scholarly journals Evolution of Precipitated Phases during Creep of G115/Sanicro25 Dissimilar Steel Welded Joints

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5018
Author(s):  
Maohong Yang ◽  
Zheng Zhang ◽  
Linping Li
Keyword(s):  
Laves Phase ◽  
Creep Process ◽  
M23c6 Carbide ◽  
Second Phase ◽  
Creep Tests ◽  
Dissimilar Steel ◽  
Fine Grain ◽  
Microstructure Morphology ◽  
Precipitated Phases ◽  
The Relationship

This paper studies the evolution of the microstructure and microhardness in the G115 side of the G115/Sanicro25 dissimilar steel welded joint during the creep process. The joints were subjected to creep tests at 675 °C, 140 MPa, 120 MPa and 100 MPa. A scanning electron microscope equipped with an electron backscattering diffraction camera was used to observe the microstructure of the cross-section. The fracture position of the joint and the relationship between the cavity and the second phase were analyzed. The microstructure morphology of the fracture, the base metal and the thread end was compared and the composition and size of the Laves phase were statistically analyzed. The results show that the fracture locations are all located in the fine-grain heat-affected zone (FGHAZ) zone, and the microstructure near the fracture is tempered martensite. There are two kinds of cavity in the fracture section. Small cavities sprout adjacent to the Laves phase; while large cavities occupy the entire prior austenite grain, there are more precipitated phases around the cavities. The Laves phase nucleates at the boundary of the M23C6 carbide and gradually grows up by merging the M23C6 carbide. Creep accelerates the coarsening rate of the Laves phase; aging increases the content of W element in the Laves phase.

Evolution of Laves-Phase Particles in a Low Carbon 9%Cr Martensitic Steel during Creep at 650°C

2014 ◽  
Vol 922 ◽  
pp. 155-160 ◽  
Author(s):  
Irina Fedorova ◽  
Andrey Belyakov ◽  
Pavel Kozlov ◽  
Vladimir Skorobogatykh ◽  
Izabella Schenkova ◽  
...  
Keyword(s):  
Structural Changes ◽  
Laves Phase ◽  
Second Phase ◽  
Low Carbon ◽  
Creep Tests ◽  
Creep Time ◽  
Term Creep ◽  
Lath Structure ◽  
Evolution Of Microstructure ◽  
Relationship Of

The evolution of microstructure in low carbon heat resistant steel of P92-type modified with 3%Co was examined during creep tests at 923K for 500, 1500, 6000 and 16000 hours. After tempering at 1023K (750°C), the steel was composed of martensite lath structure with numerous precipitates of MX-type carbonitrides and rare M23C6-type carbides. The structural changes during creep tests are characterized by an increase in the sizes of laths and second phase particles. Moreover, the Fe2W Laves-phase precipitates during long-term creep. The Laves-phase particles grow accordingly to power-law relationship of creep time.

Zener Pinning Pressure in Tempered Martensite Lath Structure

2012 ◽  
Vol 715-716 ◽  
pp. 745-750 ◽  
Author(s):  
Dmitro Kolesnikov ◽  
Andrey Belyakov ◽  
Alla Kipelova ◽  
Valeriy Dudko ◽  
Rustam Kaibyshev ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Metallic Matrix ◽  
Laves Phase ◽  
Second Phase ◽  
Tempered Martensite ◽  
Creep Tests ◽  
Zener Pinning ◽  
Second Phase Particles ◽  
Lath Structure

The Zener drag force exerted by M23C6carbides, Fe2(W,Mo) Laves phase and M(C,N) particles for migration of different grain boundaries in P92-type and P911+3%Co heat-resistant steels was calculated. In particular, the prior austenite grain boundaries (PAGB), boundaries of packets and blocks, which are mainly high-angle boundaries (HAGB), were addressed. Zener pinning pressures were determined for each type of dispersoids separately taking into account that the M23C6carbides, Fe2(W,Mo) Laves phase are inhomogeneously distributed such that they are mainly located at the boundaries, and the M(C,N) dispersoids are uniformly distributed throughout the metallic matrix. In the both steels, the pinning pressure from the second phase particles located at grain boundaries is about an order of magnitude higher than that caused by homogeneously distributed MX precipitates. In spite of numerous second phase particles precipitated during tempering, grain growth (although rather moderate) occurred during the creep tests of the studied materials. The driving pressure for grain boundary motion might be mostly associated with high dislocation density retained in the tempered martensite structure. The resulting pressure for grain growth in the P92-type steel under creep conditions at 600 and 650°C is somewhat higher than that for the P911 steel.

The Effect of Titanium Addition on Microstructure and Properties of Laves Phase Cr2Nb Alloy Synthesized by Hot Pressing

2011 ◽  
Vol 328-330 ◽  
pp. 1102-1108 ◽  
Author(s):  
Xuan Xiao ◽  
Shi Qiang Lu ◽  
Xian Juan Dong ◽  
Ming Gang Huang ◽  
Jun Wei Liu
Keyword(s):  
Fracture Toughness ◽  
Mechanical Alloying ◽  
Hot Pressing ◽  
Laves Phase ◽  
Nominal Composition ◽  
Second Phase ◽  
Titanium Addition ◽  
Fine Grain ◽  
The Matrix ◽  
Homogeneous Composition

The composite materials with a nominal composition of Cr2Nb-24wt.%Ti were fabricated by mechanical alloying followed by hot pressing. The microstructures and properties were investigated on the composites contained with Laves phase prepared through 20 hours mechanical alloying of chromium, niobium and titanium elemental powders and hot pressing at 1250°C for half an hour. The results indicate that the near full-dense Laves phase Cr2(Nb,Ti) based alloy with homogeneous composition and microstructure is obtained by mechanical alloying and hot pressing techniques. The dispersed soft second phase Nb solid solutions with the fine grain size less than 1μm are distributed uniformly on the matrix. The sample has a relative density of 99%, fracture toughness of 5.32MPa•m1/2 and compress strength of 2080MPa. Due to the effect of fine-grain and alloying addition, the toughening of the Cr2(Nb,Ti) based alloy has been fully realized.

Investigation on Creep Properties of Welded Joint of Modified 9Cr-1Mo Martensitic Heat-Resistant Steel

2019 ◽  
Vol 795 ◽  
pp. 312-317
Author(s):  
Fa Cai Ren ◽  
Xiao Ying Tang ◽  
Jun Si
Keyword(s):  
Creep Rupture ◽  
Creep Process ◽  
Metallographic Analysis ◽  
Resistant Steel ◽  
Test Results ◽  
Creep Tests ◽  
Heat Resistant Steel ◽  
Fine Grained ◽  
Heat Resistant ◽  
The Relationship

The creep rupture behavior of weld joint of modified 9Cr-1Mo martensitic heat-resistant steel is investigated by conducting creep tests. The creep strain-time curves of 838K under different stress levels are obtained. The effects of different stress conditions on the creep rupture lifetime are analyzed. Based on the creep test data, the relationship between minimum creep rate and stress, creep rupture time is analyzed. The test results show that the creep rupture occurred in the fine-grained heat-affected zone. The microstructure evolution during creep process is studied by metallographic analysis and fracture analysis.

Morphology of Σ3{/70.53°} grain boundaries in a C15 intermetallic compound

1994 ◽  
Vol 52 ◽  
pp. 684-685
Author(s):  
Fuming Chu ◽  
D. P. Pope ◽  
D. S. Zhou ◽  
T. E. Mitchell
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Crystallographic Analysis ◽  
Laves Phase ◽  
Second Phase ◽  
Bright Field Image ◽  
Boundary Edge ◽  
Arc Melting ◽  
Fcc Lattice ◽  
Diffraction Patterns

A C15 Laves phase, HfV2+Nb, shows promising mechanical properties and here we describe the structure of its grain boundaries. The C15 Laves phase has a fcc lattice with a=7.4Å. An alloy of composition Hf14V64Nb22 (including a C15 matrix and a second phase of V-rich bcc solution) was made by arc-melting. The alloy was homogenized at 1200°C for 120h. Preliminary study concentrated on Σ3{<110>/70.53°} grain boundaries in the C15 phase using Philips 400T and CM 30 microscopes.The most-commonly observed morphology of Σ3{<110>/70.53°} grain boundaries in the C15 phase is a faceted boundary. A bright field image (BFI) of the faceted boundary and the corresponding diffraction patterns with the grain boundary edge-on are shown in Fig. 1(a). From the diffraction patterns using a <110> zone axis for both grains, it is obvious that this is a Σ3{<110>/70.53°} grain boundary. Crystallographic analysis shows that the Σ3{<110>/70.53°} grain boundaries selectively facet with the following relationships between the two grains: {111}1//{111}2, {112}1//{112}2, {111}1//{115}2, and {001}1//{221}2.

scholarly journals Effect of Nano-Y2O3 Addition on Microstructure and Tensile Properties of High-Nb TiAl Alloy Prepared by Spark Plasma Sintering

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1048
Author(s):  
Yingchao Guo ◽  
Yongfeng Liang ◽  
Junpin Lin ◽  
Fei Yang
Keyword(s):  
Tensile Strength ◽  
Spark Plasma Sintering ◽  
Tial Alloy ◽  
Second Phase ◽  
Fine Grain ◽  
Fine Grain Strengthening ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Y2o3 Addition ◽  
Powder Metallurgy Route

Nano-Y2O3 reinforced Ti-47.7Al-7.1Nb-(V, Cr) alloy was fabricated by a powder metallurgy route using spark plasma sintering (SPS), and the influence of nano-Y2O3 contents on the microstructure and mechanical properties were investigated systematically. The results revealed that the ultimate tensile strength and elongation of the alloy were 570 ± 28 MPa and 1.7 ± 0.6% at 800 °C, 460 ± 23 MPa and 6.1 ± 0.4% at 900 °C with no nano-Y2O3, 662 ± 24 MPa and 5.5 ± 0.5% at 800 °C, and 466 ± 25 MPa and 16.5 ± 0.8% at 900 °C with 0.05 at% nano-Y2O3 addition, respectively. Due to the fine-grain strengthening and the second-phase strengthening, both tensile strength and elongation of the high-Nb TiAl alloy were enhanced with the addition of nano-Y2O3.

A Study on Estimation of Internal Pressure Creep Life Using Small Punch Creep (SPC) Tests for Boiler Pipes

2009 ◽  
Author(s):  
Toshimi Kobayashi ◽  
Toru Izaki ◽  
Junichi Kusumoto ◽  
Akihiro Kanaya
Keyword(s):  
Internal Pressure ◽  
Residual Life ◽  
Test Results ◽  
Creep Life ◽  
Creep Tests ◽  
Good Correspondence ◽  
Small Punch ◽  
Uniaxial Creep ◽  
Wide Range ◽  
The Relationship

The small punch creep (SPC) test is possible to predict residual creep life at a high accuracy. But, the results of SPC tests cannot be compared with uniaxial creep or internal pressure creep results directly. In this report, the relationship between SPC test results and uniaxial creep test results in ASME A335 P11 (1.25Cr-0.5Mo Steel) was studied. The obtained relationship between SPC load and equivalent uniaxial creep stress formed a simple linear equation under the wide range of test temperature and test period. Then, the SPC results can be compared with uniaxial results by converting SPC loads to the equivalent uniaxial creep stresses. The relationship between SPC test results and internal pressure creep tests results was also studied. The internal creep life of as-received P11 pipe was almost same as SPC result when the hoop stress was converted to the SPC load. The creep lives of internal pressure creep influenced materials also showed good correspondence with SPC results. Therefore SPC can estimate the residual life of internal pressure creep influenced materials.

scholarly journals Coherent Precipitation and Strengthening in Compositionally Complex Alloys: A Review

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 878 ◽  
Author(s):  
Qing Wang ◽  
Zhen Li ◽  
Shujie Pang ◽  
Xiaona Li ◽  
Chuang Dong ◽  
...  
Keyword(s):  
Solid Solution ◽  
High Performance ◽  
Particle Morphology ◽  
Precipitation Strengthening ◽  
Second Phase ◽  
High Entropy ◽  
Second Phase Particles ◽  
Alloy Strength ◽  
Solid Solution Matrix ◽  
The Relationship

High-performance conventional engineering materials (including Al alloys, Mg alloys, Cu alloys, stainless steels, Ni superalloys, etc.) and newly-developed high entropy alloys are all compositionally-complex alloys (CCAs). In these CCA systems, the second-phase particles are generally precipitated in their solid-solution matrix, in which the precipitates are diverse and can result in different strengthening effects. The present work aims at generalizing the precipitation behavior and precipitation strengthening in CCAs comprehensively. First of all, the morphology evolution of second-phase particles and precipitation strengthening mechanisms are introduced. Then, the precipitation behaviors in diverse CCA systems are illustrated, especially the coherent precipitation. The relationship between the particle morphology and strengthening effectiveness is discussed. It is addressed that the challenge in the future is to design the stable coherent microstructure in different solid-solution matrices, which will be the most effective approach for the enhancement of alloy strength.

Growth Mechanism vs Matter Transport in Thermally Growing Oxides on High Temperature Materials: A Brief Survey Based on the Case Study of Alumina Formers

2009 ◽  
Vol 289-292 ◽  
pp. 385-395 ◽  
Author(s):  
Jerzy Jedlinski
Keyword(s):  
Growth Mechanism ◽  
Experimental Approach ◽  
Experimental Results ◽  
Metallic Materials ◽  
High Temperature Materials ◽  
Matter Transport ◽  
Alumina Formers ◽  
Microstructure Morphology ◽  
The Relationship

This paper reviews briefly the relationship between the growth mechanism and matter transport using as an example the best currently applied metallic materials being alumina formers. The attention is paid to the experimental approach as well as to the interpretation procedure of experimental results. The scale structure, microstructure, morphology and phase composition are indicated as factors strongly affecting its growth mechanism. The attempt is made to elucidate the possible relationships between the obtained experimental results and actual scale growth mechanisms operating during oxidation exposures.

Microstructure of Friction Stir Processed Mg-Y-Zn Alloy

2007 ◽  
Vol 558-559 ◽  
pp. 777-780 ◽  
Author(s):  
Taiki Morishige ◽  
Masato Tsujikawa ◽  
Sung Wook Chung ◽  
Sachio Oki ◽  
Kenji Higashi
Keyword(s):  
Equal Channel Angular Extrusion ◽  
Second Phase ◽  
Ingot Metallurgy ◽  
Friction Stir ◽  
Fine Grained ◽  
Probe Diameter ◽  
Fine Grain ◽  
Second Phase Particles ◽  
The Matrix ◽  
Zn Alloy

Friction stir processing (FSP) is the effective method of the grain refinement for light metals. The aim of this study is to acquire the fine grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Such bulk alloy can be formed by the superplastic forging. The microstructure of as-cast Mg-Y-Zn alloy was dendrite. The dendrite arm spacing was 72.5 [(m], and there are the lamellar structures in it. FSP was conducted on allover the plate of Mg-Y-Zn alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. The matrix became recrystallized fine grain, and interdendritic second phase particles were dispersed in the grain boundaries. By using FSP, cast Mg-Y-Zn alloy could have fine-grained. This result compared to this material produced by equal channel angular extrusion (ECAE) or rapid-solidified powder metallurgy (RS P/M). As the result, as-FSPed material has the higher hardness than materials produced by the other processes at the similar grain size.

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