A methodology for the creation of 304LSS-CNT metal matrix composites using the mechanical alloying approach is presented. Planetary ball milled powders were both melted and hot pressed and achieved up to 96% theoretical density. High resolution scanning electron microscopy, Scanning Transmission Electron Microscopy, X-ray diffraction, energy dispersive spectroscopy, thermal diffusivity measurements, and Vickers microhardness measurements are used to characterize as processed and heat treated composites. Melted and solidified samples show highly anisotropic austenite/martensite microstructures with the presence of large dendritic carbon agglomerations, while hot-pressed samples show equiaxed austenite/martensite grains with a large number density of carbide precipitates. Grain size and thermal diffusivity decrease while microhardness increases up to 36% with up to 2% carbon nanotube addition for hot-pressed samples. Thus, mechanical alloying has been shown to be a potential option for the production of homogeneous 304LSS-CNT metal matrix composites for applications requiring increased strength.
A challenging issue in armor mechanics is to optimize the impact resistance of a target per unit areal mass. Herein, the penetration resistance of an A356 alloy–ceramic lattice structure with ceramic tiles encapsulated in the metal matrix is experimentally and computationally studied to achieve this objective. A hybrid additive manufacturing/metal‐casting technique is used to fabricate the structure. The performance is experimentally evaluated by impacting the tiles at normal incidence with 0.30‐cal armor‐piercing projectiles and 7.62 M80 rounds traveling at high speed. X‐ray imaging and electron microscopy techniques are used to ascertain the quality of the castings and the damage caused to the target by the projectiles. The cast material is tested following ASTM standard E8/E8M to determine the yield stress and hardening coefficients in the Johnson–Cook model. Large deformations of the components are analyzed using the finite element software LS‐DYNA. The penetrator's computed residual velocities differ from their test values by less than 4% for the 0.30‐cal projectiles and 19% for the ball rounds. The effects of several design variables (e.g., tile thickness and location, among others) are numerically scrutinized. The proposed design is ≈20% lighter than the solid metal target to achieve the same residual velocity of the penetrator.
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