scholarly journals Effect of Different Precipitation Routes of Fe2Hf Laves Phase on the Creep Rate of 9Cr-Based Ferritic Alloys

2021 ◽  
Vol 11 (5) ◽  
pp. 2327
Author(s):  
Satoru Kobayashi ◽  
Toru Hara
Keyword(s):  
Phase Transformation ◽  
Creep Rate ◽  
Early Stage ◽  
Ferrite Matrix ◽  
Laves Phase ◽  
Creep Tests ◽  
Ferritic Alloys ◽  
Δ Ferrite ◽  
The Matrix ◽  
Creep Regime

We performed creep tests for three types of Fe-9Cr-Hf alloys with a ferritic matrix w/o Fe2Hf Laves phase particles formed by two precipitation routes: (1) with fine Fe2Hf particles formed by the conventional precipitation route (hereafter the particles are called CP particles), namely formed in the α-ferrite matrix after γ-austenite ® α-ferrite phase transformation; (2) with fine Fe2Hf particles formed by interphase precipitation (hereafter called IP particles) during δ-ferrite ® γ-austenite phase transformation before γ ® α phase transformation and (3) without Laves phase particles. CP particles were found to be effective in reducing the creep rates from the transient creep regime to the early stage of a slowly accelerating creep regime but were coarsened after the creep tests. IP particles were less effective in reducing the creep rate in the early creep stages but showed a higher stability against particle coarsening than CP particles in the creep tests, suggesting their effectiveness in delaying the recovery and recrystallization processes in the matrix and thereby retarding the onset of a rapid creep acceleration and creep rupture. The effects of the different precipitation routes are discussed based on the results obtained.

Formation of the Fe2Hf Laves Phase through Eutectoid Type Reaction of δ→γ+Fe2Hf in Ferritic Heat Resistant Steels

2015 ◽  
Vol 1760 ◽  
Author(s):  
Satoru Kobayashi
Keyword(s):  
Phase Transformation ◽  
Ferritic Steel ◽  
Laves Phase ◽  
Ferritic Steels ◽  
Microstructural Observation ◽  
Interphase Precipitation ◽  
Δ Ferrite ◽  
Term Creep ◽  
Heat Resistant Steels

ABSTRACTPeriodically arrayed rows of fine Fe2Hf Laves phase particles were found to form in 9Cr ferritic steel. Microstructural observation demonstrates that the particles were formed on cooling through the interphase precipitation on the phase transformation from the δ ferrite to the γ austenite along the eutectoid transformation route of δ → γ+Fe2Hf and subsequently a phase transformation from the austenite to the α ferrite took place. This eutectoid route is expected to be effectively used for improving the long term creep strength of ferritic steels with Laves phase.

Magnetic Field-Induced Granular Pearlite at Early Stages of Phase Transformation

2013 ◽  
Vol 650 ◽  
pp. 178-184 ◽  
Author(s):  
Xiao Ling Zhou ◽  
Ke Han ◽  
Zhong Ming Ren ◽  
Zeng Li
Keyword(s):  
Phase Transformation ◽  
Early Stage ◽  
Ferrite Matrix ◽  
Nucleation Mechanism ◽  
High Magnetic Fields ◽  
Eutectoid Temperature ◽  
Tem Analysis ◽  
Granular Pearlite ◽  
Lamellar Pearlite ◽  
Lamellar Cementite

ffects of high magnetic fields (HMF) up to 19.81T on pearlite phase transformation are studied by examination of the microstructures of a Fe-0.47C-2.3Si-3.2Mn (wt %) alloy partially isothermally processed above the eutectoid temperature. The results show that granular pearlite (GP) can be obtained at earlier transformation stages. The evolution of the granular pearlite is always accompanied by the formation of lamellar pearlite. TEM analysis reveals the existence of sub-grain boundaries within GP colonies and indicates that the nucleation of ferrite matrix in GP belongs to multiple nucleation mechanism. Most of carbides at the early stage of pearlite formation are found to precipitate at the α/γ interface--the growing front of ferrite phases, and some of coarse carbides can further develop into thin lamellar cementite.

Investigation on Behavior of the early Stage of Aging in C17200 Alloys

2013 ◽  
Vol 275-277 ◽  
pp. 1878-1883
Author(s):  
Hua Feng Lou ◽  
Qiang Song Wang ◽  
Guo Liang Xie ◽  
Li Jun Peng
Keyword(s):  
Phase Transformation ◽  
Aging Time ◽  
Spinodal Decomposition ◽  
Early Stage ◽  
Stable Phase ◽  
The Matrix

An investigation on behavior of the early stage of aging and its influence on theperformance of C17200 alloys is conducted in this paper. It is indicated that spinodal decomposition occured when the specimen is aged at 320 °C ,leading to the formation of G.P zones. A phase transformation from metastable precipitates to stable phase occurred with the increasing aging time, the sequence of which is believed as G..P→γ′′→γ′→γ. Spinodal decomposition and ordering of the matrix are found together in C17200 alloy.

From symmetry to entropy: Crystal entropy difference strongly affects early stage phase transformation

2019 ◽  
Vol 115 (26) ◽  
pp. 264103
Author(s):  
C. H. Hu ◽  
Y. C. Chen ◽  
P. J. Yu ◽  
K. Y. Fung ◽  
Y. C. Hsueh ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Early Stage

scholarly journals Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 48
Author(s):  
Wenjun Song ◽  
Min Lei ◽  
Mingpan Wan ◽  
Chaowen Huang
Keyword(s):  
Phase Transformation ◽  
Volume Fraction ◽  
Austenite Formation ◽  
Steel Matrix ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Continuous Cooling ◽  
The Matrix ◽  
Dimensional Growth ◽  
Kinetics Of

In this study, the phase transformation behaviour of the carburised layer and the matrix of 23CrNi3Mo steel was comparatively investigated by constructing continuous cooling transformation (CCT) diagram, determining the volume fraction of retained austenite (RA) and plotting dilatometric curves. The results indicated that Austenite formation start temperature (Ac1) and Austenite formation finish temperature (Ac3) of the carburised layer decreased compared to the matrix, and the critical cooling rate (0.05 °C/s) of martensite transformation is significantly lower than that (0.8 °C/s) of the matrix. The main products of phase transformation in both the carburised layer and the matrix were martensite and bainite microstructures. Moreover, an increase in carbon content resulted in the formation of lamellar martensite in the carburised layer, whereas the martensite in the matrix was still lath. Furthermore, the volume fraction of RA in the carburised layer was higher than that in the matrix. Moreover, the bainite transformation kinetics of the 23CrNi3Mo steel matrix during the continuous cooling process indicated that the mian mechanism of bainite transformation of the 23CrNi3Mo steel matrix is two-dimensional growth and one-dimensional growth.

scholarly journals Oxygen Induced Phase Transformation in TC21 Alloy with a Lamellar Microstructure

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 163
Author(s):  
Shu Wang ◽  
Yilong Liang ◽  
Hao Sun ◽  
Xin Feng ◽  
Chaowen Huang
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Oxygen Uptake ◽  
Titanium Alloys ◽  
Electron Backscatter Diffraction ◽  
Lamellar Microstructure ◽  
Α Phase ◽  
Transmission Electron ◽  
The Matrix ◽  
Oxygen Ingress

The main objective of the present study was to understand the oxygen ingress in titanium alloys at high temperatures. Investigations reveal that the oxygen diffusion layer (ODL) caused by oxygen ingress significantly affects the mechanical properties of titanium alloys. In the present study, the high-temperature oxygen ingress behavior of TC21 alloy with a lamellar microstructure was investigated. Microstructural characterizations were analyzed through optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Obtained results demonstrate that oxygen-induced phase transformation not only enhances the precipitation of secondary α-phase (αs) and forms more primary α phase (αp), but also promotes the recrystallization of the ODL. It was found that as the temperature of oxygen uptake increases, the thickness of the ODL initially increases and then decreases. The maximum depth of the ODL was obtained for the oxygen uptake temperature of 960 °C. In addition, a gradient microstructure (αp + β + βtrans)/(αp + βtrans)/(αp + β) was observed in the experiment. Meanwhile, it was also found that the hardness and dislocation density in the ODL is higher than that that of the matrix.

Microstructural Changes of Welded Zn-AI Alloy

1994 ◽  
Vol 367 ◽  
Author(s):  
Yao Hua Zhu
Keyword(s):  
Phase Transformation ◽  
Early Stage ◽  
Dendritic Structure ◽  
Metastable Phases ◽  
Grain Structure ◽  
Al Alloy ◽  
Cast State ◽  
Microstructural Changes ◽  
Fine Grain ◽  
Ageing Processes

AbstractExtruded eutectoid Zn-Al alloy was welded by a melt of the same eutectoid alloy. Two different microstructures were observed in the joint part and the bulk of the welded alloy. Typical dendritic structure of as cast Zn-Al alloy was observed in the joint part of the welded alloy. The bulk ofthe welded Zn-Al alloy appeared as fine grain structure. Two different metastable phases η'T decomposed from η's of chilled as cast state and η'E of extruded state were found to be unstable during early stage of ageing. A four phase transformation occurred after the decompositions of these two metastable phases of η'T. Microstructures of both joint part and bulk of the welded alloy were investigated parallely during ageing processes.

Atomic Resolution Microscopy of Nitrides in Steel

2014 ◽  
Vol 783-786 ◽  
pp. 1617-1622
Author(s):  
Hilmar Kjartansson Danielsen
Keyword(s):  
Amorphous Layer ◽  
Ferrite Matrix ◽  
Atomic Resolution ◽  
Incoherent Interface ◽  
The Matrix ◽  
Cr Steels

MN and CrMN type nitride precipitates in 12%Cr steels have been investigated using atomic resolution microscopy. The MN type nitrides were observed to transform into CrMN both by composition and crystallography as Cr diffuses from the matrix into the MN precipitates. Thus a change from one precipitate type to another does not necessarily involve nucleation of the new precipitate type followed by dissolution of the old precipitates. By studying the interface between these nitrides and the matrix, it could be observed that the MN and CrMN type precipitates had a few nanometers thick amorphous layer between the crystalline nitride and ferrite matrix. Usually precipitates are described as having (semi) coherent or incoherent interfaces, but in this case it is more energetically favourable to create an amorphous layer instead of the incoherent interface.

scholarly journals Squamous Cell Carcinoma in a Calyceal Diverticulum Detected by Percutaneous Nephroscopic Biopsy

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Taku Mitome ◽  
Tadashi Tabei ◽  
Yukio Tsuura ◽  
Kazuki Kobayashi
Keyword(s):  
Computed Tomography ◽  
Squamous Cell Carcinoma ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Early Stage ◽  
High Grade ◽  
Curative Intent ◽  
The Matrix ◽  
Calyceal Diverticulum ◽  
Pathological Assessment

A 73-year-old woman was referred to our department with a complaint of asymptomatic gross hematuria. Dynamic computed tomography revealed a complicated (Bosniak type IIF) cyst in the upper pole of her right kidney, which was diagnosed as a calyceal diverticulum. The diagnosis was confirmed by ureteroscopy. The diverticulum was filled with a soft protein matrix that was difficult to completely remove from the inner surface of the calyceal diverticulum. Endoscopy combined with intrarenal surgery (ECIRS) was performed to completely remove the matrix. Percutaneous nephroscopy further revealed papillary lesions on the surface of the diverticulum, confirmed as squamous cell carcinoma on pathological assessment. A laparoscopic right radical nephroureterectomy was performed, with curative intent. Pathological assessment confirmed a high-grade squamous cell carcinoma with renal parenchymal invasion (pT3). Although carcinomas in a calyceal diverticulum are highly uncommon, when present, these tend to be high-grade neoplasms that deeply invade the parenchymal wall. As the effective management of these lesions is difficult, early-stage diagnosis is required for curative treatment. We report the case of squamous cell carcinoma in a calyceal diverticulum that was difficult to diagnose on preoperative computed tomography, urinal cytology examination, and ureteroscopy but was found during ECIRS.

Microstructures and Creep of AM50-Sb-Gd Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 749-752 ◽  
Author(s):  
Su Gui Tian ◽  
Keun Yong Sohn ◽  
Hyun Gap Cho ◽  
Kyung Hyun Kim
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Mechanism ◽  
Creep Resistance ◽  
Fine Particles ◽  
Dislocation Climb ◽  
The Matrix

Creep behavior of AM50-0.4% Sb-0.9%Gd alloy has been studied at temperatures ranging from 150 to 200°C and at stresses ranging from 40 to 90 MPa. Results show that the creep rate of AM50-0.4%Sb-0.9%Gd alloy was mainly controlled by dislocation climb at low stresses under 50 MPa. The activation energy for the creep was 131.2 ± 10 kJ/mol and the stress exponent was in the range from 4 to 9 depending on the applied stress. More than one deformation-mechanism were involved during the creep of this alloy. Microstructures of the alloy consist of a–Mg matrix and fine particles, distinguished as Mg17Al12, Sb2Mg3, and Mg2Gd or Al7GdMn5 that were homogeneously distributed in the matrix of the alloy, which effectively reduced the movement of dislocations, enhancing the creep resistance. Many dislocations were identified to be present on non-basal planes after creep deformation.

Sign in / Sign up

Export Citation Format

Share Document