Abstract: The synthesis of the country in recent years with a highly dense tungsten penetrator research progress, then strain and add trace elements alloying strengthening rotary forging, torsional deformation, such as the implementation of hydrostatic extrusion alloys, and for adiabatic shear mechanism and numerical simulation The research status and progress of experimental study on the latest pre-oxidized activated sintering and other special preparation of the technical aspects of mechanical alloying provisioning nano tungsten alloy composite powder, temperature and pressure forming. Through a comprehensive analysis of some of the main problems with the experimental study of armor piercing high density tungsten alloy exists, made of high-density tungsten alloy penetrators with the main direction of future research, as well as strategies and measures to promote high performance armor piercing tungsten alloy developed to be taken.
High density tungsten alloy is a kind of tungsten-based (tungsten content is usually 80% to 97%), and added with Ni, F, Mn, Co, Cu, Mo, Cr equal to the element alloy having a density of up to 16.5 ~ 19.0g / cm 3. High-density tungsten alloy not only density, but also has a series of excellent properties such as high strength, high hardness, ductility, good machining properties, thermal expansion coefficient, thermal conductivity, anti-oxidation and corrosion resistance, and can be welded and good. These properties make it excellent in the field of cutting-edge technology, military and civilian industry has been widely used, for example, as rod kinetic energy penetrator bomb core material, the counterweight components, inertial sensors, radiation shielding materials [1]. With the main battle tanks, armored ships and a variety of military fortifications increasingly strengthened, armor-piercing capability for higher and higher requirements. High-density tungsten alloy rod kinetic energy penetrators, not only has good armor-piercing power, and compared with depleted uranium alloy penetrators with non-toxic, non-radioactive pollution, etc., are the main countries in the world equipped with armor-piercing materials, but also the future development of the penetrator The main direction. Therefore, this article intends to review the latest developments through the use of armor-piercing alloy developed high-density tungsten, analyzes the main existing problems and causes, and then discuss specific measures to address these issues and strategies.
The main progress in a recent study
With the rapid development of science and technology and the level of armor protection technology continues to improve, with a high density of tungsten alloy shells have become increasingly demanding, particularly those that require both high strength and good toughness at high density to ensure the premise. Therefore, how to enhance and improve the high-density tungsten alloy after deformation enhanced strength and ductility is currently one of the important research topic. In recent years, in order to further enhance the strength and toughness of tungsten alloy, domestic alloying, deformation strengthening, adiabatic shear, numerical simulation and preparation process technology a lot of research has made significant progress and numerous scientific research.
1.1 Micro Alloying
Strengthening mechanisms are mainly tungsten solid solution strengthening, dispersion strengthening, precipitation hardening and strengthening the interface and so on. There are solid solution strengthening elements Re, Me, Nb, Ta, Ir and the like. Tungsten alloy Mo, Ta, Re, Nb, Hf, V and Cr, and W are the same elements have a body-centered cubic lattice; they may be dissolved in the W, to a certain extent can be dissolved in the binder phase , so as to achieve a solid solution strengthening tungsten heavy alloy, wherein Hf maximum strengthening effect, followed by Ta, Nb, and Re [2].
Enhanced dispersion strengthening, including direct and indirect strengthening, strengthening the direct interaction of dislocations and mainly from the particle dispersion, and indirectly strengthened mainly due to the high density of dislocations network composed of sub-grain interactions to improve strength of the alloy. The main interface is optimized to strengthen the grain boundaries (grain boundary strength improve or reduce impurities in the grain boundary segregation), and if the formation of a solid solution at the interface, the interface can enhance binding force and improve the material strength. In addition, because has a good interface, the binder phase can be passed through the interface will stress tungsten particles, which can effectively reduce the carrying capacity of the binder phase, so that the binder phase and matrix deformation coordination, reduce the occurrence of cracks along the grain, which feeds strength of the material [3]. Precipitation strengthening phase precipitation method of inhibiting the precipitation strengthening, precipitation strengthening and second phase dispersion strengthening three kinds of tungsten. Inhibition of precipitation phase precipitation is an effective way to improve and enhance the performance of tungsten alloy, the general solution + hardening heat treatment process to avoid precipitation phase precipitation, while suppressing impurity elements in the interface segregation, to get cleaner tungsten / matrix interface [ 4]. In the W-Ni-Fe alloy of high density can be enhanced to add a small amount of Co relative to the base particles of tungsten wettability of the surface of the tungsten particles are more rounded, more conducive to plastic deformation of the alloy can enhance the tungsten particles and the matrix phase of the interfacial bond strength, thereby improving the strength and elongation of the alloy. Meanwhile, adding Co, the initial liquid phase sintering, iron and nickel is formed preferentially with a low melting point, good flowability of crystals promote good diffusion of atoms in the liquid phase component, thereby accelerating the process of liquid phase sintering, alloy microstructure refinement [5]. Zhiguo other successfully prepared a new W-Ni-Fe-TiB2 alloy, TiB2 and found uniformly distributed in the binder phase alloying TiB2 than 2% TiB2 alloy No relative density and hardness is high, can The adhesive material from the strengthening effect of the phase [6].冯庆芬 etc. then for La Ce alloy for 93WniFe dynamic tensile properties have been studied and found that these two elements can improve the dynamic performance of tungsten alloy, and a solid solution strengthening and interface purification [7].
Tungsten impurity elements include H, O, C, N, P, S and Si. Due to the smaller atomic radius of these elements, there is a strong diffusion capacity in tungsten alloys, and thus more likely to occur in high-energy grain boundary position, phase boundaries, such as segregation, even generate brittle phase, thereby reducing the performance of tungsten alloy . These hazards are larger impurity elements H, it is mainly distributed in the binder phase and tungsten / interfacial bonding leads to embrittlement, hydrogen embrittlement is the main method to eliminate the protection of hydrogen gas (N2, Ar) annealed especially in the vacuum heat treatment works best. P is for tungsten alloy great harm another element, because it is easy to segregate P to make tungsten alloy / binder phase interface embrittlement, when the P content in the W phase or exceeds its limit of solubility of the binder phase will occur P generating NiP2 segregation and precipitation. Another impurity associated with P is S, it can also be segregated in the W / binding phase interface, 93W-4.9Ni-2.1Fe alloy, when the S content of 0.01% decreased the impact toughness of the alloy. Further, S may be formed with the compound K and O, gathered on the inner surface of the pores. Si and Na are the raw material of tungsten powder in the other two kinds of impurity elements in common, they are usually present in the form of SiO2 and NaSiO3. Na and Si doping density of the alloy, tensile strength, elongation, etc. necked rate decreased, the allowable limit of the tungsten content of the alloy: Si, 210 × 10-6; Na, 150 × 10-6; larger than this limit will have a huge impact on the content of the alloy performance [8]. (To be continued)
References
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