Abstract
Microstructure, thermal, electrical and mechanical properties of the hot-extruded and hot-rolled AlMnScZr alloys were studied. The electrical resistometry and microhardness together with differential scanning calorimetry measurements were compared with microstructure development observed by transmission electron microscopy, X-ray diffraction, and electron backscatter diffraction.
Fine subgrain or grain structure developed and fine coherent AL(3)(Sc,Zr) particles precipitated during hot deformation and subsequent cooling. The distinct resistivity changes are mainly caused by precipitation of Mn-containing particles.
The pronounced two-stage development of the AL(6)(Mn,Fe)-phase precipitation was observed. Nevertheless, the precipitation has a negligible effect on microhardness.
The presence of the Mn-containing particles with a size of similar to 50 nm inside subgrains or grains and similar to 2 mu m at subgrain or grain boundaries has a significant antirecrystallization effect. The combination of Mn, Sc and Zr additions to Al suppresses recrystallization during isothermal annealing at 550 degrees C.
Hot deformation has no effect on the apparent activation energy values of the Al3Sc-phase precipitation (Q = 109 kJ mol(-1)) and Al6Mn-phase precipitation (Q = 156 kJ mol(-1)).