Effect of nuclear radiation on the microhardness of SAV-1 avials

Abstract

The microhardness of the initial specimens of SAV-1 avials was experimentally investigated. Modification of this mechanical characteristic as a result of alloy irradiation in the channels of a research nuclear reactor WWR-SM was studied. The nonlinear pattern of material hardening after irradiation at low fluence rates (10 10 15 18 -neutron/cm 2 ) was revealed. The radiation effect of avial microhardness variations is established to be a certain function of irradiation doses and indentation loads. The possible reasons of an increase in hardness of irradiated specimens are discussed. The radiation-induced hardening of aluminum alloys is assumed to be determined by generation of point flaws and dislocations, blocked by defects and interstitial phase decay products.The microhardness test is one of the key methods, sensitive to structural changes in the surface and subsurface layers of the materials. It is currently central for studying the mechanical properties of solids and their microstructure as well as for understanding different physicomechanical processes, caused by the deformation of materials. It is even more essential for analysis of the radiation treatment of structural materials, used for manufacturing the components and units of the active zone of nuclear reactors.Though this method is used in physical experiments [1-3], a number of problems has not been solved as yet. Thus, physical phenomena observed in fracture of crystals under the indenter, crack growth and cracking around the imprint with an increase in loads are discussed in [4,5]. The photomechanical effect influenced by imprint formation conditions as well as the mechanism of its formation are examined in [4][5][6][7]. Relaxation processes in inorganic glasses and the temperature dependence of microhardness are investigated in [8,9].As is known, different steels and alloys are widely used as structural materials for nuclear reactors. Their mechanical properties are covered in many studies. Particular emphasis has been placed on radiation effects, e.g., on their creep, strength, etc. Data on the changes in mechanical properties, in particular microhardness, of aluminum alloys, irradiated in the reactor are rather scarce in the literature. Thus, changes of the properties and phase state of an Fe 3 Al alloy after neutron irradiation are examined in [10], corrosion of fuel rod shells made of a SAV-1 alloy and appearance of new phases are discussed in [11].The objective of the present investigation is to study the effect of low neutron fluence rates (10 10 15 18 -neutron/cm 2 ) on the mechanical parameters of some avials, in particular SAV-1 aluminum alloys, being a promising material for manufacturing fuel rod shells of nuclear reactors. The experiment of 2008 was performed in a WWR-SM reactor with an IRT-3M fuel rod assembly at a power of 10 MW and active zone charge with UO 2 -Al fuel enriched to 36% in U [12]. A set of specimens Nos. 1, 2, and 3 in the form of disks (d =15 mm and h = 2 mm) were irradiated in vertical channels of the reactor Nos. ...