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Self-consolidation mechanism of nanostructured Ti5Si3 compact induced by electrical discharge.

Lee WH, Cheon YW, Jo YH, Seong JG, Jo YJ, Kim YH, Noh MS, Jeong HG, Van Tyne CJ, Chang SY - ScientificWorldJournal (2015)

Bottom Line: A solid bulk of nanostructured Ti5Si3 with no compositional deviation was obtained in times as short as 159 μsec by the discharge.Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3 compact.Complete conversion yielding a single phase Ti5Si3 is primarily dominated by the solid-liquid mechanism.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 143-747, Republic of Korea.

ABSTRACT
Electrical discharge using a capacitance of 450 μF at 7.0 and 8.0 kJ input energies was applied to mechanical alloyed Ti5Si3 powder without applying any external pressure. A solid bulk of nanostructured Ti5Si3 with no compositional deviation was obtained in times as short as 159 μsec by the discharge. During an electrical discharge, the heat generated is the required parameter possibly to melt the Ti5Si3 particles and the pinch force can pressurize the melted powder without allowing the formation of pores. Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3 compact. Three stepped processes during an electrical discharge for the formation of nanostructured Ti5Si3 compact are proposed: (a) a physical breakdown of the surface oxide of Ti5Si3 powder particles, (b) melting and condensation of Ti5Si3 powder by the heat and pinch pressure, respectively, and (c) rapid cooling for the preservation of nanostructure. Complete conversion yielding a single phase Ti5Si3 is primarily dominated by the solid-liquid mechanism.

No MeSH data available.


Related in: MedlinePlus

SEM micrographs of the cross-sections of consolidated Ti5Si3 compacts obtained by (a) hot-pressing at 1200°C in a vacuum of 2 × 10−6 torr for two hours with a pressure of 10 tons and electrical discharge consolidation using (b) 7.0 kJ and (c) 8.0 kJ of input energy.
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fig4: SEM micrographs of the cross-sections of consolidated Ti5Si3 compacts obtained by (a) hot-pressing at 1200°C in a vacuum of 2 × 10−6 torr for two hours with a pressure of 10 tons and electrical discharge consolidation using (b) 7.0 kJ and (c) 8.0 kJ of input energy.

Mentions: The MAed Ti5Si3 powder was consolidated by a conventional hot-pressing process. As shown in Figure 4(a), the consolidation process at 1200°C in a vacuum of 2 × 10−6 torr for two hours by applying a pressure of 10 tons did not successfully produce the compact in a bulk type, resulting in the formation of a porous structure. As listed in Table 1, the hardness of MAed Ti5Si3 powder was found to be about Hv 1120, but that of the hot-pressed Ti5Si3 compact decreased down to Hv 800. The decreased hardness can be attributed to the release of strain energy during a hot-pressing and also to the porous structure of the compact. The cross-section views of EDC Ti5Si3 compacts at the input energy of 7.0 and 8.0 kJ are shown in Figures 4(b) and 4(c), respectively. The compacts were composed of powder particles that were completely deformed and welded together by the electrical discharge. The density of the solid core of EDC Ti5Si3 compacts is approximately ~99% of theoretical value. From XRD patterns of the EDC Ti5Si3 compacts as shown in Figure 5, only peaks corresponding to the phase of Ti5Si3 have been found. It can be known that the unique phase of Ti5Si3 has not been altered by the electrical discharge process. The average crystallite size of EDC Ti5Si3 compacts was determined as 93–101 nm by using Suryanarayana and Grant Norton's formula [19]. Measured hardness of EDC Ti5Si3 compacts is also listed in Table 1, indicating that the hardness can be increased by the electrical discharge.


Self-consolidation mechanism of nanostructured Ti5Si3 compact induced by electrical discharge.

Lee WH, Cheon YW, Jo YH, Seong JG, Jo YJ, Kim YH, Noh MS, Jeong HG, Van Tyne CJ, Chang SY - ScientificWorldJournal (2015)

SEM micrographs of the cross-sections of consolidated Ti5Si3 compacts obtained by (a) hot-pressing at 1200°C in a vacuum of 2 × 10−6 torr for two hours with a pressure of 10 tons and electrical discharge consolidation using (b) 7.0 kJ and (c) 8.0 kJ of input energy.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4389978&req=5

fig4: SEM micrographs of the cross-sections of consolidated Ti5Si3 compacts obtained by (a) hot-pressing at 1200°C in a vacuum of 2 × 10−6 torr for two hours with a pressure of 10 tons and electrical discharge consolidation using (b) 7.0 kJ and (c) 8.0 kJ of input energy.
Mentions: The MAed Ti5Si3 powder was consolidated by a conventional hot-pressing process. As shown in Figure 4(a), the consolidation process at 1200°C in a vacuum of 2 × 10−6 torr for two hours by applying a pressure of 10 tons did not successfully produce the compact in a bulk type, resulting in the formation of a porous structure. As listed in Table 1, the hardness of MAed Ti5Si3 powder was found to be about Hv 1120, but that of the hot-pressed Ti5Si3 compact decreased down to Hv 800. The decreased hardness can be attributed to the release of strain energy during a hot-pressing and also to the porous structure of the compact. The cross-section views of EDC Ti5Si3 compacts at the input energy of 7.0 and 8.0 kJ are shown in Figures 4(b) and 4(c), respectively. The compacts were composed of powder particles that were completely deformed and welded together by the electrical discharge. The density of the solid core of EDC Ti5Si3 compacts is approximately ~99% of theoretical value. From XRD patterns of the EDC Ti5Si3 compacts as shown in Figure 5, only peaks corresponding to the phase of Ti5Si3 have been found. It can be known that the unique phase of Ti5Si3 has not been altered by the electrical discharge process. The average crystallite size of EDC Ti5Si3 compacts was determined as 93–101 nm by using Suryanarayana and Grant Norton's formula [19]. Measured hardness of EDC Ti5Si3 compacts is also listed in Table 1, indicating that the hardness can be increased by the electrical discharge.

Bottom Line: A solid bulk of nanostructured Ti5Si3 with no compositional deviation was obtained in times as short as 159 μsec by the discharge.Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3 compact.Complete conversion yielding a single phase Ti5Si3 is primarily dominated by the solid-liquid mechanism.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 143-747, Republic of Korea.

ABSTRACT
Electrical discharge using a capacitance of 450 μF at 7.0 and 8.0 kJ input energies was applied to mechanical alloyed Ti5Si3 powder without applying any external pressure. A solid bulk of nanostructured Ti5Si3 with no compositional deviation was obtained in times as short as 159 μsec by the discharge. During an electrical discharge, the heat generated is the required parameter possibly to melt the Ti5Si3 particles and the pinch force can pressurize the melted powder without allowing the formation of pores. Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3 compact. Three stepped processes during an electrical discharge for the formation of nanostructured Ti5Si3 compact are proposed: (a) a physical breakdown of the surface oxide of Ti5Si3 powder particles, (b) melting and condensation of Ti5Si3 powder by the heat and pinch pressure, respectively, and (c) rapid cooling for the preservation of nanostructure. Complete conversion yielding a single phase Ti5Si3 is primarily dominated by the solid-liquid mechanism.

No MeSH data available.


Related in: MedlinePlus