THE INFLUENCE OF ECAP ON MECHANICAL PROPERTIES OF A TWIN-ROLL CAST Al-Mn-Fe-Si-Zr ALLOY

The Al-Mn-Fe-Si-Zr alloy was twin-roll cast and a part of the material was after casting annealed at 450 degrees C for 8 hours in order to allow the precipitation of the Al3Zr phase. Both modifications were further processed by equal channel angular pressing (ECAP) at room temperature. The influence of increasing number of ECAP passes on the microstructure was studied using transmission electron microscopy. The character of interfaces formed during ECAP was studied using electron back-scatter diffraction. The room temperature mechanical properties were investigated by microhardness measurements and by tensile tests. It was found that the highest increase in strength characteristics occurs already during the first ECAP pass when the dislocation density is enormously increased. A partial recovery of dislocation structure and formation of high angle boundaries were observed during following ECAP passes. Consequently, the increase in strength characteristics reveals a saturation effect especially in the annealed material.