Effect of cold rolling on precipitation processes in Al-Mn-Sc-Zr alloy

Thermal, mechanical and electrical properties and microstructure of the as-cast and cold-rolled AlMn-ScZr alloys were studied. Samples were isochronally annealed up to 570 degrees C. The electrical resistometry and microhardness together with differential scanning calorimetry measurements were compared to microstructure development that was observed by transmission and scanning electron microscopy and also X-ray diffraction. Due to fine, coherent, and uniformly distributed Al3Sc particles, the hardening effect occurred in the studied alloys. The cold rolling at room temperature that was prior to a heat treatment has no substantial effect on temperature range of the Al3Sc-phase precipitation. However, the cold rolling accelerates the precipitation of Mn-containing particles. This precipitation is dependent on deformation degree. The formation of Mn-containing particles is responsible for the intensive resistivity decrease in the cold-rolled materials compared to the as-cast material. The apparent activation energy for precipitation of the Al3Sc and Al6Mn particles in the cold-rolled AlMnScZr alloy was determined as 116 +/- 9 kJ mol(-1) and 162 +/- 22 kJ mol(-1) respectively. (C) 2012 Elsevier B.V. All rights reserved.