Deformation behavior of nanocrystalline Zn-22wt%Al alloy using thermornechanical controlling process

The deformation behavior of nanocrystalline Zn-22mass%Al alloy that was produced by using the ThermoMechanical Controlling Process (TMCP) technology had been characterized over a wide range of strain rates between 10(-6) to 10(-1) s(-1) in air at temperatures from 273 to 473 K. The microstructure of Zn-22mass%Al alloy by means of the TMCP technology had both a random distribution of equiaxed Al-rich and Zn-rich phases with grain size of 1.3 mum. and many nanocrystalline Zn particles in Al-rich phases. Since the flow stress in the deformation near room temperature was much larger than that in superplastic deformation and a maximum m-value is only 0.3 (n = 3) at low strain rates below 10(-5) s(-1), the pure superplastic behavior may not be observed near room temperature. However it was noted that the large elongation of similar to200% was observed at 10(-5) s(-1). It seems that the various mechanisms contribute to the deformation at room temperature because the m-value strongly depends on the testing temperature.