**4. Axisymmetrically drawn fcc metals**

internal stress due to defects such as vacancies and dislocations. Therefore, the texture

growth direction ]111[ ]001[

Greiser et al. [25] measured the microstructure and texture of Ag thin films deposited on different substrates using DC magnetron sputtering under high vacuum conditions (base pressure: 10-8 mbar, partial Ar pressure during deposition: 10-3 mbar). A weak <111> texture in a 0.6 µm thick Ag film deposited on a (001) Si wafer with a 50 nm thermal SiO2 layer at room temperature becomes stronger with increasing thickness. It is generally accepted that a random polycrystalline structure is obtained up to a critical film thickness unless an epitaxial growth condition is satisfied. Therefore, the <111> texture developed in the 0.6 µm film was weak and became stronger with increasing thickness. This is consistent with the preferred growth model [26]. They also found that the texture of the film deposited at room temperature was "high <111>", whereas the texture of the film deposited at 200 °C was characterized by a low amount of the <111> component and a high amount of the random component. This is also consistent

Post-deposition annealing was carried out in a vacuum furnace at 400 °C with a base pressure of 10-6 mbar, a partial H2 pressure of 10 mbar, and under environmental conditions. The postdeposition grain growth was the same for annealing in high vacuum and in environmental conditions. A dramatic difference in the extent of growth was recognized in the micrographs of the 0.6 and 2.4 µm thick films. The 0.6 µm thick film showed normally grown grains with the <111> orientation; the average grain size was about 1 to 2 µm. This can be understood in light of the surface energy minimization. In contrast, in 2.4 µm thick films, abnormally large grains with the <001> orientation were found. These grains grew into the matrix of <111> grains. The grain boundaries between the abnormally grown grains have a meander-like shape unlike the usual polygonal shape. They could not explain the results by the model of Carel, Thomson, and Frost [27]. According to the model, the strain energy minimization favors the growth of <100> grains. The growth mode should be affected by strain and should not be sensitive to the initial texture. These predictions are at variance with the experimental results in which freestanding, stress-free films also showed abnormal growth of giant grains with <001> texture. The 2.4 µm thick films deposited at 100 °C or below could have dislocations whose density was high enough to cause Rex, which in turn gave rise to the texture change from <111> to <001> regardless of the existence of substrate when annealed, as explained in the previous section. Thus, the <111> to <100> texture change in the 2.4 µm thick films is compatible with

transition is consistent with the prediction of SERM.

16 Recent Developments in the Study of Recrystallization

with the preferred growth model.

SERM [28].

**Figure 15.** Thin arrows (AMSDs) and thick arrows (GD) in [111] and [001] Cr crystals.

It is known that the texture of axisymmetrically drawn fcc metals is characterized by major <111> + minor <100> components, and the drawing texture changes to the <100> texture after Rex [29,30]. Figure 16 shows calculated textures in the center region of 90% drawn copper wire taking work hardening per pass into account. The drawing to Rex texture transition was explained by SERM [4]. Since the drawing texture is stable, we consider the [111] and [100] fcc crystals representing the <111> and <100> fiber orientations constituting the texture. Figure 17 shows tetrahedron and octahedron consisting of slip planes (triangles) and slip directions (edges) for the [111] and [100] fcc crystals. The slip planes are not indexed to avoid complica‐ tion. The slip-plane index can be calculated by the vector product of two of three slip directions (edges) of a triangle constituting the slip-plane triangle. It follows from Figure 17a that three active slip directions that are skew to the [111] axial direction are [101], [110], and [011]. It should be noted that these directions are chosen to be at acute angles with the [111] direction (Section 2). Therefore, AMSD // ([101] + [110] + [011]) = [222] // [111]. That is, AMSD is along the axial direction. According to SERM, AMSD in the deformed matrix is along MYMD in the Rexed grain. MYMDs of most of fcc metals are <100>. Therefore, the <111> drawing texture changes to the <100> Rex texture. Now, the evolution of <100> Rex texture in the <100> deformed matrix is explained. Eight active slip systems in fcc crystal elongated along the [100] direction are calculated to be (111)[1 0-1], (-111)[101], (1-1 1)[110], (1 1-1)[1-1 0], (111)[1-1 0], (-111)[110], (1-1 1)[10-1], and (1 1-1)[101], if the slip systems are {111}<110> [32]. It is noted that the slip directions are chosen to be at acute angles with the [100] axial direction. These slip systems are shown in Figure 17 b. AMSD is obtained, from the vector sum of the active slip directions, to be parallel to [100], which is also MYMD of fcc metals. Therefore, the <100> drawing texture remains unchanged after Rex (1st priority in Section 2), and the <111> + <100> orientation changes to <100> after Rex, regardless of relative intensity of <111> to <100> in the deformation texture. The <100> grains in deformed fcc wires are likely to act as nuclei for Rex. The texture change during annealing might take place by the following process. The <100> grains retain their deformation texture during annealing by continuous Rex, or by recoverycontrolled processes, without long-range high-angle boundary migration. The <100> grains grow at the expense of their neighboring <111> grains that are destined to assume the <100> orientation during annealing.

**Figure 16.** Calculated IPFs in centeral axis zone of Cu wire drawn by 90% in 14 passes (~15% per pass) through coni‐ cal-dies of 9° in half-die angle, taking strain-hardening per pass into count [31].

**Figure 17.** Tetrahedron and octahedron representing slip planes (triangles) and directions (edges) in [111] and [100] fiber oriented fcc crystals. Thick arrows show (a) [111] and (b) [100] axial directions.

#### **4.1. Silver**

Cold drawn Ag wires develop major <111> + minor <100> at low reductions (less than about 90%) as do other fcc metals, whereas they exhibit major <100> + minor <111> at high reductions (99%) as shown in Figure 18 [32]. This result is in qualitative agreement with that of Ahlborn and Wassermann [33], which shows that the ratio of <100> to <111> of Ag wires was higher at 100 and -196o C than at room temperature. They attributed the higher <100> orientation to Rex and mechanical twinning, because Ag has low stacking fault energy. They suggested that the <111> orientation transformed to the <115> orientation by twinning, which rotated to the <100> orientation by further deformation.

The hardness of deformed Ag wires as a function of annealing time at 250 and 300 o C indicated that Rex was completed after a few min. This was also confirmed by microstructure studies [32]. Figure 18 shows the annealing textures of drawn Ag wires of 99.95% in purity, which shows that drawing by 61 and 84% and subsequent annealing at 250 o C for 1 h gives rise to nearly random orientation. Ag wires with the <111> + <100> deformation texture develop Rex textures of major <100> and minor <111>, or major <100> + its twin component <122> and minor <111>. The almost random orientation can be seen in Figures 19 d. Figure 20 shows the IPFs of 99% drawn 99.99% Ag wire annealed at 600 ℃ for 1 min to 200 h. Their microstructures showed that the specimen annealed at 600 o C for 1min is almost completely Rexed. The specimen has major <100> + minor <111> as the specimens annealed at 300 o C. After annealing at 600 o C for 3min, some grains showed abnormal grain growth (AGG), indicating complete Rex, and the intensity of <100> component increased. However, as the annealing time incresed, the orientation density ratio (ODR) of <111> to <100> increased, accompanied by grain growth. It is noted that the annealing texture is diffuse at the transient stage from <100> to <111> (5 min in Figure 20 and Figure 19d). The <100> to <111> transition is associated with AGG in low dislocation-density fcc metals, which has been discussed in [31,32]. The Rex results before AGG lead to the conclusion that the Rex texture of the heavily drawn Ag wires is <100> regardless of relative intensity of <111> and <100>, as expected from SERM.

state. Park and Lee [35] studied drawing and annealing textures of a commercial electrolytic tough-pitch Cu of 99.97% in purity. A rod of 8mm in diameter, whose microstructure was characterized by equiaxed grains having a homogeneous size distribution, was cold drawn by 90% reduction in area in 14 passes through conical dies of 9° in half-die-angle with about 15% reduction per pass. The drawing speed was 10 m/min. The drawn wire was annealed in a salt bath at 300 or 600 °C and in air, argon, hydrogen or vacuum (< 1x10-4 torr) at 700 °C for various periods of time. Figure 21 shows orientation distribution functions (ODFs) for the 90% drawn Cu wire. The drawing texture can be approximated by a major <111> + minor <100> duplex fiber texture. The orientation density ratio of the <111> to <100> components is about 2.6. The

<sup>b</sup> a c <sup>d</sup> <sup>100</sup>

**Figure 18.** IPFs of (a) 61, (b) 84, (c) 91, and (d) 99% drawn Ag wires (initial texture: random) of 99.95% in purity (top)

**Figure 19.** IPFs of 99.99% pure Ag wires (a) drawn by 90% and (b) annealed at 300 °C for 1 h; (c) drawn by 99% and

min 1 min 3 min 5 min 60 min 12000

**Figure 20.** IPFs of 99.99% Ag wire drawn by 99% and annealed at 600 °C for 1-12000 min [32].

111

110 100

111

http://dx.doi.org/10.5772/54123

19

Recrystallization Textures of Metals and Alloys

110

110

111

111

110

100

110

110 100

a b c d

111

110

100

111

100

111

before and (bottom) after annealing at 250 °C for 1 h [32].

110

111

100

(d) annealed at 300 °C for 1 h [32].

100

orientation densities were obtained by averaging the f(g) values on the [*φ*1=0-90o

, Φ=0<sup>o</sup> ,

#### **4.2. Aluminum, copper, and gold**

Axisymmetrically extruded Al alloy rod [34], drawn Al wire [30] and Cu and some Cu alloy wires [29] generally have major <111> + minor <001> double fiber textures in the deformed

[101]

18 Recent Developments in the Study of Recrystallization

**4.1. Silver**

100 and -196o

orientation by further deformation.

that the specimen annealed at 600 o

**4.2. Aluminum, copper, and gold**

[111]

10]1[

fiber oriented fcc crystals. Thick arrows show (a) [111] and (b) [100] axial directions.

1]1[0

01]1[

a b

[011] [110]

1]1[0

C indicated

C for

C for 1 h gives rise to

C. After annealing at 600 o

[100]

C for 1min is almost completely Rexed. The specimen has

[110]

[101]

]1[10

0]1[1

1]1[0

[011]

C than at room temperature. They attributed the higher <100> orientation to Rex

**Figure 17.** Tetrahedron and octahedron representing slip planes (triangles) and directions (edges) in [111] and [100]

Cold drawn Ag wires develop major <111> + minor <100> at low reductions (less than about 90%) as do other fcc metals, whereas they exhibit major <100> + minor <111> at high reductions (99%) as shown in Figure 18 [32]. This result is in qualitative agreement with that of Ahlborn and Wassermann [33], which shows that the ratio of <100> to <111> of Ag wires was higher at

and mechanical twinning, because Ag has low stacking fault energy. They suggested that the <111> orientation transformed to the <115> orientation by twinning, which rotated to the <100>

that Rex was completed after a few min. This was also confirmed by microstructure studies [32]. Figure 18 shows the annealing textures of drawn Ag wires of 99.95% in purity, which

nearly random orientation. Ag wires with the <111> + <100> deformation texture develop Rex textures of major <100> and minor <111>, or major <100> + its twin component <122> and minor <111>. The almost random orientation can be seen in Figures 19 d. Figure 20 shows the IPFs of 99% drawn 99.99% Ag wire annealed at 600 ℃ for 1 min to 200 h. Their microstructures showed

3min, some grains showed abnormal grain growth (AGG), indicating complete Rex, and the intensity of <100> component increased. However, as the annealing time incresed, the orientation density ratio (ODR) of <111> to <100> increased, accompanied by grain growth. It is noted that the annealing texture is diffuse at the transient stage from <100> to <111> (5 min in Figure 20 and Figure 19d). The <100> to <111> transition is associated with AGG in low dislocation-density fcc metals, which has been discussed in [31,32]. The Rex results before AGG lead to the conclusion that the Rex texture of the heavily drawn Ag wires is <100> regardless

Axisymmetrically extruded Al alloy rod [34], drawn Al wire [30] and Cu and some Cu alloy wires [29] generally have major <111> + minor <001> double fiber textures in the deformed

The hardness of deformed Ag wires as a function of annealing time at 250 and 300 o

shows that drawing by 61 and 84% and subsequent annealing at 250 o

major <100> + minor <111> as the specimens annealed at 300 o

of relative intensity of <111> and <100>, as expected from SERM.

[011]

**Figure 18.** IPFs of (a) 61, (b) 84, (c) 91, and (d) 99% drawn Ag wires (initial texture: random) of 99.95% in purity (top) before and (bottom) after annealing at 250 °C for 1 h [32].

**Figure 19.** IPFs of 99.99% pure Ag wires (a) drawn by 90% and (b) annealed at 300 °C for 1 h; (c) drawn by 99% and (d) annealed at 300 °C for 1 h [32].

**Figure 20.** IPFs of 99.99% Ag wire drawn by 99% and annealed at 600 °C for 1-12000 min [32].

state. Park and Lee [35] studied drawing and annealing textures of a commercial electrolytic tough-pitch Cu of 99.97% in purity. A rod of 8mm in diameter, whose microstructure was characterized by equiaxed grains having a homogeneous size distribution, was cold drawn by 90% reduction in area in 14 passes through conical dies of 9° in half-die-angle with about 15% reduction per pass. The drawing speed was 10 m/min. The drawn wire was annealed in a salt bath at 300 or 600 °C and in air, argon, hydrogen or vacuum (< 1x10-4 torr) at 700 °C for various periods of time. Figure 21 shows orientation distribution functions (ODFs) for the 90% drawn Cu wire. The drawing texture can be approximated by a major <111> + minor <100> duplex fiber texture. The orientation density ratio of the <111> to <100> components is about 2.6. The orientation densities were obtained by averaging the f(g) values on the [*φ*1=0-90o , Φ=0<sup>o</sup> , *φ*2=45o ] line representing the <100> fiber texture and the [0-90o ,55o ,45o ] line representing <111> in the *φ*2=45o section of ODF. When annealed at 300 and 600 °C, the specimen developed textures of major <100> + minor <111> as expected from SERM. However, after annealing at 700 o C for 3 h, the grain size is so large that the ODF data consist of discrete orientations and the density of the <100> orientation is reduced while the density around the <1 1 1.7> orientation increases drastically. This is due to AGG and not discussed here. Wire drawing undergoes homogeneous deformation only in the axial center region, textures of the center regions were measured using electron backscatter diffraction (EBSD). The EBSD results are shown in Figure 22. The center region of the as-drawn specimen develops the major <111> + minor <100> fiber duplex texture as expected for axisymmetric deformation. The texture of the center region is similar to the gloval texure in Figure 21 because the deformation in wire drawing is relatively homogeneous. The annealing textures obtained at 700 °C is not the primary Rex texture.

Equivalent grain size,

ing (Figure 20).

fective strain of 11.4.

and is more rapid at 400 o

(solid symbols) and 400 °C (open symbols) [36].

function of annealing time at 300 and 400 o

1 10 100 1000 10000 100000

Volume

**Figure 24.** Grain size and volume fraction of ● ○ <111> and ▲△ <100> grains in Au wire vs. annealing time at 300 °C

Figure 23 shows ODR of <100> to <111> of the 90% drawn Cu wire as a function of annealing time at 700 °C. The ratio increases very rapidly up to about 1.8 after annealing for 180 s, wherefrom it decreases and reaches to about 0.3 after 6 h. The increase in the ratio indicates the occurrence of Rex and the decrease indicates the texture change during subsequent grain growth, that is, AGG. A similar phenomenon is observed in drawn Ag wire during anneal‐

Cho et al. [36] measured the drawing and Rex textures of 25 and 30 µm diameter Au wires of over 99.99% in purity, which had dopants such as Ca and Be that total less than 50 ppm by weight. The Au wires were made by drawing through a series of diamond dies to an ef‐

Figure 24 shows the grain size and the volume fraction of the <111> and <100> grains as a

ments. The aspect ratio of grain shape was in the range of 1.5 - 2, which is little influenced by annealing time and temperature [36]. The grain growth occurs in whole area of the wire

grain boundaries. The volume fraction of the <111> grains decreases and that of the <100>

The annealing texture of single-phase crystals of Al-0.05% Si of the Goss orientation {110}<001> deformed in channel-die compression was studied by Ferry et al. [37]. In the channel-die compression, the compression and extension directions were <110> and <001> directions, respectively. Their experimental results showed that, even after deformation to a true strain of 3.0 which is equivalent to a compressive reduction of 95%, the original orienta‐ tion was maintained as shown in Figure 25a. Figure 25b shows one (110) pole figure typical of a deformed crystal after annealing at 300 °C for 4 h. The comparison of Figures 25a and 25b suggests that the annealing texture is essentially the same as the deformation texture.

grains increases with annealing time when Rex takes place, as expected from SERM.

C than at 300 o

**5. Plane-strain compressed fcc metallic single crystals**

**5.1. Channel-die compressed {110}<001> aluminum single crystal**

fraction

0.6

0.8

0.2 0.4

1 10 100 1000 10000 100000

Recrystallization Textures of Metals and Alloys

http://dx.doi.org/10.5772/54123

21

annealing s time,

C. These values are based on EBSD measure‐

C as expected for thermally activated motion of

grains 100 &111except grains

annealing s time,

m

**Figure 21.** ODFs of 90% drawn Cu wire (a) before and after annealing at (b) 300, (c) 600, (d) 700 °C for 3 h, measured by X-ray [35].

**Figure 22.** IPFs for center regions of 90% drawn Cu wires after annealing at 300 and 700oC [35].

**Figure 23.** ODR of <100> to <111> of 90% drawn Cu wire vs. annealing time at 700oC [35].

*φ*2=45o

700 o

in the *φ*2=45o

by X-ray [35].

1

 45 <sup>2</sup>

20 Recent Developments in the Study of Recrystallization

:level 1,1.5,2,2. max3.9 5,3,3.5,

drawn -as

max.26.7

7.6

111

a c

min 1-C300

max.2.8

b

1,1.5,2,2. max3.9 5,3,3.5,

**Figure 21.** ODFs of 90% drawn Cu wire (a) before and after annealing at (b) 300, (c) 600, (d) 700 °C for 3 h, measured

contour 5,10,20 3, 2, 1.5, 1.2, 1,:level

h 3-C300

**Figure 22.** IPFs for center regions of 90% drawn Cu wires after annealing at 300 and 700oC [35].

**Figure 23.** ODR of <100> to <111> of 90% drawn Cu wire vs. annealing time at 700oC [35].

max.4.4

s 30-C700

min 10-C700

max.4.0

max.3.6

100

] line representing the <100> fiber texture and the [0-90o

,55o ,45o

section of ODF. When annealed at 300 and 600 °C, the specimen developed

1,1.5,2,2. max3.4 5,3,

textures of major <100> + minor <111> as expected from SERM. However, after annealing at

C for 3 h, the grain size is so large that the ODF data consist of discrete orientations and the density of the <100> orientation is reduced while the density around the <1 1 1.7> orientation increases drastically. This is due to AGG and not discussed here. Wire drawing undergoes homogeneous deformation only in the axial center region, textures of the center regions were measured using electron backscatter diffraction (EBSD). The EBSD results are shown in Figure 22. The center region of the as-drawn specimen develops the major <111> + minor <100> fiber duplex texture as expected for axisymmetric deformation. The texture of the center region is similar to the gloval texure in Figure 21 because the deformation in wire drawing is relatively homogeneous. The annealing textures obtained at 700 °C is not the primary Rex texture.

] line representing <111>

max44.5 18, 2,6,10,14, d 7.111

1h-C700

max.3.3

**Figure 24.** Grain size and volume fraction of ● ○ <111> and ▲△ <100> grains in Au wire vs. annealing time at 300 °C (solid symbols) and 400 °C (open symbols) [36].

Figure 23 shows ODR of <100> to <111> of the 90% drawn Cu wire as a function of annealing time at 700 °C. The ratio increases very rapidly up to about 1.8 after annealing for 180 s, wherefrom it decreases and reaches to about 0.3 after 6 h. The increase in the ratio indicates the occurrence of Rex and the decrease indicates the texture change during subsequent grain growth, that is, AGG. A similar phenomenon is observed in drawn Ag wire during anneal‐ ing (Figure 20).

Cho et al. [36] measured the drawing and Rex textures of 25 and 30 µm diameter Au wires of over 99.99% in purity, which had dopants such as Ca and Be that total less than 50 ppm by weight. The Au wires were made by drawing through a series of diamond dies to an ef‐ fective strain of 11.4.

Figure 24 shows the grain size and the volume fraction of the <111> and <100> grains as a function of annealing time at 300 and 400 o C. These values are based on EBSD measure‐ ments. The aspect ratio of grain shape was in the range of 1.5 - 2, which is little influenced by annealing time and temperature [36]. The grain growth occurs in whole area of the wire and is more rapid at 400 o C than at 300 o C as expected for thermally activated motion of grain boundaries. The volume fraction of the <111> grains decreases and that of the <100> grains increases with annealing time when Rex takes place, as expected from SERM.
