The study of
mushy
-
zone
deformation in steels is importan
t for
limit
ing
defect formation in
continuous casting. Here, we use
in situ
synchrotron radiography to
quantify the shear
deformation mechanisms of
a
n equiaxed
carbon steel at
a
solid
fraction >0.9
and to understand
how these mechanisms lead to casting defects
. We show that the grain assembly undergoes
shear
-
induced dilation
(Rey
nolds’
dilatancy)
which
opens liquid
-
filled fissures
and
cracks
at
high solid fraction
. We further show a
complex interaction between grain rearrangement, grain
deformation and local coarsening, where rearrangement
reduces
the grain
-
grain contact area
and
coordination number which alters the stress network
and
also
drives coarsening
as grains
move apart.