Modification of the wrought aluminum alloy 1933 through irradiation by the intense microsecond relativistic hollow electron beam was studied. Fracture mechanisms for both irradiated and non-irradiated samples, changes in the structure and chemical composition were investigated. The thermal model describing the beam-metal interaction was developed based on the hyperbolic relaxation heat transfer equation, weakly coupled theory of thermoelasticity and Stefan problem. We used the finite difference method to perform calculations according to this model. We determined experimentally as well as numerically the areas of modified and non-irradiated material, localized the quenched, heat-affected and shock-wave-affected zones

Horodek, P.R.

Kobets, A.G.

Lon, U.F.

Lytvynenko, V.V.

Ponomarev, A.G.

Startsev, O.A.

Uvarov, V.T.

English

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 3 No 2, 02MAN11(3pp) (2014)   2304-1862/2014/3(2)02MAN11(3) 02MAN11-1  2014 Sumy State University Modification of Aluminum Alloy 1933 by the High-Current Electron Beam Irradiation  A.G. Kobets1, 2, P.R. Horodek1, V.V. Lytvynenko2, U.F. Lonin3,  A.G. Ponomarev3, O.A. Startsev2,*, V.T. Uvarov3  1 JINR, 141980 Dubna, Moscow region, Russia 2 Institute of Electrophysics and Radiation Technologies, National Academy of Sciences of Ukraine, 28, Chernyshevsky Str., PO 8812, 61002 Kharkiv, Ukraine 3 National Science Center Kharkiv Institute of Physics and Technology,  1, Akademichna Str., 61108 Kharkiv, Ukraine  (Received 10 August 2014; published online 29 August 2014)  Modification of the wrought aluminum alloy 1933 through irradiation by the intense microsecond rela-tivistic hollow electron beam was studied. Fracture mechanisms for both irradiated and non-irradiated samples, changes in the structure and chemical composition were investigated. The thermal model describ-ing the beam-metal interaction was developed based on the hyperbolic relaxation heat transfer equation, weakly coupled theory of thermoelasticity and Stefan problem. We used the finite difference method to per-form calculations according to this model. We determined experimentally as well as numerically the areas of modified and non-irradiated material, localized the quenched, heat-affected and shock-wave-affected zones.  Keywords: Aluminum, Electron beam, Ablation.   PACS numbers: 61.80.Fe, 61.82.Bg, 81.40.Wx                                                             * startsev-alex@ukr.net 1. INTRODUCTION  The effects observed during the interaction of high-current electron beams (HCEB) with metals and alloys are considered as a good basis to develop the new radi-ation nanotechnologies for surface modification in order to enhance physical and mechanical characteristics [1]. The modifying effect is achieved due to a great variety of different combined processes in the target: fast heat-ing, melting, evaporation, elastic and shock wave for-mation and propagation, formation and expansion of gas plasma torch etc. The main feature of e-beam tech-nologies that distinguishes them from the treatment methods based on impact by the other concentrated energy flows (lasers, plasma), is the maximum of ener-gy deposition, which releases more deeply (related to the surface) in the bulk, than the others. Industrial aluminum alloy 1933 of Al-Zn-Mg-Cu system was selected for study [2]. Nowadays, it is wide-ly used because of it light density and high durability, typically it operates under cyclic loads [3]. Alloy 1933 has found numerous applications in the aircraft pro-duction of An-148, SSJ-100, as well as military aircraft and missile technology, significantly reducing the weight, fuel consumption, increasing weight efficiency of technology, its durability and service life. Alloys of the Al-Zn-Mg-Cu system are wrought alloys, and they are commonly used in quenched and artificially aged condition. These high-strength alloys have high vibra-tion resistance, fatigue strength and favorably differ from other series of aluminum alloys [2]. On the other hand, these high strength alloys have bad weldability, ductility, malleability; it is also required to improve their crack and corrosion resistance. E-beam processing is one of possible ways to improve the physical and me-chanical properties of alloy 1933. Moreover, to optimize the process of technological HCEB-processing it is im-portant to study in more detail the physical peculiari-ties of modifying mechanisms and develop the simple describing model.  2. MATERIALS AND METHODS  The irradiated sample was a square plate of alumi-num alloy 1933 (6.35% Zn; 1.6% Mg; 1% Cu; 0.1% Mn; 0.2% Fe; 0.1% Si; 0.06% Ti; 0.05% Cr; 0.1% Zr; 0.0001% Ве; the balance Al, % wt.) with the thickness ~ 2 mm and the side length ~ 10 mm [2]. One-impulse irradia-tion was conducted under the pressure about 10-5 Torr at the MIG-1 accelerator at the NSC Kharkiv Institute of Physics and Technology, with the following parame-ters: electron energy ~ 0.35 MeV, beam current ~ 2 kA, 5 µs beam pulse in the intensity range up to 1012 W/m2. The pulse durationτimpwas much longer that the elec-tron–phonon relaxation time τr (10−11 s). The Gaussi-an-shaped hollow beam had the inner radius of 1.5 mm; the outer radius of 2.3 mm. Energy density released on the surface of the irradiated target was less than 5 MJ/m2. Linear dimensions of the plate were larger than the typical size of the interaction region.  Preliminary visual and morphological analysis of the irradiated sample was performed using the optical microscope Bresser BioLux NV. SEM, fractographic analysis and X-ray microanalysis were conducted using JEOL JSM-840. We also used the method of positron annihilation spectroscopy at LEPTA (JINR, Dubna, Russia) [4] to analyze the changes in the defect sub-structure. To conduct numerical calculations upon the stated below problem, the smoothing coefficients meth-od was used. Numerical model based on Crank–Nicolson method was implemented in CodeTyphon 4.80, 64-bit Ubuntu 14.04 LTS.    A.G. KOBETS, P.R. HORODEK, ET AL. PROC. NAP 3, 02MAN11 (2014)   02MAN11-2 3. RESULTS  3.1 Thermal Model of E-Beam Ablation  The mathematical model of evolution of the thermal field we build according to the relaxation model of the heat flux q and the temperature gradient T (3.1), with a goal to describe physically correctly the propagation of the thermal front with a finite velocity and fulfill the maximum principle. We use the energy conservation equation (3.2), the power of internal heat source w is de-fined in (3.3). After substitution of (3.1) into (3.2) we obtain the hyperbolic heat conduction equation (3.4):   ( , ) ( , )( , ) ( , ) r rq r t T r tq r t λ T r t τ λτt t, (3.1)  ( , ) 1( )T r t wdiv qt ρc ρc, (3.2)  ( , ) ( , ) ( , )w r t ζ j r t S r t drdt , (3.3)  22 22( ) rr rT T λ T w τ wτ T τt t ρc t ρc ρc t,(3.4)  where λ – the coefficient of thermal conductivity, c – the thermal capacity, ρ – the material density,j – the beam current density, S – the energy-deposition profile [5], and the dimensional coefficient ζ = 1 ∙ 106 J/MeV ∙ C. Then, we discretize our problem into two separate parts: on finding the temperature field and the thermo-mechanical part. We can apply the weakly coupled dy-namic theory of thermoelasticity, taking into account the impact of the deformation rate e  on the temperature in-crementT , if the conditions (3.5 – 3.6) are fulfilled [3.6]:   2 2002(3 2 )12Tλ μ α Tδλ μcρρ, (3.5)  02 / 32TeT, (3.6)  where ', ' –  the Lame coefficients, αT – the linear coefficient of thermal expansion. While the energy deposi-tion S has a maximum at a depth about 120 µm, melting begins earlier in the bulk than on the surface (we do not consider the sublimation processes). The surface layer irradiated with a dose which is not enough for its melting, prevents the evaporation and ejection of the melted mate-rial at the mentioned depth under the surface. Conse-quently, it leads to the formation of the metastable phase in the volume (e.g. superheated liquid melt). The thermo-mechanical part considers the destruction of the afore-mentioned layer. It happens when the local ultimate strength Ω is equal to a jump of the mechanical tension │Ξ│. According to [3.6], we may simply estimate an upper bound of │Ξ│using its normal-to-surface component σzz, which defines a tensile jump at the front of thermoelastic wave (3.7):   0max( ) (3 2 ) ( ( , ) ( ,0))zz T T z t T z ,(3.7)  The initial temperature is T0. The boundary conditions are based on assumptions that the surface temperature at a remote, non-irradiated side is constant and equals to T0 (3.8), but the incident surface is exposed to the intense irradiation which results in the multiphase transitions, melting, evaporation, thermal radiation and partial backward condensation of ejected material onto the target (3.9):   0zT T , (3.8)  2 40 0 0beam condz z R z surfTλ βT n σε T q qr,(3.9)  where β – the heat transfer coefficient, εR – the integral emissivity, n – the refractive index of the environment (n ≈ 1). beamsurfq denotes the heat flux per unit area absorbed by the target (3.10), condq describes an amount of heat released during the backward condensation of ablation products onto the surface (3.11 – 3.12):   ( , ) ( )beamsurfq ζ j r t S r dzdt , (3.10)  abl T Tmeltm ρdV , (3.11)  2( )2( ( ) ) ( )t φcond Dabl melt o kkq θm c T T L j t e ,(3.12)  where mabl – the ablated mass, Tmelt –  the melting tem-perature, θ – the condensation coefficient (θ ~ 1/6), kL  – the latent heat per unit of volume, D = 1 s-2, φ –  a param-eter, which denotes a delaytime of the condensation on the target surface relatively to the beginning of irradiation (φ ~ τimp/2). At the moving boundary of phase transition we also set the next conditions (3.13 – 3.14):   1 ,( 0, ) ( 0, )j j tran kT ξ t T ξ t T , (3.13)  11j jj j kT T dξλ λ L ρr r dt, (3.14)  where ξ –  the front of k-phase transition, which occurs at the transition temperature Ttran,k.  3.2 Experimental and numerical results  Experimental results showed that HCEB irradiation caused significant erosion to sample. The nature of sam-ple cross-fractures was investigated. It was found that the modified volume consists of the quenched zone (QZ), heat-affected (HAZ) and shock-wave-affected zones (SWZ) differed one form each other by their microstruc-ture, chemical composition, fracture mechanisms (Fig. 1), concentration and kinds of defects. However, we have not noticed the considerable differences between HAZ and SWZ due to the annealing effect of e-beam pro-cessing, thus we considered those two zones as one. QZ has the closely packed, highly disperse nonporous struc-ture, which consists of misoriented grains with linear dimensions in rage of 1 – 3 μm, its fracture is dimpled and quasi-fibrous. QZ with a thickness about 200 μm was formed as a result of the high-speed cooling and the back-ward condensation of ablated material. HAZ and SWZ with a thickness up to 400 μm were formed due to the influence of rapid thermal fixation of the shock-wave ef-fect on the melt. It is characterized by the micro-ductile fracture mechanism and nonporous fine structure of high-ly melted facets with a linear size 1 μm without any spe-cific orientation. Non-modified alloy is characterized by the well-organized structure of quasi-cleavage crack facets within the size interval 0.6 – 1.5 μm.   MODIFICATION OF ALUMINUM ALLOY 1933 BY THE HIGH-CURRENT … PROC. NAP 3, 02MAN11 (2014)   02MAN11-3 The results obtained numerically according to the developed thermal model are in good agreement with the experimental data. We obtain numerically the penetra-tion depth into the sample and it is not more than 0.8 mm at the irradiation epicenter (peak flux density of up to 109 W/sm2). The microstructure of the modified alloy depends on the heating and cooling rates (Rht, Rcl), on the corresponding temperature gradients (Ght, Gcl), which in turn depend on the heat and mass transfer in the system, which finally influences on the alloy compo-sition. The computed heating rate Rht ~ 108 – 109 K/s and the heating gradient Ght ~ 106 – 108 K/m in the near-surface region (less than 200 µm). The thickness of the quenched layer does not exceed 300 μm in the pe-ripheral regions (flux densities up to 106 W/sm2) and 100 – 200 μm at the irradiation epicenter, the cooling rate and temperature gradient Rcl ~ 107 – 108 K/s and Gcl ~ 107 – 108 K/m respectively. The thickness of the melting and shock-wave-affected zone is up to 500 μm at the depth of 600 – 800 μm relatively to the surface, Rcl ~ 104 – 106 K/s and Gcl ~ 103 – 105 K/m. Evolution of the ablation interface is characterized by some impulsive-ness due to the inhomogeneous volumetric heat dissipa-tion and localization of stresses. The temperature maxi-mum in the bulk eventually disappears, and the crater is broadened. After 2 – 3 μs the temperature maximum moves almost onto the surface, and the velocity of the interface between the modified and non-treated material goes in the stationary mode 100 m/s. EPMA of the sample showed a substantial enrich-ment (20%) by the major alloying elements Zn, Mg and Cu in the quenched zone at the depth to 120 μm with the maximal concentrations at the surface; probably this effect occurred due to the diffusion of fusible compounds onto the surface.We also conducted EPA analysis of our samples (Fig. 2). At the beginning the Doppler parame-ter s increases linearly with E (i.e. with depth) describ-ing by that way a presence of the oxide layer on the sur-face. The large peak in the interval 2-10 keV showed a decline in the degree of crystallinity (little amorphiza-tion) which might be caused by the accumulation of any kind defects, redistribution of alloying elements, relaxa-tion of high residual stresses near the surface. It should be noted, that such a phenomenon could not be caused by the influence of the elastic, shock waves, since all the investigated volume was formed during the fast crystal-lization of the melt after the irradiation. Recrystalliza-tion processes formed almost all the modified structure, as evidenced by the small change of s-parameter. The e-beam irradiation affected the type of defects towards increasing the number of vacancy defects, as indicated by the change in slopes of the straight lines.    a b Fig. 1 – Fractures of irradiated material in QZ (a) and (b) non-irradiated material.    a b Fig. 2 – Dependences ofs-parameter on E positron energy (a) and s-parameter on w-parameter (b) for unmodified bulk and irradiated (in HAZ and SWZ area) alloy 1933.  4. CONCLUSIONS  The modification of industrial aluminum alloy 1933 by the high-current electron beam was studied. The ther-mal model was developed correspondingly. The e-beam irradiation resulted in a significant enrichment of alloy-ing elements Mg, Zn, Cu in the subsurface quenched zone, compared to non-irradiated sample. The topologi-cal changes of fracture from the quasi-cleavage crack facets in the unmodified area to tearing dimples, to high-ly melted facets in the transition zone, and dimpled, dull, quasi-fibrous fracture in the quenched zone were observed. It was proved that the HCEB treatment in-creased the proportion of micro-ductile fracture of alu-minum alloy 1933.  AKNOWLEDGEMENTS  This research was supported by the National Acad-emy of Sciences of Ukraine (grant of the Presidium of NAS of Ukraine № ЦО – 16-2/2014).   REFERENCES  1. V.I. Boiko, A.N. Valyaev, A.D. Pogrebnyak, Sov. Phys. Usp. 169, 11 (1999). 2. Aluminum Alloys (Ed. I.N. Fridlyander) (Кiev: Komintech: 2005). 3. V.P. Poida, D.E. Pedun, V.V. Bryukhovetskii, A.V. Poida, R.V. Sukhov, A.L. Samsonik, V.V. Litvinenko, Phys. Met. Metallogr. 114, 9 (2013). 4. P. Horodek, A. Kobets, I. Meshkov, V. Pavlov, A. Rudakov, A. Sidorin, S. Yakovenko, Proc. RUPAC2012, WEPPC044 (2012). 5. V. Gann, H. den Hartog, A. Sugonyako, D. Vainshtein, Proc. EPAC 2004, 2756 (2004). 6. E.M. Kartashov, L.M. Ozherelkova, Matematicheskoe Modelirovanie 14, 2 (2002).  

Modification of Aluminum Alloy 1933 by the High-Current Electron Beam Irradiation

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 3 No 2, 02MAN11(3pp) (2014) 
 
 
2304-1862/2014/3(2)02MAN11(3) 02MAN11-1  2014 Sumy State University 
Modification of Aluminum Alloy 1933 by the High-Current Electron Beam Irradiation 
 
A.G. Kobets1, 2, P.R. Horodek1, V.V. Lytvynenko2, U.F. Lonin3,  
A.G. Ponomarev3, O.A. Startsev2,*, V.T. Uvarov3 
 
1 JINR, 141980 Dubna, Moscow region, Russia 
2 Institute of Electrophysics and Radiation Technologies, National Academy of Sciences of Ukraine, 
28, Chernyshevsky Str., PO 8812, 61002 Kharkiv, Ukraine 
3 National Science Center Kharkiv Institute of Physics and Technology,  
1, Akademichna Str., 61108 Kharkiv, Ukraine 
 
(Received 10 August 2014; published online 29 August 2014) 
 
Modification of the wrought aluminum alloy 1933 through irradiation by the intense microsecond rela-
tivistic hollow electron beam was studied. Fracture mechanisms for both irradiated and non-irradiated 
samples, changes in the structure and chemical composition were investigated. The thermal model describ-
ing the beam-metal interaction was developed based on the hyperbolic relaxation heat transfer equation, 
weakly coupled theory of thermoelasticity and Stefan problem. We used the finite difference method to per-
form calculations according to this model. We determined experimentally as well as numerically the areas 
of modified and non-irradiated material, localized the quenched, heat-affected and shock-wave-affected 
zones. 
 
Keywords: Aluminum, Electron beam, Ablation. 
 
 PACS numbers: 61.80.Fe, 61.82.Bg, 81.40.Wx 
 
 
                                                          
* startsev-alex@ukr.net 
1. INTRODUCTION 
 
The effects observed during the interaction of high-
current electron beams (HCEB) with metals and alloys 
are considered as a good basis to develop the new radi-
ation nanotechnologies for surface modification in order 
to enhance physical and mechanical characteristics [1]. 
The modifying effect is achieved due to a great variety 
of different combined processes in the target: fast heat-
ing, melting, evaporation, elastic and shock wave for-
mation and propagation, formation and expansion of 
gas plasma torch etc. The main feature of e-beam tech-
nologies that distinguishes them from the treatment 
methods based on impact by the other concentrated 
energy flows (lasers, plasma), is the maximum of ener-
gy deposition, which releases more deeply (related to 
the surface) in the bulk, than the others. 
Industrial aluminum alloy 1933 of Al-Zn-Mg-Cu 
system was selected for study [2]. Nowadays, it is wide-
ly used because of it light density and high durability, 
typically it operates under cyclic loads [3]. Alloy 1933 
has found numerous applications in the aircraft pro-
duction of An-148, SSJ-100, as well as military aircraft 
and missile technology, significantly reducing the 
weight, fuel consumption, increasing weight efficiency 
of technology, its durability and service life. Alloys of 
the Al-Zn-Mg-Cu system are wrought alloys, and they 
are commonly used in quenched and artificially aged 
condition. These high-strength alloys have high vibra-
tion resistance, fatigue strength and favorably differ 
from other series of aluminum alloys [2]. On the other 
hand, these high strength alloys have bad weldability, 
ductility, malleability; it is also required to improve 
their crack and corrosion resistance. E-beam processing 
is one of possible ways to improve the physical and me-
chanical properties of alloy 1933. Moreover, to optimize 
the process of technological HCEB-processing it is im-
portant to study in more detail the physical peculiari-
ties of modifying mechanisms and develop the simple 
describing model. 
 
2. MATERIALS AND METHODS 
 
The irradiated sample was a square plate of alumi-
num alloy 1933 (6.35% Zn; 1.6% Mg; 1% Cu; 0.1% Mn; 
0.2% Fe; 0.1% Si; 0.06% Ti; 0.05% Cr; 0.1% Zr; 0.0001% 
Ве; the balance Al, % wt.) with the thickness ~ 2 mm 
and the side length ~ 10 mm [2]. One-impulse irradia-
tion was conducted under the pressure about 10-5 Torr 
at the MIG-1 accelerator at the NSC Kharkiv Institute 
of Physics and Technology, with the following parame-
ters: electron energy ~ 0.35 MeV, beam current ~ 2 kA, 
5 µs beam pulse in the intensity range up to 1012 W/m2. 
The pulse durationτimpwas much longer that the elec-
tron–phonon relaxation time τr (10−11 s). The Gaussi-
an-shaped hollow beam had the inner radius of 1.5 mm; 
the outer radius of 2.3 mm. Energy density released on 
the surface of the irradiated target was less than 5 
MJ/m2. Linear dimensions of the plate were larger 
than the typical size of the interaction region.  
Preliminary visual and morphological analysis of 
the irradiated sample was performed using the optical 
microscope Bresser BioLux NV. SEM, fractographic 
analysis and X-ray microanalysis were conducted using 
JEOL JSM-840. We also used the method of positron 
annihilation spectroscopy at LEPTA (JINR, Dubna, 
Russia) [4] to analyze the changes in the defect sub-
structure. To conduct numerical calculations upon the 
stated below problem, the smoothing coefficients meth-
od was used. Numerical model based on Crank–
Nicolson method was implemented in CodeTyphon 
4.80, 64-bit Ubuntu 14.04 LTS. 
 
 
 A.G. KOBETS, P.R. HORODEK, ET AL. PROC. NAP 3, 02MAN11 (2014) 
 
 
02MAN11-2 
3. RESULTS 
 
3.1 Thermal Model of E-Beam Ablation 
 
The mathematical model of evolution of the thermal 
field we build according to the relaxation model of the 
heat flux q and the temperature gradient T (3.1), with 
a goal to describe physically correctly the propagation of 
the thermal front with a finite velocity and fulfill the 
maximum principle. We use the energy conservation 
equation (3.2), the power of internal heat source w is de-
fined in (3.3). After substitution of (3.1) into (3.2) we 
obtain the hyperbolic heat conduction equation (3.4): 
 
 
( , ) ( , )
( , ) ( , ) r r
q r t T r t
q r t λ T r t τ λτ
t t
, (3.1) 
 
( , ) 1
( )
T r t w
div q
t ρc ρc
, (3.2) 
 ( , ) ( , ) ( , )w r t ζ j r t S r t drdt , (3.3) 
 
2
2 2
2
( ) rr r
T T λ T w τ w
τ T τ
t t ρc t ρc ρc t
,(3.4) 
 
where λ – the coefficient of thermal conductivity, c – the 
thermal capacity, ρ – the material density,j – the beam 
current density, S – the energy-deposition profile [5], and 
the dimensional coefficient ζ = 1 ∙ 106 J/MeV ∙ C. 
Then, we discretize our problem into two separate 
parts: on finding the temperature field and the thermo-
mechanical part. We can apply the weakly coupled dy-
namic theory of thermoelasticity, taking into account the 
impact of the deformation rate e  on the temperature in-
crementT , if the conditions (3.5 – 3.6) are fulfilled [3.6]: 
 
 
2 2
0
0
2
(3 2 )
1
2
Tλ μ α Tδ
λ μ
cρ
ρ
, (3.5) 
 
0
2 / 3
2
Te
T
, (3.6) 
 
where ', ' –  the Lame coefficients, αT – the linear 
coefficient of thermal expansion. While the energy deposi-
tion S has a maximum at a depth about 120 µm, melting 
begins earlier in the bulk than on the surface (we do not 
consider the sublimation processes). The surface layer 
irradiated with a dose which is not enough for its melting, 
prevents the evaporation and ejection of the melted mate-
rial at the mentioned depth under the surface. Conse-
quently, it leads to the formation of the metastable phase 
in the volume (e.g. superheated liquid melt). The thermo-
mechanical part considers the destruction of the afore-
mentioned layer. It happens when the local ultimate 
strength Ω is equal to a jump of the mechanical tension 
│Ξ│. According to [3.6], we may simply estimate an upper 
bound of │Ξ│using its normal-to-surface component σzz, 
which defines a tensile jump at the front of thermoelastic 
wave (3.7): 
 
 0max( ) (3 2 ) ( ( , ) ( ,0))zz T T z t T z ,(3.7) 
 
The initial temperature is T0. The boundary conditions 
are based on assumptions that the surface temperature at 
a remote, non-irradiated side is constant and equals to T0 
(3.8), but the incident surface is exposed to the intense 
irradiation which results in the multiphase transitions, 
melting, evaporation, thermal radiation and partial 
backward condensation of ejected material onto the target 
(3.9): 
 
 0zT T , (3.8) 
 2 40 0 0
beam cond
z z R z surf
T
λ βT n σε T q q
r
,(3.9) 
 
where β – the heat transfer coefficient, εR – the integral 
emissivity, n – the refractive index of the environment 
(n ≈ 1). beamsurfq denotes the heat flux per unit area absorbed 
by the target (3.10), condq describes an amount of heat 
released during the backward condensation of ablation 
products onto the surface (3.11 – 3.12): 
 
 ( , ) ( )beamsurfq ζ j r t S r dzdt , (3.10) 
 abl T Tmeltm ρdV , (3.11) 
 
2( )
2( ( ) ) ( )
t φ
cond D
abl melt o kkq θm c T T L j t e ,(3.12) 
 
where mabl – the ablated mass, Tmelt –  the melting tem-
perature, θ – the condensation coefficient (θ ~ 1/6), kL  – 
the latent heat per unit of volume, D = 1 s-2, φ –  a param-
eter, which denotes a delaytime of the condensation on the 
target surface relatively to the beginning of irradiation 
(φ ~ τimp/2). At the moving boundary of phase transition 
we also set the next conditions (3.13 – 3.14): 
 
 1 ,( 0, ) ( 0, )j j tran kT ξ t T ξ t T , (3.13) 
 
1
1
j j
j j k
T T dξ
λ λ L ρ
r r dt
, (3.14) 
 
where ξ –  the front of k-phase transition, which occurs at 
the transition temperature Ttran,k. 
 
3.2 Experimental and numerical results 
 
Experimental results showed that HCEB irradiation 
caused significant erosion to sample. The nature of sam-
ple cross-fractures was investigated. It was found that 
the modified volume consists of the quenched zone (QZ), 
heat-affected (HAZ) and shock-wave-affected zones 
(SWZ) differed one form each other by their microstruc-
ture, chemical composition, fracture mechanisms 
(Fig. 1), concentration and kinds of defects. However, we 
have not noticed the considerable differences between 
HAZ and SWZ due to the annealing effect of e-beam pro-
cessing, thus we considered those two zones as one. QZ 
has the closely packed, highly disperse nonporous struc-
ture, which consists of misoriented grains with linear 
dimensions in rage of 1 – 3 μm, its fracture is dimpled and 
quasi-fibrous. QZ with a thickness about 200 μm was 
formed as a result of the high-speed cooling and the back-
ward condensation of ablated material. HAZ and SWZ 
with a thickness up to 400 μm were formed due to the 
influence of rapid thermal fixation of the shock-wave ef-
fect on the melt. It is characterized by the micro-ductile 
fracture mechanism and nonporous fine structure of high-
ly melted facets with a linear size 1 μm without any spe-
cific orientation. Non-modified alloy is characterized by 
the well-organized structure of quasi-cleavage crack facets 
within the size interval 0.6 – 1.5 μm.  
 MODIFICATION OF ALUMINUM ALLOY 1933 BY THE HIGH-CURRENT … PROC. NAP 3, 02MAN11 (2014) 
 
 
02MAN11-3 
The results obtained numerically according to the 
developed thermal model are in good agreement with the 
experimental data. We obtain numerically the penetra-
tion depth into the sample and it is not more than 0.8 
mm at the irradiation epicenter (peak flux density of up 
to 109 W/sm2). The microstructure of the modified alloy 
depends on the heating and cooling rates (Rht, Rcl), on 
the corresponding temperature gradients (Ght, Gcl), 
which in turn depend on the heat and mass transfer in 
the system, which finally influences on the alloy compo-
sition. The computed heating rate Rht ~ 108 – 109 K/s 
and the heating gradient Ght ~ 106 – 108 K/m in the 
near-surface region (less than 200 µm). The thickness of 
the quenched layer does not exceed 300 μm in the pe-
ripheral regions (flux densities up to 106 W/sm2) and 
100 – 200 μm at the irradiation epicenter, the cooling 
rate and temperature gradient Rcl ~ 107 – 108 K/s and 
Gcl ~ 107 – 108 K/m respectively. The thickness of the 
melting and shock-wave-affected zone is up to 500 μm at 
the depth of 600 – 800 μm relatively to the surface, Rcl ~ 
104 – 106 K/s and Gcl ~ 103 – 105 K/m. Evolution of the 
ablation interface is characterized by some impulsive-
ness due to the inhomogeneous volumetric heat dissipa-
tion and localization of stresses. The temperature maxi-
mum in the bulk eventually disappears, and the crater is 
broadened. After 2 – 3 μs the temperature maximum 
moves almost onto the surface, and the velocity of the 
interface between the modified and non-treated material 
goes in the stationary mode 100 m/s. 
EPMA of the sample showed a substantial enrich-
ment (20%) by the major alloying elements Zn, Mg and 
Cu in the quenched zone at the depth to 120 μm with the 
maximal concentrations at the surface; probably this 
effect occurred due to the diffusion of fusible compounds 
onto the surface.We also conducted EPA analysis of our 
samples (Fig. 2). At the beginning the Doppler parame-
ter s increases linearly with E (i.e. with depth) describ-
ing by that way a presence of the oxide layer on the sur-
face. The large peak in the interval 2-10 keV showed a 
decline in the degree of crystallinity (little amorphiza-
tion) which might be caused by the accumulation of any 
kind defects, redistribution of alloying elements, relaxa-
tion of high residual stresses near the surface. It should 
be noted, that such a phenomenon could not be caused 
by the influence of the elastic, shock waves, since all the 
investigated volume was formed during the fast crystal-
lization of the melt after the irradiation. Recrystalliza-
tion processes formed almost all the modified structure, 
as evidenced by the small change of s-parameter. The e-
beam irradiation affected the type of defects towards 
increasing the number of vacancy defects, as indicated 
by the change in slopes of the straight lines. 
 
 
 a b 
Fig. 1 – Fractures of irradiated material in QZ (a) and (b) non-
irradiated material. 
 
 
 a b 
Fig. 2 – Dependences ofs-parameter on E positron energy (a) 
and s-parameter on w-parameter (b) for unmodified bulk and 
irradiated (in HAZ and SWZ area) alloy 1933. 
 
4. CONCLUSIONS 
 
The modification of industrial aluminum alloy 1933 by 
the high-current electron beam was studied. The ther-
mal model was developed correspondingly. The e-beam 
irradiation resulted in a significant enrichment of alloy-
ing elements Mg, Zn, Cu in the subsurface quenched 
zone, compared to non-irradiated sample. The topologi-
cal changes of fracture from the quasi-cleavage crack 
facets in the unmodified area to tearing dimples, to high-
ly melted facets in the transition zone, and dimpled, 
dull, quasi-fibrous fracture in the quenched zone were 
observed. It was proved that the HCEB treatment in-
creased the proportion of micro-ductile fracture of alu-
minum alloy 1933. 
 
AKNOWLEDGEMENTS 
 
This research was supported by the National Acad-
emy of Sciences of Ukraine (grant of the Presidium of 
NAS of Ukraine № ЦО – 16-2/2014). 
 
 
REFERENCES 
 
1. V.I. Boiko, A.N. Valyaev, A.D. Pogrebnyak, Sov. Phys. 
Usp. 169, 11 (1999). 
2. Aluminum Alloys (Ed. I.N. Fridlyander) (Кiev: Komintech: 
2005). 
3. V.P. Poida, D.E. Pedun, V.V. Bryukhovetskii, A.V. Poida, 
R.V. Sukhov, A.L. Samsonik, V.V. Litvinenko, Phys. Met. 
Metallogr. 114, 9 (2013). 
4. P. Horodek, A. Kobets, I. Meshkov, V. Pavlov, A. Rudakov, 
A. Sidorin, S. Yakovenko, Proc. RUPAC2012, WEPPC044 
(2012). 
5. V. Gann, H. den Hartog, A. Sugonyako, D. Vainshtein, 
Proc. EPAC 2004, 2756 (2004). 
6. E.M. Kartashov, L.M. Ozherelkova, Matematicheskoe 
Modelirovanie 14, 2 (2002). 
 


https://essuir.sumdu.edu.ua/bitstream/123456789/37187/1/kobets_luminum.pdf

Modification of Aluminum Alloy 1933 by the High-Current Electron Beam Irradiation

Abstract

Similar works

Full text

Available Versions

Electronic Sumy State University Institutional Repository

SocioEconomic Challenges Journal (Sumy State University)