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The study deals with the optimisation of medium-to highstrength aluminium wrought alloys. The goal is to define processing routes in order to improve the mechanical properties if compared to their commercial counterparts. It is shown for the Al-Mg-Si and the Al-Cu-Mg-Si system that the application of ECAP enables a significant increase in strength. The strengthening as well as the grain size reduction respectively, benefit from increasing alloying as well as from the degree of aging. It is also shown that the presence of a considerably fine particulate reinforcement hardens the material tremendously during ECAP. The combination of a pre-or post-ECAP heat treatment enables the improvement of the workability on the one hand, reducing the loads on the die, and also gives a better ductility on the other hand. This positive effect is particularly pronounced for low alloying contents and high aging temperatures and can be attributed to the interaction of deformation induced defects and the precipitation activity. The combination of an appropriate set of ECAP parameters (heat treatment condition, ECAPstrain, -temperature, -backpressure) enables the efficient production of outstanding properties. Due to the low workability of AA7075 (Al-Zn-Mg-Cu system) no significant improvement in properties was achieved.

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Based on metallographic studies the states of composite powder formation during high-energy ball milling will be discussed. Spherical powder of aluminium alloy AA2017 was used as feedstock material for the matrix. SiC and Al 2 O 3 powders of submicron and micron grain size (<2 lm) were chosen as reinforcement particles with contents of 5 and 15 vol.-% respectively. The milling duration amounted to a maximum of 4 hours. The abrasion of the surface of the steel balls, the rotor and the vessel is indicated by the content of ferrous particles in the powder. High-energy ball milling leads to satisfying particle dispersion for both types of reinforcement particles. Further improvements are intended. The microstructure of compact material obtained by hot isostatic pressing and extrusion was studied in detail by scanning and transmission electron microscopy. For both types of reinforcement the microstructure of composites is similar. The microporosity is low. The interface between reinforcement particles and matrix is free of brittle phases and microcracks. In the case of SiC reinforcement particles, a small interface interaction is detectable which implies a good embedding of reinforcement particles. High-energy ball milling under air-atmosphere leads to the formation of the spinel phase MgAl 2 O 4 during the subsequent powder-metallurgical processing. Because of the size, rate and dispersion of the spinel particles, an additional reinforcement effect is expected.