Dynamic mechanical response and damage mechanisms of nacre-inspired 2024Al/B4C composite at elevated temperature

Abstract

In this study, the nacre-like 2024Al/B4C composites with a lamellar-interpenetrated architecture, virtually free of pores and cracks, were fabricated through combining freeze casting with pressure infiltration, and their quasi-static and dynamic compressive properties were investigated over the temperature ranged from 25 to 500 °C. The dynamic compressive strength and strain were greater than quasi-static ones due to strain-rate hardening and adiabatic heating softening mechanisms. Regardless of strain rates, the compressive strength decreased with temperature, while the failure strain increased. This could be explained by four main fracture phenomena including cracking of B4C and intermetallic compounds (IMCs), matrix deformation and interfacial debonding. The matrix deformation prevailed actively at high temperatures, with a reduced overall trend towards cracking and interfacial debonding. The interfacial debonding and particle cracking acted as the dominant factors that deteriorated the compressive behavior, whereas the soften matrix induced by elevated test temperatures effectively blocked the crack propagation that favorably worked for the strain. As the temperature was raised, the softened matrix destabilized particle skeleton with the deformation behavior of the composites determined by the alloy matrix. However, recrystallization occurred within the alloy matrix, accompanied by a reduction in dislocation density, which degraded the strength of the composites. The elevated temperatures significantly enhanced the strain rate sensitivity of the composites because of the matrix softening yielding a greater proportionate enhancement of particle stress at high temperature than at low temperature.