Wojciech Polkowski

Applications of Ni3Al Based Intermetallic Alloys—Current Stage and Potential Perceptivities

The paper presents an overview of current and prospective applications of Ni3Al based intermetallic alloys—modern engineering materials with special properties that are potentially useful for both structural and functional purposes. The bulk components manufactured from these materials are intended mainly for forging dies, furnace assembly, turbocharger components, valves, and piston head of internal combustion engines. The Ni3Al based alloys produced by a directional solidification are also considered as a material for the fabrication of jet engine turbine blades. Moreover, development of composite materials with Ni3Al based alloys as a matrix hardened by, e.g., TiC, ZrO2, WC, SiC and graphene, is also reported. Due to special physical and chemical properties; it is expected that these materials in the form of thin foils and strips should make a significant contribution to the production of high tech devices, e.g., Micro Electro-Mechanical Systems (MEMS) or Microtechnology-based Energy and Chemical Systems (MECS); as well as heat exchangers; microreactors; micro-actuators; components of combustion chambers and gasket of rocket and jet engines as well components of high specific strength systems. Additionally, their catalytic properties may find an application in catalytic converters, air purification systems from chemical and biological toxic agents or in a hydrogen “production” by a decomposition of hydrocarbons.

Electron Backscatter Diffraction Study on Microstructure, Texture, and Strain Evolution in Armco Iron Severely Deformed by the Differential Speed Rolling Method

Results of the electron backscatter diffraction (EBSD) study on structural changes in Armco iron subjected to severe plastic deformation by differential speed rolling (DSR) with different values of roll speed mismatch (R = 1, 2, 3, and 4) are shown in the present article. Results of the EBSD microstructure evaluation reveal that a differentiation of roll speeds results in an effect of structure refinement—iron samples processed with high roll speed mismatch are characterized by a high fraction of grains with submicron size. A microtexture examination shows that the DSR process leads to an overall texture weakening effect and a displacement (a shifting to different “stable” positions) of the basic rolling texture components, due to an additional presence of a simple shear component in the deformation gradient imposed to the material. Despite the higher hardness of the DSR-processed samples, results of the EBSD strain analysis indicate that some part of the stored deformation energy is released during rolling with an additional presence of shear strain. This finding points toward the possibility of activating a dynamic transformation of the material structure into some more stable state. However, since the observed structural changes take place inside deformation bands and do not lead directly to the formation of a fully equiaxed grain structure, it seems to be more reasonable to call the observed structure transformation a subgrain structure evolution through accumulated shear deformation, which may be related to the dynamic recovery process.

Effect of hot differential speed rolling on microstructure and mechanical properties of Fe3Al-based intermetallic alloy

Abstract Results of the first study on hot differential speed rolling (DSR) of Fe3Al-based intermetallic alloy are given in the present paper. The material was subjected to hot rolling at 1100°C with equal and non-equal (the DSR) speed of working rolls. The results of structural examinations indicate that the additional shear strain imposed to the material upon the DSR processing facilitates the activation of dynamic recrystallization. As opposed to the material hot deformed with equal speed of both rolls, the DSRed Fe3Al alloy was characterized by a fully transformed, close to equiaxed grain structure (average grain size of ∼120 μm). The observed structural evolution leads to a higher mechanical strength in DSRed samples as compared to the undeformed counterparts, however it does not result in a substantial improvement of the materials ductility.

Advanced Image Analysis of the Surface Pattern Emerging in Ni3Al Intermetallic Alloys on Anodization

Anodization of Ni3Al alloy is of interest in the field of industrial manufacturing, thanks to the formation of protective oxide layer on the materials working in corrosive environments and high temperatures. However, homogeneous surface treatment is paramount for technological applications of this material. The anodization conditions have to be set outside the ranges of corrosion and “burning”, which is the electric field enhanced anodic dissolution of the metal. In order to check against occurrence of these events, proper quantitative means for assessing the surface quality have to be developed and established. We approached this task by advanced analysis of scanning electron microscope images of anodized Ni3Al plates. The anodization was carried out in 0.3 M citric acid at two temperatures of 0 and 30°C and at voltages in the range of 2 12 V. Different figures can be used to characterize the quality of the surface, in terms of uniformity. Here, the concept of regularity ratio spread is used for the first time on surfaces of technological interest. Additionally, the Minkowski parameters have been calculated and their meaning is discussed.

Analysis of the Effect of the Wearing Type on Surface Structural Changes of Ni3Al-Based Intermetallic Alloy

Results of an analysis of effect of wearing type on surface structural changes of a Ni3Al intermetallic alloy, are shown in the present paper. A microstructure evaluation was carried out by Quanta 3D FEG field emission gun scanning electron microscope (FEG SEM) equipped with an integrated EDS/WDS/EBSD system. The Ni3Al-based intermetallic alloy with an addition of boron, zirconium and chromium was examined. The investigated material had γ’ single-phase, ordered solid solution structure with 20 μm grain size. An electron backscatter diffraction (EBSD) method was applied to visualize surface structural changes upon an abrasive, a cavitational and a tribological wearing of the material.An observation of surface layer after the abrasive wear was carried out on samples examined in loose abradant by T-07 tester and according to GOST 23.2008-79 norm. An analysis of cavitational wear on changes in the near surface area of Ni3Al-based alloy was performed on an impact-jet stand. Observed structural changes were described based on results of the SEM/EBSD complex structural examination and hardness measurements. It was found, that the EBSD is an effective and sensitive method that allows estimating surface strain introduced during analyzed wearing types.

The Effect of Aluminum Content on the Microstructure and Cavitation Wear of Feal Intermetallic Alloys

Abstract Intermetallic-based alloys (so called intermetallics) of the Fe-Al binary system are modern construction materials, which in recent decades have found application in many branches of the power, chemical and automotive industries. High resistance of FeAl based alloys to cavitational erosion results first of all from their high hardness in the as-cast state, large compressive stresses in the material, as well as homogeneous structure. In the present paper, the effect of aluminum content on the microstructure, texture and strain implemented upon cavitation wear of FeAl intermetallic alloys, have been analyzed by field emission gun scanning electron microscopy (FEG SEM) and electron backscatter diffraction (EBSD) analysis. Obtained results of structural characterization indicates that with increasing aluminium content effects of orientation randomization (weakening of <100>//ND casting texture), grain refinement and rising of mechanical strenght (and so cavitational resistance) take place.