SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3558-4
The development of advanced titanium alloys capable of operating above 600 °C remains a critical challenge for aerospace propulsion systems, where conventional Ti alloys suffer from insufficient high-temperature strength and microstructural instability. Here, we propose a computationally driven design strategy for titanium-based medium-entropy alloys (MEAs) that integrates thermodynamic phase prediction with mechanistically informed strength modeling, enabling systematic exploration of the Ti-Nb-Al-Cr quaternary system. The optimized Ti70Nb10Al15Cr5 MEA exhibits exceptional performance metrics: 18% room-temperature ductility (as-cast), a yield strength of 520.7 MPa at 650 °C (post-aging), and an ultralow density of 4.76 g/cm3 (45% lighter than Inconel 718). Microstructural characterization reveals a metastable single-phase BCC structure in the as-cast state, which transforms into a BCC/Ti3Al dual-phase system upon aging, with temperature-dependent precipitate morphology and phase stability. The alloy demonstrates superior high-temperature strength retention up to 900 °C (>80 MPa yield strength), outperforming commercial titanium alloys (e.g., Ti-1100, TG6) and bridging the performance gap between conventional Ti alloys and nickel-based superalloys. This work establishes a multi-criteria design paradigm for entropy-engineered alloys, offering a viable pathway to lightweight, high-temperature structural materials for next-generation aerospace applications.
New Carbon Materials•2026•DOI: 10.1016/S1872-5805(26)61113-4
Porous pyrolytic carbon (PPyC) serves as the buffer layer in TRi-structural ISOtropic (TRISO) fuel particles, providing storage for fission gases, preventing damage to outer layers, and absorbing stresses caused by fuel-kernel swelling. However, the changes of PPyC micro- and meso-structure at high temperatures remain insufficiently understood. In this study, PPyC fabricated by chemical vapor deposition was heat-treated from 1200 to 1600 °C and characterized across atomic-to-mesoscopic scales. Results show that the structure changes with temperature with a transition at approximately 1400 °C. Below 1400 °C, a decrease in Raman ID/IG ratio, narrowing of the graphite diffraction peak, and increased sp2 hybridization indicate progressive ordering associated with defect redistribution. Concurrent decreases in true density and mesopore volume, together with increased closed porosity, are consistent with partial conversion of open pores into closed pores. Above 1400 °C, increased ID/IG ratio, broadening of the diffraction peak near the rhombohedral graphite (101) reflection, and transition regions between crystalline and amorphous material observed by TEM indicate increasing structural disorder. Meanwhile, initially distinct PPyC particle boundaries blur and merge into broad, plate-like domains. Subsequent decrease in closed porosity and increase in mesopore surface area are consistent with partial connection of closed pores to the open-pore network. This work shows that intrinsic coupling between atomic-scale structural change and mesoscale pore connectivity provides a basis for assessing high-temperature structural stability of PPyC in TRISO fuel particles.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4075-1
Titanium alloys, such as Ti-6Al-4V (TC4), are indispensable in aerospace, biomedical, and advanced manufacturing due to their high specific strength, corrosion resistance, and biocompatibility. However, their inherent strength-ductility trade-off and limited stiffness hinder next-generation lightweight structural applications. Traditional ceramic reinforcements (TiC, TiB2, SiC) improve strength but introduce brittleness and interfacial incompatibility, degrading plasticity and fatigue resistance. Graphene, with theoretical strength ~130 GPa and Young's modulus ~1 TPa, offers a promising two-dimensional reinforcement. This review systematically examines graphene-reinforced titanium matrix composites (TMCs), focusing on the intrinsic relationship between preparation, microstructure, and properties. Key preparation routes include powder metallurgy and additive manufacturing, with challenges in achieving uniform dispersion and controlling interfacial reactions. Recent studies demonstrate that surface modification and process optimization can form an ideal interface structure comprising a nano-TiC layer and residual graphene. Even at low graphene additions, synergistic strengthening mechanisms—load transfer, fine-grain strengthening, and Orowan dislocation bypass—significantly enhance strength, hardness, and wear resistance while preserving ductility. This review consolidates critical theoretical and experimental findings, offering guidance to overcome technological bottlenecks and promote engineering applications of graphene-reinforced TMCs.