<div>(1)</div><div>where, <i>r</i> = radius of the disc (mm), <i>h</i> = height if disc
(mm), <i>φ</i> = angle of rotation (radians) and <i>ԑ</i> = equivalent
strain value.</div><div>According to the equation the strain is directly proportional to the
radius of the disc, which indicates that at the centre the strain is
ideally zero, whereas the strain is highest at the edges of the disc.
The development of microstructure and mechanical properties have been
intensely investigated by various authors on many pure and commercially
pure (CP) metals during monotonous deformation [4-11]. Addition of
metals like Magnesium in pure Aluminium results in increase in the
strength of alloy as Mg influences dislocation generation and work
hardening [12, 13]. In addition to it, Al-Mg alloy has a lower
propensity for dynamic recovery as compared to CP Aluminium. Studies
have shown that the addition of Mg has a considerable amount of effect
on mechanical properties and microstructure during HPT processing [14,
15].</div><div>The stain path change during HPT can be easily achieved by monotonous
and reversal strain deformation through the combination of monotonous
(CW) and subsequent strain reverse rotation (CW-CCW) (Fig. 1). The
strain path change in the HPT process is a continuous process and the
sample remain in the equipment throughout the processing operation.</div>