Microstructure Evolution of Beryllium Subjected to

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15 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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Microstructure Evolution of Beryllium Subjected to
Shear
-
Compression Investigated Using Synchrotron
X
-
ray Diffraction



T.A. Sisneros
1
, D. W. Brown
1
, B. Clausen
1
, C.M. Cady
1
, G.T. Gray III
1
,

E. Tulk
1

and J. Almer
2

1
Los Alamos National Laboratory, Los Alamos, New Mexico

2
Argonne National Laboratory, Argonne, Illinois

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Compressive strain transverse to the basal pole.



Basal slip is off, Prismatic slip and tensile twinning are active.



Balance between slip and twin modes affected by strain rate.


High strain rate favors twinning

Low symmetry of hexagonal crystal allows
control of deformation modes

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Discrete crystal
reorientation


Near one
-
to
-
one
switching of 00.2 and
10.0 poles


Monitor with X
-
Ray
diffraction

Crystallography of (10.2)<10.1> twinning in
beryllium

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Texture signature is distinctive feature of
twinning deformation

1/sec

5000/sec

0.0001/sec

As
-
Rolled

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-2000
-1500
-1000
-500
0
-0.2
-0.15
-0.1
-0.05
0
In Plane
Through Thickness
Applied Stress (MPa)
Plastic Strain
500 MPa
The mechanical properties of beryllium can be
very anisotropic

As
-
Rolled

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As
-
Rolled

RN

RD

A

B


Sample A Shear is 45 degrees
from basal pole



May be parallel to twin
plane


Sample B Shear is normal to
basal pole



Rolling of beryllium results in strong
crystallographic texture

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Orientation of crystals with respect to load axis is
critical

(002)

(10.0)

(11.0)

B

A

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Beryllium is brittle at room temperature in tension,
ductility was observed in shear

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Measurements on 1
-
ID at Advanced Photon
Source

h



X
-
ray energy = 65KeV.



Beam cross section: 100mm X 100mm



Collection time: seconds.



Precision translation and rotation stages for mapping.



15kN load frame.



~1200C furnace
.

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We use in
-
situ diffraction to learn about
deformation

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Basal peak intensity begins to increase markedly from the
initial value, signaling the detection of deformation twins

Deformed Slow

Post
-
deformation

Deformed
Fast

Post
-
deformation

Pre
-
deformation

Normalized basal pole intensities (002)
along the loading direction (Long.)

Deformation
twins

Deformation
twins

0.4mm, 0.001/sec

0.2mm,1/sec

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A


B

Pre
-

deformation

Post
-

deformation

Evolution of microstructure dependent upon
orientation of load WRT texture

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A


B

Pre
-

deformation

Post
-

deformation

Evolution of microstructure dependent upon
orientation of load WRT texture

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Conclusions


X
-
ray
diffraction can
be used to monitor
evolution
of microstructure during
deformation.


Deformation
twinning in
hexagonals

has a strong
signal in
X
-
ray diffraction.


Data
is being used to develop and validate rate
dependent polycrystalline plasticity models
.

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