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F. H. Samuel - One of the best experts on this subject based on the ideXlab platform.
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Statistical analysis of porosity in Al-9 wt% Si-3 wt% Cu-X alloy systems
Journal of Materials Science, 1996Co-Authors: N. Roy, P. R. Louchez, F. H. SamuelAbstract:A set of 72 solidification experiments was carried out on Al-9 wt% Si-3 wt% Cu- X alloys, varying the additives (namely, strontium, grain refiner and other alloying elements), Hydrogen Level and thermal parameters in order to obtain a statistical analysis of the resulting porosity in such alloy systems. For all the cases studied, it was found that in each case, the smaller sized pores (in terms of pore length or pore area) could be described by an exponential function, while the larger sized pores were distributed in an irregular fashion, “small” and “large” being distinguished by that limiting value of pore length or area at which the average value equalled the standard deviation. Two different approaches i.e. factorial and regression methods were utilized to quantify the importance of the parameters controlling the pore size and porosity volume fraction. Two main observations were made: (i) Hydrogen is the strongest parameter enhancing porosity formation, with the Hydrogen-grain refiner, strontium, strontium-titanium and solidus velocity-solidification time interactions being the other parameters that contribute significantly to porosity formation and increase in pore size; (ii) the grain refiner, Hydrogen-phosphorus, strontium-magnesium and iron-phosphorus interaction parameters reduce the porosity, though in different magnitudes. The reliability of predicting the observed effects by the two methods has been discussed.
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Influence of casting and heat treatment parameters in controlling the properties of an Al-10 wt% Si-0.6 wt% Mg/SiC/20p composite
Journal of Materials Science, 1994Co-Authors: A. M. Samuel, F. H. SamuelAbstract:The influence of melting, casting and heat treatment parameters in determining the quality and tensile properties of an Al-10wt% Si-0.6wt% Mg/SiC/20p composite in comparison to its base alloy (359) has been studied. For the composite, melt-temperature, Hydrogen Level, and the cleanliness and stirring procedure, control, respectively, the harmful melt reactions of the SiC reinforcement with the alloy matrix, gas porosity, inclusion and oxide-film contamination, whereas casting conditions are mainly controlled through the use of a proper mold temperature and appropriate mold coating materials that enhance the feedability and reduce or eliminate the effects of shrinkage. The beneficial effect of the SiC reinforcement particles is two-fold: 1. they act as preferential sites for the nucleation of the eutectic silicon particles, leading to an overall refinement of the latter and lowering the amount of strontium modifier required from 150 to 90 ppm to achieve the same Level of refinement in the as-cast microstructures of both composite and base alloy; 2. their presence also results in a more uniform redistribution of the silicon particles in the as-cast structure (cf. the large, irregular interdendritic regions of eutectic silicon observed in the base alloy). Both composite and base alloy exhibit a similar heat treatment response with respect to tensile properties for the various heat treatments applied. Addition of 20 vol% SiC to the base alloy (359) is seen to increase the Young's modulus and yield strength by 30–40%, marginally affect the ultimate tensile strength, but reduce the ductility by almost 80%.
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The reduced pressure test as a measuring
Metallurgical Transactions A, 1993Co-Authors: A. M. Samuel, F. H. SamuelAbstract:Porosity is one of the important factors critical to the production of optimum aluminum alloy castings. Hydrogen is mainly responsible for the “gas porosity” in such castings, which is also affected by other factors including melt cleanliness. The importance, therefore, of obtaining a reliable estimate of the melt Hydrogen Level prior to casting has led to the development of several techniques, among which the reduced pressure test (RPT), basically a comparative, qualitative test, appears to be the one popularly used in foundries due to its simplicity and easy adaptation to the foundry floor. Attempts have been made to quantify the test by correlating the densities of reduced pressure samples with the Hydrogen contents of their melts. In the present study, the RPT was tested as a means of determining the Hydrogen content in Al-7 wt pet Si-10 vol pet SiC composite melts as part of an on-going study being carried out in our laboratories on such composites. The results reveal that rather than indicating the Hydrogen content of the melt, the RPT is a better indicator of the porosity content of the cast sample and can be employed as a melt quality measuring tool, provided the sample density is correctly related to said po- rosity. Qualitative analysis is substantiated throughout by pore size and distribution data ob- tained from image analysis. It is also found that compared to the unreinforced A356 matrix alloy, the composite material has a beneficial effect on the formation of porosity due to the tendency of the SiC reinforcement particles to restrict the growth of the pores. This, coupled with the microporosity associated with the presence of the SiC particles, results in the skewed pore size distribution curves typically observed for the composite samples.
Nitin Saini - One of the best experts on this subject based on the ideXlab platform.
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microstructure and mechanical property relationship for different heat treatment and Hydrogen Level in multi pass welded p91 steel joint
Journal of Manufacturing Processes, 2017Co-Authors: Chandan Pandey, M M Mahapatra, Pradeep Kumar, Nitin Saini, A SrivastavaAbstract:Abstract The effect of heat treatment condition and diffusible Hydrogen Level on microstructure and mechanical properties of multi-pass shielded metal arc welded (SMAW) P91 steel butt joints of 18 mm thickness has been studied. Field-emission scanning electron microscope (FESEM), Mercury diffusible Hydrogen measurement, Charpy test, room-temperature tensile testing, hardness measurement and energy dispersive X-ray spectroscopy (EDS) were performed to characterize the multi-pass SMAW joints in as-welded, post-weld heat treatment (PWHT) and normalizing/tempering (N&T) state. The P91 steel butt joints with low Level of diffusible Hydrogen exhibited higher tensile strength and toughness. Both PWHT and N&T treatment provided similar mechanical properties but a significant microstructure variation was noticed for different zones of P91 welds. N&T treatment produced the homogenize microstructure along the P91 weldments both in terms of microstructure and micro-hardness.
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Effect of diffusible Hydrogen content on embrittlement of P92 steel
International Journal of Hydrogen Energy, 2017Co-Authors: Nitin Saini, Chandan Pandey, Manas Mohan MahapatraAbstract:Abstract In the present investigation, varying electrode conditions (dried and contaminated) have been employed during welding of P92 steel to study the effect of diffusible Hydrogen Level on Hydrogen-assisted cracking (HAC). Shielded metal arc welding process was employed to deposit the metal on a P92 steel plate. To evaluate HAC, the Granjon implant test with varying diffusible Hydrogen content in the deposited metal was utilized. The diffusible Hydrogen Level was measured in the deposited metal by using the mercury method. Lower critical stress (LCS), embrittlement index (EI) and normalized critical stress ratio were evaluated from the Granjon implant test. The fracture surface morphology of fractured implant specimens has been studied by using a field emission secondary electron microscope. The P92 steel plate welded by the contaminated electrode with a high Level of diffusible Hydrogen was found to be more susceptible to HAC. As diffusible Hydrogen content increased in the deposited metal, the LCS value and EI were observed to be decreased.
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Diffusible Hydrogen Level in Deposited Metal and Their Effect on Tensile Properties and Flexural Strength of P91 Steel
Journal of Engineering Materials and Technology, 2017Co-Authors: Chandan Pandey, Pradeep Kumar, Manas Mohan Mahapatra, Nitin SainiAbstract:In a “very high-temperature reactor” (VHTR), the Nb–V-modified 9Cr–1Mo creep strength enhance the ferritic (CSEF) steel which is the chosen material for fabrication of reactor pressure vessels and piping because of its excellent high temperature thermal and mechanical properties. In such CSEF steel weldments, the Hydrogen-induced cracking (HIC) is a critical issue. In the present work, the different Levels of Hydrogen have been induced in P91 CSEF weld metal to study their effect on HIC. The HIC susceptibility of P91 steel welds has been studied by carrying out the tensile test and flexural test for the different Level of diffusible Hydrogen. The Hydrogen Levels in deposited metals have been measured by using the mercury method. The fracture tensile and flexural test samples have been characterized based on the field-emission scanning electron microscope (FE-SEM). It is concluded that higher the Level of diffusible Hydrogen in deposited metal, more is the susceptibility of P91 steel to HIC. The minimum flexural and tensile strength are 507.45 MPa and 282 MPa, respectively, for 12.54 ml volume of diffusible Hydrogen in 100 g of deposited weld metal.
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Hydrogen induced cold cracking of creep resistant ferritic P91 steel for different diffusible Hydrogen Levels in deposited metal
International Journal of Hydrogen Energy, 2016Co-Authors: Chandan Pandey, Nitin Saini, Manas Mohan Mahapatra, Pradeep KumarAbstract:Abstract Hydrogen-assisted cracking (HAC) is a serious issue in P91 steel welds because of unwanted martensitic metallurgical-transformation in the heat affected zone (HAZ). In the present research, different electrode conditions have been employed during welding of P91 steel to study their effects on HAC. The HAC susceptibility of cast and forged (C&F) P91 steel welds produced by shielded metal arc welding (SMAW) process has been evaluated through implant test with respect to the different Level of diffusible Hydrogen content in the deposited metal. The weld implant test results such as applied stress vs time to failure, the lower critical stress (LCS), embrittlement index (EI) and normalized critical stress ratio (NCSR) were evaluated with respect to the different Level of Hydrogen content in the deposited metal. The microstructure of coarse grain heat affected zone (CGHAZ) and weld metal in different condition have been characterized by using scanning electron microscope (SEM). The fracture morphology of implant specimen was characterized by using the SEM. The paper also describes the effect of hydrocarbon contamination (oil or grease) in low-Hydrogen basic SMAW electrode for P91 steel. It can be concluded that P91 steel welded by the electrode having higher contamination (high Hydrogen Level) is more susceptible to HAC. The LCS value was observed to be decreasing with the increase in the diffusible Hydrogen content in deposited metal and minimum value was measured to be 180 MPa for 12.54 ml of diffusible Hydrogen per 100 g of deposited metal.
P Gouttebroze - One of the best experts on this subject based on the ideXlab platform.
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Radiative transfer in cylindrical threads with incident radiation V. 2D transfer with 3D velocity fields
Astronomy & Astrophysics, 2008Co-Authors: P GouttebrozeAbstract:Context. Time-resolved observations of loops embedded in the solar corona show the existence of motions of matter inside these structures, as well as the global motions of these objects themselves. Aims. We have developed a modeling tool for cylindrical objects inside the solar corona, including 2-dimensional (azimuth-dependent) radiative transfer effects and 3-dimensional velocity fields. Methods. We used numerical methods to simultaneously solve the equations of NLTE radiative transfer, statistical equilibrium of Hydrogen Level populations, and electric neutrality. The radiative transfer equations were solved using cylindrical coordinates and prescribed solar incident radiation. In addition to the effects of anisotropic incident radiation, treated in previous papers, we took into account the Doppler shifts produced by a 3-dimension velocity field. Results. The effects of different types of velocity fields on Hydrogen line profiles and intensities are described. Motions include loop oscillations, rotation, and longitudinal flows, which produce different deformations of profiles. Doppler brightening and dimming effects are also observed. Conclusions. This is a new step in the diagnostic of physical conditions in coronal loops, allowing the study of dynamical phenomena.
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Radiative transfer in cylindrical threads with incident radiation - IV. Time-dependent and thermal equilibrium models
Astronomy & Astrophysics, 2007Co-Authors: P GouttebrozeAbstract:Context. Relatively cool and dense structures embedded in the solar corona (filaments, prominences, spicules, etc.) may be observed in Hydrogen lines. Sometimes they last during several solar rotations. Aims. Our goal is to evaluate the lifetime of cool structures of the solar corona, determine their evolution from given physical conditions, and compute models in thermal equilibrium. Methods. We use numerical methods to simultaneously solve the equations of NLTE radiative transfer, statistical equilibrium of Hydrogen Level populations, and electric neutrality. Radiative transfer equations are solved using cylindrical coordinates and prescribed solar incident radiations. The computation of internal energy and radiative losses and gains yields the rates of temperature evolution. Results. For isothermal-isobaric cylinders with prescribed physical conditions, we determine the lifetimes and evolution rates for different positions along the radius. For models with prescribed diameter and pressure, we determine the run of temperature vs. radius corresponding to thermal equilibrium. This equilibrium is found to be stable for the whole range of parameters under investigation. Conclusions. The cores of large and high-pressure cylinders are found to evolve very slowly. This opens the possibility of observing these cool structures at temperatures somewhat different from that corresponding to theoretical radiative equilibrium.
Chandan Pandey - One of the best experts on this subject based on the ideXlab platform.
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microstructure and mechanical property relationship for different heat treatment and Hydrogen Level in multi pass welded p91 steel joint
Journal of Manufacturing Processes, 2017Co-Authors: Chandan Pandey, M M Mahapatra, Pradeep Kumar, Nitin Saini, A SrivastavaAbstract:Abstract The effect of heat treatment condition and diffusible Hydrogen Level on microstructure and mechanical properties of multi-pass shielded metal arc welded (SMAW) P91 steel butt joints of 18 mm thickness has been studied. Field-emission scanning electron microscope (FESEM), Mercury diffusible Hydrogen measurement, Charpy test, room-temperature tensile testing, hardness measurement and energy dispersive X-ray spectroscopy (EDS) were performed to characterize the multi-pass SMAW joints in as-welded, post-weld heat treatment (PWHT) and normalizing/tempering (N&T) state. The P91 steel butt joints with low Level of diffusible Hydrogen exhibited higher tensile strength and toughness. Both PWHT and N&T treatment provided similar mechanical properties but a significant microstructure variation was noticed for different zones of P91 welds. N&T treatment produced the homogenize microstructure along the P91 weldments both in terms of microstructure and micro-hardness.
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Effect of diffusible Hydrogen content on embrittlement of P92 steel
International Journal of Hydrogen Energy, 2017Co-Authors: Nitin Saini, Chandan Pandey, Manas Mohan MahapatraAbstract:Abstract In the present investigation, varying electrode conditions (dried and contaminated) have been employed during welding of P92 steel to study the effect of diffusible Hydrogen Level on Hydrogen-assisted cracking (HAC). Shielded metal arc welding process was employed to deposit the metal on a P92 steel plate. To evaluate HAC, the Granjon implant test with varying diffusible Hydrogen content in the deposited metal was utilized. The diffusible Hydrogen Level was measured in the deposited metal by using the mercury method. Lower critical stress (LCS), embrittlement index (EI) and normalized critical stress ratio were evaluated from the Granjon implant test. The fracture surface morphology of fractured implant specimens has been studied by using a field emission secondary electron microscope. The P92 steel plate welded by the contaminated electrode with a high Level of diffusible Hydrogen was found to be more susceptible to HAC. As diffusible Hydrogen content increased in the deposited metal, the LCS value and EI were observed to be decreased.
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Diffusible Hydrogen Level in Deposited Metal and Their Effect on Tensile Properties and Flexural Strength of P91 Steel
Journal of Engineering Materials and Technology, 2017Co-Authors: Chandan Pandey, Pradeep Kumar, Manas Mohan Mahapatra, Nitin SainiAbstract:In a “very high-temperature reactor” (VHTR), the Nb–V-modified 9Cr–1Mo creep strength enhance the ferritic (CSEF) steel which is the chosen material for fabrication of reactor pressure vessels and piping because of its excellent high temperature thermal and mechanical properties. In such CSEF steel weldments, the Hydrogen-induced cracking (HIC) is a critical issue. In the present work, the different Levels of Hydrogen have been induced in P91 CSEF weld metal to study their effect on HIC. The HIC susceptibility of P91 steel welds has been studied by carrying out the tensile test and flexural test for the different Level of diffusible Hydrogen. The Hydrogen Levels in deposited metals have been measured by using the mercury method. The fracture tensile and flexural test samples have been characterized based on the field-emission scanning electron microscope (FE-SEM). It is concluded that higher the Level of diffusible Hydrogen in deposited metal, more is the susceptibility of P91 steel to HIC. The minimum flexural and tensile strength are 507.45 MPa and 282 MPa, respectively, for 12.54 ml volume of diffusible Hydrogen in 100 g of deposited weld metal.
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Hydrogen induced cold cracking of creep resistant ferritic P91 steel for different diffusible Hydrogen Levels in deposited metal
International Journal of Hydrogen Energy, 2016Co-Authors: Chandan Pandey, Nitin Saini, Manas Mohan Mahapatra, Pradeep KumarAbstract:Abstract Hydrogen-assisted cracking (HAC) is a serious issue in P91 steel welds because of unwanted martensitic metallurgical-transformation in the heat affected zone (HAZ). In the present research, different electrode conditions have been employed during welding of P91 steel to study their effects on HAC. The HAC susceptibility of cast and forged (C&F) P91 steel welds produced by shielded metal arc welding (SMAW) process has been evaluated through implant test with respect to the different Level of diffusible Hydrogen content in the deposited metal. The weld implant test results such as applied stress vs time to failure, the lower critical stress (LCS), embrittlement index (EI) and normalized critical stress ratio (NCSR) were evaluated with respect to the different Level of Hydrogen content in the deposited metal. The microstructure of coarse grain heat affected zone (CGHAZ) and weld metal in different condition have been characterized by using scanning electron microscope (SEM). The fracture morphology of implant specimen was characterized by using the SEM. The paper also describes the effect of hydrocarbon contamination (oil or grease) in low-Hydrogen basic SMAW electrode for P91 steel. It can be concluded that P91 steel welded by the electrode having higher contamination (high Hydrogen Level) is more susceptible to HAC. The LCS value was observed to be decreasing with the increase in the diffusible Hydrogen content in deposited metal and minimum value was measured to be 180 MPa for 12.54 ml of diffusible Hydrogen per 100 g of deposited metal.
Chris Bryan - One of the best experts on this subject based on the ideXlab platform.
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brittle nature and the related effects of zirconium hydrides in zircaloy 4
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2019Co-Authors: Chinthaka M. Silva, Fadilah Ibrahim, Elizabeth G Lindquist, Jake W Mcmurray, Chris BryanAbstract:Abstract The use of zirconium alloys such as Zircaloy-4 in nuclear reactors is limited by brittle hydride formation, for example in harsh reactor operating conditions such as those in the pressurized water reactors. Even though much research has studied this phenomenon, a more systematic, in-depth study of the effects of hydrides on the properties of Zircaloy-4, using various analytical techniques, can add more details to the understanding of these effects. In the current study, Hydrogen charging was performed on Zircaloy-4 at different Levels compatible with commercial reactor operating conditions and conditions in accident scenarios. Effects of hydriding on the Zircaloy-4 (α-(hcp)-Zr) tensile properties, together with an in-depth study of any relationship between tensile and the microstructural properties of the material, are discussed. While a moderate pinning effect on the equiaxed α-Zr grain size was observed, no significant change in bulk texture of the Zry-4 was revealed as the Hydrogen Level increased up to nominally 1230 wppmH. At a nominal value of 490 wppmH, Zircaloy-4 fractured at a low strain value just above the yielding point, and brittle tensile fracture was observed in a sample H-charged to nominally 1230 wppmH. The low ductility and brittle fracture of the samples were attributed to the presence of brittle inter-grain boundary hydrides. It was observed that brittle fracturing was also supported by intra-grain boundary hydrides that were affected by the tensile deformation of the sample.
