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Friction Stir Casting Modification

Casting is a very widely used manufacturing technique because of its unique ability to produce complex shaped part at low cost. However, its performance is limited by many metallurgical features, such as, dendritic porosity, particulate oxides/inclusions, secondary dendritic arm spacing (SDAS), and iron-phase intermetallics. FSP provides an unique opportunity to embed ‘wrought’ microstructure in ‘cast’ component by localized modification. Such approach for components requiring higher performance would lead to the best combination, low overall cost due to casting and higher performance in localized areas due to wrought microstructure. Table 4 gives an example of localized property improvement in A356 aluminum alloy. FSP results in dramatic improvement of ductility and strength. Testing of multiple specimens showed very significant improvement in Weibull modulus and quality index (often used for castings).

Table 4. Tensile properties of as-cast and FSP A356 at room temperature using mini-tensile specimens.
  UTS, MPa YS, MPa El., %


As FSP (700rpm/8ipm)

FSP + T6 (700rpm/8ipm)

169 ± 10

251 ± 5

301 ± 7

132 ± 5

171 ± 14

216 ± 14

3 ± 1

31 ± 1

28 ± 3