and ND directions. For the TD direction, the Schmid factors of 4Bc
sample were zero, and that of the other 3 samples were very close
to zero, which indicated that it was difficult to start the basal slip
systems in the TD direction during the tensile testing. For the ED
direction, the Schmid factors were also close to zero except for the
4Bc sample, which had greater values of 0.4523 in 1120̅ and
0.3534 in 1210̅ . Opposite numbers of Schmid factors were observed
in ND directions of 4Bc sample, which coincided with the
50.5° intersection angle of ( ) 0001 basal plane with the observation
plane. The rotation of the ( ) 0001 basal plane was close to the shear
plane and was raised to a higher Schmid factor of basal slip, which
led to easier dislocation movements on the predominant slip plane
of ( ) 0001 . Thus, it was easily understood that the yield strength in
ED and ND directions were lower than that in the TD direction for
sample 4C, which is shown in Fig. 4c.
The Schmid factors for 4A, 4Ba and 4C samples in the TD, ED
and ND directions were all very close to zero (but not zero). This is
attributed to the ( ) 0001 basal plane parallel with the observation
plane in spite of the crystal direction. Sample 4A showed that
there was a reverse relationship between the YS and sum of
Schmid factor in basal slip systems [24]. The relationship was also
suitable for 4Bc and 4C samples, as shown in Fig. 7b and c, respectively.
It can be concluded that the main deformation system
of tensile test at room temperature for 4Bc and 4C samples was
still the basal slip. In sample 4Ba (Fig. 7a), the reverse relationship
between yield strength and Schmid factor sum of basal slip system
did not play a role. For sample 4Ba, the YS in the TD direction—
which had a basal slip systems Schmid factor sum of 0.194—was
and ND directions. For the TD direction, the Schmid factors of 4Bcsample were zero, and that of the other 3 samples were very closeto zero, which indicated that it was difficult to start the basal slipsystems in the TD direction during the tensile testing. For the EDdirection, the Schmid factors were also close to zero except for the4Bc sample, which had greater values of 0.4523 in 1120̅ and0.3534 in 1210̅ . Opposite numbers of Schmid factors were observedin ND directions of 4Bc sample, which coincided with the50.5° intersection angle of ( ) 0001 basal plane with the observationplane. The rotation of the ( ) 0001 basal plane was close to the shearplane and was raised to a higher Schmid factor of basal slip, whichled to easier dislocation movements on the predominant slip planeof ( ) 0001 . Thus, it was easily understood that the yield strength inED and ND directions were lower than that in the TD direction forsample 4C, which is shown in Fig. 4c.The Schmid factors for 4A, 4Ba and 4C samples in the TD, EDand ND directions were all very close to zero (but not zero). This isattributed to the ( ) 0001 basal plane parallel with the observationplane in spite of the crystal direction. Sample 4A showed thatthere was a reverse relationship between the YS and sum ofSchmid factor in basal slip systems [24]. The relationship was alsosuitable for 4Bc and 4C samples, as shown in Fig. 7b and c, respectively.It can be concluded that the main deformation systemof tensile test at room temperature for 4Bc and 4C samples wasstill the basal slip. In sample 4Ba (Fig. 7a), the reverse relationshipbetween yield strength and Schmid factor sum of basal slip systemdid not play a role. For sample 4Ba, the YS in the TD direction—which had a basal slip systems Schmid factor sum of 0.194—was
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