Mechanical behavior of freeze-cast Ti foams with varied porosity

Abstract

Titanium (Ti) foams with relative densities of 0.32, 0.37, and 0.49 were processed via freeze casting. The mechanical characteristics of samples with different porosities were studied in uniaxial compression tests at initial strain rates between 0.001 and 0.5 s−1. According to the results, the stress–strain response does not significantly depend on the strain rate, at least up to the applied maximum stress, which corresponds to 0.1–0.3 engineering strain. In-situ acoustic emission (AE) experiments have revealed that the stress drop beyond the maximum stress corresponds to the formation and propagation of macrocracks. However, cracks were also initiated below the maximum stress, particularly, in samples with higher relative densities. The analysis of the Young's modulus and yield strength versus the porosity exhibits a power law relationship with a high exponent (approximately 4–5). This high exponent is reasonable if the decrease in the porosity level is associated with a change in the deformation mechanism from the compression model to the Gibson–Ashby (GA) model between 0.37 and 0.49 relative density.