Self-Healing of SiC-Al2O3-B4C Ceramic Composites at Low Temperatures

Self-healing ceramics have been researched at high temperatures, but few have been considered at lower temperatures. In this study, SiC-Al2O3-B4C ceramic composite was compacted by spark plasma sintering (SPS). A Vickers indentation was introduced, and the cracks were healed between 600 °C and 800 °C in air. Cracks could be healed completely in air above 700 °C. The ceramic composite had the best healing performance at 700 °C for 30 min, recovering flexural strength of up to 94.2% of the original. Good crack-healing ability would make this composite highly useful as it could heal defects and flaws autonomously in practical applications. The healing mechanism was also proposed to be the result of the oxidation of B4C.

Non-equiatomic W10Mo27Cr21Ti22Al20 high-entropy alloy produced by mechanical alloying and spark plasma sintering: Phase evolution and mechanical properties

In this work, non-equiatomic W10Mo27Cr21Ti22Al20 refractory high-entropy alloy (RHEA) was produced using mechanical alloying followed by spark plasma sintering. The phase formation, microstructure, and compressive mechanical properties of the alloy were studied. During mechanical alloying, a Body-centered cubic (BCC) solid solution phase with a particle size of less than 1 µm was obtained after 18 h ball milling. The microstructure of the sintered sample exhibits three distinct phases consisting of two solid solution phases BCC1 and BCC2 as well as fine TiCxOy precipitates distributed in them. The volume fractions of each phase were about 79%, 8%, and 13%, respectively. The sintered W10Mo27Cr21Ti22Al20 showed yield strengths of 2465, 1506, 405, and 290 MPa at room temperature 600, 1000, and 1200°C, respectively, which are about twice that of the same refractory high-entropy alloy produced by vacuum arc melting. At 1000 and 1200°C, the strength after yielding gradually increased to 970 and 718 MPa at a compressive strain of 60%. The studied refractory high-entropy alloy can have good potential in high-temperature applications due to its high specific strength at elevated temperatures compared to conventional Ni-based superalloys and most as-reported refractory high-entropy alloys.