**1.2.1.1 Particles composed of Al, Fe, Mn and Si**

It has been proven that in the case of the AA7020 aluminum alloy Al, Fe, Mn and Sicontaining particles have the Al17(Fe3.2,Mn0.8)Si2 stoichiometric composition and are mostly located at the grain boundaries and therefore are called GB particles [4]. GB particles deteriorate the hot workability of the alloy in addition to mechanical properties since they are hard and brittle especially when located at the grain boundary regions. In order to avoid the detrimental effects of these particles, they should be dissolved during the homogenization treatment. If the particles are not dissolvable, they should be spheroidized.
