A copper single crystal was tested at room temperature in air and in a 0.1M HClO4 solution under the symmetric tension-compression load mode, with loading axis parallel to the [013] direction. The dislocation structures were characterised using the electron channeling contrast (ECC) technique of scanning electron microscopy (SEM) and using transmission electron microscopy (TEM). The results show that the saturation dislocation structures in samples subjected to corrosion fatigue in the 0.1M HClO4 aqueous solution manly had the form of cells, dislocation wall-like and veins, which differ from the dislocation structures of dislocation wall-like and veins in the air environment

Jia, W. P.

Ke, W.

Mai, Y-W.

Yang, J. H.

Zhang, X. P.

University of Queensland eSpace

SIF2004 Structural Integrity and Fracture. http://eprint.uq.edu.au/archive/00000836 
Saturation Dislocation Microstructures In A Copper Single Crystal  
During Fatigue In HClO4 Aqueous Solution 
J H Yang1, X P Zhang1, Y -W Mai1, W P Jia2 and W Ke 2 
1 Centre for Advanced Materials Technology (CAMT), School of Aerospace, Mechanical and  
Mechatronic Engineering, The University of Sydney, NSW 2006, Australia 
2 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China 
ABSTRACT: A copper single crystal was tested at room temperature in air and in a 0.1M HClO4 solution 
under the symmetric tension-compression load mode, with loading axis parallel to the [013] direction. The 
dislocation structures were characterised using the electron channeling contrast (ECC) technique of scanning 
electron microscopy (SEM) and using transmission electron microscopy (TEM). The results show that the 
saturation dislocation structures in samples subjected to corrosion fatigue in the 0.1M HClO4 aqueous 
solution manly had the form of cells, dislocation wall-like and veins, which differ from the dislocation 
structures of dislocation wall-like and veins in the air environment.  
1 INTRODUCTION 
The dislocation structure of a material is directly associated with its mechanical behaviour. The 
dislocation structures of cyclically deformed specimens [Ackermann et al., 1984; Basinski and 
Basinski, 1992; Suresh, 1998], especially for single crystals of copper [Laird et al., 1986; Yang et al., 
2003; Mughrabi, 1983], have been extensively studied. Cyclic deformation and persistent slip bands 
(PSBs) are both important to crack initiation and crack propagation [Zhang et al., 2001]. Many 
investigators have found that the service properties of components subject to corrosion fatigue 
conditions are considerably degraded compared with the fatigue properties in air environments 
materials [Ortner et al., 1987; Yan et al., 1985]. Moreover, the corrosion fatigue properties of the 
materials have been found to be even worse than the simple sum of the separate effects of cyclic 
loading and corrosion [Yan et al., 1985]. Therefore, a study of environmental effects on cyclic 
deformation and PSB behavior can be expected to improve our understanding of the mechanism of 
corrosion fatigue, crack nucleation and life behavior. Unfortunately, this subject has rarely been 
studied in recent years because the phenomena are complicated. Most attention has been devoted to 
crack propagation. Contrary to the abundant availability of dislocation structures in specimens 
cyclically tested in air, TEM and SEM observations of specimens fatigue-tested in corrosive 
environments are still very limited [Hahn and Duquette, 1978; Yan et al., 1985]. The present 
investigation examines dislocation structures in a copper single crystal that has been subjected to 
corrosion fatigue testing, so as to provide a better understanding of environment-cyclic deformation 
interactions without the complicating factor of the crack path sensitivity of grain boundaries. 
Figure 1 shows the location of the orientations of Cu single crystal in the stereographic standard 
triangle and the classification of different types of slip orientations. In Fig.1, the three pinnacles 
correspond to [001], ]111[  and [011] multiple-slip-oriented orientations, respectively, and the three 
sides correspond to quite different double-slip orientations, i.e., coplanar slip (011/ 111 ), conjugate 
slip (001/ 111 ) and critical slip (001/011) orientations, respectively. The [013] orientation locates at 
the (001/011) side, and corresponds to a critical double slip. In this work, fatigue tests were 
performed on a copper single crystal with loading axis parallel to [013] double-slip-oriented at room 
temperature in air and 0.1 M HClO4 solution respectively, under the symmetric tension-compression 
load mode. Dislocation structures were observed and characterized using TEM and the ECC 
technique of SEM. 
 
 
SIF2004 Structural Integrity and Fracture. http://eprint.uq.edu.au/archive/00000836 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 1. Stereographic triangle showing the orientations of Cu single crystal 
and the classification of orientations with different slip systems.   
2 EXPERIMENT MATERIAL AND PROCEDURE 
The material used in the present work was a copper single crystal grown from OFHC copper with a 
purity of 99.999% by the Bridgman technique. Specimens used for corrosion fatigue tests were cut 
by electric discharge machining, which had the final dimension of 7 × 10 ×  75 mm3 and a gauge 
section of 7 × 5 ×  15 mm3, as shown in Fig.2. The tensile axis of the specimens is parallel to the 
[013] orientation. The orientation of the specimens was determined by the Laue back-reflection 
technique with accuracy within ± 2°. To eliminate any residual stress effect, all specimens were 
electro-polished before testing. 
 
 
 
 
 
 
 
 
 
 
 
Fig. 2. The size and shape of specimens used in this study.  
 
A special apparatus was designed to keep the specimen under well-controlled corrosion fatigue 
conditions. Figure 3 shows schematically the configuration of the testing system, which consisted of 
four parts: mechanical testing machine (Parts 5 and 6), solution deaeration system (Part 1), argon 
purification train (Parts 2 and 3), and potential control electronics (Part 4). Deaerated 0.1 M HClO4 
solution was applied as the aqueous environment. Fatigue tests were conducted in symmetric 
tension-compression load mode at room temperature under the plastic strain control and potential 
control conditions using an Instron servohydraulic testing machine (8501, 100 kN). A triangular 
waveform signal with frequencies  of 0.05-0.5Hz was used for the constant plastic strain amplitude 
7
20
5
15
75
20
10
[013] [013]
013
001 011
111
Multiple slip Multiple slip
Multiple slip
Critical double slip
Co
nju
gat
e d
ou
ble
 sli
p
Coplanar double slipSingle slip
SIF2004 Structural Integrity and Fracture. http://eprint.uq.edu.au/archive/00000836 
control. The applied plastic shear strain amplitudes were 1.6 × 10-3 and 6.8 × 10-3, respectively. 
Stress-strain hysteresis loops were on-time recorded and monitored on an X-Y recorder. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 3. Schematic diagram of testing system. 
 
Specimens were deformed cyclically up to the occurrence of the saturation stage of cyclic 
deformation. Thin foils for TEM studies were first sliced from the gauge part of the corrosion 
fatigued specimen parallel to some specific crystallographic planes (111), ( )111  and )121( , by 
electric discharge machining; then mechanically thinned down to dozens of micron thick and finally 
polished by a conventional twin-jet method. TEM observations were performed using JEOL-
2000FX II electron microscope operated at 200kV. The experiment parameters used in corrosion 
fatigue are shown in Table 1.    
  
Table 1 Experiment parameters in corrosion fatigue tests 
Specimen 
designation  
Plastic strain 
amplitude  
Environment 
solution 
Potential (VSCE) 
S1 6.8 × 10-3 Air N/A 
S2 1.6 × 10-3 0.1N HClO4 Free Corrosion 
S3 6.8 × 10-3 0.1N HClO4 0.005 
S4 1.6 × 10-3 0.1N HClO4 0.005  
    
  
3 RESULTS AND DISCUSSIONS 
3.1 Cyclic hardening curve of specimens tested in air 
Figure 4 shows cyclic hardening curves of the [013] double-slip-oriented copper single crystal 
which was tested at room temperature in air at plastic shear strain amplitude of 1.6 × 10-3 and 6.8 × 
10-3. It can be seen from Fig. 4 that the shear stress increases with increasing number of cycles and 
finally reaches constant and enters a saturation state. Moreover, the hardening curves for the 
different environmental conditions (see Table 1) showed no significant differences. This implies that 
the environment has no significant influence on the hardening process.   
 
1 2 3
5 64
So
lu
tio
n 
in
A
rg
on
 in
Solution outArgon out
1. Solution reservoir                     2. Argon purification furnace
3. Argon cylinder                         4. Potentiostat
5. Instron fatigue machine            6. X-Y recorder   
So
lu
tio
n 
in
A
rg
on
 in
SIF2004 Structural Integrity and Fracture. http://eprint.uq.edu.au/archive/00000836 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4. Cyclic hardening curves of  [013] double-slip-oriented copper single crystals  
under two different plastic strain amplitudes.  
3.2 Surface morphology and saturation dislocation structures in specimens tested in air 
Figure 5 shows observations of the surface deformation morphology and dislocation structures of 
the specimen S1 cyclically loaded in air for 3500 cycles (by this cycle number the specimen was in 
the saturation stage of cyclic deformation). In Fig.5 (a), the parallel macro deformation bands (DBs), 
at an angle of 45° with respect to the loading direction, can be seen clearly. These macro DBs can 
spread over the whole surface. In Fig. 5 (b), the dislocation structure mainly consists of dislocation 
wall-like and vein structures. The observed plane is (111). Regarding the critical double-slip crystals, 
Gong et al. [Gong et al., 1996] reported that PSB ladders, veins and labyrinths constitute the main 
dislocation features in the critical double-slip crystal cycled at intermediate strain amplitudes and 
cell structures developed at higher strain amplitudes. Jin and Winter (Jin and Winter, 1984) also 
found PSB ladders and veins in the [012] critical double-slip crystal cycled at an intermediate strain 
amplitude of 3.0× 10−3. Recently Li et al. [Li et al., 2002] reported that the labyrinth structure 
becomes the main dislocation configuration in cyclically deformed [017] critical double-slip 
crystals (γpl = 1.2 × 10-4 ) and some narrow PSB ladder-like structures are embedded in the labyrinth 
structures (γpl = 9.4 × 10-4 ). The present work revealed that the dislocation wall-like and vein 
structures become the main dislocation configuration in the [013] critical double-slip copper single 
crystal.  
 
 
 
  
 
 
 
 
 
 
 
 
 
 
Fig. 5.  SEM images of specimen S1: (a) surface morphology; and  
 (b) SEM-ECC image of dislocation wall-like and vein microstructures 
0 1000 2000 3000 4000
10
20
30
40
50
60
70
 6 .8x10 -3
 1 .6x10 -3
A
xi
al
 s
tre
ss
 M
P
a
C yc lic  num ber 
(a)
DB
(11
1)
25 µm
PS
Bs
Di
slo
ca
tio
n w
all
-li
ke
(b)
SIF2004 Structural Integrity and Fracture. http://eprint.uq.edu.au/archive/00000836 
3.3 Surface morphology and saturation dislocation structures in specimen S2   
Figure 6 shows observations of the surface deformation morphology and dislocation structures of 
the specimen S2 which was cyclically tested in a 0.1M HClO4 aqueous solution at free corrosion 
potential for 4000 cycles (also being in the saturation stage of cyclic deformation). In the 0.1 M 
HClO4 aqueous solution, without any corrosion product that does not dissolve in water was formed 
on the specimen surface, a copper atom is easy to lose electron to become a copper ion and dissolve 
in medium solution, is typical active system. Observation shows that the surface has slip traces and 
partial dissolution of copper atoms, without any apparent oxide films formed (see Fig.6a).  SEM-
ECC and TEM observations show that the saturation dislocation structures, after corrosion fatigue 
in 0.1M HClO4 aqueous solution, are manly consisted of dislocation walls-like, veins (see Fig.6b) 
and cells (see Fig.6c).  
 
 
 
 
 
 
 
 
 
 
                                                                       
 
 
 
 
   
 
 
 
 
 
 
 
Fig. 6. SEM and TEM images of saturation dislocation structures of fatigued copper single crystal 
in 0.1M HClO4 solution at free corrosion potential: (a) surface morphologies;  (b) SEM-ECC 
images of dislocation walls-like and vein microstructures; (c) TEM image of dislocation cells. 
 
Yan et al. [Yan et al., 1985] have studied the dislocation structure of copper single crystals 
oriented for single slip cycled in 0.1M HClO4 and under different polarization potentials. TEM 
samples were observed both after saturation and after fracture. They reported that although much 
higher strain localization was observed in the crystals cycled at anodic potentials, the dislocation 
structures observed were very similar to those of specimens tested at cathodic potentials and in air. 
For a plastic shear strain amplitude of 2.0× 10−3, regular loop patches (veins) and dipolar walls 
(dislocation wall) were observed. For a higher strain amplitude of 4.0×  10−3, dipolar walls 
associated with secondary slip were found in addition to regular primary walls. We have studied the 
dislocation structure of copper single crystals oriented for double slip cycled in 0.1M HClO4 and 
under free corrosion potential for 4000 cycles (also being in the saturation stage of cyclic 
(a)
Primary slip
Dislocation wall-like
Veins
10 µm
(b)
400 nm
(c)
Cell
SIF2004 Structural Integrity and Fracture. http://eprint.uq.edu.au/archive/00000836 
deformation). The present work revealed that the saturation dislocation microstructures, after 
corrosion fatigue in the aqueous solution of 0.1M HClO4, are manly consisted of dislocation wall- 
like, veins and cells, which differ from the dislocation structures in the air. 
4 CONCLUSIONS 
1) The dislocation walls-like and veins constitute the main dislocation feature in the critical double-
slip copper single crystals cycled deformation in open-air condition. 
2)  For double-slip-oriented copper single crystal cyclically stressed to the saturation stage in a 0.1 
M HClO4 aqueous solution, the specimen surface has slip traces and partial dissolution of copper 
atoms, but without oxide film formed. 
3) The saturation dislocation microstructures, after corrosion fatigue in the aqueous solution of 
0.1M HClO4, are manly consisted of dislocation walls-like, veins and cells, which differ from 
dislocation structures of dislocation wall-like and veins in open-air condition. 
ACKNOWLEDGMENTS  
Support of this work by the Australian Research Council (ARC) through a Large Grant (A10009166) 
is gratefully acknowledged. YWM also acknowledges the award of an Australian Federation 
Fellowship tenable at the University of Sydney. 
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Saturation Dislocation Microstructures In A Copper Single Crystal During Fatigue In HClO4 Aqueous Solution

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Saturation Dislocation Microstructures In A Copper Single Crystal During Fatigue In HClO4 Aqueous Solution

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