Classical Phase Diagram Research Articles

Interphase and antiphase boundary stability in bcc compounds under irradiation

To model the behaviour under irradiation of a bcc alloy presenting the B2-A2 order-disorder transition, we propose a mean-field approximation of a kinetic model with two atomic exchange mechanisms acting in parallel: thermally activated and forced jumps. By integration of deterministic evolution equations, we show that irradiation can induce the stabilization of a two-phase alloy, while the classical equilibrium phase diagram only displays single-phase fields (the B2-A2 transition is second order). Steady-state diagrams are computed: in the two-phase region, surface tension-like effects are identified, antiphase boundaries are found to be unstable with respect to the disordered solid solution and smaller precipitates shrink to the benefit of the larger ones. Monte Carlo simulations confirm that the transition can become of first kind under irradiation and allow to study cascade size effects.

TEM study of the decomposition of the Heusler alloy Cu2MnAl

Investigation of the equilibrium phase precipitation in the alloy Cu2.00Mn1.00 Al1.00 performed previously by X-ray diffraction, magnesometry, SEM and resistometry was continued by means of TEM. It was found that the γ andβ-Mn precipitation mechanism was cellular in most cases. No T-phase precipitates were detected. The new results were compared with the previous ones and the temperature dependence of theβ-phase decomposition mechanism was explained in terms of the classical phase diagram of the Cu-Mn-Al system.

Unary and binary multisystems; topologic classification of phase diagrams and relation to Euler's theorem on polyhedra

Unary and binary multisystems; topologic classification of phase diagrams and relation to Euler's theorem on polyhedra

The local classification of phase diagrams in thermodynamic field space

The local classification of phase diagrams in thermodynamic field space

A classification of phase diagrams by means of “Elementary” Catastrophe Theory (ECT) II

In a previous paper it has been shown that near every type of point μ o in the field space, any GM stable C∞ unfolding Φ by appropriate diffeomorphic substitutions can be reduced to a GM standard form, i.e. an unfolding of functions, constructed from one or more simple polynomials. For μ o being a critical point the result of the reduction is compared with the Landau theory. This is followed by a complete list, up to and including four fields, of phase diagrams, described by GM standard forms, with physical examples (including e.g. critical end points and tricritical points). Symmetries are also treated. Finally remarks are made on, among other things, the “double cusp” GM standard form and a one-to-one correspondence between types of points and QLS of PS, described by GM stable Φ's, around these points.

A classification of phase diagrams by means of “Elementary” Catastrophe Theory (ECT) I

In this paper phase diagrams in field spaces are classified according to the qualitative local shapes (QLS) of their sets of first- and second-order phase transition points (PS). The QLS are defined in terms of diffeomorphisms. We proceed from a rather general Landau-type model of phase transitions and employ a variant of “elementary” catastrophe theory (ECT). This variant is developed in terms of polynomials in a more general context including also the usual “local” variant of ECT. An essential concept is GM stability of C∞ unfoldings (i.e. families) Φ of functions and a criterion for this property is derived. It is shown that, near every type of point μ0 in the field space, any GM stable Φ by appropriate diffeomorphic substitutions can be reduced to a GM standard form, i.e. an unfolding of functions, constructed from one or more simple polynomials. A finite list of GM standard forms, which is complete for less than nine fields, can be made. Further an extension of Gibbs phase rule is considered.