On the decomposition and hardening behaviour of supersaturated aluminium alloys

The effect of additions of Mn and Cr and the applied solidification technique on the structure of an Al-2.2 at% Zn-1.4 at% Mg alloy

“…These coarse precipitates are nucleated and grown during homogenization a t 490 "C, since, actually, the maximum solubility of Mn in the A1 matrix amounts t o 0.76 atyo a t the eutectic temperature of 658.5 "C, but less than 0.15 a t Yo a t 490 "C. One can expect that the precipitates of the intermetallic A1,Mn phase do not coarsen during the ageing a t 160 "C (or a t least only to an insignificant extent), since the mobility of Mn in the A1 matrix is too low a t 160 "C (see e.g. the discussion in [9]). The amount of Mn added to the Al-Zn-Mg alloy was deliberately chosen so high, because (i) itcan be expected that the amount of impurity additions will drastically increase in the future as more scrap is used (recycling) for the production of A1 alloys, and (ii) from the technological point of view, one is interested to add fairly high amounts of Mn, in order to bind elements (e.g.…”