Yumin Wang

Ti₂AlNb-based alloys are promising lightweight materials for aerospace hot-section components; however, their service reliability is limited by temperature- and strain-rate-dependent deformation damage and fracture behavior. In this study, the high-temperature failure behavior of a Ti-22Al-24Nb-0.5Mo (at.%) alloy sheet was investigated at 650–750 °C under strain-rate conditions specified by GB/T 228.2-2015. The effects of temperature and strain rate on mechanical degradation, microstructural evolution, crack propagation, and failure mechanisms were systematically analyzed.The results show that the pre-yield strain rate mainly affects yield strength, whereas the post-yield strain rate dominates tensile strength and ductility. Increasing strain rate enhances strength but reduces elongation, with stronger rate dependence observed at 700–750 °C. Elevated temperature and reduced strain rate promote the spheroidization and coarsening of secondary acicular O phase, influencing damage evolution. Fracture analysis reveals that failure occurs through ductile microvoid nucleation, growth, and coalescence. Crack propagation is governed by both phase-boundary strength and the orientation relationship between crack growth direction and O-phase lamellae. Transmission electron microscopy demonstrates a deformation mechanism transition from dislocation glide at 650 °C to thermally activated dislocation climb accompanied by dynamic recovery and recrystallization at 700–750 °C. This transition is identified as the fundamental cause of rate-dependent softening and failure behavior. The findings provide new insights into the failure mechanisms of Ti₂AlNb alloy sheets under elevated-temperature service conditions.

The SiCf/Ti composite panels are promising candidates for lightweight aerospace structures. However, their transverse behavior under dynamic loading remains poorly understood. The SiCf/TC17 composite core panel with TC4 claddings was fabricated via magnetron sputtering combined with vacuum hot-pressing (VHP). Dynamic transverse tensile tests were conducted at room temperature using a miniaturized split Hopkinson tension bar (SHTB) integrated with time-resolved X-ray phase-contrast imaging (XPCI). SEM and EBSD were used for post-mortem characterization. At the average strain rate of 1083 s⁻¹, the composite exhibits a transverse tensile strength of 396 MPa. In-situ X-ray imaging, together with fracture surface SEM and EBSD analyses, reveals a progressive failure sequence of interfacial damage, fiber fracture, matrix fracture, and final cladding fracture.