Understanding microstructure formation by 3D analysis in the micro, - PowerPoint PPT Presentation

Understanding microstructure formation by 3D analysis in the micro, nano and atomic scale Chair of Functional Materials Frank Mücklich Michael Engstler, Jeni Barrireiro, Dominik Britz

Concept of the Institute Chair of Functional Materials Material Engineering Center Institute Functional Materials Saarland Saarland University Steinbeis Research Center Basic Research Innovation & Transfer Internationality Aluminium Flavio Soldera Michael Engstler Electr.Contacts Surface Design Kim Trinh Carsten Gachot Antimicrobial Steel Michael Hans Dominik Britz Energetic Mat. Atom Probe Christoph Pauly Jeni Barrirero METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 2

Research Focal Points of the Institute Chair of Functional Materials New New Surfaces Materials   surface stability surface stability  architectured surfaces  architectured surfaces   new contact materials new contact materials  topography, phases, grains  topography, phases, grains  metallic materials Cu, Pt, Ni..  metallic materials Cu, Pt, Ni..   Laser Interference Metallurgy Laser Interference Metallurgy  energetic Materials (RuAl)  energetic Materials (RuAl)   micro / nano tribology micro / nano tribology  CNT based materials  CNT based materials new functionalities (bio…) new functionalities (bio…)   New insights into the microstructure of materials 3D  Micro – Nano – Atomic Scale Image analysis – Stereology – Tomography - 3D analysis METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 3

3D microstructure:  quantitative key to understand the genesis of processing and correlation to properties Chair of Functional Materials METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 4

the right property at the right place  various steels - aluminium - magnesium - CFRP … Chair of Functional Materials strong, well malleable trong, well malleable mulitphase steel ulitphase steel soft, well malleable soft, well malleable deep eep-drawing steel drawing steel higher strength steels magnesium agnesium highest strength steels (TRIP, TWIP) Al-based materials Quelle: Porsche METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 5

Al-Si alloys for light weight engines Chair of Functional Materials Hypoeutectic primary Al-dendrites and Al-Si eutectic binary phase diagramm „modification“ Al-Si eutectic at 577°C and 12,6% Si Alloys with 5-14% Si are of importance METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 6

Al-Si – microstructure morphology change  tremendous impact on mechanical properties Chair of Functional Materials  same processing (T, t,…)  same Al:Si ratio Modification - understand mechanism? - already optimum? Courtesy T.Herfurth, Courtesy T.Herfurth, Stiff and tough!!! Stiff and tough!!! colour: colour: Foundry Institute Düsseldorf IfG Foundry Institute Düsseldorf IfG deformation energy (a.u.) deformation energy (a.u.) different different cooling rate cooling rate stiff but brittle! plastic deformation (bending, a.u.) plastic deformation (bending, a.u.) METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 7

Tomography at the micro / submicro scale (X-ray-CT, Synchrotron) Chair of Functional Materials Pores Intermetallics Zn 2 Mg (Al Zn Mg (Al 2 Cu) F < 0.4 Cu) F < 0.4 Al Al 3 (Sc,Zr Sc,Zr) F > 0.4 ) F > 0.4 • pores (LA) pores (LA) • Zn Zn 2 2 Mg (Al Mg (Al 2 2 Cu) Cu) → 0.17 vol% 0.17 vol% > 1500/mm 3 • Al Al 3 3 (Sc,Zr) (Sc,Zr) > 1500/mm (HA) (HA) 0.3 vol% 0.3 vol% 16 16-17 vol% 17 vol% Visualization of dendrites 0.5 mm J. Kastner et al, Materials characterization 62, 99-107 (2011) Lab-CT: Resolution: µm - sub-µm 10 18 Volume: 10 -10 µm³ 0,27 × 0,29 × 0,12 mm 3 0.09 × 0.11 × 0.07 mm 3 28.10.2015 METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 8

Microstructure Analysis  Scale Bridging Chair of Functional Materials (10 mm) 3 X-ray Tomography (1 mm) 3 (Synchrotron) (100 µm) 3 FIB/SEM (10 µm) 3 (1 µm) 3 STEM APT (100 nm) 3 1 nm 10 nm 100 nm 1 µm 10 µm 100 µm METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 9

Tomography in the nano scale:  FIB/SEM-nanotomography Chair of Functional Materials Serial Sectioning 3D-Reconstruction SEM Imaging 3D-Images correlated 2D-images „Voxel“ x-y-z FIB, Ga-Ions „Pixel“ x-y Sputtering (10nm precision)  Well established contrasts in SEM available  Well established contrasts in SEM available BSE SEM-View SE Fe C Mg S Resolution: 10-30nm EBSD 4 5 EDX Volume: 10 -10 µm³ METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 10

„Al-Si modification“ = Si eutectic morphology change caused by 100ppm doping  disconnecting Si eutectic Chair of Functional Materials 100ppm Sr doping Al-Si (7% Si) primary Al eutectic Si unmodified modified 72 x 100 x 38 µm 3 37 x 17 x 35 µm 3 METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 11

Consequences for mechanical properties  3D visualization of local mean curvature Chair of Functional Materials unmodified eutectic silicon Sr-modified eutectic silicon  rounded corals  flat thin plate-like structures  spatial curvature distribution  high curvature at edges  ductility and elongation  Sharp notches: cracking! METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 12

Growth of Si into the AlSi eutectic melt Chair of Functional Materials Undistorted growth of Si  Growth along the (111) planes in [211] direction  Si-plates, (111) planes parallel to the surface Twin plane re-entrant edge (TPRE) – mechanism [1] Branching of the Si-plates by twinning  [1] EBSD [1] Kobayashi, K.F. und Hogan, L.M. Journal of Materials Science. 1985, Bd. 20, S. 1961‐1975. METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 13

Doping induced twinning – “poisoning” of growth Chair of Functional Materials Doping Induced Twinning – Theory [Lu et al.] Impurities (like Sr) cause twinning   Branching of the Si-structure The re-entrant twin grooves are poisoned by the modifying element  Radius (Sr:Si) = 1.5  max. effect! Multiplication of twins Multiplication of twins Activation of all twin Activation of all twin systems systems TPRE mechanism is retarded/hindered Sr at twins in Si and at the Al-Si interface ?  TEM and Atom Probe Tomography Lu, Shu‐Zu und Hellawell Metallurgical Transactions A. 1987, Bd. 18A, S. 1721‐1733. METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 14

TEM: compare eutectic Si (unmodified/modified) Chair of Functional Materials unmodified eutectic silicon  planar interface Si-Al  planar twin planes  Small spherical particles Sr-modified eutectic silicon  curved interface Si-Al  Irregular twin planes  Small spherical particles  Rod-shaped particles Jenifer Barrirero, Michael Engstler, Naureen Ghafoor, Niels de Jonge, Magnus Odén, Frank Mücklich; Journal of Alloys and Compounds 611 (2014) 410–421 METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 15

Looking for the Decisive Role of 100ppm Sr Doping  Tomography in Atomic Scale Chair of Functional Materials _ UHV I (x 1 |y 1 |z=„1“) HV t Al-Si Sample 0 t 1 (Temp. 40 Kelvin) + I (x 2 |y 2 |z=„2“) (x 2 |y 2 |z=„2“) t t 0 t 2 HV Laser or pulse pulse Resolution: 0.5 nm -3 -4 Volume: 10 -10 µm³ METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 16

Segregations of Sr AND Al inside of the Si-Eutectic  ratio Al : Sr is constant ! Chair of Functional Materials METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 17

Segregations of Sr AND Al inside of the Si-Eutectic  ratio Al : Sr is constant ! Chair of Functional Materials Barrirero et al., Journal of Alloys and Compounds 611 (2014) 410 METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 18

Constant atomic ratio Al : Sr  what does that mean? Chair of Functional Materials  explain the presence of Aluminium in the crystallographic defects? The Si growth is restricted by the formation of clusters of SrAl 2 Si 2 at the solidification front SrAl 2 Si 2 (τ 1 ) SrAl 4 577±1º 12.2 at.% METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 19

If that is true – than also modifications with Na atoms  should work alike ? Chair of Functional Materials METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 20

Modification via phase formation at solidification front?  Significant difference in the ratio - Al:Sr > Al:Na Chair of Functional Materials Al:Sr The Si growth is restricted by the formation of clusters of NaAlSi at the solidification front. (confirmation of analogy for Sr) Al:Na METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 21

deviations from the composion ratio of perfect phases?  limitation of contributing Al atoms Chair of Functional Materials METZ: 3D Microstructure Analysis | Frank Mücklich| muecke@matsci.uni-sb.de 22