Structure and superplasticity of the Al-Mg-TM alloy after equal channel angular pressing and rolling

The microstructure and superplastic characteristics of the commercial alloy 1570C (Al-5Mg-0.18Mn-0.2Sc-0.08Zr-0.01Fe-0.01Si, wt.%) subjected to equal channel angular pressing (ECAP) at the temperature of 325 degrees C (about 0.6T(m)) to the effective strain of 8 and subsequent isothermal rolling at the same and room temperatures with reductions 86 and 80 %, respectively, were compared. It has been found that the development of ultrafine grained structure under ECAP with the grain size of about 1 mu m and the volume fraction of 0.60 - 0.70 led to the unique alloy superplastic properties with the maximum elongations-to-failure up to 3300 % in a wide temperature-strain rate range. Subsequent warm rolling resulted in increased to 0.80 - 0.85 volume fraction of ultrafine grains with no changes in their size, while cold rolling, in contrast, provided a heavily deformed (work hardened) structure with a high dislocation density. Despite such difference in the structures formed, the alloy superplastic behavior in both rolled states was nearly similar with maximum elongations about 2800 % at the temperature of 520 degrees C and the strain rate of 1.4 x 10(-2) s(-1). Also, roughly similar microstructures were developed under such optimum alloy superplastic deformation conditions, irrespectively of its rolling temperature.