Search Results (3)

The improvement of densification and fracture toughness in high-entropy ceramics is important to realizing their practical applications. In this study, SiC whiskers and metal Ni additions were incorporated to solve these problems of high-entropy boride ceramics. The influence of sintering temperatures (1450–1650 °C) on the densification, microstructure, hardness, fracture toughness, and bending strength of (M_0.2Ti_0.2Ta_0.2V_0.2Nb_0.2)B₂-SiC_w-Ni (M=Hf, Zr, or Cr) composites prepared by hot-pressing technology were studied. Results showed that when SiC whiskers and metal Ni additions were used as additives, increasing sintering temperatures from 1450 to 1600 °C promoted the densification of high-entropy boride ceramics. This was mainly attributed to the high sintering driving force. However, when the temperature further increased to 1650 °C, their densification behavior decreased. At a sintering temperature of 1600 °C, these high-entropy borides ceramics all had the highest densification behavior, leading to their high hardness and fracture toughness. The highest relative density was 96.3%, the highest hardness was 22.02 GPa, and the highest fracture toughness was 13.25 MPa·m^1/2, which was improved by the co-function of SiC whiskers and plastic metal Ni. Meanwhile, in the adopted sintering temperature range of 1450 to 1650 °C, the highest bending strength at room temperature of these high-entropy boride ceramics could reach 320.8 MPa. Therefore, this research offers an effective densification, strengthening, and toughening method for high-entropy boride composites at a low sintering temperature. Full article

The extreme environment of aerospace requires severe material properties, and in situ autogenous ZrC–NbC dual-phase reinforced titanium matrix composites have attracted much attention. In this study, TiC/Ti composites (TMC1–TMC4) with different NbC contents (0–9 wt%) were prepared and investigated in depth by various means and ANSYS simulations. The results show that the variation in NbC content significantly changes the TiC morphology from fine needles at 0 wt% to needles with a small amount of ellipsoidal grains at 3 wt%, to an ideal uniform distribution (mostly granular or nearly spherical) at 6 wt%, and to a large number of aggregates (dendritic or coarse rod-like) at 9 wt%. In terms of mechanical properties, the compressive strength and elongation firstly increased and then decreased, and reached the optimum at 6 wt% NbC, with the ultimate compressive strength as high as 1379.50 MPa, the compressive yield strength at 817.3 MPa, the compressive strain up to 38.73%, and typical ductile fracture characteristics; at 9 wt%, it transformed into a mixed fracture mode, with a decrease in performance. ZrC and NbC synergistically stabilize the microstructure, with the best synergistic effect at 6 wt% NbC, which effectively improves the overall performance and meets the requirements of aerospace applications. The simulation is highly compatible with the experiment and verifies the experiment; this helps to reveal the mechanism, provides guidance for the design of high-performance materials, and promotes the development of materials technology in the aerospace field. Full article

In aerospace applications, titanium matrix composites (TMCs) must balance high strength, thermal stability, and vibration resistance. This study investigates the microstructural evolution and multi-property correlations in single-phase ZrC-reinforced (TMC1) and dual-phase ZrC-NbC-co-reinforced (TMC2) TMCs via SEM/TEM, XRD, tensile testing, and ANSYS simulations. The in situ reaction (Ti + ZrC/NbC → TiC + Zr/Nb) and NbC-induced grain boundary pinning drive microstructural optimization in TMC2, achieving 30% higher reinforcement homogeneity and 5 μm grain refinement from 15 μm to 10 μm. TMC2’s tensile strength reaches 1210 MPa, a 15% increase over TMC1, with an elongation at a break of 4.74%, 2.2 times that of TMC1. This performance stems from synergistic Hall–Petch strengthening and nano-TiC dispersion strengthening. Modal simulations show TMC2 exhibits a first-mode natural frequency of 98.5 kHz, 1.1% higher than TMC1’s 97.4 kHz, with maximum displacement reduced by 2.3%. These improvements correlate with TMC2’s elevated elastic modulus (125 GPa vs. 110 GPa) and uniform mass/stiffness distribution. The ZrC-NbC synergy establishes a microstructural framework for the concurrent enhancement of static and dynamic properties, offering critical insights for a high-performance TMC design in extreme environments. Full article