Characterization of hot deformation behavior of a Zn-10.2Al-2.1Cu alloy using processing maps

The hot deformation behavior of Zn82.7-Al10.2-Cu2.1 (in wt.%) was investigated by means of hot compression tests in the temperature range of 180-330 degrees C and strain rate range of 0.01-10 s(-1). Processing maps were developed on the basis of experimental data and using the principles of the dynamic materials model (DMM). The results show that the maximum stress decreases with decreasing strain rate and increasing temperature, and that the activation energy is about 141.895 kJ/mol. It is found that the strain has insignificant effect on the power dissipation maps. The maps exhibit two domains. The first domain occurs in the temperature range of 218-270 degrees C and strain rate range of 0.04-1.2 s(-1) with the peak efficiency of 0.53. The second domain occurs in the temperature range of 290-330 degrees C and strain rate range of 0.01-0.18 s(-1) with the peak efficiency of 0.58. Microstructural observations reveal that the partial dynamic recrystallization (DRX) of the Zn-rich phase occurs in the first domain and the full DRX of that occurs in the second domain. The dendritic structure is partially fragmented and elongated within the eutectic matrix and some initial laminar Al-rich phase is transformed into a spherical shape in the two domains. The large regime of flow instability is observed at the higher strain rates and all the tested temperatures with strain higher than 0.3. It expands when strain is increased. The flow instability predicted by processing maps is manifested as adiabatic shear bands, micro-cracks and macro-shear cracks. (C) 2012 Elsevier Ltd. All rights reserved.