Low superheat pouring with a Shear Field in rheocasting of aluminum alloys

Abstract

A new rheocasting process, Low Superheat Pouring with a Shear Field (LSPSF), was developed to produce semi-solid slurry for the rheo-forming process. The LSPSF process is one of controlled nucleation and limited growth techniques in which effective nucleation rate is controlled by passive mixing and localized rapid cooling near the liquidus temperature; dendrite growth is limited by a much slower cooling process. The experimental results of rheocast Al-Cu alloy 201 and secondary diecasting alloy A380 demonstrate that LSPSF process is capable of producing high-quality slurry in a matter of seconds. It is concluded that maximizing nucleation and nuclei survival directly lead to the grain refinement of the rheocasting microstructure, and high nuclei density combined with a slower cooling afterwards leads to a globular structure of primary phases.

Keywords

semi-solid processing / aluminum alloys / nucleation / grain growth

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