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Effect of deformation and strain rate on diminishing of microstructure of aluminium alloys (AlCu4Zr0.5 and AlZn6Mg3CuZr)
|Beata Leszczyńska-Madej 1, Maria Richert 1, Krzysztof J. Kurzydlowski 2|
1. AGH University of Science and Technology (AGH), al. Mickiewicza 30, Kraków 30-059, Poland
Intensive deformations influence strongly microstructure. The very well known phenomenon is the diminishing dimension of grain size in materials deformed by the Severe Plastic Deformation (SPD) methods. The nanometric features of microstructure were discovered after the SPD deformation of various materials, such as aluminium alloys, iron and others. The observed changes depended on the kind of the deformed material, amount of deformation, strain rate, existence of different phases and stacking fault energy. The influence of the strain and strain rate on the microstructure is commonly investigated nowadays. It was found that the high strain rates activate deformation in shear bands, microbands and adiabatic shear bands and its effect is similar as exertion of very large strains.
The results of two aluminium alloys: AlCu4Zr0.5 and AlZn6Mg3CuZr deformed by hydrostatic extrusion process were presented. The samples were deformed at the strain rate of 7.4x101÷3.84x102s-1and in the range of true strains φ=1.39÷2.4.
After the deformation process the samples were investigated using an optical and electron microscopy. Also the statistical analysis of geometry of microbands observed in the microstructure was performed and the microhardness was measured. The average width of microbands and microhardness served to outline the Hall - Petch relationship. It was found that the inclination of the diagrams depends on the kind of the alloy. The Hall - Petch relationship is fulfilled only for AlZn6Mg3CuZr alloy.
A characteristic feature of the microstructure was large density of the microbands with a great misorientation to the surrounds. The increase of the strain rate and the deformation caused the reduction of the microbands width in AlZn6Mg3CuZr alloy. In both alloys after true strain φ=2.4 the mean width of the microbands was placed in the range of d=100÷120nm.
The aim of the present study was to establish the influence of the strain rate and the deformation on the possibility of microstructure refinement in the AlCu4Zr0.5 and AlZn6Mg3CuZr alloys.
Presentation: Oral at E-MRS Fall Meeting 2009, Symposium H, by Beata Leszczyńska-Madej
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-11 16:26 Revised: 2009-06-07 00:48