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45XV International Symposium on Self-Propagating High-Temperature Synthesis
NI-AL BASED REACTIVE MATERIAL: MECHANICAL PROPERTIES AND FEATURES OF COMBUSTION
S. A. Seropyan*", I. V. Saikov", V. G. Salamatov", M. I. Alymov", A. V. Dolmatovfi, and P. Yu. GulyaevA
aMerzhanov Institute of Structural Macrokinetics and Materials Science Russian Academy of
Sciences, Chernogolovka, 142432 Russia
bYugra State University, Khanty-Mansiysk, 628012 Russia
*e-mail: stepan.seropyan@mail.ru
DOI: 10.24411/9999-0014A-2019-10154
Reactive materials are a class of energetic materials characterized by high energy intensity, low sensitivity under normal conditions, and the ability for intense chemical reaction under highspeed impact and heating conditions. Reactive materials are typically compressed powder [1-3].
The creation of structural reactive materials that combining a required set of physico-mechanical characteristics and high energy release are associated with a number of physico-chemical limitations and technological difficulties [4-6]. Such research, as a rule, are purely experimental and are distinguished by the complexity of studying fast-acting physicochemical processes directly in the process of explosive loading of the reaction mixture, which is characterized by high rates of deformation, pressures, and temperatures. The current problem is the development of consolidation methods that would preserve the ability to achieve sufficient structural strength of the material as a whole.
The studies were carried out with a powder mixture of Ni-Al of the composition Ni + 31.5 wt % Al, the reagents of which were Ni powders (grade PNE-1) and Al (grade ASD-4). Mixing of powders of a given composition was carried out in a Turbula type mixer for 4 h. Green mixture was molded in the form of parallelepipeds, including with reinforcing inserts (boron fibers (diameter of 140 |im) or tungsten wires (diameter of 300 |im)). Samples (20 x 5 x 5 mm) with reinforcing inserts were prepared as follows: the green mixture for one sample was divided into 5 equal parts, which were poured into the mold. Then the reinforcing elements in the amount of 5 (tungsten) or 6 (boron fiber) were placed between these layers. The obtained composites were subjected to one-side pressing to a relative density of 0.7^0.8.
In separate experiments, a mixture of (1 - x)(Ni + 31.5 wt % Al) + xTf was used as a charge between reinforcing elements, where x is wt % of Teflon (Tf). The amount of Teflon varied in the range of 1^25 wt %. The relative density of the resulting composites was 0.83^0.99.
The effect of heat treatment on the strength characteristics of composites was investigated. The samples were heated in a furnace in an atmosphere of air. The exposure time of the samples varied from 1 to 4 h, and the temperature changed from 300 to 550°C.
Tests to determine the strength of samples with three-point bending conducted on the equipment Instron 1195 according to GOST 25282-93. The combustion was initiated from the lateral end by a heated electric wire in air at normal pressure. After initiation, a self-sustaining reaction wave propagated along the sample (with an average burning rate of 60-100 mm/s). The burning of composites takes place in a non-stationary mode and is characterized by the presence of reaction foci (average size of 400 |im), which randomly move in front of the front. Investigation has shown that reinforcement of samples with boron fibers or tungsten wires increases the strength of the reactive materials. Boron fibers increase the strength by 1.6 times compared to non-reinforced samples. Reinforcing tungsten wire increases the strength of 3.8 times compared with non-reinforced. The cause for this effect is due to the redistribution of the
ISHS 2019 Moscow, Russia
load from the matrix to the reinforcement inserts. It is necessary to note the problem of insufficient adhesion of the fiber with the matrix, as a result of which their entire resource is not used. For reinforced samples, the number of fibers is an important parameter. Adding Teflon allows for a higher density. Reinforcement with boron fibers increases strength by 2 times at 1 wt % Tf. A further increase in the content of Teflon leads to a decrease in strength. The reinforcement of composites with a high content of Teflon does not lead to a significant increase in strength.
Heat treatment of unreinforced samples increases strength: at 300°C and 3 h, by 1.3 times; at 400°C and 4 h, by 3.7 times; at 500°C and 1 h, by 5.7 times; at 550°C and 3 h, by 6.3 times. Heat treatment of the samples reinforced with boron fibers made it possible to increase the strength under the following conditions: at 400°C and 2 h, by 1.6 times; at 500°C and 1 h, by 3 times. The samples reinforced with tungsten fibers after heat treatment: increased strength: at 400°C and 3 h, by 1.8 times. After heat treatment in air, the samples increase their mass by
0.5.5.5%. With an increase in temperature and exposure time, the increase in mass linearly increases.
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