FK, DFK models and a new theory of metal alloys are used to explain the Portevin-Le Chatelier effect.

Quote from [1,2]: -

“Many experiments measuring the deformation of solids under static loads have revealed sudden yielding and other deviations from normal behavior, now known as the “Portvin-Le Chatelier effect.” If we follow historical truth, then the honor of the discovery of this phenomenon should be associated with the names of Felix Savard (1837) and Antoine Philibert Masson (1841). Masson described a steep, almost vertical (σ-ε diagram) increase in stress, accompanied by very little deformation, up to a value at which there was a sudden sharp increase in deformation at constant stress. In experiments of this type with dead loads used in testing machines in the 19th century, this phenomenon took on the form that later led to the use of the term "staircase effect."

For small and large deformations, this effect has been studied by many over the past two centuries, but a satisfactory explanation has not yet been achieved.

It makes sense to compare the experimental ladders of the Portvin-Le Chatelier effect [1,2] with the already existing theoretical ladders [3,4].

In [1,2], in experiments on stretching AL with a purity of 99.99% shows several detailed graphs of the σ-ε dependence, for example, [1, p. 74] and [2, p. 288].

If you compare the staircase [1, p. 74] with the staircases [3,4], then their similarities are revealed - they almost coincide. But if you look at [1, p. 74] more carefully, especially at the initial stretching section, then qualitative differences are noticeable. First of all, this is the absence of strictly vertical segments in the experimental graphs. Consequently, the FK model is not enough to explain the EPLC, so it needs to be modified and replaced with the DFK model.

From the point of view of the DFK model, the initial stretching segment is associated with the general stretching of two CHs united by the potential V_lj. Further, at a certain critical force F_c, failure occurs with compression of CH2 and abrupt stretching of CH1 followed by interchain capture. The process is repeated until the sample breaks.

The first prediction of the new model is that when stretched, the sample becomes chemically inhomogeneous in length and composition of m and M atoms.

The most important question for the EPLC within the framework of the DFK model arises - the nature of Hooke's chains.

If stretchable CH1 is logically associated with an AL crystal, then the nature of CH2 may be associated with metal impurities. Let's follow this hypothesis.

In metals with a small number of impurities, for example, in ALR_%, the metal impurity R_% is capable of being ordered into a cubic crystal at high temperatures. Impurity period CH2 – one-dimensional projection of the crystal R_% we evaluate as , where % is the number of impurities in the main matrix. Suppose that in our case % = 10^-6, then the period CH2 R ≈ 100.

Comparing the number of steps [1, p. 74] with R=100, we find an approximate match.

As a result of stretching, the period of the R-sublattice changes from r=100 to r=1.

From the temperature graphs of the EPLC [2] it is clear that the EPLC disappears at T> T_c.

EPLC is a special case of phenomena in metal alloys A_xB_1-x.