Hanwei He and Shouya Jia- Direct Electrodeposition of Cu-Ni-W Alloys for the Liners for Shaped Charges

8/3/2019 Hanwei He and Shouya Jia- Direct Electrodeposition of Cu-Ni-W Alloys for the Liners for Shaped Charges

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J. Mater. Sci. Technol., 2010, 26(5), 429-432.

Direct Electrodeposition of Cu-Ni-W Alloys

for the Liners for Shaped Charges

Hanwei He † and Shouya Jia State Key Lab of Powder Metallurgy, Central South University, Changsha 410083, China

[Manuscript received March 20, 2009, in revised form June 21, 2009]

The Cu-Ni-W alloys for the liners for shaped charges were successfully prepared by direct current (DC) elec-trodeposition. The influence of cathode current density on morphology, microstructure and composition of theCu-Ni-W alloys was investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD)and energy dispersive spectrometry (EDS). With the increasing of current density, the copper content reducesgradually and the nickel and tungsten content increase; the crystallite size is decreased. When the currentdensity is 15 A/dm2the tungsten content reaches 12.96 wt pct, and the crystallite size is submicron degree.The Cu-Ni-W alloy is face-centered cubic (fcc) solid solution. All of the Cu-Ni-W alloys take on (220) texture.

KEY WORDS: Electrodeposition; Cu-Ni-W alloy; Cathode current density

1. Introduction

The shaped charges are widely applied in the mod-ern ammunition and certain industries, e.g. oil, min-ing, geology, etc. In many applications it is desir-able for the jet to penetrate the target material to adepth as great as possible. A still further method formaximizing penetration depth is to change the linermaterial used for the shaped charge liner. In the pastthe liners for shaped charges have typically been com-

posed primarily of wrought copper[1], but it is knownthat other materials exhibit benefits in certain ap-plications. Because of its high density, high soundvelocity and high ductility[2], the tungsten will be atype of shaped charge liner materials. It has b eensuggested in U.S. Patent[3] that if the grain size of ahigh percentage tungsten liner is less than 1 micronthe jet so produced has properties at least comparableto that derived from a depleted Uranium (DU) liner.Tungsten is therefore one of the few readily availablematerials that may provide a serious alternative toDU.

Usually liners for shaped charges have been formed

† Corresponding author. Prof., Ph.D.; Tel.: +86 7318836264/8836311; Fax: +86 731 8710855; E-mail address:[email protected] (H.W. He).

from various materials by forming the materials intopowders and then pressing the powdered materialsinto the desired liner shape[4–6]. Liners comprisingcompressed powdered materials are very fragile andtherefore tend to disintegrate into very small pieceswhen the shaped charge assembly is actuated. How-ever, liners formed from pressed powdered materials,either sintered or unsintered, tend to be either porousor hydroscopic, or both, and therefore do not provideadequate protection for the explosive material com-

prising the shaped charge. However, these methodsdo not allow fabricating of the liners with requireddimensional accuracy.

Electroforming (electrodeposition) technique is of great interest for industrial usage. It is a straight-forward process for the shaped charges with low costand easy control. The electroforming technique hasbeen used for fabricating copper and nickel liners of shaped charges[7–9]. Fan et al.[10] regarded that thegrain size of electroformed copper liners of shapedcharges was finer than that of the spin-formed cop-per liners of shaped charges. Investigation by Fan

et al.[11] indicate that by controlling the parametersof electroforming technology, e.g. the current density,the value of pH, the rotation velocity of the substrate,etc, it makes the materials possible to have character-



430 H.W. He et al.: J. Mater. Sci. Technol., 2010, 26(5), 429–432

istic microstructures, controlled grain size and shape,ultra-fine and homogenous grain and controlled grainorientation of growth direction.

The electrodeposition of pure tungsten from aque-ous solutions has been unsuccessful, and it can becodeposited with an iron group metal. The in-

duced codeposition of tungsten with nickel has beeninvestigated[12–14]. Ni-Cu is a regular system[15,16].So far no literature data are available for this Cu-Ni-W alloy system by direct current (DC) electrodeposi-tion. The aim of this study was to prepare the Cu-Ni-W alloy for the liners for shaped charges by directcurrent (DC) electrodeposition. The effect of cathodecurrent density on morphology, texture, structure andcontent of these alloys was investigated.

2. Experimental

The alloys were plated onto copper sheetserving as cathodes with a dimension of 20 mm×20 mm×1 mm. Platinum sheets were usedas anodes. Pretreatment of the working surface be-fore plating process included degreasing in organicsolvent, water rinsing, acid pickling and chemicalpolishing in acid solution. Electrodeposition of Cu-Ni-W alloys were plated from a bath containingnickel sulphate (NiSO4·7H2O) 0.05 mol/L, sodiumtungstate (Na2WO4·2H2O) 0.15 mol/L, copper sul-phate (CuSO4·5H2O) 0.005 mol/L, sodium citrate(Na3C6H5O7·2H2O) 0.2 mol/L and organic additives

such as saccharin (SAC), all reagents of analyticalgrade. All solutions were freshly prepared with puri-fied water. The bath was maintained at pH 6.5+0.1adjusted by 0.1 mol H2SO4, temperature 55+1◦C andcurrent density ranging from 5 to 15 A/dm2, and theplating time was 30 min during which the bath wasagitated.

The contents of Cu, Ni and W of the electrode-posits were analyzed via an KYKY-2800LV EnergyDispersive Spectrometer (EDS). The structural char-acterization was performed by using an X-ray diffrac-tion spectrometer (D/AX 2550, Japan). The mor-phology of the surface of the alloys was observed via a

scanning electron microscope (SEM, KYKY-2800LV).

3. Results and Discussion

Figure 1 shows the mass contents of Cu, Ni andW of alloy electrodeposited on the various cathodecurrent densities. As can be seen, the nickel weightpercent (Ni%) in the deposits increases significantlyas cathode current density increases. This observa-tion indicates that the Cu content is more than theNi content in the alloy at low current densities andthe alloy consists of Cu, Ni and W at moderate cur-

rent densities and the Ni Content is more than theCu content conversely at high current densities. Thedependence of the composition of the Cu-Ni alloy onthe applied potential has also been reported earlier by

4 6 8 1 0 1 2 1 4 1 6

C

u

,

N

,

W

c

o

n

t

e

n

t

/

w

t

p

c

t

C u r r e n t d e n s i t y / ( A / d m

Fig. 1 Relationship between cathode current density andthe Cu, Ni and W content of the electrodeposits

Bennett et al.[16]

. They have confirmed that, at lowapplied potentials, the more noble copper is depositedeasily, but when the potential is set at a value corre-sponding to nickel, both metals will be deposited atrates limited by their relative concentrations, result-ing in a structure of unalloyed copper alternating withnickel having low copper content. Tungsten cannotbe produced by electrodeposition lonely from aque-ous solutions, unless in conjunction with depositionof nickel. So the W content of the electrodepositsincreases slightly as the content of Ni increases.

Figure 2 shows SEM micrographs of the Cu-Ni-W alloy electrodeposited on various cathode current

densities. The deposition is uniform throughout andexhibits a cauliflower-like appearance at low currentdensities, a pyramid-like appearance at moderate cur-rent densities, and a ridge-like appearance at high cur-rent densities. The decrease in grain size with increasein current density is clearly evident. According tothe Butler-Volmer equation, overpotential increasesas cathode current density increases, accordingly, canpromote the nucleation rate. When the nucleationrate exceeds the growth rate of crystal, the grains of coatings become fine.

Figure 3 illustrates the XRD patterns of the Cu-

Ni-W alloy electrodeposited on various cathode cur-rent density . All the composite coatings exhibit sin-gle phase of Cu matrix with face-centered cubic (fcc)crystal structure (PDF number:04-0836) and peakscorresponding to Ni phase is not found in the spectraindicating that crystal lattice in Cu matrix perhapshas been replaced by Ni and W partly and formedsolid solution. A shift is observed in the diffractionangle towards lower angles as the nickel and tungstencontent of the alloy is increased. To substantiate this,the lattice constant (a) of the Cu-Ni-W alloy films isdetermined using the fcc Cu-Ni diffraction angle andthe Braggs equation[17]. The lattice constant (a) of all the Cu-Ni-W alloys is larger than the lattice con-stant (a0) of the pure Cu. The atomic radius of W(0.202 nm) and Ni (0.162 nm) is larger than that of



H.W. He et al.: J. Mater. Sci. Technol., 2010, 26(5), 429–432 431

Fig. 2 SEM micrographs of Cu-Ni-W alloys the electrodeposited in different current density: (a) 5 A/dm2,(b) 7.5 A/dm2, (c) 10 A/dm2, (d) 12.5 A/dm2

3 0 4 0 5 0 6 0 7 0 8 0 9 0

2 / d e g .

A / d m

A / d m

A / d m

= 1 2 . A / d m

A / d m

( 1 1 1 )

( 3 1 1 )

I

n

t

e

n

s

t

y

/

a

.

u

.

Fig. 3 XRD patterns of Cu-Ni-W alloys electrodeposited

at different current density

Cu (0.128 nm)[18], which cannot enter into the Cucrystal lattice space. Only a Cu-Ni-W solid solutionalloy can be produced, which do not change crystallattice type, but can change the lattice constant. If atomic radius of the solute atom (W, Ni) is largerthan the solvent atom (Cu), the lattice constant of solid solution increases. The average grain size of theCu-Ni-W alloy calculated using Scherrer formula wasin the range of 0.2 to 1 µm; the higher the currentdensity, the lower is the crystallite size, in accordancewith Fig. 2. When the current density is 12.5 A/dm2,the average grain size is only 0.2 µm.

Figure 4 shows texture coefficients for the Cu-Ni-

( 1 1 1 ) ( 2 0 0 ) ( 2 2 0 ) ( 3 1 1 )

T

e

x

t

u

r

e

c

o

e

f

f

c

e

n

t

(

X

r

a

n

d

o

m

)

Fig. 4 Texture coefficients for Cu-Ni-W alloys in differ-

ent current density: (a) 5 A/dm

2

, (b) 7.5 A/dm

2

,(c) 10 A/dm2, (d) 12.5 A/dm2, (e) 15 A/dm2

W alloys. The texture coefficients, T C hkl are calcu-lated from X-ray patterns using Eq. (1):

T C hkl =I (hkl)/I 0(hkl)

1n

[I (hkl)/I 0(hkl)]

(1)

In this equation I (hkl) is the integrated peak intensityof (hkl) plane obtained from X-ray patterns. I 0(hkl) isthe corresponding integrated peak intensity of (hkl)plane in Cu powder as a polycrystalline texture free

sample. n is the number of Cu peaks in X-ray dif-fraction which is 4. As seen all of the Cu-Ni-W alloystake on (220) texture, the texture coefficients changeslightly upon cathode current density.



432 H.W. He et al.: J. Mater. Sci. Technol., 2010, 26(5), 429–432

4. Conclusion

The direct deposition technique is used to preparethe Cu-Ni-W alloys. The surface appearance of theCu-Ni-W alloy is uniform and compact, showing anickel metallic luster. The grain sizes of the Cu-Ni-W

alloy are submicron degree observed by scanning elec-tron microscopy. The Cu-Ni-W alloy is face-centeredcubic (fcc) solid solution as proven by X-ray diffrac-tion. The nickel weight percent (Ni%) in the depositsincreases significantly as cathode current density in-creases; the W content of the electrodeposits increasesslightly.

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Hanwei He and Shouya Jia- Direct Electrodeposition of Cu-Ni-W Alloys for the Liners for Shaped Charges