Affiliation:
1. Università Politecnica delle Marche
Abstract
Microstructure evolution with equal channel angular pressing (ECAP) using route Bc,
that is a 90° axial rotation of the billet between passes, up to 8 passes, was investigated by
transmission electron microscopy. The study has been focused on the induced development of
boundary misorientation and spacing toward microstructure refinement. Cell (low-angle) and grain
(high-angle) misorientation and spacing were determined from about 250 boundaries per pass of
ECAP, systematically using whether Kikuchi patterns or Moiré fringes, these latter where possible.
The average cell size and misorientation saturate within the first two passes. Misorientation and
spacing of high-angle boundaries decrease with the number of passes. After 8 passes, mean cell size
is ≈ 1.3 µm and the fraction of high-angle boundaries is ≈ 0.7. Differences in rate of grain structure
evolution per pass are linked to differences in ability of dislocations introduced in new passes to
recombine with the existing ones. As ECAP strain rises, the misorientation distribution develops
strong deviations from the MacKenzie distribution for statistical grain orientation. This is
interpreted as a result of the tendency to form equiaxed grains in a textured grain structure.
Publisher
Trans Tech Publications, Ltd.
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics,General Materials Science
Cited by
3 articles.
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