Superplasticity

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Superplasticity is an intriguing inelastic capability in solid materials to deform (tensile elongation can be more than 2000%) appearing in high homologous temperature under exceptionally low stress, which is strongly dependent on strain rate. There are two kinds of superplasticity: fine-structure superplasticity (FSS) and internal-stress superplasticity (ISS) (Motyka & Sieniawski 2007: 123). While all materials do not exhibit superplasticity, there are a wide range of materials that shows this behavior at some specific loading conditions and temperature. According to Chandra (2002: 461), materials including metals, ceramics, metallic/intermetallic/ceramics matrix composites, intermetallic and Nano crystalline materials exhibit superplasticity characteristics. Highasi holds the current world record in elongation of metals; by using commercial bronze, he managed to elongate it 8000% as shown in figure 1 (Chandra 2002: 461).

When it comes to superplasticity, grain size, temperature and strain rate has a direct correlation. It is maintained by Koch (2000: 99) that as grain size is decreased it is found that the temperature is lowered at which superplasticity occurs, and the strain rate for its occurrence is increased.

There are a few materials that possessed superplasticity characteristic. For example there are aluminum alloys, magnesium alloys and titanium alloys.

Table For Aluminum Alloys

Table for Magnesium Alloy

Table for Titanium Alloys

This phenomenon allows designers to make complex and detailed designs to be in apiece structure. It is maintained that superplastic forming also enhances design freedom, minimizes the amount of scrap produced, and reduces the need for machining. In addition, it reduces the amount of material used, thereby lowering overall material costs (Tan, Thiruvarudchelvan & Liew 2004).

Bibliography

Motyka, M. & Sieniawski, J. 2007. ‘Superplasticity in Titanium Alloys.’...
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