In situ manipulation of cooling rates during planar-flow melt spinning processing

Planar-flow melt spinning (PFMS) is a single stage rapid manufacturing/solidification technique for producing thin metallic sheet or foil. A new technology, envisioned to allow real-time manipulation of the local cooling rates and properties in melt-spun ribbon, has been tested successfully when casting Al–7%Si. Pulsed laser heating, directed low on the upstream meniscus, or on the substrate, leaves patterns of ‘dimples’ in the ribbon. Typical cooling rates of 104 K/s have been measured using a control-volume approach. Secondary dendrite arm spacing (SDAS) has been measured through the thickness of ribbons showing areas both affected by the laser heating and unaffected by the laser. Through a correlation of cooling rates and SDAS, it is shown that the unmodified ribbon has an average cooling rate similar to that measured macroscopically. The cooling rate underneath a laser dimple is estimated to be six times slower near the contact surface. It is envisioned that the technology described may bring the concept of ‘casting-by-design’ one step closer to realization.