Skip navigation, view page content
Special Seminar
Wednesday, June 3, at 12:30 p.m.
Room 131 Fontana Labs
Jacques Lacaze
Senior Scientist,
Centre Interuniversitaire de Recherche et d'ingŽnierie des MATŽriaux,
CIRIMAT, UniversitŽ de Toulouse
Phase Diagram, Microsegregation, and Solidification Path
Abstract
The development of solidification microstructures proceeds for most of the casting processes with very limited departure from equilibrium at the liquid/solid interface. Accordingly, the relevant equilibrium phase diagrams may be used as reference to express and calculate nucleation and growth conditions of solid phase(s) from the liquid. To deal with solidification of multi-component (commercial) alloys, most of the simulation approaches rely nowadays on thermodynamic databases and associated calculation softwares. The development of such databases using the CALPHAD method will be shortly described in the case of aluminium alloys.An example of phase diagram study will be detailed with the Al-Fe-Mn-Si system. The only extensive work on the Al corner of this particular system goes back to the mid 20^th century and consisted in thermal analysis records and observation of the resulting microstructures. These results thus include the solidification path as affected by nucleation undercooling of the various phases, kinetic undercooling and microsegregation build-up during solidification. It will be illustrated how much complicated may be the analysis of (very) common aluminium cast alloys.
Microsegregation that develop during the solidification process are of prime importance as they remain nearly unchanged after further cooling and may affect materials properties unless adequate (and costly) heat treatments are performed. The way microsegregations are usually characterized will be shortly described, including an evaluation of the related distribution statistics. Such distributions are sometimes used for validating numerical softwares developed for simulating solidification. In turn, they are also sometimes used to characterize liquid/solid equilibrium through the evaluation of the so-called partition coefficient. Possible problems arising from such a methodology will be described.
Bio
After a PhD at the School of Mines in Paris that was defended in 1982, Jacques Lacaze took a position at the School of Mines in Nancy as research fellow of the French National Centre for Scientific Research (CNRS). His interest was there casting and solidification of metallic alloys, with particular emphasis on coupling of the formation of microstructure and the development of chemical heterogeneities at local scale. During this first period, he worked on wrought aluminium alloys, nickel-base superalloys and stainless steels. As invited researcher for a one year stay at the Royal Institute of Technology in Stockholm, (1985-1986), he started working on nodular cast iron and using CALPHAD approach for simulation and calculation of thermodynamic equilibria. From 1986 to 1994, he deepened his description of alloy solidification using both experimental and simulation approaches.
In 1994, Jacques Lacaze moved to Toulouse and became CNRS senior scientist in 2000. In the CIRIMAT laboratory, he is involved in a team dealing with coupling between environment, microstructure and mechanical properties of metallic alloys. Still active in the solidification field, he also works since then on oxidation and mechanical properties of various other materials, including high alloyed cast steels, aluminides, powder compacts and so on. Jacques Lacaze has supervised 15 PhDs, he is author or co-author of 140 papers, and has been coordinator of two European networks ("Microstructural Engineering by Solidification Processing - MEBSP" and "Thermodynamics of Alloyed Aluminides - THALU").
Please join our speaker for pizza and refreshments in 131 Fontana Labs prior to the talk.
Note: This talk is not part of the MSE 795 Seminar Series.
