Inhomogeneous deformation of {111} grain in cold rolled tantalum

doi:10.1016/j.jmst.2018.03.015

Abstract

Abstract:

The microstructures of {111} grain were characterized in detailed and systematically investigated with the aid of electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). The stored energy in different regions in the grain was evaluated by the band contrast values collected from EBSD. The results show that the distribution of energy is inhomogeneous through the grain. Especially, the regions containing the least and the largest energy were extracted from the EBSD data, and then quantitatively analyzed based on the misorientation and Schmid factor. Many peaks with large misorientation appeared in the region containing larger energy, and these peaks represent the existences of micro-bands and micro-shear bands in {111} grain. The results of Schmid factor suggest that the region containing larger energy is prone to deforming ahead of the region with less stored energy, implying the more serious subdivision of the microstructure of region with larger stored energy.

Key words: Tantalum, Stored energy, Misorientation, Schmid factor

Yahui Liu, Shifeng Liu, Chao Deng, Haiyang Fan, Xiaoli Yuan, Qing Liu. Inhomogeneous deformation of {111} grain in cold rolled tantalum[J]. J. Mater. Sci. Technol., 2018, 34(11): 2178-2182.

Figures/Tables 9

Table 1 Chemical composition of high purity Ta ingot (wt ppm).

C	N	H	O	Nb	Mo	W	Ti	Si	Fe	Ni	Ta
9	20	2	30	6.4	0.14	0.61	<0.001	<0.005	<0.005	<0.005	Balance

Fig. 1. Orientation imaging map (OIM) for grains after 87% rolled. (a) OIM for 87% rolled sample, (b) the region R1 in Fig. 1(a), (c) the kernel average misorientation (KAM) for R1 in Fig. 1 (a). Step size 1.2 μm for Fig. 1a, and 35 nm for Fig. 1b and 1c.

Fig. 2. Schematic diagram of the regional division of band contrast (BC) map, 40 blocks in total.

Fig. 3. Energy values for different blocks in horizontal and vertical directions.

Fig. 4. Misorientations corresponding to the testing line in block 4 and block 17, respectively. (a) Misorientation for the line in block 4, (b) Misorientation for the line in block 17.

Fig. 5. Grain boundary map and corresponding grain reference orientation deviation-hyper (GROD-Hyper) for block 4 and block 17, respectively. (a) and (c) are for block 4, (b) and (d) are for block 17.

Table 2 Euler angles and the corresponding maximum Schmid factors (SFmax) of some points.

Block	Point	Eulers (φ1,Φ,φ2)	SF_max
Block 4	P1	(330.2, 40.5, 86.5)	0.4498
	P12	(327.2, 31.5, 80.6)	0.4708
	P23	(322.8, 44.4, 3.7)	0.3974
	P35	(326.6, 37.8, 83.7)	0.4545
	P43	(334.5, 39.8, 79)	0.4658
	P58	(328.9, 44.5, 89.1)	0.4228
	P67	(321.4, 40.1, 86)	0.4303
	P79	(327.4, 35.7, 84)	0.4633
	P96	(333.3, 43.3, 80.6)	0.4507
	P107	(339, 43.1, 79.3)	0.4627
Block 17	P3	(321.2, 42.1, 14.9)	0.4428
	P19	(348.6, 37, 60.2)	0.4613
	P31	(342.7, 34.7, 71.5)	0.4847
	P42	(340.5, 38.4, 82.5)	0.4759
	P58	(340.3, 26.6, 61.4)	0.4548
	P72	(350.4, 32.5, 63.9)	0.4814
	P89	(5.3, 34.1, 44.2)	0.4131
	P97	(175.5, 42.9, 76.3)	0.4844
	P105	(155.7, 36.1, 85.6)	0.4746
	P112	(149.2, 40.4, 85.8)	0.4491

Fig. 6. Schmid factors (SFs) for the points in the lines in block 4 and block 17, respectively.

Fig. 7. TEM observation for the {111} grain.

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