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 AlMnScZr alloys were studied. Samples were isochronally annealed up to 570 °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.