PSI - Issue 21

O. Berk Aytuna et al. / Procedia Structural Integrity 21 (2019) 120–129 O. Berk Aytuna et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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a)

c)

b)

Loading direction

PLC Bands

Shear Band

Fig. 7. SEM images of (a) formed shear bands after uniaxial tension, (b) fracture surface after uniaxial tension, and (c) fracture surface after biaxial tension.

EBSD ana lysis shows the deformation microstructures and textures for both stra in paths a t a constant equiva lent stra in, ε eq = 0.18. In biaxia l stretching, deformation texture is brass (Fig. 8 and b), para llel to the observations in litera ture (Banovic and Foecke (2003)). The brass texture is not far off from the initia l copper texture. In uniaxia l condition, on the other hand, an increase in cube component of the texture is obvious. The initia l copper texture evolves into a cube texture after sufficient deforma tion as shown in Fig. 8c and 8d. Therefore, it is once aga in proved tha t the shear bands domina te the deforma tion in uniaxia l condition. Since the cube texture component is a result of shear-based deforma tion in a luminum a lloys, the increase in this texture component expla ins the re la tionship between PLC and shear bands. The texture change in the materia l is not due to a single PLC band, but ra ther a collection of them, wh ich evolve into the shear bands. The combina tion of the shear bands with the stra in pa th is responsible from the significant change in texture. The cube component of the uniaxia l condition is clearer when the EBSD ana lysis was done on the formed shear band shown in Fig. 9. The EBSD resu lt from the shear band conta ins many black spots, where the diffraction qua lity was poor. This is due to the high deforma tion amounts ( ε > 0.3) within the band, which limits the qua lity of the da ta . However, the rema ining da ta is enough to confirm that the {001}<100> texture component is activated in uniaxia l loading due to the shear bands. Lack of full-sca le PLC bands and the shear bands in biaxia l stretching prevents this kind of texture change and keeps the initia l texture with minor changes.

a)

b)

c)

Loading direction

d)

Fig. 8. EBSD analysis of the specimen (a) grain orientation map (b) 111 pole figure after equibiaxial loading, (c) grain orientationmap (d) 111 pole figure after uniaxial loading.