Js. Zhou et al., Macro- and microdamage behaviors of the 30CrMnSiA steel impacted by hypervelocity projectiles, MAT SCI E A, 282(1-2), 2000, pp. 177-182
Macro- and microdamage behaviors of a 30CrMnSiA steel under impacts of GCr1
5 steel projectiles have been studied. The results show that, in the impact
velocities of 2.5 similar to 7 km s(-1), hemispherical craters are often f
ormed in semi-infinite targets, and with decreasing the target thickness or
increasing the projectile velocity, the form of craters changes to conical
one, and obvious spall phenomenon occurs on the back face of targets. Dept
h and diameter of craters increase with the projectile velocity, and can be
calculated by the formulas: P-c = 0.47 nu(0)(2/3) and D-c = 0.85 nu(0)(2/3
). Microstructure analyses show that, there are three kinds of microdamages
: microcracks, microvoids and adiabatic shear bands, in the region around t
he crater. The size of the microdamage zone is much larger than that of the
macrodamage one for the medium thick targets, inferring that when studying
the damage behaviors of materials under impacts of hypervelocity projectil
es, attention should also be paid to microdamages besides macrodamages. Adi
abatic transformed shear bands always form networks and shows white contras
t in scanning electron microscope (SEM) micrographs. While, when these tran
sformed shear bands are studied by a SEM attachment in transmission electro
n microscope (TEM), it is found that obvious melt has occurred in the head
of bands. A lot of microcracks have been formed in the tail and many deform
ation shear bands are observed in junctures of transformed bands and the ma
trix. TEM results show that, dislocation cells are the predominant deformat
ion structure ill the region just near the crater, and with increasing the
distance from the crater, the density of dislocation decreases, and disloca
tion tangling is the main feature. Deformation twins are also found in the
region just near the crater, while only micro-twins in individual laths of
martensite are observed in the region a little farther from the crater. (C)
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