Hot deformation behavior and workability characteristics of bimodal size SiCp/AZ91 magnesium matrix composite with processing map

The hot deformation behavior of (0.2 um 1.5 vol.% + 10 um8.5 vol.%) bimodal size SiCp/AZ91 magnesium matrix composite fabricated by stir casting was investigated at the temperature of 270-420 degrees C and strain rate of 0.001-1 S (1). The flow stress at the strain of 0.5 was used for kinetic analysis. Results indicate that dislocation climb is likely to be the main deformation mechanism responsible for the present composite. By evaluating the efficiencies of power dissipation and instability parameters, the processing maps are developed to optimize the hot working processing. Two domains of dynamic recrystallization are found in the processing map. One exists at the temperature of 270-370 degrees C and strain rate of 0.001-0.01 s (1) with maximum dissipation efficiency of 38%; the other exists at 420 degrees C and 0.01 s (1) with peak dissipation efficiency of 24%. The instability region of flow behavior can also be recognized at the temperature of 270320 degrees C and the strain rate of 0.1-1 s (1). The characteristic microstructures predicted from the processing map agree well with the result of microstructure observations. (C) 2014 Elsevier Ltd. All rights reserved.