A.A. ARTSRUNI Candidate of Technical Sciences,
R.I. YUNATSKEVICH, Candidate of Technical Sciences
JSC Research Institute of Steel, Moscow, Russia.
The experience of military operations in the last decades of our time, gained in the war in Afghanistan, two wars in Chechnya and the last conflict in Nagorno-Karabakh, revealed a number of features of the use of military equipment.
Thus, the Afghan war showed the practical unsuitability of tanks in high-altitude conditions with the increasing role of light armored vehicles BMD, BMP and APC. At the same time, there was a need for a serious revision of their combat armament, which consisted, as a rule, in the course, linear, planar orientation of weapons systems, which in mountainous terrain required a decisive revision of the main armament in the direction of increasing the anti-aircraft elevation angle of the main weapon and increasing its rate of fire. This led to the emergence of a new type of light vehicles: BMP-2, BMD-2, etc.
The Chechen wars revealed during the fighting in modern cities the low efficiency of armored vehicles with the increased efficiency of scattered infantry and, accordingly, personal protective equipment (PPE) of each fighter.
The experience of combat operations in Nagorno-Karabakh demonstrated a change in the nature of modern combat and, in particular, the sharply increased defeatability of ground combat and transport equipment from the upper hemisphere due to the use of attack drones equipped with guided bombs. Barrage ammunition and bombs of attack drones attack ground transport and armored vehicles in the most weakened zone, the zone of the upper hemisphere, roof, towers, commander's and landing hatches, etc. This requires a rather serious revision of the technical characteristics of the designed products with the possible strengthening of anti-aircraft protection, with the introduction of high-explosive-buckshot types of combat shells, and the strengthening of air defense systems as part of ground combat equipment, which is becoming the main trend of our time.
Among the current urgent problems facing the Russian Federation, along with the active icebreaking development of the Arctic, is also its combat protection. And here aluminum armor is put forward in the first place, which has proven itself well from the experience of the above-described combat collisions, at the same time including a fairly extensive list of all kinds of advantages and, above all, cold resistance (cryogenicity), which will be discussed in the presented work.
Parameters of materials science and technological evaluation of aluminum and its alloys 1. Natural raw material availability;
2. Weight efficiency;
3. Features, advantages, advantages of the development (compositing) of aluminum-based alloys;
4. Production manufacturability;
5. Structural manageability;
7. Powder manufacturability;
8. Corrosion resistance;
9. Cold resistance;
11. Heat maskability;
12. Deep water;
13. Radio transparency.
1. NATURAL AVAILABILITY OF RAW MATERIALS For the production of the main raw materials of bauxite, Russia ranks seventh in the world. The highest quality bauxite is mined in the Northern Urals in the Sverdlovsk region at the North Ural bauxite Boundary (SUBR) and supplied to the Bogoslovsky and Ural aluminum plants. Bauxites are deposited in layers at a depth of up to 1 km, which makes their extraction quite expensive in comparison with the costs in a number of European countries, nevertheless, the volume of production of North Ural bauxites was more than 3 million in 2006. tons, which, however, does not exclude the purchase of bauxite abroad: in Australia, Brazil, China, Guinea, etc. At the same time, the development of new bauxite deposits continues, in particular: a deposit in the Komi Republic, whose bauxite reserves, according to modest calculations, will last our country for at least 50 years. In order to simplify the presentation, we will omit the technological operations, we will only say that their essence consists in the transition of bauxite and alumina and its subsequent electrolysis transformation into aluminum. It is clear that this requires an appropriate energy intensity of production (see Table 1).
1925 - 1930 kg
Carbon (for anode)
500 - 600 kg
50 - 70 kg
14500 - 17500 kW/h
Table 1. A feature of aluminum alloys is the possibility of their secondary use. So, in particular, aluminum armored hulls, recognized unsuitable for repair of BMD-1 and BMD-2 after combat use and stored at the tank repair plant in Kaunas, Lithuania, based on the disposal cutting schemes developed by us, were divided by thermal cutting into components suitable for furnace remelting, were transported to Russia and successfully used in the production of new batches of armor allowing up to 30-40% of returnable waste.
The technology of using recycled raw materials is particularly evident in the production of aluminum cans for beer and soft drinks: ~ 90% is recycled in Europe, up to 80% of recyclable materials in Russia.
2. WEIGHT EFFICIENCY
The operability of any structure, regardless of its functional purpose, along with strength, is also determined by its rigidity. Rigidity is the ability of a structure to resist the action of external loads with the least deformations. Rigidity is especially important for machines of a lightweight class, with strictly regulated mass characteristics, to which the machines considered in this paper belong. Stability, bending stiffness, as is known from the course of resistance of materials, is determined by the dependence
where:c is the coefficient determined by the method of applying the load; E is the modulus of elasticity; b is the thickness of the sheet (plate); l is the distance between the places of sealing of the sheets (plates). The modulus of elasticity is a value that characterizes the elastic properties of materials under small deformations. Often, it is also referred to as the modulus of longitudinal or normal elasticity, the Young's modulus or the modulus of elasticity of the first kind. It is determined experimentally as the ratio of the normal voltage to the relative elongation e = Δl / l, where the absolute elongation is, and the initial length is.
The dimension of the modulus of elasticity
The dimensions of pressure and voltage units are similar.
The presented dependence determining rigidity, with the exception of constants for each specific calculation, and, can be simplified to the form:
Thus, the bending stiffness (stability) is the product of the elastic modulus of the material by the cube of its thickness.
Before turning to a comparative assessment of the service properties of aluminum armor with other armor materials, let's consider the overall effectiveness of using aluminum alloys as an armored hull material.
The object of comparison is an aluminum alloy of medium strength, steel and titanium. So, we have a comparative series: Aluminum, Steel, Titanium.
The main comparable characteristics are presented in Table. 2 and in Fig. 1.
Fig. 1. Comparative physical parameters of aluminum (Al), titanium (Ti) and steel (C)
Table 2 Comparative analysis of the bending stiffness of metals
The density of metals (bulk mass), their strength (tensile strength), elasticity characteristic (modulus of elasticity) and stiffness with equal mass are compared. In terms of elasticity and strength, steel, in the series under consideration, is the undisputed leader. However, the correlation of the presented characteristics with the density of each of the materials under consideration and bringing them to the form /p⋅10ˉ3iσv /p, to the so-called specific elasticity and specific strength, leads the materials under consideration to almost equal indicators. At the same time, if we consider the possible thicknesses of materials under the condition of equal mass, then it is quite obvious that we should use the inverse of the density or 1/p.
We see that in this case aluminum will be 2.8 times thicker than steel and 1.6 times thicker than titanium. Titanium, in turn, is only 1.73 times thicker than steel. Thus, aluminum has the greatest absolute thickness. Stiffness, as we discussed above, is the product of the elastic modulus of a material by the cube of its thickness. The rigidity of aluminum, even taking into account the elastic modulus three times smaller than that of steel, turns out to be almost eight times greater than the rigidity of steel and almost three times greater than the rigidity of titanium. It was this circumstance that predetermined the use of aluminum armor for the manufacture of armored hulls of paintwork machines, since in the steel version, the armored hull, due to insufficient rigidity, needs to use a special frame, and does not need an aluminum version.
This, in the case of using aluminum as armor, allows us to characterize the aluminum body as a carrier that does not require a special increase in rigidity due to the use of a frame. At the same time, only by abandoning the frame, the transition from steel to aluminum booking is able to save up to 20% of the mass of the armored hull.
3. FEATURES, ADVANTAGES, ADVANTAGES OF THE DEVELOPMENT (COMPOSITING) OF ALUMINUM-BASED ALLOYS
Currently, there are over 300 grades of aluminum and its alloys grouped into 8 groups: from aluminum of different purity, double alloys (Al-Cu, Al-Si, Al-Mg, Al-Fe), triple alloys (Al-Mn-Mg, Al-Mg-Si, Al-Zn-Mg) up to complex alloyed alloys. At the same time, there is a high efficiency of the development of aluminum-based alloys, which is from 15 to 20 times the increase in properties relative to the main matrix material (aluminum), while for iron alloys (steels) it does not exceed 10 times, and for titanium alloys it is limited to only 8 times.
4. PRODUCTION MANUFACTURABILITY
The main feature of aluminum armor, as well as aluminum as such, is its wide base of shaping, including: rolling, forging, stamping, rolling and, most importantly, such an unprecedented technology as hot pressing pressing through a forming die, which opens up a unique opportunity to obtain complex structural elements of the armored hull and acts as an alternative to structurally weakening welding, providing monolithic execution of such complex and extended structures such as: upper-lobed ribbed panel BMP1 and BMP2, side-wing of BMD1 machines, a niche of a machine gun nest, a protective shaft of instruments, etc. Of course, this implies the presence of powerful pressing equipment with a capacity of up to 20 thousand tons.
5. STRUCTURAL MANAGEABILITY
Another factor is a fairly well-developed theory of slate (the structure of the fracture of aluminum armor, observed during its dynamic destruction) and is subject to control on a five-point scale of slate, which ensures satisfactory survivability of armor and its management when overcooking armor, which is actively used in the development of heat treatment modes.
The authors have developed and implemented a special sample, a fracture test, shown in Fig. 2.
Fig. 2. The scheme of cutting the sample for a break
The sample after the fracture (on any copra) represents a picture of the section H × δ, where δ is the total thickness of the plate.Blanks with dimensions L = 5δ; H = 1.5 δ are selected in two directions along and across the rolled product and, accordingly, represent the reverse live sections of the rolled material, the longitudinal sample is transverse, the transverse, respectively, longitudinal.An incision with a depth of 0.5 δ is made on the sample.The last sample is recognized as more characteristic and is accepted as the basis of the analysis. The incision is made in a plane perpendicular to the surface of the plate under study and is half the thickness of the plate in depth.
Based on the results of the work carried out, a five-point scale of slate based on the gradation of the area occupied by slate was proposed and put into practice. The scale is shown in Fig. 3. The first, second and third points are good and satisfactory types of slate, the fourth and fifth are not desirable.
Fig. 3. The scale of aluminum armor slate
The introduction of a fracture test and a slate scale confirmed the connection of the fracture structure with the survivability of armor during shelling and made it possible to predict the condition of armor according to this parameter without shelling and thereby significantly accelerate and reduce the cost of its production.
It is clear that fracture control, being an element of qualitative control of properties, is just a way of anticipating armor characteristics, but not controlling them. However, the use of the above-described method of transferring the material from the state of zone and zone-phase aging to the state of phase-coagulation aging, by means of a special overcooking mode, makes it possible to convert slate material into non-slate, which leads to an increase in the armor properties of the material.
6. WELDABILITY The weldability of aluminum armor refers to well-developed technological operations and is based on the use of classical techniques of manual, semi-automatic, automatic, argon arc welding. Wires made of AMg6 and AMg61 alloys ∅2÷3 mm (for automatic welding) and ∅1.5÷2 mm (for semi-automatic) are used as electrode and filler wires. Tungsten rods ∅26 mm are used as electrodes for manual welding, depending on the thickness of the metal being welded.
The weld material is characterized by weakened armor resistance, in comparison with the main armor. At the same time, the main feature of the adopted technology is the principle that the weakness of the seam is the strength of the adopted technology. The equal strength of the seam and armor is a vicious, extremely straining principle that can lead to the destruction of machines operating under alternating loads.
A weakened seam is a classic compensator for welding and assembly stresses that occur during the assembly of structures in assembly stands. One of the successful solutions of the adopted technology is the combination of the second stage of aging of the hulls, favorably affecting the structure of the fracture of the armor, with the removal of welding stresses, which received the designation of the mode index T2.
At the same time, the weakness of the seam requires a special approach to its placement during welding and careful development of the design of each welded joint, which is ensured by the release of a special NTD package for the design of all used armor seams with their preliminary firing on accepted models. The described technology has been widely tested in real operating conditions, estimated by almost 50 years of combat operation experience.
Currently, the global resource and strategic situation of world development is developing in favor of the constant growth of the importance of the Arctic region of Russia. This means significant opportunities for both already explored and newly discovered resources, both offshore and offshore production of hydrocarbon gas and oil raw materials, the availability of minerals and large natural resources, as well as the possibility of their simplified transportation along the Northern Sea Route. This situation is also aggravated by climatic changes and, in particular, global warming and the corresponding activation of the role of the mentioned Northern Sea Route as the most important communication trade channel in the Europe North Far East scheme.
In these circumstances, the Arctic territories of Russia need both a clear border notification, as well as ensuring their normal arrangement and functioning and, of course, their military protection. And here, with all the seeming paradoxicity, among all the known armor materials and, above all, armor plates, aluminum armor, a relative newcomer to armored vehicles, deserves special attention. To begin with, we will identify the real areas of possible use of aluminum armor. These are ground-based military transport vehicles and ship hull and above-deck armored structures.
There are quite a lot of requirements for the armor of military equipment as such. One of the main ones in this case is armor resistance, survivability, structural applicability (rigidity, weldability, corrosion resistance, etc.). For most material scientists, the problem solved in this work seems to be quite new. This is explained in two circumstances: firstly, in the closeness of the topic, and, secondly, in the lack of awareness of the effectiveness of the use of aluminum armor instead of historically traditional steel armor.
The issue of the development of the northern circumpolar territories of Russia and the possibility of building a Northern latitudinal Course has been thoroughly studied since the foundation of the Russian Geographical Society of the Russian Geographical Society in 1845. It was headed by representatives of the Russian Imperial House, outstanding scientists and prominent statesmen. The Society has made a significant contribution to the study of the north of the European part, the Urals, Siberia, and the Far East.
RGS is one of the oldest geographical societies in the world, unites specialists in the field of ethnography, geography, geology, hydrology, seismology, glaciology, including representatives of the Ministry of Russian Railways, Shipbuilding Industry and the Ministry of Defense of the country. Currently, the RGS is headed by the Minister of Defense of the country Shoigu Sergey Kuzhigetovich, which emphasizes the importance of this region in the development and protection of our Fatherland in the light of the ever-increasing threat from our potential adversaries.
However, we will return to the main course of our work and continue its presentation in accordance with the plan stated in the previously published, in the first part of the article.
So, the subject of current consideration is powder manufacturability in the light of mine resistance. We remind the reader of the accepted evaluation parameters, the first six of which were considered in the previous issue of the journal.
PARAMETERS OF MATERIALS SCIENCE AND TECHNOLOGICAL EVALUATION OF ALUMINUM AND ITS ALLOYS 1. Natural availability of raw materials;
7. Powder manufacturability, in the light of mine resistance;
Powder manufacturability, in the light of mine resistance, Aluminum foam is a relatively new material obtained by various methods from liquid and powder masses of aluminum and its alloys. The specific gravity of aluminum foam can range from 0.1 to 0.5 of the weight of monolithic aluminum. Ti, Zr, Ba, Li hydrides or so-called metallohydrides are used as a pore-forming agent. These substances in an amount of up to 10% are introduced into the liquid melt by constant mixing and after pore formation, the mass is cooled until solidification. There are also methods of pore formation by purging with oxygen.
There are foamed aluminum with open and closed pores. The former can be considered as a kind of filter, the latter as sponge aluminum. Aluminum foam in the form of spongy aluminum is a material capable of absorbing impact energy due to plastic deformation. Thus, with plastic deformation of the order of 50%, aluminum foam is able to absorb from 1000 to 4000 kgm/ dm, which is of considerable interest for the protection of ground vehicles from detonation.
Recently, there has been the use of aluminum foam as part of complex composite multicomponent armor protection systems, including steel, ceramics and aluminum armor, where aluminum foam, acting in the already named role of shock absorber, is used as an intermediate layer that reduces the dynamic deflection of the rear layer and volumetric delamination, improving structural rigidity, ballistic properties and strength of armor with less the density of the protective structure.
One of the optimal options with an inner sublayer of aluminum foam (shaded in the figure) the so-called integral armor according to the US DARPA Research Center is shown in fig. 1, option a).
Fig.1. Schemes of foreign integrated armor
The strength and plastic properties of foam significantly depend on its density, which is confirmed by the tension-compression curves, which are divided into three areas: linear elasticity, deformation and compaction (crumpling). The initial form of deformation is elastic, due to the rigidity of the cell walls, then plastic deformation of the walls of the upper cells is observed and the stress drops sharply. At the final stage, the foam gradually collapses and contracts, and it is noted that the deformation proceeds first from the sealing front, i.e. from the deformed to the undeformed region of the sample.An approximate view of the compression curve is shown in Fig. 2.
Fig. 2. Compression curve of the foam aluminum sample
Like any other new material, aluminum foam required the creation of a new methodological apparatus for assessing its performance characteristics, since it is expensive and uninformative to conduct an assessment only on full-scale samples of armored vehicles.
The shock-wave effect on the barrier during mine detonation is a combination of spherical stretching, spherical shear and plane shear of wave fronts. Aluminum foam with rounded hydrogen-filled pores increases the rise time of the wave voltage and delays the destructive effect of explosives during explosions.
When analyzing the results of mine detonation tests, it is usually estimated: The encountered or so-called surface density. The resulting topography of foam aluminum plates (PAP) (thickness in the lesion, mono or polycracy of the lesion). The geometry of the front and back plates-overlays and linings with photo fixation of the target situation. A comparative assessment of the protective characteristics of PAP with different matrix chemistry, porosity and obtained by quenching with different temperature conditions is carried out first on a small stand, where the most energy-intensive PAP are selected, then the effectiveness of these plates is evaluated on a large stand simulating the real bottom of lightly armored vehicles.
Tests for explosion absorption (survivability and durability) are carried out in strict accordance with the Methodology for assessing the service properties of mine-resistant foam aluminum plates developed by JSC Research Institute of Steel and Federal Research Institute of Geodesy (Krasnoarmeysk).
When using the so-called ground blasting scheme, the role of the anvil is assumed by a steel plate placed on the ground, on the surface of which the test sample is installed. A marker made of 1 mm thick steel sheet was placed on top.
The named scheme is the basis for assessing the survivability of the undermined aluminum foam material (Fig. 3,4).
Fig. 3. Steel plate (top) with a foam aluminum sample and a BB charge (bottom) for testing the survivability and durability of the PAP sample
Fig. 4. The scheme of the foam aluminum test for survivability:
2 foam boards;
3 steel base plate 46 mm;
4 disposable lightweight wooden cabinet;
5 cover sheet
The criterion of survivability is the presence or absence of dynamic destruction of the test material (from cracks to complete destruction), while single small cracks are recognized as a satisfactory characteristic, and extended splitting cracks and complete destruction are naturally considered a sign of low survivability.
The second characteristic of the service properties of the protective material is the characteristic of its durability.
The problem can be solved through the amount of real energy absorption under dynamic action from the upper hemisphere by a certain explosive charge. This problem is solved through the reception of basic calibration on a special bench stand (Fig. 5).
Fig. 5. The scheme of tests for the assessment of durability:
5 cover sheet;
6 calibration steel plate;
7 bench type installation stand
The considered technique consists in using a special bench frame stand with an open opening. A steel calibration sheet (plate) with a thickness of 8-15 mm with an installation plane of 500x500 mm is installed in the opening, which is subjected to a series of successive explosions with an increasing mass of explosives from the upper hemisphere at a clearance (450 mm) distance until a visually observable residual plastic deformation with a deflection arc of 10-15 mm is achieved. At this stage, the mass of explosives that led to similar results is fixed, after which the deformable plate is removed from the bench opening and replaced with a similar new one, on which the experimentally investigated material is installed.
This is followed by a series of explosions with a starting value of the explosive mass equal to the mass that led to the specified plastic deformation of the calibration steel plate. The tests continue until the deformation of the steel calibration plate with a deflection arc is reached, similar to the one obtained in the experiment of blasting the calibration plate. After that, the mass of explosives that led to this result is recorded. The resulting mass of explosives is compared with the mass of explosives that led to plastic deformation of the original calibration steel sheet. The recorded difference is a direct characteristic of the energy absorption of the test sample of aluminum foam. For example, according to our experimental data, the use of a foam aluminum plate (40x500x500 mm, density 0.7 g / cm3) can increase mine resistance by 50% (1.5 times) in accordance with the desired 3 mm steel sheet.
The next stage of the work was to assess the correlation of the results of blasting on a large layout with a lower detonation (Fig. 6) with previously carried out work on a small stand with an upper detonation.
Fig. 6. View of a large stand. Inside it, at a distance of 450 mm from the ground, the tested structure of the bottom with 2x2m foam aluminum is installed and fixed.
The purpose of these tests is to assess the durability of the bottom of the layout when detonating a shell-less explosive device.
A fragment of the protection of the bottom with an area of 2000x2000 mm was an armored barrier made of aluminum face plate, aluminum foam (40 mm thick) and a back layer of aluminum alloy. A fragment of the bottom was installed in a special slipway (stand) and fixed on the walls of the slipway. The explosive charge weighing 6 kg was placed in a wooden box, covered with a layer of sand 80 mm and installed on a metal plate 60 mm thick. The distance from the masking layer of sand to the fixed fragment of protection (bottom) was 450 mm.
The results of undermining the bottom layout are shown in Fig. 78.
Fig. 7. View of the bottom after blasting 6 kg of explosives. The outer (front) layer has cracks, but the back layer is not broken and its deflection is within tolerance.
Fig. 8. The intermediate layer of aluminum foam after testing (the front layer is removed). It can be seen that in the epicenter of the explosion, the aluminum foam is crushed by 3/4 (in the foreground, a piece of crumpled PAP in comparison with the PAP at the edge of the plate), absorbing a significant share of the energy of the explosion.
These tests showed that the structural integrity of the bottom fragment is not broken (without cracks, splits, crumples and destruction), the boom of residual deflection is insignificant.
Thus, it can be stated that the developed elements of the test methodology for aluminum foam materials for armor purposes can be used to select materials and evaluate their mine-resistant characteristics. This technique includes five main stages: Assessment of the dynamic survivability of the ground blasting of aluminum foam materials on a steel platform. Calibration tests on a light stand, as a qualitative and quantitative assessment of the effectiveness of obstacles. Calibration tests on a reinforced heavy stand with an opening. Bench strain tests as a metrological characteristic of the effectiveness of aluminum foam plates. Enlarged tests on the model of the bottom of the BTW to confirm the results.
In addition, the results of the tests showed that in the future it is advisable to use aluminum foam more widely in integrated circuits for booking BTW LCM.
The above once again emphasizes the role of aluminum foam as a very promising material for the needs of armor protection.
Aluminum, even in the form of the simplest protective structure of a monolithic plate, gives a gain in mine resistance of up to 65%. This is due to the rigidity of the structure and the unique anti-shatter resistance of aluminum. However, a much higher effect can be achieved using the high plastic properties of aluminum alloys. So one of the solutions protected by the copyright certificate suggests using special aluminum profiles, which absorb the energy of the explosion due to deformation.
Fig. 9. Comparative mine resistance of various armor materials
The absorption of the energy of the explosion here occurs due to the deformation of sufficiently thick U or W shaped profiles facing each other in a mirror and offset by half a step relative to each other (see Fig. 10).
Fig.10. The principle of operation of the energy-absorbing system with W-shaped and U-shaped profiles
The schematic diagram of the mine bottom with energy-absorbing profiles is shown in Fig.11.
Fig.11. The design of the mine bottom:
1 aluminum armor plate;
2 aluminum profile construction.
Unlike foams and honeycomb structures, which are used today in mine protection structures, in this design, energy absorption increases with increasing deformation, which leads to an increase in the mine resistance of the bottom structure.
Corrosion resistance The analysis of the corrosion resistance of aluminum alloys and iron will begin with the consideration of a rather capacious comparative table borrowed from the first volume of the classic reference work of I.V. Kudryavtsev Materials in Mechanical Engineering. Selection and application, representing an assessment of the influence of more than thirty corrosive media (see Table 1).
Table 1. Influence of various media on the corrosion resistance of aluminum, deformable aluminum alloys and iron
Thus, of the 31 media presented, aluminum alloys are characterized as resistant in 7 media, reacting little in 14 media, reacting poorly in 9 media, and 1 medium (mineral water) is particularly unfavorable. While iron: is resistant only in 3 environments, reacts little in 8 environments, reacts poorly also in 8 environments, and 4 environments are marked as particularly unfavorable.
As you can see, there is an absolute superiority of the corrosion resistance of aluminum alloys.
At the same time, it can be additionally noted that aluminum armor alloys significantly increase their corrosion resistance due to the peculiarities of the chemical composition (exclusion of copper and manganese in the composition) and special heat treatment (overcooking).
It is clear that steel armor also noticeably activates the fight against corrosion.
Special protective, masking paint coatings play a special role here.
In a normal atmosphere, the most unfavorable for corrosion of aluminum alloys is their contact with copper and copper alloys, with nickel, nickel alloys and nickel coatings, with silver.
In conditions of immersion in sea or fresh water, contact with copper and copper alloys, titanium and titanium alloys, stainless steel, nickel and nickel coatings, tin and tin coatings, lead, silver, magnesium and magnesium alloys is unacceptable. Under the same conditions, contact with aluminum alloys of various compositions, zinc and zinc coatings, cadmium and cadmium coatings is permissible.
Corrosion protection. Aluminum alloys are protected from corrosion by metal coatings (cladding, electroplating) and non-metallic coatings (oxide films, paint coatings, lubricants).
For protective and decorative purposes, as well as to increase wear resistance, chrome or nickel-chrome electroplating coatings are used. The use of oxide films obtained by chemical or electrochemical method is one of the main methods of corrosion protection of aluminum alloys. Oxide films also have good adhesive properties, and therefore they are used as a basis for applying paint coatings.
Anodic films are also used as decorative coatings. In this case, they are filled with special organic or inorganic dyes. The system or method of protection with the use of various paint coatings with or without pre-oxidation is chosen in relation to the working conditions of this part or product. Special preservative lubricants are used to protect aluminum alloys during transportation and storage.
The cold resistance or strength and ductility of metals at low temperature, or, in other words, its cryogenic characteristics, are the main key parameter of the comparative evaluation of traditional steel and aluminum armor materials.
Many steel alloys, especially structural ones, exhibit a tendency to brittle fracture at low temperatures. A very important property of many structural steels is that they show a tendency to brittle fracture only under shock loading conditions with a combination of low temperatures. In this case, the starting temperature is the temperature starting from minus 20 degrees Celsius (see Fig. 12).
Fig. 12. Determination of the critical brittleness interval based on the test results of a series of samples made of low-carbon coarse-grained steel at low temperatures under shock loading
Here, bearing in mind the climatic features of the Arctic and the presence of temperature values up to minus 5070 ° C as typical long-period conditions, we denote the main feature of aluminum armor aluminum armor, like all aluminum alloys, does not tend to embrittlement at low temperatures (see Tables 2-5). The latter contrasts sharply with the known data on embrittlement of sufficiently thin (up to three times thinner with an equal weight with aluminum) rolled steel armor, where, starting from a temperature already at minus 20 ° C, the concept of semi-fragility is known, that is, a 50% loss of such important characteristics of armor as its armor resistance and survivability.
Table 2. Mechanical properties of pressed strips of alloys AK4 (numerator) and VD17 (denominator) at room and negative temperatures
Table 3. Mechanical properties of semi-finished products made of aluminum deformable alloys at different test temperatures
Table 4. Mechanical properties of annealed sheets with a thickness of 3 mm made of alloy 1545K manufactured by JSC VILS and welded joints at room and cryogenic temperatures, average values
A detailed examination of the presented tables 25 allows us to state with absolute certainty the complete superiority of aluminum and its alloys, starting with an increase in the modulus of elasticity at low temperatures (see Figure 13), and ending with a steady increase in the strength and ductility of all aluminum alloys, in contrast to the reverse trend characteristic of all variants of both structural and armor steels in the conditions of their use in low-temperature areas of use, not to mention other, as we think, the advantages of aluminum and its alloys considered in detail.
Fig. 13. Modulus of elasticity of aluminum, E
Available graphic forms of presentation of materials (see Fig. 14) when comparing the low-temperature characteristics of alloys of the so-called duralumin group of Al-Cu alloys with armor alloys of the Al-Zn-Mg system, they indicate the fundamentally important superiority of aluminum armor alloys in terms of ductility characteristics, and hence the survivability of aluminum armor is almost 23 times superior to the duralumin group.
Fig. 14. Evaluation of cryogenic characteristics of duralumin group alloys (left figure) and armor alloys
The characteristic of antimagnetism is quite obvious in the case of using aluminum armor in the manufacture of all-aluminum hulls and towers. The technique of antimagnetic protection of steel armored vehicles with special coatings that has taken place recently leaves questions about the rise in the cost of operating combat vehicles and once again confirms the effectiveness of aluminum armored hull production.
Thermal maskability is one of the most important characteristics of the camouflage of combat vehicles. In the case of aluminum armored vehicles, the issue can be solved by using special heat-insulating aluminum foam materials with closed gas-filled pores as part of the armored hull material (see the section powders). At the same time, a side effect of using aluminum foam is a noticeably increasing buoyancy characteristic of the object of protection.
The last 50 years have been marked by the greatest achievements in the exploration of the cosmic depths of the universe. At the same time, another problem of mankind, the development of the oceanic depths of the sea, has remained, as it were, out of the sphere of attention. Meanwhile, this problem is one of the strategic problems of the defense capability of any coastal country and can be formulated quite simply as a struggle for the depth of scuba diving.
The submarine Fleet seriously asserted itself at the beginning of the twentieth century, and its appearance was the determining factor in the almost complete defeat of three fleet squadrons and serious human losses of the Russian Empire in the Russo-Japanese War of 1904-1905. But Japan only needed, it would seem, a small detachment and 12 submarines to completely destroy the most powerful Russian fleet: highly professional, deeply patriotic and, as the military actions showed, truly selflessly heroic.
So, the struggle for the depths and problems of materials science, and here we are forced to turn to a comparative analysis of our classical materials science triad described in the first sections of our publication (see section 2 of the list of evaluation parameters published in the first part of the publication steel-titanium-aluminum) and declare the absolute superiority of aluminum in this triad in its rigidity characteristics, depending on the cube thickness, this makes aluminum alloys a very promising material for creating deep-sea vehicles.
Experimental and theoretical studies have fully confirmed the high potential of using aluminum armor alloys for volumetrically loaded underwater vehicles with a design pressure of up to 400 atm. (depths up to 4 km). This is achieved due to the unique possibility of obtaining the main loaded body in the form of a thick-walled, monolithic, large-diameter pipe billet obtained by hot extrusion by pressing through a die technology inherent only in aluminum alloys, of course using powerful presses. These main thick-walled elements were combined with annular hemispheres of the same thickness, obtained by stamping and forged (or rolled) connecting mounting rings.
The proposed solution may be of interest for underwater deep-water tracking devices, unmanned vehicles, which have recently become increasingly popular in the development of underwater vehicles.
Radio transparency the passage of radio waves through the analyzed object of protection without restrictions with low losses. In aluminum cases, it increases markedly with the use of aluminum foam materials with closed pores. The foamed material is characterized as highly effective protection against electromagnetic waves, along with the already mentioned heat-insulating and sound-absorbing properties, which leads material scientists to develop sandwich structures using aluminum foam, this sharply distinguishes the radio transparency of aluminum armored hulls from steel and serves as a favorable element of maskability.
Returning to the epigraph presented at the beginning of this publication, which literally contains the visionary formula of M.V. Lomonosov, the authors of the publication consider it their well-founded right to supplement it to the following detailed formulation: Russian power will grow by Siberia and the Northern Ocean and their protection will be provided by Russian Aluminum Armor, on which, in fact, this publication ends.
1. Artsruni A.A., Kupryunin D.G. Aluminum armor for military equipment. Theory, technology, practice. Ed. RadioSoft. M. 2017.
2. Materials in mechanical engineering. T1. Non-ferrous metals and alloys. Izd. Mashinostroenie. M.1967.
3. Vintage of steels. Edited by Ya.I. Kulandin. TSNIITMASH. M.1956.
4. Artsruni A.A., Zazhilov A.A. On the relevance of the problem of promoting aluminum armor in the Arctic latitudes. Arctic and aluminum armor. Report to VIAM, Gelendzhik, 2019
5. VEALS' work on deformable aluminum alloys of the Al-Mg-Sc system. History of creation, structure, properties, application experience, problems and prospects. Filatov Yu.A. Journal Technology of Light Alloys No. 3, 2017.
6. Strength and ductility of metals at low temperatures. G.V. Uzhik. Ed. Academy of Sciences of the USSR. M. 1957.
7. The Maritime Doctrine of the Russian Federation for the period up to 2030, approved by the President of the Russian Federation on 26.07.2015. [ Electronic resource] : URL:http://legalacts.ru/doc/morskaja-doktrina-rossiiskoi-federatsii-na-period-do /(Accessed 10.05.2021).
8. Resolution of the Council of Ministers of the Government of the Russian Federation No. 174 of 01.03.1993. On improving the activities of departmental ACCS for the prevention and elimination of emergencies at sea and water basins of Russia /Internet источникhttp://www.consultant.ru/cons/cgi/online.cgi?req=doc&base=EXP&n=225141#05690033363800673 / (Accessed 10.05.2021)
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