Dynamic compressive strength and mechanism of failure of Al-W fiber composite tubes with ordered mesostructure

Abstract

The split Hopkinson pressure bar was used to investigate the dynamic behavior of high density aluminum alloy (Al 6061-T6) – tungsten (W) fibers composite tubes with periodic arrangements of W fibers in axial and hoop directions processed by using the combination of Cold Isostatic Pressing (CIPing) and Hot Isostatic Pressing (HIPing). Additional heat treatment of some samples allowed them to regain the original strength of Al 6061-T6, which was annealed during HIPing. The high-strain-rate deformation resulted in the strength increase for both types of samples (with and without the heat treatment) compared to quasi-static deformation. Samples after additional heat treatment exhibited higher dynamic strength. We consider that the strain rate sensitivity of the composite samples is caused by W fibers, which are responsible for the high strength of the samples and mechanism of their fracture.After dynamic tests, the Al matrix was chemically removed from the heavily deformed samples to reveal the mode of deformation of the W fibers: microbuckling and kinking in the axial direction. These mechanisms initiated the fracture of the composite samples followed by sample bulging due to plastic flow of the Al matrix and the subsequent fracture of W fibers in the hoop direction.