ISSN 20751133, Inorganic Materials: Applied Research, 2015, Vol. 6, No. 3, pp. 199–204. © Pleiades Publishing, Ltd., 2015. Original Russian Text © V.I. Vysotskii, A.O. Vasylenko, V.B. Vassilenko, M.V. Vysotskyy, 2014, published in Fizika i Khimiya Obrabotki Materialov, 2014, No. 1, pp. 5–11. 199 INTRODUCTION At the present time, the treatment of materials is often carried out using laser emission in the form of a sequence of short pulses with moderate energy, but with great power [1]. The laser cutting technique was developed for decreasing the pulse duration to attain a sharp boundary of the temperature field. This trend is evident with respect to the classical heat conduction theory, according to which the temperature wave damps at a distance approximately equal to its length. The shorter the duration of the temperature pulse, the greater its energy fraction corresponding to highfre quency heat waves, which damp at small distances, which, in turn, leads to heating localization. However, another situation is possible in nonequi librium models of heat conduction. In particular, models with lag τ of setting the local temperature [2, 3] may demonstrate the existence of undamped temper ature waves because of the presence of defined phase relationships [4, 5]. The feature of the appearance of this effect is that, according to the theoretical analysis, a decrease in the damping coefficient must occur in some frequency range with increasing frequency, and the propagation of temperature waves without damp ing is possible at certain frequencies depending on the parameters of the medium and magnitude of τ. The undamped wave frequency is immediately determined via the medium relaxation time, which characterizes the establishment of thermodynamic equilibrium in an elementary subsystem. In the case of the medium with components having various kinetic properties (metal, semiconductors, plasma), it is appropriate to use twotemperature models [6–8], where the heavy ion system and the electron gas are characterized by various proper tem peratures. As a result, this medium is described by the pair of heat conduction equations interconnected via heat exchange between the ion and electron compo nent. The twotemperature models are successfully used for description of metal heating by nano and picosecond pulses. It should, however, be taken into account that, during fast heating, a substantial factor is not only the difference in temperatures of the electron gas and the lattice but also the need to use the non equilibrium models of the heat conduction. In [8], the author considered a generalized twotemperature model with a hyperbolic equation of heat conduction, the range of the applicability of which is bounded by small lag τ satisfying the condition ωτ  1, where ω characterizes the rate of change in thermodynamic values in the particular process. On the basis of this limitation, it is evident that the magnitude of the “small lag” is determined by the dynamics of actual processes. The present research considers the twotempera ture model based on the equation with lag. TWOTEMPERATURE MODEL OF HEAT CONDUCTION The nonequilibrium heatconduction models can be constructed if the partial time derivative of the dis tribution function is considered in the kinetic equa tion: (1) ∂ f ∂ t  v∇f + f f 0 – τ  – . = ENERGY FLUX EFFECT ON MATERIALS Nonequilibrium Thermal Effects during Pulsed Action on Conducting Medium V. I. Vysotskii a , A. O. Vasylenko a , V. B. Vassilenko b , and M. V. Vysotskyy a a Taras Shevchenko National University of Kyiv, ul. Vladimirskaya 60, Kyiv, 01601 Ukraine b NOVA University of Lisbon, 1099085 Lisbon, Portugal email: vivysotskii@gmail.com Received July 16, 2013; in final form, October 20, 2013 Abstract—The twotemperature model for a medium with free electrons subject to nonequilibrium heat transfer is considered. The possibility is shown for tailing of heating area boundaries and the existence of undamped heat waves due to the small duration of temperature pulses acting on the material. A quantitative estimate is made for parameters of the temperature mode when the tailing of heating area boundaries appears according to heat conduction models. Keywords: treatment of materials, short laser pulses, metal, plasma, heat conduction, nonequilibrium heat conduction DOI: 10.1134/S2075113315030144