High‑performance ceramics and their composites are essential materials for advanced manufacturing and high‑end equipment, and their sintering process directly dictates the microstructure and service performance. Among these, Al 2 O 3 /TiC p composites stand out for cutting‑tool applications. However, the final microstructure and mechanical properties are critically determined by the sintering process. Conventional hot pressing (HP) often suffers from incomplete densification, residual porosity, and exaggerated grain growth, which compromise strength and reliability. Spark plasma sintering (SPS) offers rapid heating but still faces scalability issues and non‑uniform temperature fields.
Hot oscillatory pressing (HOP), proposed in 2014, has emerged as a promising oscillatory‑pressure‑assisted technique. It applies cyclic pressure during heating, which has been shown to enhance densification and suppress grain coarsening in several material systems. Nevertheless, the fundamental mechanisms underlying these benefits—particularly the synergistic interplay between pressure amplitude, frequency, and waveform—remain largely elusive. Process optimization currently relies on empirical trial‑and‑error, consuming significant time and resources, and hindering the transition from laboratory prototypes to industrial production lines. This knowledge gap creates an urgent need for systematic mechanistic studies that can guide rational parameter design.
Recently, a team of material scientists led by Gang Shao from Zhengzhou University, China reported the mechanism of oscillatory pressure on densification and microstructural evolution in Al 2 O 3 /TiC p ceramic composites.
This work integrates sintering kinetics with metal hysteresis theory to elucidate the promoting mechanism of dynamic pressure during sintering and the influence of dynamic parameters on cyclic behavior, thereby providing a solid foundation for advancing oscillatory sintering theory and accelerating its widespread adoption.
The team published their work in Journal of Advanced Ceramics on June 22, 2026.
“In this report, we introduce, for the first time, the concept of the hysteresis loop from metal fatigue theory into hot oscillatory pressing. This method enables real‑time monitoring of the ceramic sintering behavior under oscillatory pressure, revealing the activation of viscoelastic grain boundaries and the hardening/softening stages associated with cyclic grain‑boundary sliding. Combined with AFM and TEM characterization, our approach clearly elucidates how dynamic pressure facilitates densification and suppresses grain growth.” said Gang shao, professor at School of Materials Science and Engineering at Zhengzhou University (China), an expert whose research interests focus on the field of ceramics material and composites.
“Our results provide unambiguous evidence for the beneficial effects of oscillatory pressure. First, the in situ densification curves reveal that HOP accelerates the densification, and the appearance of hysteresis loops at 1600 °C confirms that grain boundaries behave like viscoelastic fluids under cyclic shear, facilitating particle rearrangement and pore elimination. Second, XRD patterns show that dynamic pressure effectively relieves residual macro stresses, while SEM image analysis demonstrates a reduction in average grain size compared with static pressing, confirming the grain growth inhibition capability. Third, AFM and TEM measurements quantitatively prove that oscillatory pressure reduces grain boundary energy and decreases boundary thickness, which collectively lower the driving force for coarsening.”
“The HOP‑processed composites achieved near‑full density (>99.5% theoretical), with Vickers hardness of 21.8 ± 0.3 GPa and flexural strength of 795 ± 29 MPa—a >21% improvement over conventional hot‑pressed samples.” said Gang shao.
However, more delicate research works are still needed to explore the cutting performance of the Al 2 O 3 /TiC p ceramic composites prepared by HOP.
Other contributors include Hongtian He from the Dungguan University of Technology and Linan An from Southwest Jiaotong University, China.
About Author
Gang shao is a professor at the School of Materials Science and Engineering, Zhengzhou University, China. His research focuses on three main areas: polymer‑derived ceramics, extreme‑environment sensors, and field‑assisted ceramic fabrication technologies. He has led more than 10 major research projects, including grants from the National Key Research and Development Program of China, the National Natural Science Foundation of China (three projects), the Equipment Pre‑research Program of the Central Military Commission, industry‑university‑research projects with AECC (Aero Engine Corporation of China), and the Excellent Youth Foundation of Henan Province.
Funding
This work was supported by the National Natural Science Foundation of China (Grant Nos. 52072344, U1904180, 52502058), Excellent Young Scientists Fund of Henan Province (Grant No. 202300410369), Henan Province University Innovation Talents Support Program (Grant No. 21HASTIT001), and Basic and Applied Basic Research Foundation of Guangdong Province (Grant No. 2024A1515110198).
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC’s 2025 IF is 14, ranking in Top 1 (1/34, Q1) among all journals in “Materials Science, Ceramics” category, and its 2025 CiteScore is 24.6 (6/133) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
DOI: 10.26599/JAC.2026.9221341
Journal of Advanced Ceramics
Mechanism of oscillatory pressure on densification and microstructural evolution in Al2O3/TiCp composites
22-Jul-2026