J. Pawlicki

Effect of Compression with Oscillatory Torsion Processing on Structure and Properties of Cu

The results presented in this study were concerned with microstructures and mechanical properties of poly-crystalline Cu subjected to plastic deformation by a compression with oscillatory torsion process. Different deformation parameters of the compression with oscillatory torsion process were adopted to study their effects on the microstructure and mechanical properties. The deformed microstructure was characterized quantitatively by electron backscattered diffraction (EBSD) and scanning transmission electron microscopy (STEM). Mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. From the experimental results, processes performed at high compression speed and high torsion frequency are recommended for refining the grain size. The size of structure elements, such as average grain size (D) and subgrain size (d), reached 0.42 μm and 0.30 μm, respectively, and the fraction of high angle boundaries was 35% when the sample was deformed at a torsion frequency f = 1.6 Hz and compression rate v = 0.04 mm/s. These deformation parameters led to an improvement in the strength properties. The material exhibited an ultimate tensile strength (UTS) of 434 MPa and a yield strength (YS) of 418 MPa. These values were about two times greater than those of the initial state.

Studies of NiTi Shape Memory Alloy after Severe Plastic Deformation

The results presented here concern the NiTi alloy subjected to plastic deformation by compression combined with reversion oscillating torsion. The compression rate was 0.05 mm/s and the torsion frequency and angle were 1Hz and ± 3o, respectively. The maximal strain obtained was c = 6.20. The structure of the deformed samples was studied with the use of X-ray phase analysis and TEM observations. It was found that the structure consists of a mixture of highly deformed B2 parent phase and B19’ martensite. The strain distribution after the applied plastic deformation was not uniform, the highest strain region was in the middle of the cylinder sample. In these regions small amount of the Ni2Ti phase was indentified. The TEM studies revealed some amorphous areas in the most strained region of the samples.

Strength–Energy and Structural Effects of Dynamic Deformation of Aluminum Alloy

This paper presents the results of dynamic deformation tests performed on aluminum alloy PA4. The studiem was carried out by using rotary hammer, in the range of high rate of deformation: 400 – 2000 s-1. The test were carried using a rotary hammer of RSO type owned by Silesian Technical University in Institute of Technology Metals. Before the dynamic deformation, the heating treatment was carried out allowed for eliminating structural effects resulting from the previous technological treatments and for obtaining the homogenous grain structure. The tests were carried out with linear velocity in the range of 5 – 30 m/s. After deformation the following mechanical characteristics were determined: deformation limit εg, strain rate , tensile strength UTS, impact strength U. Independently of the dynamic deformation tests were carried out tensile test under static conditions. Moreover bending test were performed on Charpy type hammer with initial impact energy equal 300 J. The analysis of the microstructure was carried out using scanning electron microscopy Hitachi S–3400 N.

Mechamism of Grain Refinement in Al after COT Deformation

The microstructure of Al processed by compression with oscillatory torsion (COT) method have been studied. This method was applied to refine the grain structure to ultrafine dimension. The aim of the study was to examine how severe plastic deformation technique (COT) - alter the microstructure. The second aim is to understand the mechanism of grain refinement. The microstructure was characterized using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with electron back scattered diffraction (EBSD) facility.

The impact of compression with oscillatory torsion on the structure change in copper

The influence of compression with oscillatory torsion on the copper structure and force parameters are presented. The compression with oscillatory torsion method, developed in the Faculty of Materials Science and Metallurgy at the Silesian University of Technology, is used to achieve severe plastic deformation resulting in homogeneous ultrafine-grained structure of metals. The deformation resistance of copper for various torsion frequency and compression rate is presented. The results of microstructural observations by using LM (light microscope) and TEM (Transmission Electron Microscope) technique are displayed as well. The geometrical parameters of structure elements and their misorientation angles were characterized by using TEM method. Application of compression with oscillatory torsion was found to cause a remarkable decrease of deformation resistance as compared to compression without torsion. Plastic flow localized in shear bands was observed. Structures with large misorientation occur in microbands areas. The banded structure formed during compression with oscillatory torsion consists of well-formed, elongated subgrains.

Changes in Structure and Hardness of CuFe2 Alloy during Rolling with Cyclic Movement of Rolls

In this article, the results of microstructure and hardness investigation performed on CuFe2 alloy processed by rolling with cyclic movement of rolls (RCMR) were presented. The investigations were focused on cross section planes of deformed samples. This results were compared with the ones obtained for samples after conventional rolling. It was shown that in the initial passes, the additional movement of rolls in RCMR method generate in material heterogeneous microstructure and hardness. With increase of deformation the microstructure and hardness distribution is more homogeneous.

Deformation-Induced Grain Refinement in AlMg5 Alloy

The results presented in this paper are concerned with the microstructure and the mechanical properties of the AlMg5 alloy subjected to severe plastic deformation by multiple compression in two orthogonal directions. Four experiments with an increasing number of passes were conducted on the Gleeble MAXStrain system in order to obtain various effective strain levels. The deformed microstructure was investigated by means of the light microscopy (LM) and the scanning transmission electron microscopy (STEM). The mechanical properties were determined for the most deformed, central parts of samples. Investigations revealed that severe cold deformation of the AlMg5 alloy leads to strong grain refinement. Moreover, fragmentation of large intermetallic inclusions and their regular distribution were obtained in the analysed, central parts of the samples. Microstructural changes led to significant improvement in the strength properties. After reaching the effective strain of 9, the AlMg5 alloy exhibited UTS, YS and HV values almost two times higher than corresponding values determined for the starting, annealed material.

Structure and Functional Properties of Microcrystalline NiTi Alloy after Severe Deformation and Subsequent Annealing

Thermomechanical treatment was applied to a binary NiTi alloy in order to improve its functional properties by forming nanocrystalline structure of the alloy. The alloy deformation was obtained by cold rolling combined with transverse movement of the rolls. This technique allowed us to obtain high strain (c ≈ 6) for the relatively large specimens. Subsequently, the samples were annealed in the temperature range 300 -500oC in order to form a nano-, submicro –and/or microcrystalline structure. The evolution of the structure and associated changes of the transformation sequences and functional properties were studied with the use of TEM, X-ray phase analysis, DSC and bend and free recovery ASTM tests. A mixed amorphous/crystalline structure was obtained after severe deformation, the martensitic transformation was completely suppressed in the sample. Annealing at lower temperatures caused formation of nanocrystalline structure that grew to the microcrystalline and finally well-defined polygonized structure in annealed at 500oC specimens.