Semi-Solid Casting of Metal Matrix Nanocomposites

Abstract:

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Semi-solid casting (SSC) techniques have proven useful in the mass production of high integrity castings for the automotive and other industries. Recent research has shown metal matrix nanocomposite (MMNC) materials to have greatly improved properties in comparison to their base metals. However, current methods of MMNC production are costly and time consuming. Thus development of a process that combines the integrity and cost effectiveness of semi-solid casting with the property improvement of MMNCs would have the potential to greatly improve cast part quality available to engineers in a wide variety of industries. This paper presents a method of combining SSC with MMNC in a way that benefits from MMNCs’ tendency to naturally form the globular microstructure necessary for SSC. This method uses ultrasonically dispersed nanoparticles as nucleating agents to achieve globular primary grains such that fluidity is maintained even at high solid fractions. Once particle dispersion is achieved, the material needs no further processing to become a semi-solid slurry of globular primary grains as it cools. This quiescent method of slurry production, while still imposing some constraints on cooling rates, has a large process window making this process capable of industrial rates of throughput. It was found that the key factor to achieving globular microstructure is a sufficiently slow cooling rate at the onset of solidification such that particle-induced nucleation can occur. Once nucleation occurs, continued cooling is virtually unconstrained, with globular microstructure evident in quenched samples as well as samples cooled at rates as slow as 1 °C/min. This method was demonstrated in several material systems using zinc (Zn), aluminum (Al), and magnesium (Mg) alloys and nanoparticles of aluminum oxide (Al2O3), silicon carbide (SiC), and titanium oxide (TiO2). Additionally, several nucleation models are examined for applicability to nanoscale composites.

Info:

Periodical:

Solid State Phenomena (Volumes 116-117)

Edited by:

C.G. Kang, S.K. Kim and S.Y. Lee

Pages:

478-483

DOI:

10.4028/www.scientific.net/SSP.116-117.478

Citation:

M. De Cicco et al., "Semi-Solid Casting of Metal Matrix Nanocomposites", Solid State Phenomena, Vols. 116-117, pp. 478-483, 2006

Online since:

October 2006

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Price:

$35.00

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