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Hydrostatic extrusion and nanostructure formation in an aluminium alloy

Malgorzata Lewandowska 2Halina Garbacz 2Waclaw Pachla 1Krzysztof J. Kurzydlowski 2

1. Polish Academy of Sciences, High Pressure Research Center (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland
2. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland


Severe plastic deformation has become a popular method for processing ultrafinegrained microstructures. The most widely used deformation methods are: equal channel angular pressing (ECAP), torsion under compression (TUC) and multi-step forging (MSF). Large plastic strain may also be achieved by a hydrostatic extrusion which results in ultrafine and homogenous structure in the entire volume of the material. The aim of this work was to show that hydrostatic extrusion can be used to obtain nanostructured materials.
The material used in this study was an Al-4Cu-1Mn-0,5Mg aluminium alloy. The material in the form of 30 mm diameter rod was fully recrystallized with the mean grain size of 50 μm. The specimens were subjected to the hydrostatic extrusion under high pressure. The final diameter was 3 mm. The microstructure of the alloy was examined using light and electron transmission microscopy and image analysis. Microhardness measurements and tensile tests were performed to characterize the mechanical properties.
Microstructure observations by transmission electron microscope have revealed the grain refinement down to nanometer scale. Quantitative analysis of the grain size has shown its uniform distribution with mean equivalent diameter of 70 nm. Microhardness measurements suggest that the microstructure is homogenous on the cross section of the rod. Results of tensile tests indicate also significant increase in the flow stresses.


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Presentation: poster at E-MRS Fall Meeting 2003, Symposium G, by Malgorzata Lewandowska
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-04-23 13:52
Revised:   2009-06-08 12:55