Effect of VGCNF on high-temperature deformation performance and softening mechanism of aluminum matrix

Abstract Vapor-grown carbon nanofiber (VGCNF) reinforced aluminum (Al) matrix composites were prepared by spark plasma sintering. Isothermal compression experiments were conducted over a temperature range of 573 K–723 K at strain rates from 0.01 s−1 to 1 s−1. The effect of the addition of VGCNF on the thermal deformation properties of Al matrix was investigated by comparison with pure Al. The results indicate that the composite material has greater high-temperature strength than pure Al. VGCNF withstands stress through the load transfer mechanism in the Al matrix, however, it causes a significant change in the microstructure of the Al matrix. Lattice distortion of the base metal and grain refinement improve the strength of the material. During the thermal deformation process, the VGCNF/Al composite clearly exhibited softening. The difference in the morphology of the reinforced mass before and after the thermal deformation indicated that the sliding of tubular VGCNF was one of the factors leading to the softening. The microstructure after thermal deformation was analyzed by electron backscatter diffraction. It was found that VGCNF promoted the continuous dynamic recrystallization of the Al matrix, which led to softening of the material.