Electromagnetic processing during directional solidification of particle strengthened Aluminum alloys for additive manufacturing

Rise of metal additive manufacturing technology has increased the demand for high performance alloys such as metal matrix composites (MMC). Metallurgical production of MMC remains a challenge. The nano-powder of dielectric particles does not mix well into the liquid metal because of several reasons. On a macroscopic level, the powder is rejected by the molten metal through buoyancy and surface tension forces. On a microscopic level, the particles are held together by Van der Waals forces forming particle agglomerates. Our research strategy is to address these issues separately in two steps. We are investigating electromagnetically assisted MMC casting method for production of particle strengthened directionally solidified aluminum alloys. In the first step, nanoparticles are mixed into melt while it is in a semi-solid state by efficient permanent magnet stirrers. Then the alloy is subjected to ultrasound treatment for fine particle dispersion. Semi-continuous casting of MMC is used to obtain material for additive manufacturing process. Material is casted in 6-20 mm rod by direct chill casting method, which can be made into wire with the application in wire-feed additive manufacturing. We investigate the possibility to improve Al alloy SiC composite material properties by applying electromagnetic interaction during solidification. Electric current and moderate static magnetic field (0.1-0.5 T) creates melt convection in mushy zone. Such interaction enhances heat and mass transfer near the solidification interface and hinders the reagglomeration of the added particles.