Lecture

Germination: Theory and Applications in Materials Science

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In course

MSE-302: Phase transformations

Ce cours est une introduction aux transformations de phases liquide-solide et solide-solide. Il aborde les aspects thermodynamiques et cristallographiques. Il traite principalement des matériaux métalliques, et établira des ponts vers les céramiques et la ...

Description

This lecture provides an introduction to the theory of homogeneous and heterogeneous germination, focusing on the significance of nucleation in materials science. It discusses the impact of germination on grain size, particularly in aluminum alloys, where the addition of grain refiners like TiB₂ and Ir can drastically alter grain structure. The instructor explains the processes involved in achieving fine grain sizes, which are crucial in industries such as watchmaking. The lecture also covers the Czochralski process for growing single crystals, emphasizing the importance of grain size in microelectronics. Additionally, it addresses the challenges of avoiding crystallization in bulk metallic glasses (BMGs) and the conditions necessary for their formation. The theory of germination is explored, including the concepts of clusters and the critical radius for nucleation. The lecture concludes with a discussion on the interfaces between solid and liquid phases, highlighting their role in the solidification process and the implications for material properties.

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Instructor

Cyril Cayron

1992-1995 Engineering School. Ecole des Mines de Nancy. 1994-1995 Master's degree in Materials Science (rank = 1st) 1995-1996 Military Service 1996-2000 PhD at EPFL-CIME. Precipitation in 6xxx alloys and composites. 2000-2014 Researcher, Engineer and Group leader on materials for new energies at CEA-Grenoble, France. 2012 Habilitation to supervise researches (HDR) 2014-now Senior Scientist at EPFL-LMTM Creator of the computer programs GenOVa and ARPGE (in Python). I currently work on crystallographic models of martensitic transformations and deformation twinning.

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Related concepts (32)

Thermodynamics

Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics.

Laws of thermodynamics

The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium. The laws also use various parameters for thermodynamic processes, such as thermodynamic work and heat, and establish relationships between them. They state empirical facts that form a basis of precluding the possibility of certain phenomena, such as perpetual motion.

Chemical thermodynamics

Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics. Chemical thermodynamics involves not only laboratory measurements of various thermodynamic properties, but also the application of mathematical methods to the study of chemical questions and the spontaneity of processes. The structure of chemical thermodynamics is based on the first two laws of thermodynamics.

Non-equilibrium thermodynamics

Non-equilibrium thermodynamics is a branch of thermodynamics that deals with physical systems that are not in thermodynamic equilibrium but can be described in terms of macroscopic quantities (non-equilibrium state variables) that represent an extrapolation of the variables used to specify the system in thermodynamic equilibrium. Non-equilibrium thermodynamics is concerned with transport processes and with the rates of chemical reactions.

Second law of thermodynamics

The second law of thermodynamics is a physical law based on universal experience concerning heat and energy interconversions. One simple statement of the law is that heat always moves from hotter objects to colder objects (or "downhill"), unless energy in some form is supplied to reverse the direction of heat flow. Another definition is: "Not all heat energy can be converted into work in a cyclic process." The second law of thermodynamics in other versions establishes the concept of entropy as a physical property of a thermodynamic system.

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