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 °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 °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 °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.

Aluminum alloy (Al7075) composites reinforced with a high volume fraction of silicon carbide (SiC) were produced by a liquid-pressing process. The characterization of their microstructure showed that SiC particles corresponding to a volume fraction greater than 60% were uniformly distributed in the composite, and Mg₂Si precipitates were present at the interface between the matrix and the reinforcement. A superior compressive strength (1130 MPa) was obtained by an effective load transfer to the hard ceramic particles. After solution heat treatment and artificial aging, the Mg₂Si precipitates decomposed from rod-shaped large particles to smaller spherical particles, which led to an increase of the compressive strength by more than 200 MPa. The strengthening mechanism is discussed on the basis of the observed microstructural evolution.

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 μm) was 75% smaller than that of the SC composite (68.06 μm). 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 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–Al composite fabricated at 1000 °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–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.

Metal matrix composites (MMCs) produced through the unique liquid pressing infiltration (LPI) process exhibit significant industrial potential. In this study, TiC/FC250 metal matrix composites were fabricated using the liquid pressing infiltration process, and the effects of austempering and quenching–tempering heat treatments on the microstructure and wear characteristics were investigated in comparison to as-cast specimens of both the FC250 gray cast iron matrix material and the TiC/FC250 metal matrix composites without heat treatment. The results indicated that the quenching–tempering heat treatment effectively enhanced the dry sliding friction and wear characteristics compared to the as-cast condition. The heat-treated specimens, under optimal conditions, demonstrated superior properties compared to other heat treatments and the matrix material. Although the metal matrix composites were successfully produced via the liquid pressing infiltration process and optimal heat treatment, some graphite morphology transformed from a flake to a spherical shape due to the high temperature and slow cooling rate during the process. With the quenching–tempering heat treatment, the wear resistance increased by approximately 41.53% in the matrix material and by 53.38% in the metal matrix composites compared to the as-cast specimens. The TiC/FC250 metal matrix composite heat-treated under optimal conditions exhibited an approximate 58.28% reduction in the friction coefficient compared to the FC250 gray cast iron.

A metal matrix composite was developed through a unique liquid pressing infiltration process to study the wear mechanism of a TiC reinforced AISI 1020 steel matrix. The microstructure, hardness, and wear behaviors of the TiC/AISI 1020 composite were compared with commercial AISI 52100 bearing steel. Microstructural analysis showed that there were no defects, such as pores or agglomeration of reinforcement particles, and about 60% of the volume of TiC was uniformly dispersed. In the case of the AISI 52100 alloy, the hardness was 62.42 HRC, which was similar to the 62.84 HRC value of the as-cast TiC/AISI 1020 composite. After the quenching heat treatment, the Rockwell hardness of the composite increased to 76.64 HRC, which was attributed to the martensitic transformation of the AISI 1020 matrix. As a result of the pin-on-disc wear test with high contact pressure, the wear width of AISI 52100 was 2937 μm, which was approximately 4.3 times wider than that of the heat-treated metal matrix composite (682 μm). The wear depths of AISI 52100 and the heat-treated composite were 2.6 μm and 0.5 μm, respectively, indicating that TiC/AISI 1020 exhibited excellent wear resistance compared with bearing steel. Improved wear resistance of the TiC/AISI 1020 composite originates from uniformly distributed TiC, with an increase in the hardness due to the heat treatment.