Precipitation and recrystallisation in Al–Mn–Zr with and without Sc

The transition elements Zr and Mn form dispersoids in aluminium alloys and are extensively used in order to control the microstructure during heat exposure, i.e. to prevent recrystallisation and strength loss after deformation hardening. Additions of Zr have, through the formation of a dense dispersion of coherent and metastable Al3Zr-dispersoids, proved to be beneficial in many alloys. In the Al–Mn–Zr-alloy studied here, TEM-investigations of homogenised material have shown that these phases are heterogeneously distributed. However, by adding Sc a high density of small and well-dispersed Al3(Sc, Zr)-dispersoids is obtained during homogenisation, and the Sc-containing variant consequently displays a higher recrystallisation resistance after cold rolling.