Hot deformation behavior and microstructure evolution of twin-roll-cast Mg-2.9Al-0.9Zn alloy: A study with processing map

The hot deformation behavior and microstructure evolution of twin-roll-cast of Mg-2.9Al-0.9Zn-0.4Mn (AZ31) alloy has been studied using the processing map. The tensile tests were conducted in the temperature range of 150-400 degrees C and the strain rate range of 0.0004-4 s(-1) to establish the processing map. The different efficiency domains and flow instability region corresponding to various microstructural characteristics have been identified as follows: (i) the continuous dynamic recrystallization (CDRX) domain in the range of 200-280 degrees C/<= 0.004 s(-1) with fine grains which provides a potential for warm deformation such as deep drawing; (ii) the discontinuous dynamic recrystallization (DDRX) domain around 400 degrees C at high strain rate (0.4 s(-1) and above) with excellent elongation which can be utilized for forging, extrusion and rolling; (iii) the grain boundary sliding (GBS) domain at Slow Strain Fate (below 0.004 s-1) above 350 degrees C appears abundant of cavities, which result in fracture and reduce the ductility of the adopted material; and (iv) the flow instability region which locates at the upper left of the processing map shows the metallographic feature of flow localization. (C) 2008 Elsevier B.V. All rights reserved.