Microstructural Evolution of Alloy 617 and Alloy 230 Following High Temperature Aging

2010 ◽  
Author(s):  
Kun Mo ◽  
Gianfranco Lovicu ◽  
Hsiao-Ming Tung ◽  
Xiang Chen ◽  
James F. Stubbins
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Microstructural Evolution ◽  
Microstructure Evolution ◽  
Electron Backscatter Diffraction ◽  
Degradation Process ◽  
Mechanical Tests ◽  
Evolution Process ◽  
Precipitation Process ◽  
Alloy 617

Alloy 617 and Alloy 230 are solid-solution strengthened nickel based superalloys, which have been considered two of the most promising structural materials for the Very-High-Temperature Reactor (VHTR). In order to have a better understanding of the degradation process of the materials in the VHTR, long-term aging experiments have been carried out to investigate the dynamic process of microstructure evolution at 900 and 1000°C for Alloy 617 and Alloy 230. The microstructural evolution process in different aging periods (up to 3000 hours) was analyzed by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD). A diffusion-controlled precipitation and coarsening of carbide particles (mainly M23C6 and M6C) for both alloys was observed. The corresponding characteristics of the precipitates, i.e. type, size and coherence, were analyzed. The coarsening rate of the intergranular precipitates in Alloy 617 was found to be much faster compared to Alloy 230’s. The inhomogeneous precipitation process in the transverse plane of Alloy 617 was observed, which may be attributed to the alignment of the inclusion particles induced by the hot rolling. Hardness and tensile tests were carried out to investigate the aging impacts on materials’ strength. Both alloys obtained increased hardness and strength during early stages of aging and softened after elongated time. The results of mechanical tests were in a good agreement with the microstructure evolution process.

High Temperature Aging and Corrosion Study on Alloy 617 and Alloy 230

2010 ◽  
Vol 133 (5) ◽  
Author(s):  
Kun Mo ◽  
Gianfranco Lovicu ◽  
Hsiao-Ming Tung ◽  
Xiang Chen ◽  
James F. Stubbins
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Temperature ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Degradation Process ◽  
Grain Boundary Character Distribution ◽  
Alloy 617 ◽  
Production Of Hydrogen ◽  
Nuclear Systems

The very high temperature gas-cooled reactor (VHTR), with dual capacities of highly efficient electricity generation and thermochemical production of hydrogen, is considered as one of the most promising Gen-IV nuclear systems. The primary candidate materials for construction of the intermediate heat exchanger (IHX) for the VHTR are alloy 617 and alloy 230. To have a better understanding of the degradation process during high temperature long-term service and to provide practical data for the engineering design of the IHX, aging experiments were performed on alloy 617 and alloy 230 at 900°C and 1000°C. Mechanical properties (hardness and tensile strength) and microstructure were analyzed on post-aging samples after different aging periods (up to 3000 h). Both alloys attained increased hardness during the early stages of aging and dramatically soften after extended aging times. Microstructural analysis including transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscatter diffraction was carried out to investigate the microstructure evolution during aging. A carbide particle precipitation, growth, and maturing process was observed for both alloys, which corresponds to the changes of the materials’ mechanical properties. Few changes in grain boundary character distribution and grain size distribution were observed after aging. In addition, high temperature corrosion studies were performed at 900°C and 1000°C for both alloys. Alloy 230 exhibits much better corrosion resistance at elevated temperature compared with alloy 617.

High Temperature Aging and Corrosion Study on Alloy 617 and Alloy 230

2010 ◽  
Author(s):  
Kun Mo ◽  
Gianfranco Lovicu ◽  
Hsiao-Ming Tung ◽  
Xiang Chen ◽  
James F. Stubbins
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Electron Backscatter Diffraction ◽  
Microstructural Analysis ◽  
Degradation Process ◽  
Grain Boundary Character Distribution ◽  
Alloy 617 ◽  
Grain Boundary Character ◽  
Production Of Hydrogen ◽  
Nuclear Systems

The very high temperature gas-cooled reactor (VHTR), with dual capacities of highly efficient electricity generation and thermochemical production of hydrogen, is considered as one of the most promising Gen-IV nuclear systems. The primary candidate materials for construction of the intermediate heat exchanger (IHX) for the VHTR are Alloy 617 and Alloy 230. To have a better understanding of the degradation process during high temperature long-term service and provide practical data for engineering design of the IHX, aging experiments were performed on Alloy 617 and Alloy 230 at 900 and 1000°C. Mechanical properties (hardness and tensile strength) and microstructure were analyzed on post-aging samples after different aging periods (up to 3000 h). Both alloys attained increased hardness during the early stages of aging, and dramatically soften after extended aging times. Microstructural analysis including Transmission Electron Microscopy (TEM), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) were carried out to investigate the microstmcture evolution during aging. A carbide particle precipitation, growth and maturing process was observed for both alloys, which corresponds to the changes of materials’ mechanical properties. Few changes in grain boundary character distribution (GBCD) and grain size distribution were observed after aging. In addition, high temperature corrosion studies were performed at 900 and 1000°C for both alloys. Alloy 230 exhibits much better corrosion resistance at elevated temperature compared to Alloy 617.

scholarly journals Effects of Silicon Content and Tempering Temperature on the Microstructural Evolution and Mechanical Properties of HT-9 Steels

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 972 ◽  
Author(s):  
Junkai Liu ◽  
Wenbo Liu ◽  
Zhe Hao ◽  
Tiantian Shi ◽  
Long Kang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Microstructural Evolution ◽  
Charpy Impact ◽  
Hardness Test ◽  
Mechanical Tests ◽  
Fourth Generation ◽  
Martensitic Steels ◽  
Microscopic Mechanism ◽  
Tempering Temperature

Two kinds of experimental ferritic/martensitic steels (HT-9) with different Si contents were designed for the fourth-generation advanced nuclear reactor cladding material. The effects of Si content and tempering temperature on microstructural evolution and mechanical properties of these HT-9 steel were studied. The microstructure of experimental steels after quenching and tempering were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM); the mechanical properties were investigated by means of tensile test, Charpy impact test, and hardness test. The microscopic mechanism of how the microstructural evolution influences mechanical properties was also discussed. Both XRD and TEM results showed that no residual austenite was detected after heat treatment. The results of mechanical tests showed that the yield strength, tensile strength, and plasticity of the experimental steels with 0.42% (% in mass) Si are higher than that with 0.19% Si, whereas hardness and toughness did not change much; when tempered at 760 °C, the strength and hardness of the experimental steels decreased slightly compared with those tempered at 710 °C, whereas plasticity and toughness increased. Further analysis showed that after quenching at 1050 °C for 1 h and tempering at 760 °C for 1.5 h, the comprehensive mechanical properties of the 0.42% Si experimental steel are the best compared with other experimental steels.

Microstructure Evolution of the as Tempered P92 Steel at High Temperature Exposure

2020 ◽  
Vol 998 ◽  
pp. 21-29
Author(s):  
Yang Xu ◽  
Tao Lei ◽  
Xi Sheng Yang ◽  
Che Chang ◽  
Lin Feng Qian ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
High Temperatures ◽  
Microstructure Evolution ◽  
Thermal Exposure ◽  
Lath Boundary ◽  
P92 Steel ◽  
Subgrain Growth ◽  
Long Time ◽  
Dislocation Annihilation

The microstructure evolution during aging at high temperatures is usually used to thermodynamically simulate those cases of aging at low temperatures but for a very long time for P92 steel, because high temperature can accelerate the microstructure process. Therefore, in the present research, in order to comprehensively understand the microstructure evolution mechanisms during aging at especially high temperatures, the as-tempered P92 steel was exposed at 790 °C. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the microstructures. The dominant mechanisms at the four stages in microstructure evolution process during thermal exposure are (I) dislocation annihilation, (II) lath broadening and equiaxed subgrain nucleation, (III) equiaxed subgrain growth, (IV) recrystallization nucleation and growth. The martensitic lath broadening is dominated by both the motion of “Y”-type lath boundary and the combination of parallel lath boundary. The subgrain growth is by virtue of both the combination of the equiaxed subgrain and the bowing out of subgrain boundary.

scholarly journals Microstructure Evolution and Mechanical Stability of Retained Austenite in Thermomechanically Processed Medium-Mn Steel

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 501 ◽  
Author(s):  
Adam Grajcar ◽  
Andrzej Kilarski ◽  
Aleksandra Kozłowska ◽  
Krzysztof Radwański
Keyword(s):  
Electron Microscopy ◽  
Martensitic Transformation ◽  
Microstructure Evolution ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Electron Backscatter Diffraction ◽  
Bainitic Ferrite ◽  
Tensile Tests ◽  
Central Regions ◽  
Deformation Level

A microstructure evolution of the thermomechanically processed 3Mn-1.5Al type steel and mechanical stability of retained austenite were investigated during interrupted tensile tests. The microstructural details were revealed using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) techniques. It was found that the strain-induced martensitic transformation began in central regions of the largest blocky-type grains of retained austenite and propagated to outer areas of the grains as the deformation level increased. At rupture, the mechanical stability showed only boundaries of fine blocky grains of γ phase and austenitic layers located between bainitic ferrite laths. The effects of various carbon enrichment, grain size, and location in the microstructure were considered. The martensitic transformation progress was the highest at the initial stage of deformation and gradually decreased as the deformation level increased.

scholarly journals Microstructure and Mechanical Properties of an Extruded 6005A Al Alloy Composite Reinforced with TiC Nanosized Particles and Strengthened by Precipitation Hardening

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1050 ◽  
Author(s):  
Iria Feijoo ◽  
Pedro Merino ◽  
Gloria Pena ◽  
Pilar Rey ◽  
Marta Cabeza
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Precipitation Hardening ◽  
Electron Backscatter Diffraction ◽  
High Energy ◽  
Mechanical Tests ◽  
Grain Structure ◽  
Ex Situ ◽  
Al Alloy ◽  
Scanning Calorimetry

High-energy ball milling was carried out to disperse 3 vol% TiC nanoparticles (ex situ reinforcement) in a high-pressure inert gas-atomised prealloyed micron-sized 6005A Al alloy (AA6005A), with a Si/Mg atomic ratio of 1.32 powder matrix. Nanocomposite powders were consolidated by hot extrusion in strip shape at 500 °C, followed by a T6 ageing heat treatment. The microstructural features of the consolidated and precipitation hardening nanocomposites specimens were studied using X-ray diffractometry (DRX), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). The consolidated nanocomposites consisted of approximately equiaxed grains of different grain sizes with a high fraction of high-angle grain boundaries with average misorientation angles of approximately 35°. The nanocomposites showed remarkably higher hardness, Young’s modulus, yield, and ultimate strengths at room temperature than the extruded profiles of unreinforced milled AA6005A powders obtained through refinement of the Al alloy grain structure and a strong particle–matrix bonding, although with a drop in their ductility. The consolidated nanocomposite showed a weak response to industrial ageing heat treatment, as demonstrated by microstructural analyses and mechanical tests.

Characterization of Rare-Earth Fluoride Anti-Stokes Phosphors by Scanning arid Transmission Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 142-143
Author(s):  
N. M. P. Low ◽  
L. E. Brosselard
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Elevated Temperatures ◽  
Stoichiometric Composition ◽  
Rare Earth Ions ◽  
Crystalline Solid ◽  
Precipitation Process ◽  
Rare Earth Fluoride ◽  
Earth Fluoride ◽  
Rare Earth Fluorides

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.

Albumins as Embedding Media for Electron Microscopy

1969 ◽  
Vol 27 ◽  
pp. 422-423 ◽  
Author(s):  
J. L. Farrant ◽  
J. D. McLean
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Temperature ◽  
Biological Material ◽  
Globular Proteins ◽  
The Past ◽  
Antibody Staining ◽  
Thin Sectioning ◽  
Embedding Medium

For electron microscope techniques such as ferritin-labeled antibody staining it would be advantageous to have available a simple means of thin sectioning biological material without subjecting it to lipid solvents, impregnation with plastic monomers and their subsequent polymerization. With this aim in view we have re-examined the use of protein as an embedding medium. Gelatin which has been used in the past is not very satisfactory both because of its fibrous nature and the high temperature necessary to keep its solutions fluid. We have found that globular proteins such as the serum and egg albumins can be cross-linked so as to yield blocks which are suitable for ultrathin sectioning.

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