The DRECE method belongs to the severe plastic deformation (SPD) processes used for the refinement of sheet metal elements. A forming device used in this method is currently being installed in the workplace in the Centre of Advanced Innovation Technologies, VSB Technical University of Ostrava. In the present work the structural characteristics and fracture morphology of Ck55 carbon steel after the application of the DRECE method with a forming tool angle of 118? are presented. The microstructure results are linked to selected mechanical properties. The tensile, hardness, and fatigue tests are performed. The methodology of non-destructive residual stresses measurement in the carbon steel after the extrusion and application of tensile tests on small samples are important for their use in technical practice. The paper presents the original results of selected properties after the application of the DRECE method on Ck55 steel, which will be used in the future to assess the application of the DRECE method and to determine other directions of the processing of ferrous alloys and steels.

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The comparative analysis of mechanical properties using a digital image correlation by Vic 2D software was performed for two types of high-strength materials. The strain analysis during tensile tests was carried out on the cylinder tensile specimens of 34CrMo4 steel and IN 738LC superalloy. Both materials showed similar strength but different ductility. While the 34CrMo4 steel showed typical necking of tensile specimens with ductile fracture surfaces, cracking of the IN 738LC became without necking, and the fracture morphology displayed mixed feature with ductile dimples or quasi-cleavage areas and cracked carbides. Microhardness measurements completed metallographic and fractographic studies of tensile samples.

The stress analysis using digital image correlation was carried out on cylindrical tensile specimens made from low carbon 34CrMo4 steel. The results obtained by conventional tensile test were compared with the results obtained by digital image correlation. The true stresses were evaluated from the compiled true stress-strain diagrams and compared with the engineering stresses. The average values of the yield stress and tensile strength reached of 945±15 MPa and 1039±5 MPa, respectively. Thus, parameters obtained from tensile test were plotted in the engineering diagrams that represent often starting diagrams for engineering practice. Based on results of digital image correlation the possibility of construction of the true stress-strain diagrams is discussed with regard to more exact values of stress for use in practice. The evaluation and compilation of the true stress-strain diagrams were carried out by means of image correlation software Vic 2D.

The aim of the article is piston damage evaluation of a highly exposed combustion engine. The analysed piston was made of an AlSi-based alloy. Atypical damage, which occurred relatively early in the lifetime of the component, was evaluated by metallographic and fractographic analyses. The analysis took into account influences of mechanical and thermal fatigue processes in relation to the microstructure of the material. The metallographic observations of the microstructure revealed the occurrence of cracks extending over the secondary phases and precipitates. Cracks were initiated on the coarser Si phase particles. The crack initiation site is located at the root of the bridge between the sealing piston rings. The damage of the piston was metallographically documented in wide range.