High pressure die casting is widely used for the possibility of obtaining net-shape components of complex geometry and thin wall thickness at high production rates. Unfortunately, conventional die casting has a major limitation that is the presence of defects, which prevents its use on a larger scale. Semi-solid metalworking is a complex process to obtain high integrity die casting components. During semi-solid process a partially liquid–partially solid metal mixture is injected into the die cavity. Castings produced using semi-solid process with hypo-eutectic Al-Si alloys have little or no defects with higher mechanical properties. The non-dendritic microstructure is constituted of solid phase globules, surrounded by an Al-Si eutectic matrix. This paper describes the influence of temperature and time on the obtaining of such globular microstructure during partial remelting and isothermal holding of an A356 thixocasting alloy. Dynamic observations of microstructural evolution with respect to temperature and time are then in-situ monitored by heating the thixocasting specimens in an environmental scanning electron microscope (ESEM) provided by a heating stage module.

Microstructural evolution in semi-solid A356 alloy during partial remelting

BONOLLO, FRANCO;TIMELLI, GIULIO;
2007

Abstract

High pressure die casting is widely used for the possibility of obtaining net-shape components of complex geometry and thin wall thickness at high production rates. Unfortunately, conventional die casting has a major limitation that is the presence of defects, which prevents its use on a larger scale. Semi-solid metalworking is a complex process to obtain high integrity die casting components. During semi-solid process a partially liquid–partially solid metal mixture is injected into the die cavity. Castings produced using semi-solid process with hypo-eutectic Al-Si alloys have little or no defects with higher mechanical properties. The non-dendritic microstructure is constituted of solid phase globules, surrounded by an Al-Si eutectic matrix. This paper describes the influence of temperature and time on the obtaining of such globular microstructure during partial remelting and isothermal holding of an A356 thixocasting alloy. Dynamic observations of microstructural evolution with respect to temperature and time are then in-situ monitored by heating the thixocasting specimens in an environmental scanning electron microscope (ESEM) provided by a heating stage module.
2007
EUROMAT 2007
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2531477
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