9 vol.% SiC-reinforced composite after the DC process, respectively. The electron backscatter diffraction (EBSD) analysis showed that the grain size of the 9 vol.% SiC-reinforced DC composite (17.67 &mu, m) was 75% smaller than that of the SC composite (68.06 &mu, m). The average tensile strength and hardness of the 9 vol.% SiC-reinforced DC composite were 2 times higher than those of the AA2024 matrix. The superior mechanical properties of the DC-processed composite can be attributed to the increase in dispersivity of the SiC particles and to decreases in defects and grain size during the DC process.

This study was carried out to observe and measure the microstructure, distance between dendrite arms, aspect ratio, and Knoop hardness change of extruded material formed by the hydro co-extrusion of Al3003/Al4004 clad material manufactured by the duo-casting method. The specimen of duo-casted Al3003/Al4004 clad materials was circle shaped, it was composed of Al3003 (outside) and Al4004 (inside) materials. The manufacturing conditions of the hydro co-extruded specimen were 423 K temperature and 6.5 ratio of extrusion. At the interface of the duo-casted Al3003/Al4004 clad material, a non-junction at the interface and non-metallic inclusions of Si- and Mn-based oxides were observed. Al3003 exhibits equiaxed crystals, Al4004 has a casted structure with dendrites before extrusion, showed slight deformation during extrusion, and then finally exhibited completely deformed structures after extrusion. In the cast material, the distance between dendrite arms increased, and the aspect ratio of dendrites tended to decrease from the surface to the center. However, in the case of the extruded material, neither Al3003 nor Al4004 changed significantly from the surface to the inside. As extrusion progressed, the Knoop hardness value at the interface of Al3003/Al4004 increased rapidly compared with those of Al3003 and Al4004 matrixes.

Functionally graded MWCNT-HA composites were fabricated via hetero-aggregation and spark plasma sintering (SPS) process. The functionally-graded MWCNT–HA composites were further pressurelessly sintered at 1373 K in air condition to decompose the MWCNTs in the HA matrix. Consequently, structurally graded porous hydroxyapatite (HA) was successfully fabricated by introducing, followed by decomposing, of gradiently-included multi–walled carbon nanotubes (MWCNTs) at volume of 0–5 vol.%. Microstructure and Raman spectra of the sample clearly showed that no MWCNTs were present in the HA matrix. Moreover, pore and grain size of the structurally graded porous HA decreased with increasing MWCNT contents. It is expected that percolated MWCNTs make a degassing path for CO2 gas generated by MWCNT decomposition, and also prohibit grain growth of HA. The results indicate that these advanced, layered, structure-controlled functionally graded MWCNT–HA composites and structurally graded porous HA are promising for a variety of new and challenging structural and biomaterial applications.

Carbon-nanofiber (CNF) reinforced aluminum (Al) matrix composites were fabricated by a unique liquid pressing process. The mechanical properties of the CNF–Al composites, both with and without titanium dioxide (TiO 2 ) coating layers on the CNF surface, have been studied. The compressive yield strength of the TiO 2 coated CNF–Al composite dramatically increased (over nine times), as compared with that of an Al alloy. TiO 2 coated CNFs are expected to be a highly sustainable and dispersible reinforcement for metal matrix composites (MMCs) that are fabricated by a metal melting process.

The degradation behaviors of Ti1−xZrxN coatings on SUS304 were investigated through an accelerated test method using a pulsed laser to induce thermal shock. The accelerated test was designed based on the Arrhenius model, and the changes in surface roughness were measured to determine the failure of the coating specimens. The predicted lifetimes obtained by a statistical analysis of the failure time data were increased by a factor of ~1.5 according to the increase in the Zr ratio from 10 to 50 wt%. The increase of the lattice parameters and hardness for the as-deposited specimens indicated lattice volume expansion and distortion according to the Zr addition, respectively. Depth profiles for the coating (Ti, Zr) and the substrate (Fe, Cr) atoms revealed that the atomic diffusion distance by laser ablation decreased with lattice distortion. Delamination of the coating layer was only observed in the specimen with 10 wt% of Zr after repeated thermal shock. The coating thickness decreased with surface cracks and was suppressed in the specimens with 30 and 50 wt% of Zr by the increase of ZrN formation.

High-pressure die-cast (HPDC) AlSi10MnMg (AA365) has been widely used in the manufacturing of automotive components because it has excellent castability, is lightweight, and possesses good mechanical strength. In particular, this alloy must be capable of withstanding long-term exposure to high temperatures in order for these automobile parts to be useable. To investigate the viscoelastic behavior of HPDC AA365 with the aim of improving the long-term structural performance at high temperatures, we performed a creep test in the temperature range of 373–573 K with a constant applied stress of 64–217 MPa. A micro-hardness test of the HPDC AA365 alloy, performed after the creep test, yielded hardness values of 64.0 HV and 49.9 HV for the gauge and grip sections, respectively. The observed grain-size differences between the sections may have led to this difference in micro-hardness. Moreover, both values of micro-hardness were relatively low compared with the value of 93.5 HV for HPDC AA365 before the creep test. This was because of recovery and recrystallization. The creep tests also showed that the minimum creep rate increased with increasing applied stress for each temperature, causing a decrease in the time to failure. Based on the true stress exponent (n) on a scale of 1 to 90, various creep mechanisms for HPDC AA365 were revealed, including the Harper-Dorn, dislocation, and power-law breakdown mechanisms. The specific creep mechanism depended on temperature and applied stress. Furthermore, owing to the presence of the threshold stress, the apparent creep activation energy (259.08 kJ/mol) was substantially higher than that of aluminum (Al) self-diffusion (Qd = 143 kJ/mol). The existence of the threshold stress can also be demonstrated by a high n value that does not correspond to the n of pure Al under certain conditions. Failure in these alloys can be caused by void coalescence, cracked-brittle Si particles, and intermetallic phases that served to initiate and propagate the crack. Our results demonstrated that the fracture mechanism changed from transgranular to intergranular fracture in response to the applied stress and temperature. Our findings can improve the applications of high-pressure die-cast aluminum alloys.

Aluminum matrix composites with a high SiC particle volume fraction (55 vol%) have been fabricated by utilizing an innovative liquid pressing process. The microstructure of the fabricated composites was investigated. The effects of interface oxidation and reinforcement particle size on sliding wear behavior were studied using the pin-on-disk test against SAE 52100 steel counterfaces. The different wear behaviors of high volume fraction Al/SiC composites were compared to low volume fraction composites. Larger reinforcement shows improved wear resistance because it helps composites maintain rigidity under severe shear deformation. In addition, the SiC interface modification increased the wear resistance of the composites by preventing the formation of interfacial cracks between the matrix and reinforcement. The results of this study present the enhancement of the wear properties through interface modification of high volume fraction-reinforced metal matrix composites.

A TiC reinforced steel composite was fabricated by a liquid pressing infiltration (LPI) process. The TiC reinforced steel composites with density

This study was conducted on titanium diboride (TiB2) reinforced Al metal matrix composites (MMCs) with improved properties using a TiB2 and aluminum (Al) 1050 alloy. Al composites reinforced with fine TiB2 at volume ratios of more than 60% were successfully fabricated via the liquid pressing infiltration (LPI) process, which can be used to apply gas pressure at a high temperature. The microstructure of the TiB2&ndash, Al composite fabricated at 1000 &deg, C with pressurization of 10 bar for 1 h showed that molten Al effectively infiltrated into the high volume-fraction TiB2 preform due to the improved wettability and external gas pressurization. In addition, the interface of TiB2 and Al not only had no cracks or pores but also had no brittle intermetallic compounds. In conclusion, TiB2&ndash, Al composite, which has a sound microstructure without defects, has improved mechanical properties, such as hardness and strength, due to effective load transfer from the Al matrix to the fine TiB2 reinforcement.

High-temperature compressive strengths of titanium carbide (TiC) reinforced stainless steel composites fabricated by liquid pressing infiltration process were investigated at various temperatures. Effect of TiC on compressive strength of SUS431 was found to increase with increasing testing temperature. TiC reinforcement successfully suppressed softening of SUS431 matrix, resulting in about 5 times higher strength than that of SUS431 at 1050 °C. The novel SUS431 composites reinforced with uniformly dispersed, high volume fraction TiC show great promise for applications in high-temperature environments.

This study proposes an automated quantification technique for reinforcement dispersion in metal matrix composites. While a fine and homogeneous dispersion of reinforcements is necessary to achieve an optimum reinforcing effect in metal matrix composites, there have been few studies on the quantitative measurement of reinforcement dispersion. The proposed technique extracts reinforcement information from a given microscopic image through image analysis with minimized human interruption and quantifies the reinforcement dispersion automatically using a statistical approach. The feasibility of the proposed technique is shown by analyzing the effect of the hot rolling process on the reinforcement dispersion in a B4C/Al metal matrix composite and comparing it with the as-cast state.

In this study, a hybrid Al-matrix composite reinforced with both SiC and B4C ceramic particulates (SiCp or B4Cp, respectively) was fabricated to increase the volume fraction of ceramics by a liquid pressing process, and its dynamic and ballistic properties were compared with those of monolithic Al-matrix composites reinforced with SiCp or B4Cp. The hybrid composite demonstrated a very high dynamic compressive strength (over 1.5 GPa), along with a good total strain of 11.7%, which readily reached an undiscovered strength area (far over 1.2 GPa) of typical composites. This was basically attributed to the highest ceramic fraction (60 vol%), together with strongly-bonded ceramic/Al interfaces and synergetic hybrid effects of SiCps and B4Cps. After the ballistic test, the hybrid composite was radially cracked with a small hole-mark and a few fallen-off debris, which indicated the higher ballistic properties than those of the SiCp- or B4Cp-reinforced composite because of outstanding dynamic compressive strength and strain.