CALPHAD-based ICME for Additive Manufacturing. Wei Xiong

Transcription

1 CALPHAD-based ICME for Additive Manufacturing Wei Xiong +1 (412) Physical Metallurgy and Materials Design Laboratory University of Pittsburgh, Pennsylvania, USA CALPHAD: Calculation of Phase Diagrams ICME: Integrated Computational Materials Engineering Collaborators: Albert To (Pitt-MEMS), ANSYS Inc., Thermo-Calc Inc., Greg Olson (Northwestern) Acknowledgements:

2 CALPHAD / Materials Genome / ICME / ICMD Gregory B. Olson, Charles J. Kuehmann, Scripta Materialia, 70 (2014) Wei Xiong, Gregory B. Olson, MRS Bulletin, 40 (2015) Wei Xiong, Gregory B. Olson, npj Computational Materials, nature publishing group, 2 (2016) Additive Manufacturing SelectiveLaserMelting ORNL WireEBAM(electronbeam),Sciaky LaserEngineeredNetShaping Jacob Smith, Wei Xiong, et al., Computational Mechanics, April 2016, Volume 57, Issue 4, pp

3 Design constraints for different applications Time and cost efficiency Avoid postprocessing Allow postprocessing 1 I want to have components with 2 outstanding properties and low cost Cost is not a big issue, just give me a 3D component with outstanding properties 3 I wish to get good/outstanding properties for the as-built alloy Difficult Easy Major Challenges in Processing Optimization and Alloy Design for Additive Manufacturing 1. Extreme thermal-profile with cyclic heating and cooling Current measurement cannot capture the rapid cooling (>>10 4 K/s, can be 10 9 K/s) Highly rely on thermal modeling with unknown uncertainties 2. Complex process-structure relationship Complex liquid-solid transformations cover wide range of solidification velocity Difficult to control the grain structure and segregation Lack of CCT/CHT/TTT diagrams for existing AM alloys (e.g. Inconel 718) Causing anisotropic microstructure-property relation Many more Lack of standards for additive manufacturing Machine stability CCT: Continuous-Cooling-Transformation; CHT: Continuous-Heating-Transformation; TTT: Temperature-Time-Transformation

4 Challenge 1: Complex thermal history Accurate measurements of temperature profile with such high cooling/heating rate is a big challenge Cooling/heating profiles are difficult to measure B. Zheng, Y. Zhou, J.E. Smugeresky, J.M. Schoenung, E.J. Lavernia, Metallurgical and Materials Transactions A. 39 (2008) Challenge 1: Complex thermal history The present understanding of the thermal history is highly rely on thermal modeling with unknown uncertainties. Phase Transformation Temperature Constant Composition Dependent Finite element thermal modeling Latent Heat Heat Release Constant Constant Comp./Temp. Dependent Comp./Temp. Dependent Heat Capacity Constant Comp./Temp. Dependent Heat Conductivity Constant Comp./Temp. Dependent CALPHAD (Calculation of Phase Diagrams)-informed Thermal Modeling Alloy thermodynamics are available!

5 Ref: Jacob Smith, Wei Xiong, Jian Cao, Wing Kam Liu, "Thermodynamically Consistent Microstructure Prediction of Additively Manufactured Materials", Computational Mechanics, 57 (2016) Solid Phase Fraction Temperature Profile Challenge 2: Complex process-structure relation Bulk microstructure Anisotropic Grain Structure Nonstable phases Segregation Building direction

6 Case study on Inconel 718 superalloy under SLM Grain texture simulation for laser powder bed fusion: - Scan velocity 1 m/s, 120 grains, 600 micron - Total simulation time is 4 minutes on a desktop computer With these technical difficulties, can we still perform Alloy Design & Process Optimization for Additive Manufacturing? Of course!

7 Post-processing design for grain refinement Cyclic austenitizing Martensitic transformation can be considered as the spontaneous plastic deformation of a crystalline solid in response to internal chemical forces. Temperature Ac1 Ms Time Temperature map for cyclic austenitizing [T. Furuhara, 2008] Ref: Fuyao Yan, Wei Xiong, Greg Olson, Unpublished work, 2018 Post-processing design for grain refinement Cyclic Austenitizing LENS manufactured PH48S

8 Post-processing design for grain refinement Cyclic Austenitizing PH48S maraging steel Homogenization: 1200 o C/12hrs/WQ Cycle: 800 o C/1min/WQ Ref: Fuyao Yan, Wei Xiong, Greg Olson, Unpublished work, 2018 Fuyao Yan, Wei Xiong, Eric J. Faierson, Materials, 10 (2017) Zener-pinning particles in as-built 316L by SLM Nano-scale Rhodonite (MnSiO 3 ) particles Fuyao Yan, Wei Xiong, Greg Olson, Scripta Materialia, Accepted, 2018

9 Grain structure evolution during 1200oC isothermal annealing 316L Stainless Steel by SLM Fuyao Yan, Wei Xiong, Greg Olson, Scripta Materialia, Accepted, 2018 Thermodynamics of observed oxides (Spinel/Rhodonite) Spinel took over after 1 hr 1200oC annealing 1200oC 7&)( Spinel (MnCr2O4) PDF #: oc, 1 hr Annealing Fuyao Yan, Wei Xiong, Greg Olson, Scripta Materialia, Accepted, 2018

10 Thermodynamics of observed oxides (Spinel/Rhodonite) Stable diagram with Spinel Metastable diagram with Rhodonite Fuyao Yan, Wei Xiong, Greg Olson, Scripta Materialia, Accepted, 2018 Relationship of hardness and grain size Relationship of hardness and grain size for SLM 316L in the as-built state (black), SLM 316L in the heat-treated state (blue) and commercial 316L in the heat-treated state (red). Fuyao Yan, Wei Xiong, Greg Olson, Scripta Materialia, Accepted, 2018

11 Take-home Message There are some challenges of monitoring thermal history and capturing supercooling/heating effects by laser melting. Although high-fidelity model/databases are difficult to achieve in a short time, alloy design and processing optimization can be performed based on the pre-existing models for casting and welding before we develop more effective AM models. Reliable studies in additive manufacturing require both modeling and experiments. Efforts need to be made through collaboration between mechanical and materials engineers/scientists. Future of Next-Generation Alloy Design Keeping balance between science and engineering Science Engineering There are many opportunities in front of us!

12 Pasteur Quadrant of Computational Materials Design Empirical Good NotVeryUsefulfor application VeryUseful Canbe foundin textbook Evenbetter PhysicalBasis Physical Metallurgy & Materials Design Lab Advanced Materials and Manufacturing Bridge Improved Fundamentals and Engineering Applications Sponsors

13 HEA High Entropy Alloys Physical Metallurgy & Materials Design Laboratory Thank You for Your Attention!