Advanced Materials Technology (FKMN20) PDF

Advanced Materials Technology (FKMN20) Prof. Dmytro ORLOV Division of Materials Engineering, LTH [email protected] Microstructure Characteriza/on and Analysis...

Advanced Materials Technology (FKMN20) Prof. Dmytro ORLOV Division of Materials Engineering, LTH [email protected] Microstructure Characteriza/on and Analysis (Sec$ons 5.1-5.8) Advanced Materials Technology (FKMN20) Prof. Dmytro ORLOV, Division of Materials Engineering, LTH, [email protected] GOALS 1. Understanding Electrons and X-rays based analytical techniques used for the characterisation and analysis of material surface and structure; 2. Understanding limitations and complementarity of the techniques along with their practical applications. 1  Created when high-energy electrons knock out inner-shell electrons Characteristic X-rays from atoms in a target material. Elelctrons from higher energy levels the fill these vacanies. Emitting X-rays in the process Specific and discrete, linked to atomic structure of target K(alfa): Electron from L joins shell K K(beta): Elenctron from M joins shell K L(alfa): Electron from M joins shell L The energy neccesary for electron to switch shells is unique for each material White Radiation and Characteristic Peaks Bremsstrahlung (braking radiation) High energy electrons are decelerated upon colliding with a target material (like metal) in a X-ray tube. As the electrons loose energy, they emit X-rays across a continous range a wavelengths Appears white due to wide range of X-ray energies Used in medical imaging and industrial application. Broad and continous 5.3 X-ray diffraction analysis 169 Characteristic Lines: Specific wavelengths of X-rays emitted Characteristic Lines and the by characteristic X-ray Absorption Edge Ka1 Ka 2 Ka m/r 5.3 X-ray diffraction analysis 169 300 Absorbation edge: Specific energy threshold at which there is a Relative intensity sharp increase in the absobration coefficient. Occurs when energy Mass absorption 1-54 1-542 1-544 200 coefficient nm!10 K-absorption Kb of the incomingX-ray matches the binding energy of an electron in shell K a1 edge 100 (Ni) Ka m /r Ka2 0 0 0.2 0.6 1.0 1.4 0.2300 0.6 1.0 1.4 1.8 Relative intensity 1-544nm!10 nm!10 Mass absorption 1-54 1-542 Wavelength 200Wavelength coefficient nm ! 10 K - absorption = 𝐼! 𝑒 "#$ (a) Kb (b) FIGURE 5.7 𝐼 100 edge I0 and I are the initial and final intensities; (a) Distribution of X-ray intensity from a copper target and (b) dependence of mass absorption coefficient on μ is a constant 0 (the linear absorption coefficient 0 0.2for nickel. X-ray wavelength 0.6 1.0 1.4 which depends on0.2 0.6 of 1.0 the wavelength the 1.4 1.8 nm !10 X-rays and the nature of the absorber), nm ! 10 Wavelength x is the thickness of a specimen Wavelength X-rays are a form of electromagnetic radiation differing from light waves (λ 5 400!800 nm) in (a) that they have a shorter wavelength (b) (λ " 0.1 nm). These rays are produced when a metal target is bombarded with fast electrons in a vacuum tube. The radiation emitted, as shown in Figure 5.7(a), FIGURE 5.7 can be separated into two components, a continuous spectrum which is spread over a wide range of wavelengths andofa X-ray (a) Distribution superimposed intensity line fromspectrum a coppercharacteristic of dependence target and (b) the metal being bombarded. of mass The coefficient on absorption ‘white’ radiation, asforthe X-ray wavelength continuous spectrum is called, results from the deceleration of the electrons nickel. on hitting the target. A minimum wavelength λmin occurs in the white radiation which corresponds to the electron losing all its energy in one single collision, i.e. X-rays are a form eV of 5electromagnetic hν max or λmin 5 radiation hc=eV 5differing V21 light waves (λ 5 400!800 nm) in 12:4 3 103 from that they have a shorter wavelength (λ " 0.1 nm). These rays are produced when a metal target is and the tail inwith bombarded the spectrum with wavelength fast electrons greater in a vacuum tube. λmin radiation thanThe results from the electron emitted, losing in as shown its Figure 5.7(a), 2 energy by multiple collisions. The total intensity of white radiation is related to the atomic number can be separated into two components, a continuous spectrum which is spread over a wide range of Z and approximately by square of the applied voltage. The characteristic radiation is excited only  5.3 X-ray diffraction analysis 169 X-ray wave-length filtering 172 CHAPTER 5 Characterization and Analysis (mono-chromation) Ka1 Ka m/r Ka 2 which any of these planes in a crystal reflect an X-ray 300beam of wavelength λ may be calculated by Relative intensity Mass absorption inserting the appropriate 1-54 1-542 value 1-544of d into the Bragg equation. 200reflections from various crystal coefficient nm!10 law is satisfied and that To ensure that Bragg’s planes can K-absorption Kb occur, it is necessary to provide a range of either θ or100 λ values. The various ways in edge which this can (Ni) be done leads to the standard methods of X-ray diffraction, namely: (i) the Laue method and (ii) the powder method. 0 0 0.2 0.6 1.0 1.4 0.2 0.6 1.0 1.4 1.8 nm!10 nm!10 Wavelength Wavelength 5.3.3 X-ray diffraction (a) methods 𝐼 = 𝐼! 𝑒 "#$ (b) 5.3.3.1 Laue method FIGURE 5.7 In the Laue method, a stationary single crystal isI0 and bathed I are in the ainitial beam and of final‘white’ radiation. Then, intensities; (a) Distribution because of X-ray is the specimen intensity a fixed from a copper single targetthe crystal, andvariable (b) dependence necessary of mass absorption to ensure coefficient thatcoefficient the Bragg’s on law μ is a constant (the linear absorption X-ray wavelength for nickel. is satisfied for all the planes in the crystal has to bewhich depends provided byonthe therange wavelength of the of wavelengths in the X-rays and the nature of the absorber), beam, i.e. each set of crystal planes chooses the appropriate λ from the ‘white’ spectrum to give a x is the thickness of a specimen BraggX-rays reflection. Radiation are a form from a target of electromagnetic metal differing radiation having afrom highlight atomicwaves number (e.g. tungsten) (λ 5 400!800 nm) in is often that used, they havebut almost a shorterany form of ‘white’ wavelength (λ " 0.1 radiation nm). These is rays suitable. In the experimental are produced when a metalarrangement target is shown in Figure bombarded 5.9, electrons with fast either a intransmission a vacuum tube. photograph The radiationor a emitted, back-reflection as shownphotograph may be in Figure 5.7(a), taken, can be and the pattern separated into of twospots which are components, produced lie a continuous on ellipses spectrum whichinisthe transmission spread over a wide case or hyper- range of bolae in the back-reflection wavelengths and a superimposed case. Allline spots on any spectrum ellipse or of characteristic hyperbola the metalare reflections being bombarded.fromTheplanes of‘white’ a single zone (i.e. radiation, where as the all the lattice continuous spectrumplanes are parallel is called, to a common results from direction, the deceleration of thetheelectrons zone axis) on consequently, and, hitting the target.theALaueminimum pattern is able toλindicate wavelength min occurs theinsymmetry the white radiation whichFor of the crystal. corresponds example, if theto beam the electron losingalong is directed all itsaenergy [1 1 1]in orone[1single collision, i.e. 0 0] direction in the crystal, the Laue pattern will show three- or fourfold symmetry, respectively. The Laue method is used3 extensively for the determina- eV 5 hν max or λmin 5 hc=eV 5 12:4 3 10 V21 tion of the orientation of single crystals and, while charts are available to facilitate this determi- nation, and thethe tail method consistswith in the spectrum essentially wavelength of greater plottingthanthe λminzones resultstakenfrom the from the film electron losingonto its a Determines orientations of single crystals. Laue Method energy by multiple collisions. The total intensity of white radiation is related to the atomic number Z and approximately by square of the applied voltage. The characteristic radiation is excited only when a certain critical voltage is exceeded and is produced when Transmission the accelerated electrons have suf- Uses white radiation (broad-spectrum X-ray) photograph ficient energy to eject one of the inner electrons Film holder(1s-level, for for example) from its shell. The vacant back-reflection 1s-level is then occupied by one of the other electrons from a higher energy level, and during the transition an emission of X-radiation takes photograph place. If the electron falls from an adjacent shell then Polycromatic beam the radiation emitted Incident is beamknown as Kα-radiation, since the vacancy in the first K-shell n 5 1 is filled by an electron(white the second L-shell and the wavelength can 2θ fromradiation) be derived from the relation hv 5 EL 2 EK (5.5) Metal single Collimator crystal However, if the K-shell vacancy is filled by an electron from an M-shell (i.e. the next highest Goniometer quantum shell) then Kβ-radiation is emitted. Figure 5.7 shows that, in fact, one cannot be excited head without the other, and the characteristic K-radiation emittedConstruction from a copper target is in detail com- posed of a strong Kα-doublet and a weaker Kβ-line. lines to show Since the specimen is a fixed single crystal, spots lie on the Bragg’s law is satisfied for all the planes in the crystal ONLY ellipses if the range of wavelengths in the beam is used, i.e. FIGURE 5.9 each set of crystal planes chooses the appropriate λ from the ‘white’ spectrum to give a Bragg reflections. Each set of planes picks out and diffracts the particular wavelength from the white radiation that satisfies the Bragg law for of Laue method theX-ray of d and 𝜃 involved. Each curve (elliptical in transmission geometry) therefore corresponds to a valuesdiffraction. different wavelength. The spots lying on any one curve are reflections from planes belonging to one zone. Laue reflections from planes of the same zone all lie on the surface of an imaginary cone whose axis is the zone axis. Film is placed between the X-ray source and the crystal, capturing Laue Back-Reflection Method beams diffracted backward. 3 ct crystals are sharp, while those from deformed crystals are elongated. This elongated of the diffraction spots is known as asterism and it arises in an analogous way to the of light from curved mirrors. owder method r method, devised independently by Debye and Scherrer, is probably the most generally ll the X-ray techniques. It employs monochromatic radiation and a finely powdered, or d polycrystalline, wire specimen. In this case, θ is the variable, since the collection of oriented crystals will Laue contain Back-Reflection sufficient particlesPattern with the correct orientation to allow rom each of the possible reflecting planes, i.e. the powder pattern results from a series posed rotating crystal patterns. The angle between the direct X-ray beam and the y is 2θ, and consequently each set of crystal planes gives rise to a cone of reflected rays gle 2θ, where θ is the Bragg angle for that particular set of reflecting planes producing hus, if a film is placed around the specimen, as shown in Figure 5.10, the successive dif- es, which consist of rays from hundreds of grains, intersect the film to produce concen- around the entrance and exit holes. Figure 5.11 shows examples of patterns from bcc terials, respectively. measurement of the pattern of diffraction lines is required for many applications of the thod, but a good deal of information can readily be obtained merely by inspection. One this is in theLaue back reflection photographs of Zn single crystal with X-ray beam perpendicular to (A) basal plane (0001) or (B)study prism plane of1120 deformed metals,. Dashed lines are drawn to illustrate thatsince afterspotsdeformation the back-reflection lie on hyperbolae the individual spots on ion rings are blurred so much that line broadening occurs, especially at high Bragg low-temperature annealing, the cold-worked material will tend to recover and this is n the photograph by a sharpening of the broad diffraction lines. At higher annealing tem- he metal will completely regain its softness by a process known as recrystallization (see ), and this phenomenon is accompanied by the completion of the line-sharpening pro- continued annealing, the grains absorb each other to produce a structure with an overall Material is grinded into powder to ensure many small crystals are present in size and, because fewer reflections are available to contribute to the diffraction cones, Powder Method A beam of X-rays interact with the crystal lattice, diffracted at specific Incid ent angles according to Braggs law. X-ra ys 2u The diffracted X-rays are detected which results in a diffraction pattern. A B A u! 90" u! 0" B hod of X-ray diffraction. 174 CHAPTER 5 Characterization and Analysis 174 CHAPTER 5 Characterization and Analysis Powder Method N 6 8 8 6 4 2 2 4 2) 2) 1) 1) 10(!"Ka 10(!"Ka 10(!"Ka 10(!"Ka N 6 8 8 6 4 2 2 4 2) 2) 1) 1) 10(!"Ka 10(!"Ka 10(!"Ka 10(!"Ka (a) (a) N 16 19 20 20 19 16 12 11 8 43 3 4 8 11 12 2) 2) 2) 2) 1) 1) 1) 1) 24(!"Ka 27(!"Ka 27(!"Ka 24(!"Ka 24(!"Ka 27(!"Ka 27(!"Ka 24(!"Ka N 16 19 20 20 19 16 12 11 8 43 3 4 8 11 12 2) 2) 2) 2) 1) 1) 1) 1) 24(!"Ka 27(!"Ka 27(!"Ka 24(!"Ka 24(!"Ka 27(!"Ka 27(!"Ka 24(!"Ka (b) FIGURE 5.11 (b) Powder photographs taken in a Philips camera (114 mm radius) of (a) iron with cobalt radiation using an iron filter Powder FIGURE photographs taken in a Philips camera (114 mm radius) of (a) iron with cobalt radiation using an iron 5.11 and (b) aluminium with copper radiation using a nickel filter. filter Powder andphotographs The (b) aluminium high-angle lines withresolved are taken incopper radiation and a Philips using the separate camera amm nickel (114reflectionsfilter. for λofThe radius) Kαhigh-angle =(a) andwith 1iron λ = Kαlines are resolved 2 are observable. cobalt radiation and using anthe iron separate filter and reflections (b) aluminiumfor λwith 5 Kα copper λ 5 Kα2 are 1 and radiation observable. using a nickel filter. The high-angle lines are resolved and the separate reflections for λ 5 Kα1 and λ 5 Kα2 are observable. the lines on the powder photograph take on a spotty appearance. This latter behaviour is some- times the used lines onasthe a means powderofphotograph determining theongrain take size of a spotty a polycrystalline appearance. sample. This latter In practice, behaviour an is some- X-ray photograph times used is taken as a means for each of the of determining a series grainofsize known of a grain sizes to form polycrystalline a setInofpractice, sample. standards, an and with them an unknown grain size can be determined quite quickly by comparing X-ray photograph is taken for each of a series of known grain sizes to form a set of standards, the corre- sponding and photograph with them with the an unknown setsize grain of standards. Yet a third can be determined quiteuse of thebypowder quickly comparingmethod as an the corre- inspectionphotograph sponding technique iswithin thethe detection of a preferred set of standards. Yetorientation a third useof of thethe grains of a polycrystalline powder method as an aggregate. This is because inspection technique is in thea detection random orientation of the of a preferred grains will orientation produce of the grains aofuniformly intense a polycrystalline diffraction ring, while a preferred orientation, or texture, will concentrate aggregate. This is because a random orientation of the grains will produce a uniformly positions diffractiononring, the while ring. The details orientation, a preferred of the texture or require texture, considerable the intensity interpretation will concentrate the intensity at intense certain andatare dis- certain 4 cussed in on positions Chapter 11. The details of the texture require considerable interpretation and are dis- the ring.  Focusing Crystal circle monochromator Detector Target 2u Collimator u slit Specimen (a) Monochromator (Quartz crystal) S1 S2 S3 Specimen Scattered beam Collimator Powder Method X-ray tube Focus slits target 176 CHAPTER 5 Characterization and Analysis Detector Direct beam Geometry of (a) conventional diffractometer and 2D representation of interatomic plane (b) small-angle scattering diffractometer Receiving distance depending on orientation slit S4 (b) 1600 Focusing Crystal circle monochromator Detector Target (100) 2u counts s#1 1200 N"3 u Collimator slit Specimen (a) Monochromator (Quartz crystal) 176 CHAPTER 8005 Characterization (110) and Analysis S1 S2 S3 Specimen N"4 Scattered beam Collimator X-ray tube Focus slits Intensity target (111) (200) Detector 400 N " 8 N " 11 Direct beam Receiving slit S4 (b) (220) (222) (400) 1600 N " 12 (311) N " 19 N " 20 (331) N " 24 N " 27 N " 16 counts s#1 1200 N"3 0 40! 50! 60! 70! 80! Focusing 90! Crystal 100! 110! 120! 130! 140! 150! 160! 2qcircle monochromator 800 N"4 Detector Chart record of diffraction pattern from aluminium (c) powder with copper radiation using nickel filter. Intensity 400 N " 8 N " 11 FIGURE 5.12 Target N " 12 N " 16 N " 19 N " 20 N " 24 N " 27 2u 0 Geometry of (a) conventional diffractometer and (b) small-angle scattering diffractometer, 40! 50! 60! 70! 80!(c) 90! chart 100! 110!record 120! 130! of 140! 150! 160! Collimator 2q diffraction pattern from aluminium u powder with copper radiationslitusing nickel filter. (c) Specimen FIGURE 5.12 Geometry of (a) conventional diffractometer and (b) small-angle scattering diffractometer, (c) chart record of (a) diffraction pattern from aluminium powder with copper radiation using nickel filter. Monochromator (Quartz crystal) S1 S2 S3 Peaks correspond with crystal planes in the samples. Specimen X-ray tube Powder Method Collimator Scattered beam slits Focus target Measuring the Detector displacement of diffraction Direct 2D representation of interatomic beam plane peak positions gives another way to determine: distance depending on orientation Receiving slit S4 1) Lattice Parameters; (b) 1600 2) Phase Boundaries (100) counts s#1 1200 N"3 800 (110) N"4 Intensity (111) (200) 400 N " 8 N " 11 (220) N " 12 N " 19 N " 20 N " 24 N " 27 N " 16 0 40! 50! 60! 70! 80! 90! 100! 110! 120! 130! 140! 150! 160! 2q (c) FIGURE 5.12 Geometry of (a) conventional diffractometer and (b) small-angle scattering diffractometer, (c) chart record of diffraction pattern from aluminium powder with copper radiation using nickel filter. Small angle (SAS): Deflection of X-rays at small angles (0,1-10) Small/Wide Angle Scattering Used for studying disordered systems (polymers, colloids, bio stuff) Can provide sixe, shape and distribution of particles. Wide anle (WAS): Probes smaller length scales, atomic or molecular. Analyzing crystalline materials, information of crystallinity, phases Neutrons/X-rays must be parallel to each other (collimated) SAS: Larger structures Slit defines shape of beam (circle, square, slit) Distance from sample to detector & wavelength determines size range measured WAS: Small structures 5  Sca:ering Figure courtesy: Martin Bech, Lund University Department medical radiation physics [email protected] Small/Wide Angle Scattering real space density distribuBon MAIN BENEFIT: Features Smaller than Beam Size can be Probed MAIN DIFFICULTY: Rather Complex Data Analysis Scattering pattern calculated from the Fourier transform of the real-space density distribution; Form factors are the sum of scattering from every point inside a particle Pattern for most shapes must be solved analytically Full field: Captures entire area of interest simultaniously. Allows Full field vs pencil beam analysis of large samples or complex structures Non-destructive, useful in quality controle Pencil beam: Narrow and focused radiation beam across sample Precise controle which makes it suitable for detection of specific elements in small volumes. Figure courtesy: Martin Bech, Lund University Department medical radiation physics [email protected] 6  By using wave-optical principles, the technique can achive higher spatial ‘Wave-Op)cal’ X-ray Radiography: Phase Contrast resolution compared to conventional X-rays methods, better contract Coherent X-ray beam -> Waves (radiation) spread out and interacts with material -> Creates pattern based on how they affect the material -> Phase contrast, hilights small differences -> Final image with a lot of details. Figure courtesy: Martin Bech, Lund University Department medical radiation physics [email protected] Optical: Uses visible light that reflects of sample, can magnify up to Optical vs Electron Microscopes 1000x, sufficient for viewing cells and larger microorganisms. Samples can be alive LM TEM SEM SEM: Scanning Elenctron Microscopy (Scans surface) Focused beam of electrons, they hit the sample and interact with atoms producing secondary elenctrons and backscattared electrons. Emitted electrons are collected by detectors, creates detailed image Resolutions of 1nm TEM: Transmission Elenctron Microscopy (Scans internally) Op/cal vs Electron Microscopes Beam of accelerated electrons passes through very thin sample Electron interacts with atoms and produces signals that are caught by detectors Possible to analyze microstructure, fine structure of cells, viruses, examining nanostructures and semi conductors. 7  History of EM development 1897 JJ Thompson - Discovery of the Electron 1926 H. Bush MagneBc/Electric Fields as Lenses 1929 E. Ruska PhD Thesis MagneBc lenses 1931 Knoll and Ruska 1st EM built 1932 Davisson and Calbrick - ElectrostaBc Lenses 1934 Driest & Muller - EM surpases LM 1939 von Borries & Ruska - 1st Commercial EM ~ 10 nm resoluBon 1945 ~ 1.0 nm resoluBon (MulBple OrganizaBons) 1965 ~ 0.2 nm resoluBon (MulBple OrganizaBons) 1968 A. Crewe - U.of Chicago - Scanning Transmission Electron Microscope ~ 0.3 nm resoluBon probe - prac$cal Field Emission Gun 1986 Ruska et al - Nobel Prize 1999 < 0.1 nm resoluBon achieved (OÅM) 2009 0.05 nm (TEAM) ‘Light’ source in Electron Microscopes ‘Light’ source in Electron Microscopes 8  Some Fundamental Proper)es of Electrons Electron Properties as a Function of Accelerating Voltage Op/cal vs Electron Microscopy 0.6 λ ρ= η sin(α ) According to the Rayleigh Criterion, the wavelength is related to the resolution as: 9  The control of beam in EM Comparison of SEM and TEM Scanning Electron Microscope Transmission Electron Microscope Accelerating voltage: 0.1 to 40 kV, AcceleraNng voltage: 100 to 300 kV , typically 5 to 25 kV for metallic materials typically 200 kV for metallic materials (limits range of X-ray energies excited). (can excite almost all X-ray energies). Beam current: 0.01nA to >3000nA, Beam current: 0.01nA to >5nA, typically around 1nA typically around 1nA (limits X-ray count-rate). (limits X-ray count-rate). Probe size: 1000nm, Probe size: 100nm, typically around 50nm typically around 10nm (typically much smaller than the width of the (will oOen limit spaNal resoluNon). volume of X-ray generation in a bulk sample). Thin-film sample 3mm diameter and Bulk sample, typically around 25mm analysis area 10 faster than Si(Li) (105 to 106 cps), as good or better resolution, Peltier cooling, 0.4 to 1mm, efficiency drops after ~8keV. Diffraction techniques available in SEM Electron backscatter diffraction (EBSD) – Conventional orientation microscopy – Measurement of micro and macro textures – Measurement of elastic stresses – 3-dimensional microstructure characterization Electron channelling contrast imaging (ECCI) – Defect observation (dislocations, stacking faults, strain fields) Kossel technique (XRD in the SEM) – absolute determination of lattice constants (elastic strains) S. Zaefferer: Plastic and elastic strain measurement 15  Microscope chamber during EBSD scan Diffraction techniques in SEM incident beam Electron channel- ~ 10 ling pattern (ECP) Electron channelling BSE Detector contrast image (ECCI) ~7 ~ 90° on 6-axis stage (tilted to Specimen 2-beam conditions) ~ 15 Spec ~ 90° ~ 35 imen EBSD ∢70° Detector on pre-tilted FSE stage Detector Electron backscatter Specimen ~5 ~ 30 diffraction pattern Orientation micros- chamber (EBSD) copy image (OMI) S. Zaefferer: State of the art of EBSD Kikuchi Lines Principle of formation Example of a Kikuchi-line map in fcc crystal 16 IntroducGon: Electron backscaIer diffracGon (EBSD) primary electron beam coherent outgoing wave field (backscatter A typical EBSD pattern (Niobium, 15 kV) diffraction) sample inelastic scattering: KAM 0…5° incoherent incoming wave field detector (with positional sensitivity) S. Zaefferer: Plastic and elastic strain measurement Electron channelling contrast imaging (ECCI) Electron coherent incoming wave channelling field (electron channelling of pattern ECP of Cu primary beam electrons) incoherent outgoing wave field (inelastic backscattering) sample detector (with integral Dislocations and stacking faults in sensitivity) high-Mn austenite S. Zaefferer: Plastic and elastic strain measurement EBSD & EBSD-based orientation microscopy e- deformed crystal structure orientaBon defect density residual stresses recrystallised grains BSEI of a partially recrystallised inverse pole grain boundary IF steel figure map character pole figures By nature a “quantitative” technique! Spatial resolution: lateral ~ 20 … 300 nm, depth ~ 10 nm Angular resolution: conventional 0.5°, special > 0.01° Measured area: µm² … cm² S. Zaefferer: Plastic and elastic strain measurement 17  Mapping and grouping into grains Microstructure of Al after e=1 (g=1.7) 1-3: dav=0.93 µm 4: dav=1.36 µm Low angle boundaries (2°≤q