The Effect of Powder Particle Size on Mechanical and Fracture Properties of Cold Sprayed Al

Thick deposits were produced from pure Al powder of three different sieve sizes using cold spraying at the same process parameters. The in-plane mechanical and fracture properties of the deposits were investigated using bending of small specimens in four specimen orientations. It was shown that increasing the Al particle size by approximately 50% and 100% leads to small, but statistically significant differences of yield strength. Further, the increase in the powder particle size led to higher fracture toughness K_IC but lower fatigue crack growth threshold ΔK_thr. This can be attributed to two different fracture mechanisms in the cold sprayed deposits. A trans-particular fracture in the near-threshold fatigue regime is controlled by the microstructure and work hardening of the particles. At higher cyclic loads and in quasi-static regime, the particle decohesion and the resulting crack path determine the fracture behavior instead. However, the observed effect of particle size was rather small, much smaller than the effect of spray process parameters observed in the previous research.