Friction stir processing of AS-CAST AA5083 Superplastic response
Hayashi, John Toshio
McNelley, Terry R.
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Plates of continuously cast AA5083 were subjected to friction stir processing (FSP) by three overlapping plunge and traverses. The FSP used a threaded pin tool with a pin diameter of 3 mm, pin length of 3 mm and a shoulder diameter of 10 mm. The process was run at constant tool rotation and traverse speeds of 800 rpm and 76.2 mm min-1, respectively. The microstructure of the processed region was examined by optical microscopy and orientation imaging microscopy. FSP of the AA5083 reduced the average grain size from approximately 60 um in the base metal to 3-4 um in the processed zone. In addition, it created a homogeneous microstructure and, in particular, a refined and homogenous particle distribution without damage to the particles. Large tensile samples with gage sections of 1x3x8 mm were prepared by wire EDM for high-temperature tension testing. Tensile tests were carried out at 450 degrees C under different strain rates. The relationship between strain rate and elongation was established. A maximum superplastic elongation of ~550% was obtained at a strain rate of 3 x 10-3 s-1. The formation mechanism of refined grain structure and the superplastic characteristic of FSP material will be discussed in this paper