ISSN:
1662-9779
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Physics
Notes:
Ever since copious nucleation was shown to be an efficient, cost effective method for producingsemi-solid slurry, many processes have been developed to take advantage of the cost savingsinherent in this method of slurry production. Despite great advances in various aspects of semi-solidprocessing, the cost competitive nature of the industry, most noticeably the auto industry, hasprevented a wider adoption of semi-solid casting technology. This research aims to realize a moreindustrial appealing process by combining the synergistic benefits of semi-solid casting technologywith metal matrix nanocomposite (MMNC) technology, thus creating higher value products withsuperior properties cost-effectively. To do this, a process that produces a semi-solid slurry thoughthe nucleation catalysis induced by nanoparticle additions as small as 1 wt. % to alloys is proposedand the results are presented in this paper. Examination of the potential for nano-scale inoculants tocatalyze nucleation of solidification showed that despite their small sizes, inoculants on the scale oftens of nanometers are capable of catalyzing nucleation in the zinc and aluminum alloys studied.Employing the differential scanning calorimetry (DSC), differential thermal analysis (DTA), anddroplet emulsion techniques with nanocomposite samples showed a significant reduction inundercooling owing to the homogeneous distribution of nanoparticles by ultrasonic mixing and thepotency of those nanoparticles to catalyze nucleation. Comparison of undercoolings betweendifferent types of nanoparticles, such as silicon carbide (SiC), gamma and alpha alumina (Al2O3),and titanium carbide (TiC), to relative potencies predicted by minimum lattice disregistry showed astrong correlation. Results were also examined in light of free growth and nucleation controlledgrain initiation. For nanoparticles predicted to be potent nucleation catalysts by lattice disregistry,the undercoolings observed fell into the free growth controlled grain initiation regime
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.141-143.487.pdf
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