Response of aluminum alloys to particle impacts

Two aluminum alloys, annealed 1100 and 7075-T6 were exposed to a stream of erosive particles in the room-temperature erosion tester at Lawrence Berkeley Laboratory. Spherical steel shot 600 to 700 μm in diameter, traveling 45 m/s at 25°C, and impacting at 30° incidence angle, were used to erode the samples until a steady-state condition was reached. Results indicate the following. Surface hardening is greater after multiple-particle impacts. Hardening extends to some constant depth below the original surface, and ripples appear to be constituted of work-hardened material that has accumulated by impact-induced plastic deformation. A model of material removal based on some form of critical strain criteria rather than a fracture flow stress is suggested.