Technische Universität München In-situ Synchrotron and Neutron Diffraction studies on phase transformation in Austempered Ductile Iron (ADI) Xiaohu Li 1, P. Saal 2, L. Meier 1,2, M. Hölzel 1, W. Gan 3, M. Hofmann 1 1 FRM II, Technische Universität München, Germany 2 utg, Technische Universität München, Germany 3 Helmholtz-Zentrum Geesthacht, Germany Funded by DFG-PE 580/14-1 Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) 2nd internal biennial science meeting of the MLZ

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Content 1. What is ADI? 2. Phase transformation during heat treatment 3. Strain induced martensite transformation 4. Conclusion Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) 2nd internal biennial science meeting of the MLZ

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Austempered Ductile Iron (ADI) Pearlite FerriteGraphite 50µm Ferrite Graphite Retained Austenite What is ADI ? Ductile Iron, as cast  Ductile Cast Iron  Heat treatment Austenitisation 850~1000°C Isothermal austempering 250~450°C  Incomplete bainitic transformation Acicular ferrite High carbon, retained austenite “Ausferrite”  Attractive engineering material 2nd internal biennial science meeting of the MLZ

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Experiments Hamburg, DESY in-situ Synchroton Diffraction 2nd internal biennial science meeting of the MLZ Phase analysis STRESS Texture analysis

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Heat treatment 2nd internal biennial science meeting of the MLZ Iron carbon phase diagram 0.8 wt% carbon after austenitization 1.2 wt% carbon by the maximum enrichment fcc bcc

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Ferrite Austenite T A = 400°C T A = 350°C T A = 300°C T γ = 900°C Ferrite Austenite T γ = 950°C  Ausferritisation rate is not related to austempering temperature T Austempering.  The higher the T Austenitisation (T γ ) is, the slower the ausferritisation will take place.  The lower the T Austempering (T A ) is, the more ferrite will form (and the austenite grain sizes get smaller). Phase transformation 2nd internal biennial science meeting of the MLZ

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Carbon diffusion in ADI during heat treatment Phase transformation 1,87 1,73 1,59 1,45 1,31 1,17 1,03 0,89 0,75 Carbon content [wt%] T γ = 950°C T A = 400°C T A = 350°C T A = 300°C ferrite austenite 2nd internal biennial science meeting of the MLZ

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Carbon gap Start of austempering: 100% austenite with 0.8 wt% C End of austempering: 10% ~ 30% austenite with 1.6~1.7 wt% C + 70% ~90% ferrite with 0.02 wt% C C in 10% austenite+90% ferrite~0.2 wt% C in 30% austenite+70% ferrite~0.5 wt% 0.3~0.6 wt% Carbon gap Where are the rest carbon atoms? Atom Probe Tomography APT (J. Wagner KIT) Carbide Fe 3 C or Fe 3 C 1-X 2nd internal biennial science meeting of the MLZ

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Strain induced transformation metastable austenite martensite plastic deformation 2nd internal biennial science meeting of the MLZ Ferrite Austenite Martensite Austenite (111) Austenite (200) Ferrite (110) Martensite (101) (110) Ex-situ measurement at

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) 950 °C 2nd internal biennial science meeting of the MLZ Martensite vs tensile deformation

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Martensite vs compressive deformation Effect of nickel Effect of austempering temperature

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Conclusion: T austempering retained austenite Austenite super saturated ferrite C C retained austenite carbide Martensite ~ plastic strain Nickel accelerate the martensitic transformation at higher temperature 2nd internal biennial science meeting of the MLZ

Technische Universität München Forschungsneutronenquelle Heinz Maier-Leibnitz (FRMII) Do you have any questions? 2nd internal biennial science meeting of the MLZ