PSI - Issue 19

Shota Hasunuma et al. / Procedia Structural Integrity 19 (2019) 194–203 Shota Hasunuma, Ogawa Takeshi/ Structural Integrity Procedia 00 (2019) 000 – 000

197

4

The microstructure of the machined surface layer was observed by electron backscatter diffraction (EBSD). EBSD measurements were performed with an ERA-8900FE field emission scanning electron microscope (Elionix, Kanagawa, Japan) equipped with an EDAX-Digi View orientation image microscopy (OIM) detector (Elionix). The OIM data were obtained using TSL OIM Data Collection 5.1 software. Specimens were cut along a radial-axial plane and machined surface was observed. Observation of No. 1 and 4 specimens are shown in Fig. 6. Fig. 6(a) shows the crystal orientation of the machined surface layer. In the layer pointed by the red arrow in Fig. 6(a), the crystal direction was determined randomly. Crystal grains of this layer were refined strongly by hard working and the grain size was small; Hasunuma et al., (2015). The depth of this layer in No. 1 is larger than that in No. 4. Fig. 6(b) shows the grain boundary map. There was much low-angle grain boundary in the area under the layer in Fig .6(a) pointed by the red arrow. Crystal grains of this layer were refined because geometrically necessary (GN) dislocation was increased by hard working and sub-grains were generated. Depth of this layer in No.1 is also larger than that in No.4.

150

A

B

(b)

(c)

(a)

100

50 Position,  m

(b)

A-A' B-B'

Loading direction

20  m

300  m

A’

B ’

−5 0

0 5

Hight,  m

Fig.5 Observation of scratch of No.4 using laser micrograph(a). (b) is close up image. Sectional configuration of surface on the A-A' and B-B' lines(c).

Radial direction

50 µm

Loading direction

No.1

No.4

(b)Grain boundary No.1

No.4

No.1

No.4  m

(a)IPF

(c)GROD

100 µm (d)Low magnification image of No.1 ’s GROD distribution

111

0 ~ 0.98 0.98 ~ 1.97 1.97 ~ 2.95 2.95 ~ 3.93 3.93 ~

2 ～ 5 ° 5 ～ 15 ° 15 ～ 180 °

001

101

Fig.6 Microstructure observation using electron back scatter diffraction pattern.