Grain orientation evolution and texture fluctuation effect of pure copper during equal channel angular pressing

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1 Vol.21 No.2 The Chinese Journal of Nonferrous Metals Feb (2011) , ( ) XRD EBSD (ECAP) (99.9%) A 101 (40 ) TG376.3 A Grain orientation evolution and texture fluctuation effect of pure copper during equal channel angular pressing GUO Ting-biao, DING Yu-tian, YUAN Xun-feng, HU Yong (Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou , China) Abstract: The polycrystalline samples of pure Cu (99.9%, mass fraction) were processed at room temperature by equal-channel angular pressing (ECAP). The microstructure and its changing mechanism after ECAP were investigated by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The results indicate that when the pure copper is extruded by route A, with the increase of strain, the original 101 texture decreases coupled with the grains refinement, and the distribution uniformity of copper is improved. With the increase of the fraction of high-angle grain boundaries (HAGBs), the peak of misorientation moves to the typical value (40 ), gradually becomes normal distribution, and the misorientation gradient decreases. The formation of texture shows a texture fluctuation effect when ECAP is a dynamic process, the direction and strength of which are closely related to the strain of the material. The texture fluctuation effect is the integrated reflection of crystal structure grain boundary character, aggregation state at a certain temperature and under the action of forces. The external force acting on crystal class then makes the segregation orientation change, in the process of internal stress transmited on the neighboring grain boundaries, the aggregation state is broken, which cause the new texture of the material interior to vanish or appear. Key words: equal channel angular pressing; electron back-scattered diffraction; grain orientation; grain boundary misorinetation distribution; texture fluctuation (SPD) [1] SPD (SB ) ( ) dingyt@int.com

2 [2] ( ) [3] SPD 111 //ND( normal direction) FCC 111 //ND SPD [4] (ECAP) SPD [5] ECAP A B C B Ba Bc [6 8] (ECAP) ( ) [9] [10] ECAP [11 13] ECAP XRD EBSD ( )ECAP A 1 ECAP 1 2 MoS 2 YT A N 10 MPa 25 mm/s 1 ECAP Fig.1 Assembly drawing of ECAP die-set: 1 Installation board; 2 Location pole; 3 Location sheathing; 4 Outside sheathing; 5 Inside sheathing; 6 Mandril location board; 7 Crest slab; 8 Upper moulding board; 9 Bolt; 10 Mandril; 11 Installation board; 12 Pin T2 70 mm Φ=105 Ψ= # 800 # 1000 # 1200 # 2000 # EBSD 500 ml +250 ml ml +50 ml +5 g 20~35 4 V 6~8 min D8 ADVANCE X XRD EBSD Nordlys EBSD Channel 5 FEI TOUANATA (0.15~2 µm )

3 µm 600 µm 4 (H) (Z)XRD XRD 2 ECAP A (111) 2 (111) (200) (220) 2 (111) (311) (222) 2 2 A XRD Fig.2 XRD patterns of pure Cu ECAP by route A (H: Transverse; Z: Normal): (a) H, 0 pass; (b) Z, 0 pass; (c) H, 1 pass; (d) Z, 1 pass; (e) H, 2 passes; (f) Z, 2 passes; (g) H, 4 passes; (h) Z, 4 passes

4 (111) (200) 2.2 EBSD X [11] 3 ECAP EBSD ( Euler ) µm µm 1 4 4(d) 4 ECAP A {111} XO (Normal direction ND ) YO (Extrution direction ED) 4 1 ( A ) 2 A 4 ( B ) A B EBSD EBSD [13] SPD XRD ECAP 3 EBSD Fig.3 EBSD orientation maps of samples ECAP after different passes (sample surface parallel to extrusion axis): (a) 0 pass; (b) 1 pass; (c) 4 passes; (d) 4 passes

5 ( ) 5(b) B ECAP ECAP 4 {111} Fig.4 {111} pole figures of samples ECAP after different passes (sample surface parallel to extrusion axis): (a) Initial condition; (b) 1 pass; (c) 2 passes; (d) 4 passes ECAP 5(a) 3 [14] ( ) ( ) ECAP ( ) EBSD ( ) ECAP : 5 ECAP Fig.5 ECAP strain subarea(a) and two grains(b) with different orientations A (111) (200) (220) (311) 3

6 (111) (111) 6 ECAP EBSD (d) A ECAP Fig.6 Inverse pole figures of samples in initial condition(a) and ECAP after 1 pass(b), 2 passes(c) and 4 passes(d) ECAP EBSD 7 7 Cu ECAP Fig.7 Misorientation angle distribution of Cu samples ECAP after different passes by route A: (a) Initial; (b) 1 pass; (c) 4 passes; (d) 8 passes

7 ~ [15 16] (40 ) ( ) 4 1) A ECAP ) 3) 4) 5) REFERENCES [1] XU C, LANGDON T G. The development of hardness homogeneity in aluminum and aluminum alloy processed by ECAP[J]. J Mater Sci, 2007, 42: [2],,. [J]., 2006, 16(9): YUN Xin-bing, SONG Bao-yun, CHEN Li. Ultra-fine grain copper prepared by continuous equal channel angular press[j]. The Chinese Journal of Nonferrous Metals, 2006, 16(9): [3],,. [M]. :, MAO Wei-min, YANG Ping, CHENG Leng. Material texture analysis principle and testing technology[m]. Beijing: Metallurgical Industry Press, [4] AZDIAR A G, CAO W Q, CHRISTOPHER H J D. An EBSD investigation of interstitial-free steel subjected to equal channel angular extrusion[j]. Materials Science and Engineering A, 2008, 497(1/2): [5] VALIEV R Z, ISLAMGALIEV R K, ALEXANDROV I V. Bulk nanostructured materials from sever plastic deformation[j]. Progress in Materials Science, 2000, 45(2): [6] SHIH M H, YU C Y, KAO P W, CHANG C P. Microstructure and flow stress of copper deformed to large plastic strains[j]. Scripta Mater, 2001, 45(7): [7] YOON S C. Preform effect on the plastic deformation behavior of workpieces in equal channel angular pressing[j]. Scripta Mater, 2006, 55(4): [8],,,. AZ31 [J]., 2005, 15(9): CHENG Yong-qi, CHEN Zhen-hua, XIA Wei-jun, FU Ding-fa. Microstructure and mechanical properties of AZ31 magnesium alloy sheet processed by equal channel angular rolling[j]. The Chinese Journal of Nonferrous Metals, 2005, 15(9): [9],,,,. ECAE [J]., 2000, 36(6): WU Shi-ding, LI Qiang, JIANG Chuan-bin, LI Guang-yi, WANG Zhong-guang. Shear characteristics of copper single crystal during equal channel angular extrusion[j]. Acta Metallurgica Sinica, 2000, 36(6): [10],,,, BUKSA M, KUNZ L. [J]., 2007, 43(5): WANG Qing-juan, XU Chang-zheng, ZHENG Mao-sheng, ZHU Jie-wu, BUKSA M, KUNZ L. Fatigue property of

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