Microstructural fingerprints of phase transitions in shock-loaded iron
S.J. Wang1, M.L. Sui2,*, Y.T. Chen3, Q.H. Lu1, E. Ma4, X.Y. Pei3, Q.Z. Li3, and H.B. Hu3
1
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese
Academy of Sciences, Shenyang 110016, China
2
Institute of Microstructure and Property of Advanced Materials, Beijing University of
Technology, Beijing 100124, China
3
Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900,
China
4
Department of Materials Science and Engineering, Johns Hopkins University, Baltimore,
Maryland 21218, USA
Supplementary Materials Includes:
Figs. S1, S2, S3, S4, S5, S6.
Tables S1, S2, S3.
Fig. S1: Microstructure of the whole shocked α-Fe grain for Fig. 2a. It includes 58
bright-field TEM images. A number of needle-type colonies mainly along two directions are
seen in the grain. The white line shows the grain boundary. Across the grain boundary, the
needle-type colonies in the neighboring grains present different orientations.
Fig. S2 One of the original TEM images of Fig. 2a without the demarcation line on the
needle-like regions. The enlarged detail shows the clear boundaries of the needle-like colony.
The red arrow indicates a small-angle boundary. Its SADP is presented in the inset.
Fig. S3: Microstructure of a shocked grain with the shock pressure direction deviating
from [001]bcc by a large angle of 30°. PTZ stands for the phase transition zone. D112T and
D332T stand for {112} and {332} deformation twins, respectively. The red arrow stands for
the projection direction of shock pressure in the observed (110)bcc plane.
In this grain, both plastic deformation and phase transition occur. The deformation twins form
along the (1-12)[-111]bcc system, for which the Schmid factor (0.39) is high, whereas phase
transition with characteristic threefold symmetry occurs only along the (-112)bcc plane
(Schmid factor is as low as 0.08 for (-112)[1-11]bcc ). For the deformation twins, the
maximum tilt angle φ of (1-12)T and (1-12)M planes is less than 2°, which is very different
from those stemming from phase transition with φ≈5°.
With the shock pressure different in every single grain in polycrystalline iron, the
morphology of the needle-like microstructure is different, but the phase transition characters
and phase transition mechanism remain the same.
Fig. S4: Experimental setup. (a) A schematic of the iron hollow cylindrical sample under
shock wave. (b) A top-view schematic of the hollow cylinder under shock-loading. The shock
wave proceeds in the radial direction of the cylinder, labeled by the purple arrows. A VISAR
was used to record the inner free surface velocity. (c) A top-view image of the experiment
setup before filling PETN.
Fig. S5: The inner free surface velocity recorded by VISAR equipment.
Fig. S6 Pressure calculations. (a) The calculated pressure history of the points at 4.6, 1.9,
1.2 mm in the experiment. (b) The inner free surface velocity curve from the calculation, in
comparison with the experiment.
The details of the statistical analysis on the angle φ and volume fraction transformed (F).
The angle φ values in Table S1 are measured in twenty diffraction patterns which were
obtained from boundaries of needle-like colonies. Statistical analysis gives the mean value
and standard deviation value. Table S2 shows the F value measured from several different
grains in the locations at radius ~1.2 mm. The corresponding peak pressure here is ~14.2 GPa.
Table S3 shows the measured F at ~1.9 mm, ~13.3 GPa.
The angle φ measured in twenty diffraction patterns.
Table S1
φ (°)
4.9
5.6
5.8
5.4
4.5
5.4
4.2
5.0
5.3
5.3
4.2
4.3
6.0
5.9
4.2
4.7
5.3
6.7
6.2
4.6
Table S2
52.3
53.8
59.2
Table S3
53.6
54.9
58.6
28.2
5.175
0.72684
54.7
mean
standard deviation
54.5625
3.18969
Measured F at ~1.9 mm (~13.3GPa).
F (under ~13.3 GPa, %)
27.3
standard deviation
Measured F at ~1.2 mm (~14.2 GPa).
F (under ~14.2 GPa, %)
49.4
mean
23.1
26.3
30.7
mean
standard deviation
27.12
2.77705