Papers by Author: Jerzy A. Szpunar

Abstract: The influence of current density and temperature on the macrotexture, the orientation and size of grains, and the corrosion resistance of tin deposits was studied. Tin coatings with two different textures, (100) and (301) fiber textures were produced by electrodeposition at 20°C by varying current density. At a lower current density of 100A/m2, (301) fibre was obtained. At the current densities of 100 and up to 400 A/m2, only (100) fibre texture was observed. An increase in current density leads to a decrease in grain size. At the same current density, the grain size of tin coatings increases with increased temperature. The influence of temperature (20, 40, 60 and 80 °C) on texture is relatively negligible. The corrosion resistance of tin coatings increases with a decrease in grain size. The corrosion resistance of tin coating with (301) fibre is higher than that of tin coating with (100) fibre texture. The results suggest that texture and microstructure play an important role in controlling corrosion rate of tin based coatings.

Abstract: Textural changes of Cu interconnects having a different line width were investigated after annealing. Texture was measured by XRD (x-ray diffraction) at different depth of the interconnect line and on the surface of interconnects using EBSD (electron backscattered diffraction) techniques. To analyze the relationship between the stress distribution and textural evolution observed in the different samples, the stresses were calculated for the different line width at 200°C using FEM (finite element modeling) along the width and depth of the line. In this investigation, it was found that the inhomogeneity of stress distribution in Cu interconnects is an important factor necessary for understanding textural transformation during annealing. Textural evolution in damascene interconnects lines during annealing is discussed, based on the state of stress in Cu electrodeposits.

Abstract: Intragranular misorientation reflects strain generated during deformation with dislocation glide. The SEM/EBSP (scanning electron microscope/ electron back scatter diffraction pattern) technique provides is “kernel average misorientation (KAM)” as the most appropriate quantity to evaluate the strain or the stored energy for a given point. The KAM is defined for a given point as the average misorientation of that point with all of its neighbors. In the present paper two analyses of the intragranular misorientation using the SEM/EBSP technique for a cyclic deformation at room temperature and a high temperature deformation in an Al-Mg-Mn alloy are reviewed.

Abstract: The textures of oxide scales grown on low carbon steel in air over the temperature range 850-950°C were investigated. The low carbon steel was oxidized with the air velocity of 4.2 cm/s for 10 s in order to approximate the formation of tertiary scales in hot rolling. At 850°C, the wüstite texture and magnetite texture are weak with no dominant components. For the temperatures of 900 and 950°C, the wüstite and magnetite phases have a cube texture {001}<100>. The experimental results indicate that during hot rolling in the g region, the texture of the oxide scale is cubic and when rolling in the a region, the texture of the oxide scale is weak with no dominant components.

Abstract: The mechanical processing of metals results often in development of preferred orientation of grains or texture. On the other hand, the orientations of grains have a significant effect on the friction and wear behaviour of materials in contact. The objective of this investigation was to determine the crystallographic anisotropy of the coefficient of friction. Medium carbon steel AISI 1045 were selected as the substrate material. Automated orientation imaging analysis system (OIM) was used to identify orientations of grains in polycrystalline specimens. Micro-friction tests were carried out using a Tribocope, a combination of nano-mechanical probe and atomic force microscope with an electrochemical cell. The micro friction tests were performed along different crystallographic directions inside different grains.The obtained results have shown that the coefficient of friction for individual grains depends on crystallographic orientation, and that the coefficient of friction for higher atomic density planes is lower than that for lower atomic density planes.

Abstract: Owing to their lower modulus, great corrosion resistance and superior biocompatibility, titanium alloys are increasingly used as artificial joint replacements. However bone bonding capability of these materials needs to be improved. Many studies are currently conducted to improve the osseo-integration of titanium based implants. In the present study, the role of crystallographic texture of titanium alloy Ti-6Al-4V on bone bonding capability was investigated in vitro systems. X-ray diffraction analysis was used to determine preferred orientation in each substrate. These substrates were seeded with preosteoblast cells to examine cell attachment and proliferation. Attachment of cells was assessed by counting the number of adhered cells within 30-240 min. The proliferation rate of cells was measured between the 3rd-11th days of incubation. The results suggest that the substrate with (100) orientation shows better osteoblastic cell adhesion and proliferation rate than the (110).

Abstract: Nonoriented electrical steels have been widely used as core materials in motors and generators. For these applications low core loss and high permeability are required. The magnetic properties of these steels depend on the grain size and crystallographic texture of the annealed final products. The problems related to grain size control have been extensively investigated, while texture control has received much less attention. The technologies used to control the grain size in nonoriented electrical steels have approached to their limits. However, there is still some possibility for improvement of the magnetic properties through texture control. In order to explore this possibility, the evolution of recrystallization texture for nonoriented electrical steels with 2% Si was systematically studied. Texture change during grain growth was additionally analyzed. The formation of recrystallization texture is explained by oriented nucleation. This is supported by the fact that the area fraction of nuclei or recrystallized grains with specific orientation to all new grains remains almost constant during the progress of recrystallization. Most nuclei have a high misorientation angle of 25~55° with the surrounding deformed matrices. During the progress of grain growth, Goss and {111}<112> components are weakened and the random texture is strengthened. The grains of the Goss and {111}<112> orientations have smaller grain size than those of random orientation.

Abstract: In this research, surface texture changes of carbon steel AISI 1045 and stainless steel AISI 304 under simultaneous wear and corrosion were investigated. A solution of 3.5 % wt. NaCl was used as the corrosion agent and a pin-on-disk tribometer was employed to perform wear and corrosion wear tests.Texture investigations of the worn samples have shown texture changes after wear and corrosion-wear tests. In worn carbon steel samples after dry wear test, {011}<100> and {111} fiber texture components were developed in initially random oriented samples, whereas under corrosive-wear conditions, {111}<011> texture and {001}<110> texture were developed. In the stainless steel samples, {112}<110> texture component was observed under both dry and corrosive wear conditions, in the samples that had random grain orientations before corrosion and corrosion-wear tests.

Abstract: Understanding of diffusion processes in polycrystalline solids is of importance for studying processes like oxidation, precipitation, creep, superplastic forming, annealing and many other processes. In this paper, we will introduce our latest software that is able to simulate the diffusion process in poly and nano-crystalline solids. The diffusion process is simulated based on Random Walk theory. The diffusion matrix can be computer generated or obtained from the experimental measurement using Orientation Imaging Microscopy. The software describes microstructure and incorporates the effects of the material’s texture, grain size and shape, grain boundary character distribution, statistical information on CSL boundary distributions, contribution from triple junctions and interfaces, the trapping of diffusing atoms and interaction of atoms with second phases and voids. A built-in database of diffusivities of various diffusing species and the user friendly interface make the software easy to use. The software is also applicable to thin films and multilayer structures. The output of simulation can be presented as a normalized concentration profile, a two-dimensional contour map of diffusing species, and also using many other statistical representations.

Abstract: A methodology for discrete simulation has been developed that incorporates many structural characteristics of polycrystalline material properties, such as: texture, grain boundaries, microstructure, phase composition, chemical composition, stored energy, and residual stresses. The computer models that have been developed to study oxidation processes are based on a quantitative description of the oxide and substrate structure. That description allows for the simulation of the transport of metal and oxygen ions along interfaces and bulk portions of material and the formation of oxide structure. The proposed model can help researchers and engineers to understand the physical mechanism of oxidation in order to predict material behavior and optimize material processing and properties. In this paper, the results on the simulation of the oxidation process are presented on different substrates of Zr-Nb alloys, which are used for the manufacturing the pressure tubes used in the CANDU nuclear reactors. The effects of substrate texture, microstructure, grain boundaries, and beta phase distribution on oxidation kinetics and hydrogen permeation are demonstrated.