Abstract
The effect of cold-rolling on mechanical and electrical properties, microstructure and recrystallization behaviour of the AlMn, AlScZr and AlMnScZr alloys was studied. The materials were investigated during isothermal annealing at 300, 400, 500 and 550 oC and during step-by-step quasilinear annealing from 200 C up to 600oC with a heating rate of 100 K/h followed by subsequent isothermal annealing at 600oC/5 h.
Precipitation reactions were studied by electrical resistometry and (micro)hardness measurements. The microstructure development was investigated by electron microscopy and electron backscatter diffraction examinations.
The hardening effect is due to uniformly distributed Al3Sc and/or Al3(Sc,Zr) particles. The distinct changes in resistivity of the alloys above ~ 300oC are mainly caused by precipitation of Mn-containing particles.
It has a negligible effect on hardness. Phase transformations in the AlMn and AlMnScZr alloys are highly enhanced by cold rolling.
The precipitation is dependent on the deformation degree - the more deformation the more intensive precipitation of the Mn-containing particles. The combination of Mn, Sc and Zr additions to Al substantially suppresses recrystallization at 550oC.
A partial recrystallization was observed in the AlScZr alloy and AlMnScZr alloy after annealing 550oC/60 min and 550oC/760 min, respectively. The decomposition sequence of the supersaturated solid solution of the AlMnScZr alloy is compatible with the decomposition sequence of the AlScZr system accompanied and/or followed by the formation of Mn-containing particles.