Papers by Keyword: Phase Identification

Abstract: In this era, technological advances in the field of construction and industry cannot be separated from welding, while the welding of medium carbon steel is a material that is widely applied using electric arc shielded electrodes and to obtain good results a post weld heat treatment (PWHT) process can be carried out. One of the heat treatments that can be applied to the post weld heat treatment is stress relief annealing. So in this paper a test was conducted to determine the value of ST70 hardness and steel phase from welding with stress relief temperature variations of annealing 600°C, 650°C, and 700°C in the weld metal area and heat affected zone. To find out the results of testing of the post weld heat treatment process with annealing stress relief method at temperatures of 600°C, 650°C, and 700°C in the weld metal area and heat affected zone, the tests used were microstructure, micro vickers hardness and X-Ray Diffraction. The results of the hardness test show that without the post weld heat treatment process the hardness in the heat affected zone is 311.8 HV and in the weld metal area is 329 HV. Whereas from the results of the diffraction phase analysis in the heat affected zone the development of grain size rises regularly along with the increase in temperature in the stress relief annealing process.

Abstract: This novel research work addresses the physical properties of Lead titanate (PT), PbTiO3 sample with additives. The modification of this sample was carried out by adding calcium in proportion of 5 to 15mol%. The samples in bulk form were synthesized by utilizing traditional method of solid state synthesis. The properties like structural analysis, and grain size determination were studied for the PbTiO3 sample & for the calcium modified lead titanate (PCT). The phase identification, structural characterizations and microstructural analysis hasanalyzed in this manuscript.

Abstract: The complex microstructure of as-cast AlSi7Mg alloy has been investigated. Microstructure observations were done using light microscopy, scanning electron microscopy and transmission electron microscopy. Chemical composition of the microstructure constituents was investigated by means of energy dispersive spectrometry, conducted both during SEM and STEM investigations. Selected area diffraction was used to identify the phases in the alloy. Microstructure of the alloy in the as-cast condition consists of Al-Si eutectic and intermetallic phases in the interdendritic regions. These are: Mg₂Si, α-AlFeMnS, β-AlFeSi and π-AlFeSiMg phases. What is more, number of fine precipitates were found within the α-Al dendrites. Only the occurrence of U1 (MgAl₂Si₂) phase has been confirmed.

Abstract: The influence of strontium addition on the microstructure of a Mg-9Al-2Ca alloy was investigated. The microstructure of Mg-9Al-2Ca-xSr alloys consists of α-Mg, (Mg,Al)₂Ca with C15 structure, Al₄Sr and Al_xMn_y phases. The addition of strontium decreases the grain size of the α-Mg phase and decreases the aluminum content dissolved in the α-Mg solid solution. Moreover, the volume fraction of the Al₄Sr phase increases with increasing strontium content. Strontium does not influence on the volume fraction of (Mg,Al)₂Ca phase.

Abstract: Titanium and its alloys have been used a lot for its special and unique properties, and characteristics under different conditions [. When we want to use one of its alloys in aerospace industry, we have to assure that in these conditions the material will resist and keep its integrity [1,. We wanted to analyse a titanium based superalloy by modeling a routine and extracting information from it about the dependence between Gibbs free energy and the amount of weight from two components, titanium and aluminium, which is the second major element according to X-ray diffraction analysis. It was concluded that increasing Ti amount, or making the alloy richer on titanium, the system leads to a higher level of energy. The opposite behaviour happens with aluminium; increasing it, the energy of the system decreases which is great, once the equilibrium is obtained with lower levels of energy. Although the analysis had been done with a general database available in the software, its possible to predict how the material will be influenced under several situations in a quick and reliable method.

Abstract: Aero engine turbine blades made of nickel-based superalloys are critical components in flight safety. Therefore, it is very important to make sure that the chemical composition, phase composition and microstructure are suitable. However, due to their chemical compositions, superalloys are prone to many transformations and the formation of deleterious phases, which deteriorate the mechanical properties. Hence, investigations concerning the structural stability and phase identification—especially topologically close-packed phases (TCP)—are necessary. Because the volume fractions of these phases are generally small, phase identification should be performed by nanodiffraction techniques in a scanning transmission electron microscope (STEM) and electron backscatter diffraction in a scanning electron microscope (EBSD/SEM). These methods complement each other, but each of them is characterized by different difficulties and limitations. In this paper we present the possibilities and limitations of phase identification in single crystal CMSX-4 superalloy after long thermal exposure.

Abstract: The phase relationship of the Mg-Ni-Y system along the Mg-NiY line has been investigated using electron probe micro analysis (EPMA) at 673 K. Three two phase regions (Mg₂Y+τ₆, Mg₂Y+ MgNiY(τ₃), MgY+Mg₃Ni₂Y₄(τ₁)) and two three phase regions (Mg₂Y+Mg₃Ni₂Y₄(τ₁)+ MgNi₂Y₂(τ₂) and NiY+Mg₃Ni₂Y₄(τ₁)+MgNi₂Y₂(τ₂)) have been identified. One new ternary compound Mg₅NiY(τ₅) was found and reported for the first time. Ternary solubility of the Mg_8-13NiY(τ₆) compound has been established which extends from 77.10 at.% Mg until 86.77 at.% Mg along the Mg-NiY section. Solubility of the third element in the binary compounds, NiY, Mg₂Y and MgY has also been determined. Keywords: Mg alloy, phase identification, phase equilibrium, isothermal section.

Abstract: Superaustenitic stainless steels exhibit excellent corrosion resistance, at a wide variety of exposure temperatures, especially in chloride containing environments, coupled with desirable mechanical properties. Previous studies have shown that these steels are prone to precipitation of secondary phases, such as sigma phase (σ), chi phase (χ), Laves-phase, carbides, nitrides or secondary austenite, when exposed at elevated temperatures, directly affecting their mechanical properties and corrosion behaviour. A detailed study of the effect of isothermal ageing on the microstructure of S32654 (Fe-24Cr-21Ni-7Mo-0.5N-0.013C) and S31254 (Fe-20Cr-18Ni-6Mo-0.2N-0.012C) superaustenitic stainless steels was carried out. Samples were aged within the temperature range of 650 ^οC to 950 ^οC for times up to 3000 h. Following ageing, precipitation of secondary phases was clearly observed with precipitates varying in volume fraction, size, shape and spatial distribution. Several secondary phases were identified via transmission electron microscopy (TEM) and electron diffraction (ED). The orientation relationships between the austenitic matrix and the secondary phases were identified. Interaction and also phase transformation among different types of precipitates, such as between precipitates and the austenitic matrix were observed and an attempt of understanding these phase transformations was carried out.

Abstract: UMo-Al specimens are analyzed using X-ray diffraction techniques. One specimen was partially irradiated using a heavy ion beam ¹²⁷I. Another specimen was thermally annealed 2h at 400°C. Those treatments result in the formation of an interaction layer between UMo particles and Al matrix. UMo, Al and UAl₃ phases are identified in the treated specimen using X-ray diffraction. Only aluminium phase exhibits a crystallographic fiber texture, the other phases having an isotropic crystallographic texture. X-ray stress analyses are performed. After irradiation, stress analyses show that UMo phase is in a compressive stress state whereas the stress level in the formed UAl₃ in the interaction layer is not that high.

Abstract: Mild steels were coated by hot-dipping in molten aluminum and aluminum-silicon baths at 700 °C for 180 seconds. Phase identification of the Fe-Al or Fe-Al-Si intermetallic compounds in the hot-dipped aluminide steel was carried out by using a combination of scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The results showed that the aluminide layer of the hot-dipped aluminum steel possessed a thicker intermetallic layer than that of the hot-dipped aluminum-silicon steel which was composed of minor monoclinic FeAl3 and major orthorhombic Fe2Al5. The intermetallic layer of the hot-dipped aluminum-silicon steel was composed of not only the same FeAl3 and Fe2Al5 phases in the hot-dipped aluminum steel but also Fe-Al-Si intermetallic compounds of hexagonal Al7Fe2Si and tetragonal (Al,Si)5Fe3.