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Spark plasma sintering (SPS) tests were designed using the Taguchi method to create high‐performance composites consisting of 60 wt% TiB2, 30 wt% TiC, and 10 wt% Ti. The effects of SPS parameters on the microstructure and mechanical properties of TiB2‐TiC‐TiB composites were systematically investigated. Additionally, the evolution of phase and microstructure during the densification of the composites was analyzed in detail. It has been demonstrated that composites can achieve a high relative density of 99.8%, a hardness of 22.2 GPa, a strength of 739 MPa, and a fracture toughness of 7.07 MPa m1/2, as well as a dense structure and small grain size. These properties can be obtained by sintering at a temperature of 1500°C, a pressure of 50 MPa, and a holding time of 5 min. Sintering temperature is the primary factor that promotes the densification of the composite and influences its relative density, grain size, and morphology. Holding time and sintering pressure are relatively minor factors, but they play important roles at different stages of the sintering process. [ABSTRACT FROM AUTHOR]

Aluminum oxynitride (AlON) ceramics doped with different sintering aids were synthesized by spark plasma sintering process. The microstructures, mechanical, and optical properties of the ceramics were investigated. The results indicate that the optimal amount of sintering aids is 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO. The addition of La3+ and Mg2+ decreases the rate of grain boundary migration in ceramics, promotes pore elimination, and inhibits grain growth. The addition of Y3+ facilitates liquid‐phase sintering of AlON ceramics. Moreover, the addition of Mg2+ effectively promotes twin formation in the ceramics, which hinders crack propagation and dislocation motion when the ceramics are loaded. Hence, the AlON ceramic doped with 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO exhibits a relative density of 99.95%, an average grain size of 9.42 μm, and a twin boundary content of 10.3%, which contributes to its excellent mechanical and optical properties. [ABSTRACT FROM AUTHOR]

Ultra-high-strength M54 steel has been considered a promising candidate for structural applications in spacecraft and aircraft because of its excellent match of strength and toughness. Spark plasma sintering (SPS) technique characterized by simultaneous uniaxial pressure and pulsed current allows achieving fully dense bulk materials at low temperature with short heating, soaking, and cooling times. SPS has been widely used to produce metal materials due to its efficiency and advantages caused by its distinctive heating mode. The sintering behaviors, structural transformations, and mechanical properties of the ultra-high-strength M54 steel prepared by spark plasma sintering (SPS) were studied in this work. The actual density of the SPSed specimen was measured according to Archimedes' principle, and X-ray diffraction (XRD) analysis was used to identify the phases of the raw powders and SPSed specimens. The microstructure of the SPSed specimens was characterized by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) coupled with an energy-dispersive spectrometer (EDS). After SPS consolidation, metallurgical bonding between powders was completed, and the ultra-high-strength M54 steel adjacent to nearly full densification was obtained directly. The quasistatic tensile tests indicated that the SPSed M54 steel exhibited better ultimate tensile strength (UTS) of 1933.88 MPa compared to the wrought M54 steel. According to TEM analysis, the primary strengthening mechanism was its lath martensite structure with high-density dislocations. The elongation was not significant due to the presence of micro-voids and inclusions. [ABSTRACT FROM AUTHOR]

AlON ceramics were prepared by spark plasma sintering (SPS) with raw materials (60 mol% Al 2 O 3 and 40 mol% AlN) and sintering aids (0.16 wt% Y 2 O 3 + 0.3 wt% MgO + 0.06 wt% La 2 O 3). The effects of the SPS parameters on the microstructures and mechanical properties of the SPSed AlON ceramics were investigated systematically. This investigation suggested that when the sintering temperature was 1580 ℃, the sintering pressure was 50 MPa, and the holding time was 5 min, the AlON ceramics with excellent mechanical and optical performances were successfully synthesized. They exhibited a high hardness of 18.97 GPa, a good bending strength of 538 MPa, a fracture toughness of 5.88 MPa·m1/2, and particularly, a high transmittance of 76.28% at 750 nm. [ABSTRACT FROM AUTHOR]

The temperature dependence of internal friction is first investigated to understand the microstructure transition during the sintering process for the green compact of aluminum powder. An internal friction (IF) peak is observed only during the first heating process while not in the subsequent cooling and repeated heating process. The temperature position of the peak is independent of the measuring frequency and the height decreases with the increasing frequency. The appearance of the peak is closely related to the weak bonding interfaces between deformed aluminum particles and increased dislocation density induced by the pressing. The appearance of the peak well responds to a recrystallization process of deformed particles and thus the formation of the grain boundary which is proven by the appearance of the grain boundary IF peak. The peak temperature position is rationalized with the onset of the recrystallization process during the sintering process. [ABSTRACT FROM AUTHOR]

B 4 C ceramic with the addition of 5 wt % (Ti 3 SiC 2 + CeO 2 /La 2 O 3) as sintering aids was fabricated by spark plasma sintering at a relatively low temperature of 1650 °C for 5 min at 80 MPa. The phase composition, microstructures, and comprehensive mechanical properties of the ceramics were studied in detail. The existence of reinforced second phase particles, the refinement of the matrix grains, the formation of residual stress along the grain boundaries and the appearance of the mixed fracture mode had a synergetic strengthening effect on the mechanical properties. The flexural strength, fracture toughness and Vickers hardness of B 4 C ceramics reached 565.2 ± 21.8/551.0 ± 25.2 MPa, 6.28 ± 0.01/6.41 ± 0.12 MPa·m0.5, and 28.51 ± 0.86/27.23 ± 1.08 GPa, respectively. In addition, to reduce the crack sensitivity of the ceramic, the ceramics were pre-oxidized at 800 °C for different durations. The flexural strength was increased by approximately 13.4% after the ceramic was oxidized at 800 °C for 45 min due to the crack-healing effect induced by the oxide glass B 2 O 3 on the ceramic surface. [ABSTRACT FROM AUTHOR]