K. Sztwiertnia

Microstructure and properties of hard magnetic FeCr30Co8 alloy subjected to plastic deformation by complex loading

Abstract The microstructural, mechanical and magnetic properties of FeCr30Co8 alloy in the a state were examined after upsetting, followed by torsion. The temperatures (750, 800, 850 and 900°C) and deformation rates corresponded to the superplasticity conditions of the Fe–Cr–Co alloys. Due to the torsional deformation, which was applied only to the bottom of the samples, a gradient microstructure was formed in the sections that were parallel to the upsetting direction. In the temperature range from 750 to 850°C, the deformation led to intermetallic r-phase precipitation. The maximum refinement of the microstructure and the maximum r-phase precipitation were observed in the material that was deformed at 800°C. Measurement of the magnetic properties showed a decreasing coercive force in the deformed alloy, in contrast to the mechanical properties of the samples after the magnetic treatment.

Advanced characterization of microstructural changes during recrystallization in aluminum alloy 6013

Aluminum alloy 6013 was chosen as an example of a material that, after thermal treatment, possesses a relatively uniform and stable bimodal distribution of fine ( 1 μm) particles. Samples of this alloy were subjected to plastic deformation by cold rolling. The presence of large and small particles has an influence on the behavior of this material during the recrystallization process. A complex investigation of the microstructural changes during annealing were carried out by means of advanced SEM and TEM techniques. Orientation mapping (OM), i.e., automatic determination of the topography of the crystallographic orientations, was performed using electron backscatter diffraction (EBSD) in the SEM and microdiffraction in the TEM experiments. These techniques were combined with in-situ heating experiments in the TEM and SEM experiments. The quantitative description of the microstructure at each step of recrystallization is presented. Changes in the microstructure of the investigated material during annealing reveal the role and impact of both types of particles on recrystallization and grain growth. The obtained results are in agreement with parallel calorimetric studies.

Microstructure of Hard Magnetic FeCr22Co15 Alloy Subjected to Tension Combined with Torsion at High Temperatures

The paper presents the results of microstructure evolution studies of hard magnetic FeCr22Co15 alloy, destructed by tension and torsion at 800 and 850°C. The temperatures and deformation rates corresponded to the condition of superplasticity of Fe-Cr-Co alloys. Observations of longitudinal section of deformed samples in scanning electron microscope showed a formation of weak gradient microstructure with highest grain refinement in the surface layer of material. Precipitation of intermetallic σ-phase was also observed, with its maximum amount in zones of the highest deformation.

Continuous and Discontinuous Recrystallization of 6013 Aluminum Alloy

In situ orientation mapping using TEM and calorimetric measurements were carried out to investigate the annealing behavior of cold-rolled 6013 aluminum alloy. The recrystallization of the material can be considered to be a number of processes that correspond to two separate stored energy release peaks. In the temperature range of the peak 1, the deformation zones around the large second-phase particles acted as sites for particle-stimulated nucleation. In the matrix, at the same time, some elongation of grains occurred. The elongated matrix grains appeared because of the reduction of the dislocation density and the annihilation of some low-angle grain boundaries between chains of subgrains lying in layers parallel to the sheet plane. The matrix processes in this temperatures range can be considered forms of continuous recrystallization. The matrix high-angle grain boundaries started to migrate at the temperature range of the peak 2. They moved mostly in the direction normal to the sheet plane. Heating of the sample for an appropriate time at those temperatures resulted in the complete discontinuous recrystallization of the material. The recrystallized microstructure was dominated now by elongated grains, which were a few times thicker than those obtained by annealing at the temperatures of the peak 1.

Orientation Imaging Microscopy Applied to Zirconia Ceramics

Abstract. Measurements of crystallographic orientations along with microscopic observations are the basis of quantitative investigations of the microstructure of crystalline materials. The technique that applies automatic orientation measurements in the transmission or scanning electron microscope is known as orientation imaging microscopy (OIM) [1]. In this paper the measurements and analyses of sets of single orientations gained from electron backscattered diffraction (EBSD) registered in a scanning electron microscope are presented. A quantitative description of microstructure of two polymorphs of zirconia, based on measurements of single orientations, is also given.

Modeling of recrystallization texture of aluminium: symmetric and asymmetric rolling

In some metallic materials the dominating recrystallization mechanism can be described by the oriented growth behaviour. Phenomenological laws state that in selected materials only these nuclei grow intensively which have a given misorientation relation with the deformed matrix. This description is frequently verified in f.c.c. metals and generally reported misorientations correspond approximately to 400 rotation around the axis. Basing on the above ideas the recrystallization model, including the compromise condition, was formulated and applied to the study of recrystallization textures of rolled polycrystalline aluminium.

Modeling of Recrystallization Texture of Rolled Polycrystalline Aluminium

In many metallic materials the dominating recrystallization mechanism can be described by the oriented growth behavior. Phenomenological laws state that only these nuclei grow intensively which have a given misorientation with the deformed matrix. This description is frequently verified in f.c.c. metals and generally reported misorientations are between 300 and 500 rotations around the <111> axis. Basing on the above ideas the recrystallization model was formulated and applied to the study of recrystallization textures in rolled polycrystalline aluminium.

Microstructure Analysis Based on Local Orientation Measurements

One of the basic tasks of material engineering is the search for relations between the particular (significant from the point of view of technology) properties of a polycrystalline material and its microstructure. Thus a quantitative, possibly complete description of the microstructure which would also allow a quantitative investigation of its relations with the material properties is essential. A basis for such a description is the information contained in a set of orientations obtained from systematical local measurements in the sample space. Such a set of measured local orientations arranged in points of a regular grid or in individual crystallites (or grains) in the sample plane will be named orientation topography [1]. It represents a rich source of information on the microstructure of the material matrix. At present, due to the progress of the automatization technique of the diffraction measurements, especially in the scanning electron microscopy, the difficulties of realizing routine rapid single orientation measurements and the determination of the orientation topography in the sample plane have been overcome [2]. New possibilities of a quantitative description of the microstructure taking into consideration aspects of crystallographic orientation have appeared.