Frontiers in Solidification Science VIII: Processing, Defects & Segregation / Steel & Cast Iron
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Chemistry and Physics of Materials Committee, TMS: Phase Transformations Committee, TMS: Solidification Committee, TMS: Computational Materials Science and Engineering Committee
Program Organizers: Damien Tourret, IMDEA Materials Institute; Amy Clarke, Los Alamos National Laboratory; Ulrike Hecht, Access e.V.; Nana Ofori-Opoku, Canadian Nuclear Laboratories; Melis Serefoglu, Marmara University; Tiberiu Stan, Asml
Thursday 8:30 AM
March 18, 2021
Room: RM 56
Location: TMS2021 Virtual
Session Chair: Hideyuki Yasuda, Kyoto University; Melis Şerefoğlu, Koç University; Joseph McKeown, Lawrence Livermore National Laboratory; Damien Tourret, IMDEA Materials
8:30 AM
Cellular Automaton Modeling of Solidification Microstructure and Microporosity in Multi-component Aluminum Alloys: Cheng Gu1; Michael Moodispaw1; Colin Ridgeway1; Alan Luo1; 1Ohio State University
With the advancement of Integrated Computational Materials Engineering (ICME) for solidification products, it is important to predict their location-specific microstructure and properties. In this talk, a three-dimensional multi-component model was developed to predict solidification microstructure and microporosity evolution by using cellular automaton method. Both the effects of hydrogen and shrinkage on microporosity formation were considered in the model. The simulations show qualitative results of evolution and morphology of microstructure and quantitative results of percentage microporosity. A wedge die casting was used to study the effect of cooling rate on microstructure and microporosity and to validate the cellular automaton simulations. X-ray micro computed-tomography was performed to obtain the relevant porosity information such as pore morphology, pore size, final porosity percentage and so on. The simulated results of porosity size, percentage and distribution agree well with experimental measurements.
8:50 AM
Effects of Process Conditions and Morphology Evolution on Microsegregation During Solidification: A Combined Phase-field and Experimental Study: Zhenjie Yao1; David Montiel1; Mei Li2; Katsuyo Thornton1; John Allison1; 1University of Michigan; 2Ford Motor Company
The microsegregation that occurs in Al-Cu alloys during different solidification processes was investigated using experimental measurements and phase-field simulations. Quantitative measurements of microsegregation were conducted using Electron Probe Micro-Analysis (EPMA). The EPMA results showed pronounced microsegregation of Cu in the center of dendrites that could not be readily explained by conventional analytical expressions. The microsegregation and dendrite morphological evolution were simulated using the quantitative phase-field model developed by Echebarria et al. To this end, a new alloy solidification application was developed within the high-performance, open-source PRISMS-PF framework. This application was then used to simulate solidification of Al-Cu alloys in 2D and 3D. The combined experimental and PRISMS-PF simulation study demonstrated that microsegregation is dependent on the process conditions and evolution of morphology. These findings were used to develop an improved analytical microsegregation model that can accurately predict microsegregation over a wide range of solidification conditions and alloys.
9:10 AM
Effect of Vacuum during Flow in High-pressure Die Casting: Water Analog Experiments: Nicole Trometer1; Xuejun Huang1; Emre Cinkilic1; Alan Luo1; 1The Ohio State University
High-pressure die casting (HPDC) is used to produce lightweight aluminum and magnesium components. However, a common defect associated with these castings is air entrainment, which negatively affects their soundness and mechanical properties. These defects can be reduced via evacuating air from the die cavity prior to metal injection in HPDC process. Water analog experiments were conducted to validate the effect of vacuum on flow and air entrainment. The experiments used a servo motor and a linear actuator to replicate the shot profile in HPDC cavity fill. A vacuum system was added to the experiments to evaluate the efficiency of vacuum and to obtain the optimal process conditions for vacuum HPDC. The results suggest that adding a vacuum to the HPDC process can significantly reduce the entrapped air during flow, which could improve the mechanical properties of aluminum and magnesium die castings.
9:30 AM Invited
Grain Selection after a Massive-like Transformation from Ferrite to Austenite during Solidification in Fe-based Alloys: Hideyuki Yasuda1; Taka Narumi1; Takeru Suga1; Yukihiko Nanri1; 1Kyoto University
The observations using time-resolved X-ray imaging techniques (transmission imaging and tomography) indicate that the peritectic reaction, which is controlled by solute diffusion, does not occur and a massive-like transformation from ferrite to austenite, which produces fine austenite grains, is dominantly selected even in the unidirectional solidification in Fe-C alloys. The volume change owing to the massive-like transformation and the coarsening of the fine austenite grains can influence solidification defects, such as deformation of solidifying shell and cracks. Time-resolved tomography (4D-CT) was used to measure the volume change and to measure the crystallographic orientations before and after the massive-like transformation. The crystallographic orientations of austenite widely distributed immediately after the massive-like transformation, but some relationships in the crystallographic orientation between austenite grains were also observed. This paper will discuss the influence of the massive-like transformation following the solidification on the microstructure evolution in Fe-C alloys.
10:00 AM
Synchrotron Examination of Nucleation and Growth of Nodular and Compacted Graphite Particles during Cyclic Solidification of Ductile Cast Iron: Chaoling Xu1; Tim Wigger2; Mohammed Azeem3; Tito Andriollo1; Samuel Clark2; Robert Atwood4; Jesper Hattel1; Peter Lee2; Niels Tiedje1; 1Technical University of Denmark; 2University College London, Mechanical Engineering; 3University of Leicester; 4Diamond Light Source
It is well acknowledged that the morphology of graphite particles in cast iron strongly affect its mechanical and physical properties. In-situ synchrotron X-ray tomography was employed to directly capture the evolution of branches and formation of coral-like particles during repetitive melting and solidification of ductile cast iron. The results show that the graphite particles initially form adjacent to austenite mainly as spheres. Subsequently branches develop and coarsen towards regions with high carbon concentration, interconnecting and constituting particles with large sizes and low sphericity. Three types of particle morphologies are identified: (1) nodules with and without polyps, (2) combination of several nodules or nodules attached to a plate, and (3) a coral like structure. Changes in the morphology are correlated to the global chemical composition and local carbon concentration. The present study makes a vital contribution to explaining and predicting the microstructures and properties of ductile and compact cast iron.
10:20 AM
In Situ Quantification of Degenerate Graphite Nodule Formation during the Solidification of Ductile Cast Iron: Tim Wigger1; Tito Andriollo2; Mohammed Azeem3; Chaoling Xu2; Samuel Clark1; Robert Atwood4; Niels Tiedje2; Peter Lee1; 1UCL; 2DTU; 3University of Leicester; 4Diamond Light Source
Ductile cast iron is of increasing importance for the transportation and renewable energy sectors. A critical factor for the mechanical characteristics of ductile iron castings is the morphology of the embedded graphite nodules, which can degenerate during solidification, degrading the material properties. In situ time resolved high-speed synchrotron X-ray tomography was used to capture the evolution of graphite nodules during solidification of cast iron, capturing the evolution of degenerate features and the carbon concentration field in the matrix. The results reveal that the dendritic austenitic phase and the distribution of the carbon concentration in the surrounding liquid phase control the graphite morphology. Changes in the sphericity of the nodule population under varying conditions are examined, showing an increase in degeneration with increasing cooling rates. These results support the validation and development of predictive numerical models and give insights into the solidification kinetics and design of advanced cast iron alloys.