ESR%20Presentation

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NATIONAL ACADEMY OF SCIENCES OF UKRAINE
EXPLOSIVE CLADDING OF BRITTLE REFRACTORY METALS
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Explosive Cladding of Brittle Refractory
Metals S.Yu. Illarionov, L.D. Dobrushin, S.D.
Ventsev, H.D. Groeneveld
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Considered as refractory metals because of their
melting point is more than 2200C
Mo W
Subject of our interest They are highly demanded
by different high-tech industries as coatings
BUT THEY ARE RELATIVE BRITTLE
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Low temperature heating prevents crack forming
in the interface
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Friction stir weld in high-strength Al alloy 7010
was destroyed when explosively clad and just with
hammer
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Successfully clad at 150
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Some materials, especially metals
with body-centered cubic lattice, have relatively
narrow brittle-ductile transition temperature
range
The simplest explanation scheme
of brittle-ductile transition effect 1
Ultimate tensile strength 2 Yield strength
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The brittle-ductile transition temperature is not
a constant for certain metal or alloy. It depends
on many factors.
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Increasing of the thickness of a cladding plate
leads to moving the brittle-ductile transition
temperature to the higher values. This can be
explained, firstly, by the fact that passage of
plastic deformation in the thicker metal is more
difficult, especially in the central part of the
plate. Secondly, the thicker plate, the higher
probability of the presence of rolling defects.
These factors impede the movement of dislocations
and, consequently, make the metal more brittle
Molybdenum
Cracks
Cracks
Copper
1 mm thickness Mo clad to copper at ambient
temperature
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1 mm thickness molybdenum successfully clad to
copper at 60C
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1000 x 600 mm copper-molybdenum plate
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0.5 mm thickness tungsten clad to copper at
ambient temperature
1 mm thickness tungsten clad to copper at 400C
0.5 mm thickness tungsten clad to copper at 400C
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Increasing the deformation velocity of a cladding
plate leads to moving the brittle-ductile
transition temperature to the higher values. The
simplified explanation is that increasing
deformation velocity leads to increasing dynamic
tensile strength and dynamic yield strength.
However, the last one grows much faster, so the
difference between them decreases. In this case,
materials becomes more brittle under explosion
loading and higher temperature is required to
avoid cracks.
Dynamic YS relative deformation
velocity dependence for low carbon steel
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0.5 mm thickness tungsten clad to copper at 400C
when D 4000 m/s
0.5 mm thickness tungsten clad to copper at 400C
when D 2000 m/s
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Cracking occurs during explosive cladding
at ambient temperature
Toughness temperature dependence test
procedures at 20400C Making tests above
400C is not reasonable
Explosive welding must be done at the
temperature 50100C higher than it was found
with toughness tests
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