manuel a. pouchon :: head of lnm :: paul scherrerinstitut · pdf file ·...

WIR SCHAFFEN WISSEN – HEUTE FÜR MORGEN

Nuclear Fuels and Materials - 151-2017-00L

Manuel A. Pouchon :: Head of LNM :: Paul Scherrer Institut

Master of Nuclear Engineering ‐ Spring Semester 2016

Nuclear Fuels and Materials - 151-2017-00L ⌸ Lecture 2 - Page 2/112

• Phase diagramso Eutectic and Eutectoid

• Ternary Phase Diagram / Scheffler Diagram• Phase Transformation Diagrams (Dynamics) - Introduction• Fe-C system

o Ferriteo Austeniteo Cementiteo Bainite, Perliteo Martensiteo Phase Transformation Diagrams – Microstructure Formation

• Criteria for material selection• Deformation• Toughness• Intro to Fatigue & Creep-Fatigue• Reactor pressure vessel (RPV)• Irradiation damage

TOC


3

One Component Phase Diagram


• Components:The elements or compounds that are mixed initially (Al and Cu).

• Phases:A phase is a homogenous, physically distinct and mechanically separable portion of the material with a given chemical composition and structure ( and ).

(darker phase)

(lighter phase)

Aluminum‐

Copper

Alloy

(fcc)

Components and Phases


©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

The aluminum-copper phase diagram and the microstructures that may develop during cooling of an Al-4% Cu alloy.

Al-Cu diagram



The aluminum-rich end of the aluminum-copper phase diagram showing the three steps in the age-hardening heat treatment and the microstructures that are produced.

αSS:supersaturated solid solution

Al-Cu: Quenching, aging


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Phase Diagrams (1): Eutectics


Constitution Point

Tie Line

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Phase Diagrams (2): Proportions of phases in two phase alloys


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Phase Diagrams (3): Metallic alloys – eutectics and eutectoids


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Fe-C Phase Diagram


Not only carbon, but also the other alloying elements like:• Cr, • Ni, • Mo or • V• etc.affect microstructure and microstructural properties. Ternary phase diagrams (shown up) and the Schaeffler Diagram (next slide) provide important information particularly for welding (which is a local melting/solidification process)

Ternary diagram of Ni-Cr-Fe at 1000 oC

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Ternary Phase Diagrams


The Schaeffler-Diagram I


Nickel-Equivalent% Ni + 30 % C + 0,5 % Mn

Nickel is a former of austenite

Chromium-Equivalent% Cr + % Mo + 1,5 % Si + 0,5 % Nb + 2 % Ti

Chromium is a former of ferrite

The Nickel-Equivalent and the Chromium-Equivalent are the key parameters which determine the microstructure.

The Schaeffler-Diagram II


The Schaeffler-Diagram III


The Schaeffler-Diagram IV: Example for SS304

The Nickel and other elements that form Austenite, are plotted against Chrome and other elements thatform ferrite, using the following formula:

Nickel Equivalent = %Ni + 30%C + 0.5%Mn

Chrome Equivalent = %Cr + Mo + 1.5%Si + 0.5%Nb

Example, a typical 304L = 18.2%Cr, 10.1%Ni, 1.2%Mn, 0.4%Si, 0.02%C

Ni Equiv = 10.1 + 30 x 0.02 + 0.5 x 1.2 = 11.3

Cr Equiv = 18.2 + 0 + 1.5 x 0.4 + 0 = 18.8


The Schaeffler-Diagram IV: Extension

Delong Diagram

This refines the Schaffler diagram by taking account of the strong austenite stabilizing tendency of nitrogen. The chromium equivalent is unaffected but the nickel equivalent is modified to

Ni (eq) = Ni + (30 x C) + (0.5 x Mn) + (30 x N)

The diagram, identifying the phase boundaries is shown below. This shows the ferrite levels in bands, both as percentages, based on metallographic determinations and as a ferrite number 'FN', based on magnetic determination methods.

http://www.bssa.org.uk/topics.php?article=121

DeLong constitution diagram for stainless steel weld metal. The Schaeffler austenite-martensite boundary is included for reference






TOC


Time-Temperature-Transformation

TTT diagram for carbon steels


TTP (time-temperature-precipitation)

M23C6 Precipitate

Precipitates

TTP-diagram of a martensitic 9-12% Cr steel


TTP diagram from Powell






TOC


Metals

Ferrous metals

Steels

Plain carbon steels

Low carbon steels

Medium carbon steels

High carbon steels

Low alloy steels

High alloy steelsStainless & Tool

steels

Cast Irons

Grey Iron

White Iron

Malleable & Ductile Irons

Non-ferrous metals

Steel Microstructures: http://www.threeplanes.net/SiteMap.html

2-6 % C

0.9-2.5 % C

0.05-0.3 % C

0.25-0.6 % C

Alloying element < 4-8%

Alloying element > 4-8%

Classification of metals


Five main constituents:• Ferrite• Austenite• Cementite• Pearlite• Martensite

Microstructure of Steel


Iron Carbon Phase Diagram


• FerriteAllotropes of ferrite include:

• α-iron (Alpha ferrite, bcc)• δ-iron (Delta ferrite, high T, bcc)• β-iron (Beta ferrite, paramagnetic form of α ferrite)• ε-iron (Hexaferrum, hcp at high pressure)• γ-iron (Gamma ferrite, fcc)

• Austenite (γ-iron + carbon in solid solution)

• Cementite (iron carbide, Fe3C)

• Graphite (allotrope of carbon)

• Martensite (BCT, metastable phase, quenching of Aust.)

• ε-carbon (transitional carbide, Fe24C)

Iron-C System I: Allotropes


The structure of pure iron. Has a body-centered cubic (BCC) crystal structure. It is soft and ductile and imparts these properties to the steel. Very little carbon (less than 0.01% carbon will dissolve in ferrite at room temperature). Often known as iron.

A photomicrograph of 0.1% carbon steel (mild steel). The light areas are ferrite.

Ferrite


Ferrite is a body-centered cubic (BCC) form of iron, in which a very small amount(a maximum of 0.02% at 1333°F / 723°C) of carbon is dissolved. This is far less carbon than canbe dissolved in either austenite or martensite, because the BCC structure has much less interstitialspace than the FCC structure. Ferrite is the component which gives steel and cast iron theirmagnetic properties, and is the classic example of a ferromagnetic material. This is also the reasonthat tool steel becomes non-magnetic above the hardening temperature - all of the ferrite has beenconverted to austenite. Most "mild" steels (plain carbon steels with up to about 0.2 wt% C) consistmostly of ferrite, with increasing amounts of cementite as the carbon content is increased, whichtogether with ferrite, form the mechanical mixture pearlite. Any iron-carbon alloy will contain someamount of ferrite if it is allowed to reach equilibrium at room temperature.

Photomicrograph of Ferrite Structure

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Ferrite II

The interstitial site for dissolving a carbon atom in alpha-Fe (which is bcc) is the 1/2 0 1/2 type positions as shown here:

This drawing is not to scale as the carbon atom is actually more than four times too large for this site. Consequently carbon solubility in alpha-Fe is quite low. (~0.02%)atomic radius: Fe: 0.127 nm / C: 0.077 nm


High temperature structure of pure iron:

This is the structure of iron at high temperatures (over 912 °C). Has a face-centre cubic (FCC) crystal structure. This material is important in that it is the structure from which other structures are formed when the material cools from elevated temperatures. Often known as iron. Not present at room temperatures.

Austenite

Interstitial solution of carbon in the high-temperature structure of gamma-Fe which is fcc. The largest interstitial site for a carbon atom is a 1/2 0 1 type position.

Homework:Determine by how much the C atom in gamma-Fe is oversize.atomic radius: Fe: 0.127 nm / C: 0.077 nm


Austenite is a metallic, non-magnetic solid solution of carbon and iron that exists in steelabove the critical temperature of 1333°F ( 723°C). Its face-centred cubic (FCC) structureallows it to hold a high proportion of carbon in solution. As it cools, this structure eitherbreaks down into a mixture of ferrite and cementite (usually in the structural forms pearliteor bainite), or undergoes a slight lattice distortion known as martensitic transformation.The rate of cooling determines the relative proportions of these materials and thereforethe mechanical properties (e.g. hardness, tensile strength) of the steel. Quenching (toinduce martensitic transformation), followed by tempering (to break down some martensite andretained austenite), is the most common heat treatment for high-performance steels. Theaddition of certain other metals, such as manganese and nickel, can stabilize the austeniticstructure, facilitating heat-treatment of low-alloy steels. In the extreme case of austeniticstainless steel, much higher alloy content makes this structure stable even at roomtemperature. On the other hand, such elements as silicon, molybdenum, and chromium tend tode-stabilize austenite, raising the eutectoid temperature (the temperature where two phases,ferrite and cementite, become a single phase, austenite).

Austenite can contain far more carbon than ferrite, between 0.8% at 1333°F (723°C) and2.08% at 2098°F (1148°C). Thus, above the critical temperature, all of the carbon contained inferrite and cementite (for a steel of 0.8% C) is dissolved in the austenite.

http://threeplanes.net/austenite.html

Austenite II


A compound of iron and carbon, iron carbide (Fe3C).

It is hard and brittle and its presence in steels causes an increase in hardness and a reduction in ductility and toughness.

Orthorhombic (Pnma)http://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cementite

Cementite


Cementite is iron carbide with the formula Fe3C, and an orthorhombic crystal structure. It is a hard, brittle material, essentially a ceramic in its pure form. It forms directly from the melt in the case of white cast iron. In carbon steel, it either forms from austenite during cooling or from martensite during tempering. Cementite contains 6.67% Carbon by weight; thus above that carbon content in the Fe-C phase system, the alloy is no longer steel or cast iron, as all of the available iron is contained in cementite. Cementite mixes with ferrite, the other product of austenite, to form lamellar structures called pearlite and bainite. Much larger lamellae, visible to the naked eye, make up the structure of Damascus steel. Fe3C is also known as cohenite, particularly when found mixed with nickel and cobalt carbides in meteorites.

Photomicrograph of Pearlite Structure(Dark bands are cementite)

http://threeplanes.net/cementite.html

Cementite II






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A laminated structure formed of alternate layers of ferrite and cementite.

It combines the hardness and strength of cementite with the ductility of ferrite and is the key to the wide range of the properties of steels. The laminar structure also acts as a barrier to crack movement as in composites. This gives it toughness.

Two-dimensional view of pearlite, consisting of alternating layers of cementite and ferrite.

Pearlite


Pearlite is a lamellar structure consisting of alternating bands of ferrite and cementite. Pearlite exists in equilibrium in carbon steels at normal temperatures.

Dark bands are cementite,light bands are ferrite

http://threeplanes.net/pearlite.html

Pearlite II


Schematic illustration of the microstructures for an iron–carbon alloy of eutectoid composition (0.77% carbon), above and below the eutectoid temperature of 727°C

Pearlite III


Photomicrographs of samples quenched from 1200oC, deformed, annealed at 800oC in different times and air cooled: • a) and b) 1 min, c) and d) 180 min• 2% Nital: a) and c) OM; b) and d) SEM

Ferrite / Pearlite1 m

in180 m

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The evolution of the microstructure of • hypoeutectoid and • hypereutectoid steels during cooling. In relationship to the Fe-Fe3C phase diagram.

Fe-C diagram: Hypo- & Hpyer-Eutectoid


Bainitic steel


A very hard needle-like structure of iron and carbon.

Only formed by very rapid cooling from the austenitic structure (i.e. above upper critical temperature). Needs to be modified by tempering before acceptable properties reached.

The needle-like structure of martensite, the white areas are retained austenite.

Body Centered Tetragonal Unit Cell (BCT)

Martensite – What is it, how does it form


Martensite is a body-centered tetragonal form of iron in which some carbon isdissolved. Martensite forms during quenching, when the face centered cubic latticeof austenite is distored into the body centered tetragonal structure without the lossof its contained carbon atoms into cementite and ferrite. Instead, the carbon isretained in the iron crystal structure, which is stretched slightly so that it is nolonger cubic. Martensite is more or less ferrite supersaturated with carbon.Compare the grain size in the micrograph with tempered martensite.

http://threeplanes.net/martensite.html

Photomicrograph of Martensite Structure

Martensite II - Description


Martensitic Transformation: Mysterious Properties ExplainedThe difference between austenite and martensite is, in some ways, quite small:while the unit cell of austenite is a perfect cube, in the transformation to martensitethis cube is distorted so that it's slightly longer than before in one dimension andshorter in the other two.The mathematical description of the two structures is quite different, for reasons ofsymmetry, but the chemical bonding remains very similar.Unlike cementite, which has bonding reminiscent of ceramic materials, the hardnessof martensite is difficult to explain in chemical terms.The explanation hinges on the crystal's subtle change in dimension, and the speed ofthe martensitic transformation. Austenite is transformed to martensite on quenchingat approximately the speed of sound - too fast for the carbon atoms to come out ofsolution in the crystal lattice. The resulting distortion of the unit cell results incountless lattice dislocations in each crystal, which consists of millions of unit cells.These dislocations make the crystal structure extremely resistant to shear stress -which means, simply that it can't be easily dented and scratched. Picture thedifference between shearing a deck of cards (no dislocations, perfect layers of atoms)and shearing a brick wall (even without the mortar).

http://threeplanes.net/martensite.html

Martensite III –How does the transformation work


Atomic movements during transformation are cooperative in a regimented fashion with distance less than one interatomic spacing

Cause shape change in the transformed region

Surface tilt if the product ’ phase intersects a free surface of the parent phase

Martensite IV


Surface tilting:Large change in shape would cause large strain.Minimized by deformationo Twinning o Slipwith no crystal structure change

Martensite V


Martensite Transformation


When martensite is tempered, it partially decomposes intoferrite and cementite. Tempered martensite is not as hard asjust-quenched martensite, but it is much tougher. Note alsothat it is much finer-grained than just-quenched martensite.

Tempered Martensite


TTT Diagram: Time-Temperature-Transformation

Dynamics of Phase Transformation I


Temperature vs time (sec, then min)

TTT diagram for isothermal transformation of steel W 1 (1% C)A = austeniteB = bainiteP = pearlite Ms = start of martensite

transformation,M50 = 50% M

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Dynamics of Phase Transformation II


• Quenching in a liquid bath at 700 oC; holding time 4 min. During this interval the C has separated out, partly as pearlite lamellae and partly as spheroidizedcementite. Hardness 225 HV.

• Quenching to 575 oC, holding time 4 s. A very fine, closely spaced pearlite as well as some bainite has formed. Note that the amount of spheroidized cementite is much less than in the preceding case. Hardness 380 HV.

• Quenching to 450 oC, holding time 60 s. The structure consists mainly of bainite. Hardness 410 HV.

• Quenching to 20 oC (room temperature). The matrix consists of, roughly, 93% martensite and 7% retained austenite. There is some 5% cementite as well which has not been included in the matrix figure. Hardness 850 HV.

Dynamics of Phase Transformation III


The unit cells for:

(a) Austenite(b) ferrite, and(c) martensite.

The effect of percentage of carbon (by weight) on the lattice dimensions for martensite is shown in (d). Note the interstitial position of the carbon atoms. (Note also the increase in dimension c with increasing carbon content; this effect causes the unit cell of martensite to be in the shape of a rectangular prism.

The Unit Cells



The effect of transformation temperature on the properties of an eutectoid steel.

Fe-C Mechanical properties


• Extremely important class of austenitic (fcc) materials based on nickel

• Strengthening Solid solution strengthened and particle strengthened (gamma prime)

• Highly corrosion resistant

• «The» high temperature alloys • IN-600, X-750, 182/82 (RPV cladding)• Will be discussed in detail for advanced nuclear

plants (Autumn course)

Nickel-base alloys






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ASM Materials Handbook on‐line 2008

Mechanical properties

• Strength- Tensile strength (ultimate strength)- Yield strength- Compressive strength

• Hardness

• Toughness- Notch toughness- Fracture toughness

• Ductility- Total elongation- Reduction in area

• Fatigue resistance

Other properties/characteristics

• Formability- Drawability- Stretchability- Bendability

• Wear resistance- Abrasion resistance- Gallic resistance- Sliding wear resistance- Adhesive wear resistance

• Machinability

• Weldability

Typical Criteria for Materials Selection


• Irradiation Damage: Hardening, embrittlement, radiation induced segregation, radiation induced phase transformation

• Corrosion damage:Uniform, Pitting, stress-corrosion cracking, irradiation assisted stress corrosion cracking

• Fatigue damage

• Different types of crack growth

What Damage occurs in Generation II/III-plants


• Strength • Ductility • Toughness • Fatigue

Properties of metallic materials






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Deformation of Single Crystals


http://www.msm.cam.ac.uk/doitpoms/

Critical resolved shear stress (Schmids Law)


Why are there slip planes?

http://practicalmaintenance.net/?p=1135


Plane designation: Miller index


DOI: http://dx.doi.org/10.1103/PhysRevB.89.144105

Slip modes in fcc, bcc, and hcp


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One gliding plane

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Example for large pillar compression –AISI 316


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Two gliding planes

http://dx.doi.org/10.1016/j.matlet.2013.01.118

Example for small pillar compression –AISI 316


Slip Lines on a Deformed Sample


The mechanical „baseline“


Upper and lower yield stressContinuous yielding

Typical Stress-Strain Curves


S. Kyriakides, Transactions of the ASME (2000)

Function of grain size (↓σU, σL & ∆ɛL ↑ ) and composition.

Extracted Single grain ?

Lüders strain


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JRQ Reference Sample – In-Situ Test


• Elastic Modulus (Hook‘s law)• Yield Stress (offset)• Hardening• Ultimate Tensile Stress• (Fracture) Elongation• Reduction of Area• Fracture appearance

• Elastic Modulus (Hook‘s law)• Yield Stress (offset)• Hardening• Ultimate Tensile Stress• (Fracture) Elongation• Reduction of Area• Fracture appearance

Important Tensile Test Parameters


http://practicalmaintenance.net/?p=1135 Stress Strain Curve






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PHWT: Post-Weld Heat Treatment

Toughness

Brittle fracture of a steel pressure vessel during proof test. (The vessel walls were 149 mm thick, and a 2-tonnefragment was thrown 46 m).DOI: 10.1098/rsta.2014.0126

Brittle fracture of a steel pressure vessel during proof test. (The vessel walls were 149 mm thick, and a 2-tonnefragment was thrown 46 m).DOI: 10.1098/rsta.2014.0126

The above picture is of a new pressure vessel that failed during its hydraulic test. The vessel had been stress relieved, but some parts of it did not reach the required temperature and consequently did not experience adequate tempering. This coupled with a small hydrogen crack, was sufficient to cause catastrophic failure under test conditions. It is therefore important when considering PWHT or its avoidance, to ensure that all possible failure modes and their consequences are carefully considered before any action is taken. (http://www.gowelding.com/met/pwht.htm)

The above picture is of a new pressure vessel that failed during its hydraulic test. The vessel had been stress relieved, but some parts of it did not reach the required temperature and consequently did not experience adequate tempering. This coupled with a small hydrogen crack, was sufficient to cause catastrophic failure under test conditions. It is therefore important when considering PWHT or its avoidance, to ensure that all possible failure modes and their consequences are carefully considered before any action is taken. (http://www.gowelding.com/met/pwht.htm)


When dropping a ceramic piece to ground it breaks – metals usually not. The quantity relating the resistance of a material to sudden (impact) loads is called Toughness.

Construction materials must have high toughness. For many metallic materials (including RPV-steels) the toughness is temperature dependent with a sudden change at a so-called transition temperature. This transition temperature can change during service (ageing) which means an increase of failure risk.

Toughness is measured with impact testing machines or with fracture mechanics samples as shown in the next viewgraphs.

Toughness of materials


• Impact testing (Charpy)• Fracture Appearance Transition Temperature (FATT)• Ductile Brittle Transition Temperature (DBTT)• Fracture Toughness (KIC)• J-Integral (JIC)

Remark for difference between DBTT and FATT:

The temperature at which behavior of the material is 50% brittle and 50% ductile is called the ductile-to-brittle-transition temperature (DBTT) while the temperature at which the fracture surface of the material is 50% flat (indication of brittle fracture) is known as fracture appearance transition temperature (FATT). In most cases, the DBTT and FATT are nearly the same. (http://dc231.4shared.com/doc/ATghg806/preview.html)

Toughness Measures


Impact Fracture Testing


Ductile-to-Brittle Transition – WWII Liberty Ships

Some of the first Liberty Ships completed suffered from hull and deck cracks and some were actually lost to these early defects. During the course of WWII there were nearly 1,500 instances of significant brittle fractures due to low grade of steel which suffered from embitterment. It was discovered by Constance Tipper of Cambridge University that ships that were used in the North Atlantic were exposed to temperatures that could fall below a critical point and cause the hull to fracture quite easily. One of the most common types of crack began at the square corner of a hatch with coincided with a welded seam with both the weld and the corner acting as stress concentrators. Along with the poor quality of steal the ships were usually grossly overloaded and many of the problems occurred during severe storms at sea that placed the ships and crew in even more danger. Various reinforcements were applied to the design to deal with the cracks.


See also : Impact testing

http://www.twi.co.uk/technical-knowledge/job-knowledge/job-knowledge-71-mechanical-testing-notched-bar-or-impact-testing/

Ductile to Brittle Transition Temperature

Impact Testing


The typical SEM images of different impact fracture surface of steel: (a) fracture 1 (brittle fracture, tempered at 200 °C); (b) fracture 2 (mixed ductile–brittle fracture, tempered at 300 °C); (c) fracture 3 (ductile fracture, tempered at 400 °C); (d) fracture 4 (ductile fracture, tempered at 500 °C).

Fracture surface


[1] http://www.efunda.com/formulae/solid_mechanics/fracture_mechanics/fm_lefm_K.cfm[2] http://www.efunda.com/formulae/solid_mechanics/fracture_mechanics/fm_lefm_stress.cfm

Crack tips produce a 1/√r singularity. The stress fields near a crack tip of an isotropic linear elastic material can be expressed as a product of 1/√r and a function of θ with a scaling factor K:

where the superscripts and subscripts I, II, and III denote the three different modes that different loadings may be applied to a crack. The detailed breakdown of stresses and displacements for each mode are summarized in [2]. The factor K is called the Stress Intensity Factor.

Stress Intensity Factor and Crack Tip Stresses


“Goofy duck” analog for three modes of crack loading. (a) Crack/beak closed. (b) Opening mode. (c) Sliding mode. (d) Tearing mode. (Courtesy of M. H. Meyers.)

Goofy Duck Analog for Modes of Crack Loading


Fracture Toughness: a quantitative impact measure


http://www.keytometals.com/page.aspx?ID=CheckArticle&site=ktn&NM=184

Development of a crack


J-Integral






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Fatigue


R = σmin/σ max

Fatigue Basics


High Cycle Fatigue

(HCF)

Low Cycle Fatigue

(LCF)

N~5000

HCF: Loading far below yield stress,Caused by vibrations, crack initiation is important. Usually, stress controlled tests

LCF: Plastic strains occur, caused by transient loads or on notches, crack propagation Is important. Usually, strain controlled tests

(or strain)

HCF-LCF


Fatigue curves


Creep fatigue life






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Parts in a nuclear reactor


Welding sections in RPV


http://engineers.ihs.com/document/abstract/VYJOIBAAAAAAAAAA

Low Alloy Steels

• Fine-grained structural steels with bainitic (BCC) microstructure and high toughness

• Quenched + tempered (Q+T) + post-weld heat treatment (PWHT)

• Mn-Mo-Ni-type (SA-508 Cl. 3 forgings, SA-533 Gr. B Cl. 1 plates, …)

• Ni-Mo-Cr-typ (SA 508 Cl. 2 forgings, …)

• S ≤ 0.01% (in very old plants up to 0.04% S)

• S ↑ EAC susceptibility ↑, fracture toughness ↓

• Cu ≤ 0.05% (in old plants, weldments contained up to 0.35% Cu)

• Cu ↑ irradiation embrittlement ↑, toughness ↓


Development of manufacturing tech. in JSW


In the this process, both acid and basic, the necessary heat for melting and working the charge is supplied by oil or gas. But the gas and air are preheated by regenerators, two on each side of the furnace, alternatively heated by the waste gases. The regenerators are chambers filled with checker brickwork, brick and space alternating. The furnaces have a saucer-like hearth, with a capacity which varies from 600 tonnes for fixed, to 200 tonnes for tilting furnaces . The raw materials consist essentially of pig iron (cold or molten) and scrap, together with lime in the basic process. To promote the oxidation of the impurities iron ore is charged into the melt although increasing use is being made of oxygen lancing. The time for working a charge varies from about 6 to 14 hours, and control is therefore much easier than in the case of the Bessemer process. The Basic Open Hearth process was used for the bulk of the cheaper grades of steel, but there is a growing tendency to replace the OH furnace by large arc furnaces using a single slag process especially for melting scrap and coupled with vacuum degassing in some cases.

http://www.steelmelters.com/steel.htm#hearth_

Open

hearth furnace

Electric Arc Furnace

Steel Making: Open-hearth processes


Video of steel making process


A ladle containing 150 tons of liquid steel is lowered into the tank degasser at Pennsylvania Steel Technologies to remove hydrogen from steel for harder railheads.

http://www.memagazine.org/backissues/membersonly/april98/features/vacuum/vacuum.html

Ladle degassing


Ring Forging Penetration welding

Reactor pressure vessel production steps


http://radona.de/index.htm

Austenitic Cladding Application


Welding techniques


A weld consists of:• Base metal• Heat affected zone• Fusion line• Weld metal

Different kinds of steel can develop. Particularly for dissimilar welds. After welding proper post weld heat treatment (PWHT) is important

A weld consists of:• Base metal• Heat affected zone• Fusion line• Weld metal

Different kinds of steel can develop. Particularly for dissimilar welds. After welding proper post weld heat treatment (PWHT) is important

Dissimilar weld (microstructure)


Production


End of (Design) Life n-Fluence (E > 1 MeV)






TOC


Defect formation


An illustration of cascade primary-damage production (iron atoms not shown in a–c and f): (a–c) MD simulation snapshots of initial intermediate and final dynamic stage of a displacement cascade; (d–e) vacancy and self interstitial defects; (f) vacancy-solute cluster complex formed after long-term cascade aging

Cascade development is depending on lattice type

Cascade illustration


ν(T) = T/2.Eth

Displacement per atom «dpa»

Irradiation Damage


Point defect reactions


Typical isochronous annealing curves for pure Cu after irradiation at 4.2 K with fast neutrons to typical doses of 10' dpa. The annealing temperature T is normalized to the melting temperature of Cu. The Romain numbers refer to the different recovery stages. (FD means Frenkel Defects), replotted from [5.1]

Frenkel defect retention


Effect Consequence in material Kind of degradation in component

Displacement damageFormation of point defect clusters and dislocation loops

Hardening, embrittlement

Irradiation-induced segregationDiffusion of detrimental elements to grain boundaries

Embrittlement, grain boundary cracking

Irradiation-induced phase transitions

Formation of phases not expected according to phase diagram, phase dissolution

Embrittlement, softening

SwellingVolume increase due to defect clusters and voids

Local deformation, eventually residual stresses

Irradiation creep Irreversible deformationDeformation, reduction of creep life

Helium formation and diffusionVoid formation (inter- and intra-crystalline)

Embrittlement, loss of stress rupture life and creep ductility

Radiation Damage


a = b = c, α = β = γ= 90°

a = b ≠ c, α = β = γ= 90°

a ≠ b ≠ c,α = β = γ= 90°

a = b = c, α = β = γ ≠ 90°

a = b ≠ c, α = β = 90°, γ = 120°

a ≠ b ≠ c, α ≠ β ≠ γ

a ≠ b ≠ c, α = γ = 90°, β ≠ 90°

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Appendix: Lattice


Appendix: Explanation Burgers Vector

manuel a. pouchon :: head of lnm :: paul scherrerinstitut · pdf file ·...

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