The effect of plastic strain on structure and mechanical properties in Al-Zr alloy

The relationship between microstructure characteristics and strain hardening was studied for pure aluminium, Al-0.039% Zr and Al-0.09% Zr alloys subjected to wire drawing deformations to these strains of 3.69 at room temperature. Pure aluminium and the Al-Zr alloys show continued linear hardening to the range of plastic deformation of Σ=3.69 after initial rapid strengthening. The accompanying microstructures evolved, in all cases in the following sequence: formation of dislocation cell structure, cell size refinement, subgrain formation and increase of misorientation angle between subgrains. The cell and subgrain structures are characterized by low angle boundaries but the subgrain structures become to be characterized by high angle boundaries with increasing plastic deformation. The subgrains are less effective as strengthening barriers, hence a single flow stress vs. substructure size relationship should not be rigorously applied. The small additions of zirconium affect the rate of substructure formation and refinement but not the relationship between substructure and strength. (author)