Effect of the structure of T110 titanium alloy on its resistance to impacts of an indenter
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EFFECT OF THE STRUCTURE OF T110 TITANIUM ALLOY ON ITS RESISTANCE TO IMPACTS OF AN INDENTER O. V. Abolikhina, S. L. Antonyuk, and O. H. Molyar
UDC 669.295
One of the most important parameters and criteria of the service reliability of special elements of airplanes is the endurance of the materials of such constructions under strong pulse-impact loads. The use of high-strength ( α + β )-titanium alloys of the transition class for this purpose has its advantages, in particular, enables one to reach a high specific strength [1]. Various technological versions of the thermomechanical treatment of alloys lead to different structural states of semifinished items, which exerts a decisive influence on their operating properties [1 – 3]. In the present paper, we describe some results of studying the effect of thermal treatment on the resistance of forge-rolled plates made of high-strength T110 titanium alloy (base Ti, 4.9% Al, 1.61 Fe, 1.25 V, 4.74 Nb, 0.9 Mo, and 0.1% Zr) to impact loads and choose the optimal mode of thermal treatment ensuring the highest endurance. Experimental Procedure We tested plates of thickness ∼ 3.2 – 3.3 mm and size 150 × 150 mm, cut out of blanks after their hot forgerolling in the ( α + β )-region. Prior to tests, the surface of plates was worked with a sand jet (specimens of group 1 to a depth of ∼ 100 μm in order to remove the gas-saturated layer, group 2 to a depth of ∼ 20 – 30 μm for partial removal of this layer, and specimens of group 3 were not worked). All specimens were annealed or subjected to thermal hardening in the two-phase ( α + β )-region at temperatures T = 750 – 850°C. The modes of thermal treatment have to ensure, on the one hand, a nonrecrystallized or a partially recrystallized structure and, on the other hand, a high strength together with a satisfactory plasticity. To satisfy the first condition, we annealed the specimens at temperatures lower than or equal to the recrystallization temperature and, to meet the second requirement, subjected the material to thermal hardening. The parameters of thermal treatment of the specimens and the results of their mechanical tests are presented in Table 1. We carried out tests for impact resistance by throwing an indenter of mass 7.9 – 8.1 g and diameter 9 mm onto the plates with a velocity of ∼ 402 – 500 m / sec. Each plate was loaded several times under contact angles between the target and indenter of 90° and 30°. The distances between the centers of indentations were 8 to 38 mm (Table 2). The damages of the material of specimens were evaluated by the depth of indentations caused by impacts, the length of formed cracks, and the specific strain energy of unit volume of the material [4, 5]: E = 1.5 ( 1 – e ) m V2 [ π h2 ( 3R – h ) ] – 1. Here, R and m are the radius (in mm) and mass (in g) of the indenter, V is its velocity (in m / sec), h is the depth of indentation (in mm), and e is the part of kinetic energy that is dissipated during impact and does not exceed 0.15 [5]. Antonov Aircraft Scientific and Technical Complex, Kyiv, Ukra
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