Characterization of dynamic recrystallisation in as-homogenized Mg-Zn-Y-Zr alloy using processing map

The hot working behavior of a as-homogenized Mg-Zn-Y-Zr alloy has been investigated in the temperature range 200-400 degrees C and strain rate range 0.0015-7.5 s(-1) using processing map. The power dissipation map reveals that a domain of dynamic recrystallisation (DRX) in the temperature range 300-400 degrees C and strain rate range 0.0015-0.15 s(-1), with its peak efficiency of 38% at 350 degrees C and 0.0015 s(-1), which are the optimum hot working parameters. The apparent activation energy in the hot deformation process is 148 +/- 3 KJ/mol that is larger than that of ZK60 alloy because of the obstruction of Y atoms for diffusion. DRX model indicates that DRX of Mg-Zn-Y-Zr alloy is controlled by the rate of nucleation, which is lower one order of magnitude than growth. And the rate of nucleation depends on the process of mechanical recovery by cross-slip of screw dislocations. (c) 2006 Springer Science+ Business Media, Inc.