Papers by Author: Bogusława Adamczyk-Cieślak

Abstract: The complex microstructure of as-cast AlSi7Mg alloy has been investigated. Microstructure observations were done using light microscopy, scanning electron microscopy and transmission electron microscopy. Chemical composition of the microstructure constituents was investigated by means of energy dispersive spectrometry, conducted both during SEM and STEM investigations. Selected area diffraction was used to identify the phases in the alloy. Microstructure of the alloy in the as-cast condition consists of Al-Si eutectic and intermetallic phases in the interdendritic regions. These are: Mg₂Si, α-AlFeMnS, β-AlFeSi and π-AlFeSiMg phases. What is more, number of fine precipitates were found within the α-Al dendrites. Only the occurrence of U1 (MgAl₂Si₂) phase has been confirmed.

Abstract: In this paper the effect of production method and heat treatment of magnesium alloys to their corrosion resistance is presented. The study was carried out on the AZ91D alloy obtained by permanent mould casting, pressure die casting and pressure die casting with the subsequent heat treatment. Studies of the microstructure were carried out using a light microscope. The corrosion resistance was examined using the Potentiodynamic Test. The surface observations after corrosion tests were carried out using the Scanning Electron Microscope (SEM). It was stated that the best corrosion resistance is typical for AZ91D alloy produced by pressure die casting method with heat treatment. The alloy after permanent mould casting has got the worst corrosive properties.

Abstract: The texture of Al – 0.7 wt. % Li alloy processed by two different methods of severe plastic deformation (SPD) has been investigated by X-ray diffraction, and analyzed in terms of the orientation distribution function (ODF). It was found that severe plastic deformation by both Equal Channel Angular extrusion (ECAE) and Hydrostatic Extrusion (HE) resulted in an ultrafine grained structure in an Al – 0.7 wt. % Li alloy. The microstructure, grain shape and size, of materials produced by SPD strongly depend on the technological parameters and methods applied. The texture of the investigated alloy differed because of the different modes of deformation. In the initial state the alloy exhibited a very strong texture consisting of {111} fibre component. A similar fibrous texture characteristic was also found after HE whereas after the ECAE the initial texture was completely changed.

Abstract: The results obtained in the present study reveal the effect of equal channel angular extrusion (ECAE) on the grain size and mechanical properties of Al-Li alloys. During 8 passes of ECAE process, coarse grain microstructure in the initial state transforms into ultrafine grained. The final grain size depends on both total strain applied and Li content in the alloy. Due to the grain refinement the microhardness and yield stress increase by 100%. During compression deformation, the coarse grain alloys exhibit continuous hardening, whereas in the ultrafine-grained alloys, a stagnation of work hardening at the beginning of compression deformation is observed. This behaviour is related to the dynamic recovery of the severely deformed microstructure.

Abstract: Equal channel angular extrusion (ECAE) was used to obtain ultrafine grain structures in two aluminium- lithium alloys. The specimens were subjected to severe plastic deformation up to strain value of 9,2 at room temperature. After ECAE deformation, the grain size was reduced from an initial value of 300 µm to 1 µm. The main purpose of this study was to examine the recrystallization characteristics of ECAE treated specimens at temperatures of T = 0,5 and T = 0,7 Tm. At each temperature the specimens were heated for 1, 10, 100 seconds. The microstructure, texture and microhardness were examined in the as-deformed condition and after the annealing. The TEM observations indicate that in the Al-0.7 wt. % Li and Al-1.6 wt. % Li alloys, recrystallization has a continuous character. The microhardness results show that the lithium content increases, in an essential way, the mechanical properties of the alloys after severe plastic deformation and subsequent annealing. During ECAE process, a well pronounced texture with the orientation of the (441)[ 12 4 ], (145)[ 7 31] and (321)[ 3 4 6 ] types are formed within about ¼ volume of the material. After the annealing the grains acquire orientations other than those observed typically in these alloys when deformed by classical straining techniques followed by recrystallization.