J. Mater. Sci. Technol. ›› 2012, Vol. 28 ›› Issue (11): 1025-1030.

• Novel Processing and Characterization Methods • Previous Articles     Next Articles

High Strain Rate Superplasticity in a Micro-grained Al–Mg–Sc Alloy with Predominant High Angle Grain Boundaries

F.C. Liu1,2), Z.Y. Ma1), F.C. Zhang2)   

  1. 1) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
    2) State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China
  • Received:2011-09-19 Revised:2011-11-16 Online:2012-11-09 Published:2012-11-09
  • Contact: Z.Y. Ma
  • Supported by:

    National Natural Science Foundation of China under Grant Nos. 50671103 and 50871111 and the National Outstanding Young Scientist Foundation of China under Grant Nos. 50525103 and 50925522

Abstract:

Friction stir processing (FSP) was applied to extruded Al–Mg–Sc alloy to produce fine-grained microstructure with a grain size of 2.2 µm. Electron backscatter diffraction (EBSD) result showed that the grain boundary misorientation distribution was very close to a random grain assembly for randomly oriented cubes. Super-plastic investigations in the temperature range of 425–500 °C and strain rate range of 1×10-2–1×100 s-1 showed that a maximum elongation of 1500% was achieved at 475 °C and a high strain rate of 1×10-1 s-1. The FSP Al–Mg–Sc exhibited enhanced superplastic deformation kinetics compared to that predicted by the constitutive relationship for superplasticity in fine-grained aluminum alloys. The origin for enhanced superplastic deformation kinetics in the FSP alloy can be attributed to its high fraction of high angle grain boundaries (HAGBs). The analyses of the superplastic data and scanning electron microscopy (SEM) examinations on the surfaces of deformed specimens indicated that grain boundary sliding is the main superplastic deformation
mechanism for the FSP Al–Mg–Sc alloy.

Key words: Superplasticity ,  Friction stir processing ,  Aluminum ,  Microstructure ,  Friction stir welding