Friction Stir Processing Alloy Research Articles

Effect of friction stir processing on the kinetics of superplastic deformation in an Al-Mg-Zr alloy

The effect of friction stir processing on the superplastic behavior of extruded Al-4Mg-1Zr was examined at 350 °C to 600 °C and at initial strain rates of 1×10−3 to 1 s−1. A combination of a fine grain size of 1.5 μm and high-angle grain boundaries in the friction stir-processed (FSP) alloy led to considerably enhanced superplastic ductility, much-reduced flow stress, and a shift to a higher optimum strain rate and lower optimum temperature. The as-extruded alloy exhibited the highest superplastic ductility of 1015 pct at 580 °C and an initial strain rate of 1×10−2s−1, whereas a maximum elongation of 1280 pct was obtained at 525 °C and an initial strain rate of 1×10−1s−1 for the FSP alloy. The FSP alloy exhibited enhanced superplastic deformation kinetics compared to that predicted by the constitutive relationship for superplasticity in fine-grained aluminum alloys. A possible origin for enhanced superplastic deformation kinetics in the FSP condition is proposed.

High strain rate superplasticity in friction stir processed Al–Mg–Zr alloy

Al–4Mg–1Zr extruded bar was subjected to friction stir processing (FSP), resulting in generation of a fine microstructure of 1.5 μm grain size. Superplastic deformation behavior of FSP Al–4Mg–1Zr alloy was investigated in strain rate range of 1×10 −3 to 1 s −1 and temperature range of 350–550 °C and compared with that of as-rolled one. It is indicated that the FSP alloy exhibited significantly enhanced superplasticity at a high strain rate of 1×10 −1 s −1, and a maximum elongation of 1280% was obtained at 525 °C and 1×10 −1 s −1. Further, the FSP Al–4Mg–1Zr alloy exhibited excellent thermal stability at high temperature, and a large elongation of 1210% was observed at 550 °C and 1×10 −1 s −1. Moreover, FSP resulted in a significant decrease in the flow stress in Al–4Mg–1Zr alloy. At a strain rate of 1×10 −2 s −1, the flow stress (∼7 MPa) of FSP Al–4Mg–1Zr at 450 °C was comparable to that of as-rolled alloy at 550 °C.