**3.3 Development of Al bi-crystal dislocation structure**

Mechanical Behavior and Plastic Instabilities of Compressed Al Metals

**3.3.1 TEM microstructure observations** 

direction (TD).

and Alloys Investigated with Intensive Strain and Acoustic Emission Methods 275

decomposition from the initial stages of deformation by rotation around the transverse

The examinations in the micro and mezzo- scale were focused on the structure and texture analyses carried out using transmission (TEM) and scanning (SEM) electron microscopy. In both cases, the observations were correlated with measurements of local orientations changes with the use of *convergent beam electron diffraction* (CBED) and *electron back scattered diffraction* (EBSD) techniques. The TEM orientation measurements were performed using semi-automatic system, while the SEM instrument equipped with field emission gun (FEG)

Fig. 13. Development of dislocation structure observed in TEM in crystallites of Al bi-crystal; (a) and (c) Goss orientation, (b) and (d) shear orientation; total deformation of bi-crystal z≅20%(c) and z≅70%(d). In the Goss orientation traces of planes, on which active slip

The observations of dislocation structure in TEM in each crystallite of the bi-crystal deformed by z≅20% and z≅70% were correlated with the local orientation measurements in

disposed of fully automated system Channe 5TM of HKL Technology firm.

(a) (b)

(c) (d)

systems operated are marked

Fig. 11. AE and force of channel-die compressed Al bi-crystal of {110}<100>/{110}<011> hard/Goss orientation reduced by z≅50%: (a) and corresponding acoustogram (b)

Fig. 12. Behavior of AE and compressive force of bi-crystal of {110}<001>/{100}<011> Goss/shear orientation. The arrows indicate the correlations between AE and drops of force

The Goss {110}<001> orientation remained stable during compression in a broad range of deformations, while the shear {100}<011> orientation was strongly unstable and underwent decomposition from the initial stages of deformation by rotation around the transverse direction (TD).
