Homogeneous deformations Crystallography H. K. D. H. Bhadeshia
body-centred tetragonal cell of austenite austenite body-centred cubic ferrite
contraction expansion
pure strain matrix symmetrical referred to principal axes principal axes are unrotated volume change = determinant of (A S A) =
u v A u v B Similarity transformation
homogeneous deformation leaves points originally in a line, colinear, and lines originally in a plane, coplanar
similarity transformation
s 1 s 1 1 uniaxial dilatation simple shear general invariant-plane strain s=0.26 =0.03
Assignment Find and expression for the magnitude of a vector u in terms of the lattice parameters and angle β in a monoclinic lattice
stretch and rotation
three simultaneous equations solved three times by substituting each eigenvalue in turn
stretch and rotation
Refinement of austenite grain size repeated recrystallisation pancaking Refinement of ferrite grain size nucleation and growth
Smallest size possible in steel ?
Yokota & Bhadeshia, 2004
Pancaking
Singh & Bhadeshia, 1998 courtesy Rongshan Qin, GIFT, POSTECH
u v v = Su
Cross Rolling x x y y first pass second pass rotate 90°
courtesy of Rongshan Qin
Chae, Qin, ISIJ International 49 (2009) 115