Frontiers in Solidification Science VIII: Melting, Nucleation & Laser Processing
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
Wednesday 8:30 AM
March 17, 2021
Room: RM 56
Location: TMS2021 Virtual
Session Chair: Julien Zollinger, Institut Jean Lamour; Amy Clarke, Colorado School of Mines; Guillaume Boussinot, Access e.V.; Tiberiu Stan, Northwestern University
8:30 AM Invited
Melting of Metastable Solid-states in Au-Si Eutectic Alloy: Güven Kurtuldu1; 1ETH Zürich
Melting of various metastable states in Au-18.6at%Si alloy has recently been achieved using fast differential scanning calorimetry (FDSC)[1]. It has been demonstrated that different solids form in this alloy, fully melt at various temperatures with completely different melting enthalpies. Moreover, the characteristic melting temperature and melting enthalpy of each solid-state enable to use of FDSC as a phase identification technique. An energy/temperature (E/T) diagram has been prepared using measured thermodynamic parameters of metastable solids. A strong phase competition between a rich variety of metastable and stable solid states present in Au-Si eutectic alloy has been investigated using the E/T diagram and crystallization pathways have been enlightened. The stochastic nature of nucleation has also been demonstrated as a critical phenomenon on phase competition between metastable phases.[1] G. Kurtuldu, J.F. Löffler, Multistep crystallization and melting pathways in the free–energy landscape of a Au-Si eutectic alloy, Advanced Science, 2020, 7, 1903544.
9:00 AM Invited
Microstructure Evolution during Melting: Guillaume Boussinot1; Mahdi Torabi Rad1; Markus Apel1; Alexandre Viardin1; 1Access e.V.
In the frame of solid/liquid transitions in metals, melting has been much less studied than solidification owing to the preeminence of traditional metallurgical techniques such as casting. However, melting receives a recent increasing attention linked to the developments of additive manufacturing processes, for which the properties of the final product depends crucially on a succession of melting and solidification stages. Here, we present our work, illustrated by phase-field simulations, on several melting scenarios such as the melting of a peritectic phase, the remelting/resolidification mechanisms taking place when, for example at the bottom of a melt pool, the mushy zone is held in a static thermal gradient, and the so-called grain boundary pre-melting for which an atomically thin liquid layer grows along the latter below the melting temperature.
9:30 AM Invited
ISRO-mediated Nucleation in Fcc Alloys during Rapid Melting and Solidification Processes: Julien Zollinger1; Ivan Cazic2; Michel Rappaz3; Benoît Appolaire1; 1Institut Jean Lamour; 2Institut Jean Lamour / Institut de Soudure; 3EPFL
Kurtuldu et al. have presented a new mechanism of nucleation in fcc alloys based on icosahedral quasicrystals (iQC) or icosahedral short-range order (ISRO) clusters formation in the liquid phase and acting as pre-nuclei for the fcc phase. Such mechanism has been evidenced in Al and Au alloys when minute additions of Cr and Ir, respectively, were added and has led to a drastic reduction of the grain size. It has also been shown that ISRO modifies the growth behavior, inducing a dendrite orientation transition. In the present work, the influence of ISRO on nucleation of various fcc alloys will be presented, with an emphasis on rapid melting and solidification processes. Based on model experiments and detailed EBSD analysis, the mechanisms of feathery grain nucleation in Al-based alloys, of divorced nucleation in Au-based alloys and of columnar-to-equiaxed transition in Ni-based superalloys will be presented.
10:00 AM
Orientation Relationships between Al3Ti and TiB2 due to Nucleation and Pushing/Engulfment: Yi Cui1; Andrew Horsfield1; Christopher Gourlay1; 1Imperial College London
Orientation relationships (ORs) can form during solidification by a variety of mechanisms that are often difficult to distinguish after solidification. Here we study ORs formed between faceted Al3Ti and TiB2 by heterogeneous nucleation and by the pushing and engulfment of TiB2. Nucleation ORs are studied by growing large TiB2 crystals, solidifying multiple small Al3Ti crystals on the (0001) facet of TiB2, and measuring the resulting ORs by electron backscatter diffraction (EBSD). Pushing and engulfment ORs are investigated by statistical analysis of EBSD measurements, density functional theory (DFT) calculations of interface energies, and imaging of cross-sections of TiB2 particles being pushed and engulfed by Al3Ti facets.
10:20 AM Cancelled
Model the Initiation of Hot Cracking in Aluminum 6061 during the Processes of Laser Welding: Guannan Tang1; Anthony Rollett1; 1Carnegie Mellon University
The current work seeks to quantitatively understand the cracking phenomenon during the laser welding process of Al 6061. To this end, a hot cracking initiation model focusing on events at a scale of the grain boundary was derived. It models the initiation of hot cracking as the coalescence of thermally induced micro-voids at the grain boundary. Within this approach, a combined Thermal Lattice Boltzmann-cellular automaton (TLB-CA) code was used to simulate thermal distribution and microstructure evolution of Al 6061 during laser welding. Validation of the results was made through Dynamic X-ray Radiography (DXR) data. Associated thermally-induced micromechanical fields were analyzed with a spectral code called Micromechanical Analysis of Stress-Strain Inhomogeneities with Fourier transforms (MASSIF). Combining results from TLB-CA and MASSIF, the current model in this work can give the prediction of local micro-void coalescence tendency and quantify it as the local susceptibility of hot cracking initiation.
10:40 AM
Using Composition and Patterning to Induce Solidification Instabilities in Al-Cu Eutectic Thin Films: Eli Sullivan1; John Tomko1; Jonathan Skelton1; James Fitz-Gerald1; Patrick Hopkins1; Jerrold Floro1; 1University of Virginia
Directional laser melting and solidification in sputtered eutectic Al-Cu thin films can produce highly regular lamellae with spacings < 50 nm. This lamellar structure resembles a network of nearly identical, parallel interfaces, which could prove useful in studying interfacial effects and anisotropy in electronic and thermal transport. Within the context of the transport, it is also interesting to create and investigate non-parallel lamellar structures. In hypoeutectic films, oscillatory instabilities can emerge, and at lower scan speeds near the transition to dendritic growth, highly tortuous lamellar structures form over extended areas. We can further attempt to tailor instability by deliberately adding physical hole defects into a eutectic film prior to melting via focused ion beam (FIB) milling. A single nanoscale FIB defect can affect lamellae several spacings away by inducing morphological tilt waves. FIB hole arrays can produce many interacting waves. Support of the NSF under grant DMR-1663085 is gratefully acknowledged.