Theoretically justified [1-4] and experimentally proved [1, 3-10] (see also paragraphs 2-8 of this section) important for the radiation physics of the condensed state the role of the formation (during corpuscular irradiation of solids by neutrons, accelerated ions and fission fragments) nanoscale zones (d ~ 5-10 nm) explosive energy release, which are thermalized for times of the order of 10-12 with the passage of dense cascades of atomic displacements, heated to 3000-6000 K and above (thermal spikes). The rapid expansion of such areas is accompanied by the emission of post-cascade shock or powerful elastic waves, the pressure at the front of which exceeds not only the real, but also the theoretical yield strength of materials.
Nanoscale radiation-dynamic effects in cascade irradiation: (a) target, e.g., pure metals (Fe, W, Zr etc.); (b) formation of post-cascade shock waves.
Such waves are able to carry out a radical restructuring of non-equilibrium (metastable[1]) condensed matter. This was not taken into account by classical radiation physics of a solid state.
Structural-phase transformations in metastable media under ion irradiation.
Transformations are initiated at the front of shock waves arising in the surface layers of materials as a result of the evolution of dense cascades of atomic collisions, and are accompanied by the formation of unique electrical, magnetic, mechanical, corrosive other properties of materials. Self-propagating phase transformations initiated by ion bombardment in metastable metal alloys aroused wide interest of Russian and foreign scientists (USA, Germany, Japan, England, Italy, etc.).
Object of research. The main advantages of ion beam treatment of these materials using radiation-dynamic effects.
Based on the analysis of the energy luminosity spectra of metal targets during their irradiation with heavy ions of low and medium energies, the existence of thermal peaks [3, 4] ‒ nanoscale regions of explosive energy release heated for ~ 10-12 s to temperatures of the order of 3000-6000 K, which are products of the evolution of dense cascades of atomic displacements, was experimentally confirmed for the first time, and the temperature of these regions in a number of metals was measured: Fe, W, Zr, Ti, Al. Thermal pressures [4] in the volume of thermal peaks (components 5-40 GPa and more) are estimated. Post-cascade powerful elastic and shock waves of compression are able to initiate volumetric rearrangements in metastable media under their surface irradiation.
The spectral composition of the glow of Fe targets under irradiation with Ar+ ions with an energy of 15 KeV: (a) experiment (Texp = 5300 K, Ttarget = 530 K); (b) diagram illustrating the formation of the spectral composition of the glow.
Another experimental confirmation of the formation of thermal peaks (thermal spikes) was obtained in experiments on irradiation with Ar+ and Xe+ (E = 20 KeV) ions of metal nanowires of pure Ni and Fe56Ni44 alloy with a diameter of 60 and 100 nm [8-10]. Areas of thermal peaks are observed by scanning electron microscopy in the form of near-surface traces of melting with a diameter of 10-20 nm.
Local melting of 60 nm thick nanowires of Fe56Ni44 in the region of thermal peaks during ion irradiation: (a) – initial state, (b) – irradiation with Ar+ ions, (c) – irradiation with Xe+ ions.
The curvature and destruction of nanowires is explained by the generation and propagation of powerful elastic and shock post-cascade waves.
The impact of ions Xe+ (131 atomic mass unit) is more intense in comparison with ions Ar+ (40 atomic mass unit). There is a more significant curvature of the nanowires with the formation of nodes ("kidneys") and even "branches", due to the possible process of splashing the areas of thermal peaks outwards from the NW. This is due to the higher (about 2.5 times) energy release per cascade atom in the case of Xe+ ions.
Comparative experiments [11] on the ion bombardment and mechanical shock loading are important evidence in favor of the hypothesis of the significant role of dynamic long-range effects in corpuscular irradiation, which are not taken into account by classical radiation physics of a solid state. These experiments on samples of the alloys VD1 and D16 of the system Al-Cu-Mg was designed in collaboration with RFNC VNIITF (Snezhinsk).
Microstructure of alloy D16: a, b − after irradiation with Ar+ ions (E = 40 KeV, j = 500 µA/cm2, F = 5×1016 cm-2); c, d − after impact: a, c − light-field images of the subgrain structure; b, d − dark-field images of Mg2Cu6Al5 particles in phase reflexes.
Cold-rolled samples of aluminum alloys VD1 and D16, identical to the irradiated accelerated ions (disks with a diameter of 30 mm from plates of the same thickness), were subjected to mechanical shock loading on special stands RFNC VNIITF, using a massive striker with a diameter of 30 mm, a thickness of 6 mm, of a material with a density of 2.65 g/cm3, moving at a speed, respectively, 399.2±0.4 and 412±0.7 m/s. The heating temperature of the samples in an inelastic interaction process did not exceed 300°C as with ion irradiation with low fluence (D < 1017 cm-2).
It was found that the changes in the microstructure of these alloys as a result of mechanical impact are similar to the changes initiated by ion bombardment (Ar+, 20-40 KeV) at relatively low fluences (1015-1016 cm-2), recruited only for 1-8 c irradiation. This refers to the transformation of the cellular dislocation structure into a subgrain and the transformation of the θ′′-phase into the Al6Cu5Mg2 phase and is an important indirect confirmation of the shock-wave nature of the process in ion bombardment.
The method of ion-beam treatment of carbonyl iron powder [12], increasing its saturation magnetization by 1.8% and providing a 5-10-fold increase in the q-factor of inductance coils for radio electronics with the core of the composite "dielectric – carbonyl iron" in the frequency range of 0.01 – 5 MHz, using the detected nanoscale dynamic effects and low-dose effects (based on fast processes within a few seconds) in cooperation with LLC "Synthesis PKZH" (Dzerzhinsk) was suggested. The observed effects are associated with the transition of the metastable medium to a more equilibrium state.
Increasing the q-factor of inductance coils for radio electronics with the core of the composite "dielectric – carbonyl iron" in 5-10 times in the frequency range 10-5000 kHz.
The phenomenon of rapid radiation annealing [13-24], within a few tens of seconds at temperatures reduced by 150-200 K, by beams of accelerated Ar+ ions with energies of 20-40 KeV, bands (1-3 mm thick) of industrial aluminum alloys of Al-Mg, Al-Li-Cu-Mg, Al-Cu-Mg, Al-Zn-Mg-Cu, Al-Mg-Li-Zn systems (used as structural materials, including in aerospace and nuclear engineering) was found. Radiation annealing leads to recrystallization processes in the entire volume of these alloys (at a penetration depth of ions < 0.1 µm). In contrast to thermal annealing, intensive processes of grinding and dissolution of coarse intermetallic compounds of crystallization origin also occur along the entire depth of the bands, and the formation of nanoscale particles of changed composition intermetallic compounds is observed, which favorably affects the mechanical and resource characteristics of these alloys.
Samples of industrial aluminum alloys (a, b, c) and metallographic analysis data indicating the recrystallization of alloy 1441 (Al-Li-Cu-Mg) over the entire thickness of the sample 3 mm as a result of irradiation with Ar+ ions (E = 40 KeV, j = 400 µA/cm2, F = 1.25×1016 cm-2, 5 s).
Mechanical properties of aluminum alloys after various types of processing
(σb is the tensile strength, σ0,2 is the conditional yield strength, δ is the elongation)
Treatment
Alloy
AMg6
1441
VD1
su, MPa
s0.2, MPa
d, %
su, MPa
s0.2, MPa
d, %
su, MPa
s0.2, MPa
d, %
Cold working
445
407
9.6
315.5
296
3.3
255
246
6.5
Commercial aging for 2 h
328
178
28
245
134
20
182
86
24
Ar+ ion irradiation for 5–30 s
335
182
28
218
130
19
185
81
23
Alloy AMg6: (a) after cold deformation (cell dislocation structures, coarse intermetallides of crystallization origin); (b) after furnace annealing, T = 320°C for 2 h (large recrystallized grains, coarse intermetallides); (c) after irradiation with ions Ar+, E = 20 KeV, j = 150 µA/cm2, tirr = 135 s (recrystallized grains, reducing the size of intermetallic compounds and their partial dissolution).
Fast cold radiation annealing of aluminum alloy AMg6 under variation of irradiation parameters
(δ is the elongation, Е is the Ar+ ions energy, j is the ions current density).
On the basis of the use of radiation-dynamic effects in conjunction with OAOC "Kamensk-Ural metallurgical plant" a method of rapid (within a few seconds) cold radiation annealing strips of industrial aluminum alloys developed. Patent: Method of obtaining a rolled sheet of aluminum alloys: RF patent № 2363755 / Ovchinnikov V.V., Gavrilov N.V. Gushchina N.V. Shkolnikov A.R., Mozharovsky S.M., Filippov A.V.; patentee of OAO "KUMZ"; Pat. attorney Yants V.K. № 2006143709/02. Declared. 08.12.2006. Publ. 10.08.2009. Bul. No. 22.
Together with FGUP "VIAM" (Moscow), the laboratory technology of intermediate between cold rolling operations of softening radiation annealing [23, 24] by a beam of accelerated ions Ar+ (E = 40 KeV) aviation alloy of the third generation 1424 (Al-Mg-Li-Zn), not amenable to thermal annealing, was developed. The alloy has a reduced density (2.54 g/cm3), increased fracture toughness. To soften this alloy, a time-consuming operation of heating for quenching and sheet cooling in a saltpeter bath is used.
Short-term irradiation of the cold-deformed alloy 1424 provides a regulated level of properties required for cold rolling, which in the long term allows to implement the technology of its roll rolling.
The mechanical properties of alloy 1424 (Al-Mg-Li-Zn) after various types of processing and the result of cold rolling of this alloy from 7.6 to 1.2 mm with intermediate radiation annealing.
Together with IMF, UB of RAS, a regime of radiation annealing of pure molybdenum by a beam of argon ions after intense plastic deformation was developed. Optimal modes of action provide a homogeneous submicrograin structure with a significant decrease in the recrystallization temperature (by 200 K, from 1323 to 1073 K) and a decrease in grain size (from 0.8 to 0.45 µm) compared to thermal annealing [25].
Mo structure after 3-turn deformation (e = 6.5) at 290 K (a) and after optimal irradiation: Е = 20 KeV, j = 300 µA/cm2, D = 1.3×1018 cm-2.
Together with the company "GAMMAMET" it is shown that the irradiation of the amorphous tape of the soft magnetic alloy Fe72.5Cu1Nb2Mo1.5Si14B9 by Ar+ ions with an energy of 30 KeV fluence of 3.75×1015 cm-2 (a dose set for ~2 s) when the tape is heated by a beam to 620 K (which is 150 K below the thermal crystallization threshold) leads to the complete crystallization of this alloy over the entire thickness of the tape (25 µm) at a projective run of argon ions of only 14.4 nm [26, 27]. This is accompanied by a change in the magnetic properties of the alloy. The degree of perfection of the resulting crystals of a solid solution of α-Fe(Si) close in composition to Fe80Si20, the stable phase of Fe3Si and metastable hexagonal phases is higher than after standard furnace annealing for 1 h at 670 K.
The process of nanocrystallization of amorphous alloy tapes Fe72,5Cu1Nb2Mo1,5Si14B9 under the influence of Ar+ ions
(E = 30 KeV, j = 300 µA/cm2, F = 3.7×1015 cm–2) : (a) initial amorphous state; (b) after furnace annealing, T = 840 K, 1 h; (c) irradiation, T = 620 K, 2 s; (d) irradiation and subsequent annealing at T = 840 K, 1 h.
In [28-31] a significant effect of radiation treatment by ion beams on the atomic and magnetic structure of transformer steels, permalloy and nanocrystalline soft magnetic materials of similar composition was found. The losses of transformer steels and nanocrystalline and amorphous bands were reduced by 5-35% in the frequency range from 50 to 10 000 Hz. Obtained a patent (jointly with IMF, UB of RAS, 2008 [32]).
Magnetic domain structure of electrical steel Fe+3 wt. % Si before (a) and after (b) irradiation with Ar+ ions (E = 20 KeV).
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[1]
These are all metal alloys, which differ by the energies of pair interatomic interactions, at temperatures < 600 to 700 K because of the icing of diffusion processes.
