Papers by Keyword: Phase Analysis

Abstract: Indefinite-chill materials are used as shell materials for cast work rolls for surface-critical applications in hot rolling mills. Besides a smooth surface quality, a low sticking tendency and low sensitivity against incidents in the rolling mill, the work rolls need the highest wear resistance possible. The microstructure of the indefinite-chill material consists of various carbides (cementite up to 40 area-%) and up to 5 area-% of graphite embedded in tempered martensite. To increase the wear resistance of this material group, the comparably soft cementite has to be replaced by more wear resistant carbides such as MC, M₂C or M₆C. This can be achieved by increasing the amount of carbide forming elements such as Nb, V, Mo, W or Cr. Nevertheless it is important to maintain a certain amount of graphite in the microstructure to avoid sticking to the rolled material and to lower the sensitivity against mill incidents. It is well known that high amounts of carbide forming elements limit the graphite precipitation and therefore a sophisticated alloying concept is required for this material type. Not only the effects of matrix elements such as Si, Mn, Ni and Co but also the effects of Cr, Mo, W, Nb and V were studied in an intensive research project. This work gives an insight in the results of the project based on the example of the effects of Si and Cr on the phase amounts and the composition of the cementite phase.

Abstract: This article presents elemental and phase analysis results of carbon soot samples obtained by electric arc method in a environment of helium, argon and the initial sample. Also analysis results of samples after extraction of carbon nanomaterials are presented (CNM)

Abstract: In the present study, dissimilar friction welding between super alloy 718 and carbon steel friction welded to evaluate the formation of microstructure in the weld interface and in superalloy 718. The temperature during friction welding at weld interface was recorded to determine the temperature effect on the microstructural changes on alloy 718 side. The finite element modeling of weld interface temperature, deformation and stresses were evaluated and validated with the experimental results. The microstructural observation along with the weld interface and adjacent regions are studied. The effect of friction welding on superalloy weld interface and microstructural formation were investigated under electron backscattered diffraction analysis to evaluate the grain size measurements. The effect of thermomechanical action on the microstructure was evaluated by texture analysis.

Abstract: A systematic study of samples of nominal composition A₁₄Cu₂₄O₄₁ (A = alkaline-earth metal) with partial replacement on the alkaline-earth metal sites and on the Cu sites was carried out. Layered cuprates of the (Sr,Ca)₂Cu₂O₃-CuO₂ series with partial substitution by Gd, Dy, and Er for Ca were obtained. X-ray powder diffraction analysis indicated that the solubility of the rare-earth metals in the Sr₈Ca₆Cu₂₄O₄₁ compound is limited to 2 atoms per formula unit. The Cu atoms in the structure of the spin-ladder phase can be replaced by Fe, Co, or Ni atoms up to the composition Sr₈Ca₆Cu₂₃Fe₁O₄₁, Sr₈Ca₆Cu₁₈Co₆O₄₁, or Sr₈Ca₆Cu₂₃Ni₁O₄₁, respectively, whereas attempts to replace part of the Cu atoms by Mn or Zn atoms were not successful.

Abstract: The mechanical strength of pulp capping material based on carbonate apatite and silica calcium-phosphate composite (CO₃Ap-SCPC) is one of the key factors for the success of the material in protecting the vitality of the pulp during the formation of apatite and dentin reparative. Modifying the material in the powder phase was known to increase the mechanical strength. The purpose of this study was to determine whether the addition of SCPC and calcium hydroxide in pulp capping materials based on CO₃Ap-SCPC would affect the compressive strength of this pulp capping material. In this study, three cement groups were used, each group consisted of dicalcium phosphate anhydrous and vaterite which added by SCPC concentration 0%, 5% and 10% and calcium hydroxide concentration 0%, 5% and 10%, respectively. All groups were tested by a compressive strength test and X-Ray diffraction (XRD) for phase analysis. The mean value of compressive strength with addition of 0% SCPC and 10% Ca(OH)₂ was 16.54 ± 1.35 MPa, addition of 5% SCPC and 5% Ca(OH)₂ of 18.55 ± 2.81 MPa, addition of 10% SCPC and 0% Ca(OH)₂ was 9.22 ± 1.21 MPa. The addition of SCPC and Ca(OH)₂ show statistically significant difference in compressive strength (p<0.05). The XRD analysis of the highest compressive strength revealed that the apatite crystal was successfully formed. It can be concluded that incorporated specific amount of SCPC and Ca(OH)₂ could improve the mechanical strength and the apatite formation of the CO₃Ap-SCPC pulp capping material.

Abstract: Sample preparation of metastable austenitic-ferritic steels can have a significant effect on the apparent microstructure due to the transformation of austenite to martensite (γ - α'). As a result, these steels often have a complex microstructure with ferrite and martensite, which have relatively similar crystal structures, making it very difficult to analyse. However, the quantitative analysis of such microstructures and the effect of the sample preparation are very important for the further study of the steel. In this research, the effect of sample preparation in metastable austenitic-ferritic stainless steel was studied by using three different sample preparation methods. In addition to conventional mechanical etching with colloidical silica and electropolishing, focused ion beam (FIB) milling was used to create an optimal sample surface to be further analysed with electron backscatter diffraction (EBSD). Micrographs were obtained from each sample before and after sample preparation using field emission scanning electron microscopy (FESEM) and laser scanning confocal microscopy (LSCM), and the microstructure was analysed using EBSD. The surface flatness required for good EBSD analysis was significantly better using FIB milling than mechanical polishing, while electropolishing results in the greatest topography and an arched sample surface. The amount of martensite was found to be dependent on the sample preparation: least martensite was formed during electropolishing, while surprisingly mechanical polishing and FIB milling resulted in equal amounts of martensite.

Abstract: The study presents the results of microstructure examinations and phase identification of precipitates in AlMn alloys containing zirconium after heat treatment and rolling. Chemical composition in microareas was determined by Energy Dispersive Spectrometry (EDS) microanalysis performed in Scanning Electron Microscope (SEM-EDS) and Scanning Transmission Electron Microscope (STEM-EDS) modes. Phase identification was carried out using Electron Backscatter Diffraction (EBSD) method. Studies have shown that Al₆Mn and α- Al₁₇(Fe_3.2Mn_0.8)Si₂ phases were formed in the melt. Microstructure examined by TEM showed the presence of finely dispersed spherical precipitates of zirconium. In the alloy with an addition of silicon and magnesium, numerous precipitates of an Mg₂Si phase were also found.

Abstract: The microstructure of magnesium alloys containing 1% and 2.5% Mg, as well as the addition of 6% Zn and 0.6% Zr was examined in as-cast and as-extruded condition. After the casting process, the presence of Mg₂Ca and Ca₂Mg₆Zn₃ phases was determined by means of the scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The microstructure of MgCa0.8Zn6.1Zr0.6 and MgCa2.8Zn6.1Zr0.6 alloys after the extrusion process revealed an impact of Zr addition on grain refinement. The electron backscatter diffraction (EBSD) analysis showed that, among all the tested alloys, the smallest grain size was found in the MgCa2.8Zn6.1Zr0.6 alloy and the mean grain diameter amounted to about 4 mm. The analysis of texture has indicated that the lattice planes most often parallel to the cross-sections of the examined magnesium rods are the crystal lattice planes (1 0-1 0).

Abstract: This paper presents the results of structural phase analysis of MAR-M247 superalloy. Analysis was performed at initial and in as casted state after various type of solution annealing in the range 900 °C to 1240 °C with cooling in water. Presented polycrystalline alloy is heat resisting nickel superalloy, especially usable for highly strained components in the industry producing stationary gas turbines and aircraft engines. Analysis was performed using of a Quanta FEG 450 scanning electron microscope with micro-analytic system Trident APEX-4 which have identified presented minor phase. Attention was also paid to its eventual changes after different type of solution annealing.

Abstract: Surface coatings protection is one of the most important processes ensuring efficient and economic use of basic materials, mostly of lower-quality. At interface of clad and basic material intermetallic phases are formed, representing quite different matrix with dissimilar properties unlike the welded materials. One type of surface coating is explosive bonding which belongs to group of pressure welding. The work is focused on some mechanical properties, micro-and nanohardness controlled by AFM and interface shape line, in homogeneities in vicinity of the wave joint both in basic material and in vicinity of the Ti and Cr/Ni stainless steel matrix weld line. Investigated weld was both in as-received state and after heat treatment carried out at 600°C/90 minutes/air. Phases has been identified X-ray diffraction performed BW-5 beamline applying synchrotron radiation, and Tiα, Fe-fcc and Fe-bcc were detected at interface area, whereas intermetallic phases were not revealed.