scholarly journals Investigation of the microstructure evolution in TP347HFG austenitic steel at 700°C and its characterization method

2021 ◽  
Vol 40 (1) ◽  
pp. 12-22
Author(s):  
Yuetao Zhang ◽  
Tingbi Yuan ◽  
Yawei Shao ◽  
Xiao Wang
Keyword(s):  
Austenitic Steel ◽  
Aging Time ◽  
Microstructure Evolution ◽  
Precipitate Phase ◽  
Dispersion Strengthening ◽  
Micro Hardness ◽  
Dispersed Particles ◽  
Nonlinear Ultrasonic ◽  
The Matrix ◽  
Solution Strengthening

Abstract This article reports the microstructure evolution in TP347HFG austenitic steel during the aging process. The experiments were carried out at 700°C with different aging time from 500 to 3,650 h. The metallographic results show that the coherent twin and incoherent twin are existed in the original TP347HFG grains, while they gradually vanished with the increase of the aging time. After aging for 500 h, a lot of fine, dispersed particles precipitated from the matrix, but they disappeared after aging for 1,500 h. When the aging time extend to 3,650 h, the precipitates appeared apparently coarse in TP347HFG steel, which include the M23C6 and σ phase; besides, the micro-hardness of TP347HFG also changes during the aging, which was closely related to the effect of dispersion strengthening and solution strengthening. The results of the nonlinear ultrasonic measurement reveal that the β′ of TP347HFG steel was also changed with the aging time. It first increased at 0–500 h, then reduced later, and increased finally at 1,500–3,650 h. The variation of β′ in TP347HFG was influenced by a combined effect of the twin microstructure and the precipitate phase, which indicate that the nonlinear ultrasonic technique can be utilized to characterize the microstructure evolution in TP347HFG.

Influence of Aging Treatments on the Microstructure Evolution in Mg-8.8Hg-8Ga (wt%) Alloys

2013 ◽  
Vol 634-638 ◽  
pp. 2565-2569
Author(s):  
Yan Feng ◽  
Ri Chu Wang ◽  
Chao Qun Peng
Keyword(s):  
Aging Time ◽  
Microstructure Evolution ◽  
Morphological Evolution ◽  
Dispersed Particles

All precipitate morphologies in Mg-8.8%Hg-8%Ga alloy for a range of aging temperatures are investigated in details using SEM, TEM and OM. The results show that Mg21Ga5Hg3 is the dominant precipitate in Mg-8.8%Hg-8%Ga alloy and precipitates in dispersed particles. This study elaborates on the morphological evolution of Mg21Ga5Hg3 precipitates as a function of aging time and temperature.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Microstructure Evolution of a Single Crystal Superalloy after Tensile Fracture at Different Temperature

2013 ◽  
Vol 721 ◽  
pp. 262-265
Author(s):  
Zhen Xue Shi ◽  
Shi Zhong Liu ◽  
J. Yu ◽  
M. Han ◽  
J.R. Li
Keyword(s):  
Single Crystal ◽  
Microstructure Evolution ◽  
Stacking Faults ◽  
Single Crystal Superalloy ◽  
Tensile Fracture ◽  
Matrix Channel ◽  
Stress Orientation ◽  
Transmission Electron ◽  
Strength Behavior ◽  
The Matrix

The tensile property tests of DD6 single crystal superalloy were performed at 25°C, 760°C and 980°C in air. Detailed microstructure evolution was carried out on the alloy to illuminate the γ phase and dislocation structure after tensile fracture by scanning electron microscope and transmission electron microscopy. The results show that the alloy has the maximum tensile strength and the minimum plasticity at 760°C. DD6 alloy has the same anomalous yield strength behavior with other single crystal superalloys. The γ phase hasve a little extension in the stress orientation after tensile fracture at 25°C. The γ phase morphology still maintains cubic after tensile fracture at 760°C. The γ phase is no longer cubic and changes into rectangular solid in the specimen tensile ruptured at 980°C. The vertical γ matrix becomes thinner and horizontal γ matrix becomes thicker slightly. The γ phase is no longer cubic and changes into rectangular solid. High density dislocations are present in the matrix channels and a lot of superlattice stacking faults are seen within γ phases in the sample tested at 25°C. A large quantities of superlattice stacking faults within γ phase and a lot of dislocations tangling in matrix channel are all present in the sample tested at 760°C. The dislocation networks have homogeneously formed at γ/γ interface in the sample tested at 980°C.

scholarly journals Rheological Solidification Behavior and Mechanical Properties of AZ91-Sn Alloys

Crystals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 641 ◽  
Author(s):  
Di Tie ◽  
Boyu Zhang ◽  
Lufei Yan ◽  
Renguo Guan ◽  
Zhaoshan Ji ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Deformation ◽  
Eutectic Reaction ◽  
Az91 Alloy ◽  
Solidification Behavior ◽  
Magnesium Matrix ◽  
Solid Solution Strengthening ◽  
The Matrix ◽  
Deformation Behaviors ◽  
Solution Strengthening

The solidification and tensile deformation behaviors of rheo-cast AZ91-Sn alloys were revealed to study the effects of Sn alloying on improvement of AZ91 alloy’s mechanical properties. Two kinds of Mg17Al12 phases precipitated from the supersaturated magnesium matrix during rheo-solidification were observed: coarse discontinuous precipitates (DP) at grain boundaries and small-sized continuous precipitates (CP) inside grains. With increasing Sn content, the amount of Mg17Al12 phases was increased whilst the amount of Al atoms in the matrix was decreased. Due to the higher melting point of Mg2Sn than Mg17Al12, Mg2Sn precipitated earlier from the melt, and therefore provided heterogeneous nuclei for Mg17Al12 during the eutectic reaction. Due to grain refinement and solid solution strengthening, AZ91-2.4Sn (mass%) gained 52% increase in tensile strength and 93% increase in elongation compared with pure AZ91 alloy. The higher-density twins and microcracks induced by Sn alloying relaxed stress concentration during plastic deformation, so the fracture mode was transformed from cleavage fracture of pure AZ91 alloy to ductile fracture of AZ91-Sn alloys.

scholarly journals Microstructure Evolution and Failure Behavior of Stellite 6 Coating on Steel after Long-Time Service

Coatings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 532 ◽  
Author(s):  
Jiankun Xiong ◽  
Fuheng Nie ◽  
Haiyan Zhao ◽  
Liangliang Zheng ◽  
Jun Luo ◽  
...  
Keyword(s):  
Fusion Zone ◽  
Microstructure Evolution ◽  
Failure Behavior ◽  
Micro Hardness ◽  
Time Service ◽  
Stellite 6 ◽  
Long Time ◽  
Metallic Compounds ◽  
Hardness Increase ◽  
Stellite Coating

The microstructure evolution, elements diffusion and fracture behavior of the Stellite 6 weld overlay, deposited on 10Cr9Mo1VNbN (F91) steel by the tungsten inert gas (TIG) cladding process, were investigated after long-time service. Obvious diffusion of Fe occurred from the steel and fusion zone to the Stellite overlay, resulting in the microstructure evolution and hardness increase in the coating, where hard Co–Fe phases, σ phases (Fe–Cr metallic compounds) and Cr-rich carbides (Cr18.93Fe4.07C6) were formed. Besides, the width of the light zone, combined with the fusion zone and diffusion zone, increased significantly to a maximum value of 2.5 mm. The fracture of the Stellite coating samples mainly occurred in the light zone, which was caused by the formation and growth of circumferential crack and radial crack under high temperature and pressure conditions. Moreover, the micro-hardness values in the light zone increased to the maximum (470–680 HV) due to the formation and growth of brittle Co–Fe phases. The formation of these cracks might be caused by formed brittle phases and changes of micro-hardness during service.

scholarly journals Fabrication and Mechanical Properties of Cnt/6063 Al Composites Prepared by Vacuum Assisted Infiltration Technique Using Cnt-Al Preforms

2012 ◽  
Vol 21 (5) ◽  
pp. 096369351202100 ◽  
Author(s):  
Bedri Onur Kucukyildirim ◽  
Aysegul Akdogan Eker
Keyword(s):  
Mechanical Properties ◽  
Matrix Composites ◽  
Reinforced Composites ◽  
Dispersion Strengthening ◽  
Al Composite ◽  
Multi Walled Carbon Nanotube ◽  
The Matrix ◽  
Infiltration Technique ◽  
Al Matrix Composites ◽  
Nano Size

Industrial type multi-walled carbon nanotube (MWCNT) reinforced aluminum (Al) matrix composites are successfully fabricated by vacuum assisted infiltration of Al into the CNTs-Al preform and compressive mechanical properties of these composites are investigated. The compressive properties and hardness of CNT reinforced composites are fairly increased compared with the previous CNT/Al composite studies. Furthermore, our study confirms that the mechanical enhancements of the composites are interrelated with bridging and pulling-out of CNTs in the fracture surfaces. Moreover, the presence of CNTs leads to dispersion strengthening of the matrix because of their nano size.

scholarly journals Morphological Evolutions of Ni-Rich Phases in Al-Si Piston Alloys during 250–400 °C Thermal Exposure Processes

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5212
Author(s):  
Haowei An ◽  
Jiwei Geng ◽  
Zeyu Bian ◽  
Gen Liu ◽  
Mingliang Wang ◽  
...  
Keyword(s):  
Morphological Evolution ◽  
Morphological Characteristics ◽  
Hardness Test ◽  
Thermal Exposure ◽  
Micro Hardness ◽  
Morphological Transformation ◽  
Alloy Hardness ◽  
The Matrix ◽  
Hardness Increase ◽  
Exposure Process

The thermal stability of the Al-Si alloys during the thermal exposure process from 250 °C to 400 °C was systematically investigated. The relationships between the morphological evolution and the mechanical changes of the alloys were determined through the Vickers hardness test and materials characterization method. Initially, the alloys exhibited similar thermal degradation behavior. For example, the exposure process of the alloy at 300 °C can be divided into two stages according to the changes of the alloy hardness and the matrix micro-hardness. In detail, the first stage (0–2 h) exhibited a severe reduction of the alloy hardness while the second stage showed a more leveled hardness during the following 98 h. There are three identified morphological characteristics of Ni-rich phases in the alloy. Furthermore, the differences in both composition and the micro-hardness between these Ni-rich phases were confirmed. The underlying relationships between the morphological transformation of the Ni-rich phases and hardness fluctuation in the alloy were correlated and elucidated. The observed alloy hardness increase when the exposure temperature was 400 °C was unexpected. This behavior was explained from the perspectives of both Ni-rich phases evolution and dispersoid formation.

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