Jean-Baptiste Leblond

Jean-Baptiste Leblond, born on 21 May 1957 in Boulogne-Billancourt, is a materials scientist, member of the Mechanical Modelling Laboratory of the Pierre-et-Marie-Curie University (MISES) and professor at the same university.
Biography.
Leblond attended his scientific preparatory classes, notably in the special M' mathematics class at the Lycée Louis-le-Grand and was admitted to the École normale supérieure de la rue d'Ulm, mathematics option, in 1976. He then joined the Corps des mines and became a doctor of physical sciences.
Leblond's kinetic theory.
This is an approach established by Leblond in his work on phase transformations.
The theory proposes an evolutionary model to quantify the composition of the different phases of a crystalline material during heat treatment.
The method is based on experimentally established CRT (Continuous Cooling Transformation) diagrams to compose TTT (Time-Temperature-Transformation) diagrams, which are widely used for numerical simulation or for the manufacture of industrial parts.
The theory posits the equivalent volume fraction of a constituent "yeq" as the stationary solution of the evolution equations describing the phase change kinetics:
We then suppose in anisothermal condition that the real fraction y is close to "yeq", it is then possible to approximate the real value "Y" by a Taylor development at order 1:
The evolution is given by :
There are also other formalisms such as the theory of Kirkaldy, Johnson-Mehl-Avrami or Waeckel. One of the most classical, quite old, is that of Johnson-Mehl-Avrami. The model proposed by Jean-Baptiste Leblod is in fact based on this classical model by generalizing it on two points: 1) it considers any number of phases and transformations between these phases, and not just two phases and a single transformation; 2) the transformations can remain, after an infinitely long time, partial, and not necessarily complete as in the Johnson-Mehl-Avrami model (this is linked to the existence, in the new model, of fractions "at equilibrium" of the phases towards which the system evolves after an infinite time, not necessarily equal to 0 or 1 but which can take any value between these limits).
The Leblond model is designed for applications in the thermometallurgical treatment of steels; this explains its success with the modellers of these treatments.