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High Dynamic Loading of Materials

Part 2

Erhardt Lach

French-German Research Institute of Saint-Louis, ISL

Materials Behaviour under Impact

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Presentation Outline

Classic armour steels(Quenched and tempered steels)

High Nitrogen Steel (HNS)Ausforming steels

Bainitic steelγ-TiAl

Ti-alloyMMC

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Tailoring of mechanical properties of:

Quenched and tempered steels:

by quenching (hardening) and subsequent tempering

Austenitic steels:

work hardening and annealing

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Shielding against low velocity fragmentsHoog K,. Lach E., Maurer R., Rössner H.: Bericht R 134/86

STRAIN

TEN

SILE

STR

ESS

Thickness of the sheet: 3mm

VI = 300 m/s

Under this condition the more ductil steel alloy NAXTRA shows a better performance than the high strength armour steel XH 129

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Classical armour steelsquenched and tempered steels

Micro structure after hot rolling

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0,00,20,40,60,81,01,21,41,6

1000 1200 1400 1600 1800 2000 2200

Em

σdyn,5%, MPa

300 400 500 600HB30

70 mmquenched and tempered steel

Ballistic Tests on Armour Steel

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0

500

1000

1500

2000

2500

0 0,1 0,2 0,3 0,4 0,5 0,6TRUE STRAIN

TRU

E ST

RES

S

C961, 480-530 HB30C963, 370-420 HB30C962, 250-300 HB30

MPa

10 -4 s -1

10 -4 s -1

10 -4 s -1

4500 s -1

4500 s -1

4500 s -1

Dyn. Compression Tests on Armour Steels

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Micro cracks along the white bands, enrichment of carbid brittle behaviour

backside of crater

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Formation of ASB

ASB and micro cracks

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Austenitic steels: Hadfield-Steel

Chem. composition: 13 % Mn und 1.3 % C

metastable austenitic structure

Recommanded for light-weight armour in: MILTECH 5/2007

Initial hardness: 200 HB

After severe deformation: 500 HB

Strongly strain hardening

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0,4

0,6

0,8

1,0

1,2

250 300 350 400 450 500 550 600

Vickershardness HV30

N-c

onte

nt

% %-N

cold workedsolution-annealed

agedworked at 400°C

shock wave hardening

Tailoring of Nitrogen Alloyed Steel

shock wave hardening

cold working:

rolling, forging

heat treatment

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Comparison of HNS and Armour Steel

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0

500

1000

1500

2000

2500

3000

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

TRUE STRAIN

TRU

E ST

RES

S

solution annealed 280HV30cold worked 380HV30cold rolled 472HV30strain ageing 510HV30

MPa

10 -4 s -12400 s -110 -4 s -1

10 -4 s -1

2000 s -1

4300 s -1

3000 s -1

Compression Test on HNSP900 (0.6 % N)

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0,0

0,4

0,8

1,2

1,6

2,0

2,4

0 200 400 600 800 1000Vickershardness HV30

Fm

a rmour steelcold working steel

P900: cold work hardened

P900 work hardened at 400 ° C

2 3

Cold worked and annealed very brittle under impact condition

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Ballistic Test without Cover Plate and Backing

Target NATO 60°

1. Plate: armour steel, treated to 530 HV30

2. Platte: HNS P900, forged at 400 °C to 500 HV30

The ballistic performance of both plates is identical

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P900 plate after test without cover plate

High density of ASBPlate was impacted in the transient and at the onset of steady state region

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The plate was impacted in the steady state region. Melting of material in ASB‘s.

Nr. 2 at 14

P900 plate after test with cover plate

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Micromechanism of HNS

no formation of deforming martensitemicro structure is absolutely stable

n =n = 0

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0,00,20,40,60,81,01,21,41,61,82,02,22,4

0 500 1000 1500 2000 2500 3000 3500Dyn. Compression Strength(10%)

Fm

MPa

Armor steelColdworking steelP900

forged at 400 °C

coldrolled

Fm vers. dyn. Compression Strength

Nr. 2 at 14

Nr. 3 at 14

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4 mm 3 mm 4 mm

2 mm 3 mm 1 mm 3 mm 2 mm

Layered Armour(japanese sword)

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Very High Hardness Steels

cold working steels

Hot Isostatic Pressed (HIPped)pressureless sinteredmelt metallurgy

In general are these steels are too brittle

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0

500

1000

1500

2000

2500

3000

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7

TRUE STRAIN

TRU

E ST

RES

S

quasistatic dynamic

MPa

armour steelhardness 630 HV30

Compression tests on Mars 300

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Ausforming Steel

ausforming (AFH) and hardening (H)

TIME in s

C

P = perlit noseA = austeniteB = bainiteM = martensiteMs = martensite startC = carbidAc = transition temperature

Tem

pera

ture

in °C

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Ausforming steels

C978: 35NCD16

C979: 45NCD16

(french Norm)

dynamicquasistatic

compression test

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Comparison of high-strength steels

C979: 45NCD16C977: Mars 300 (0.45 C)C978: 35NCD16

flow stress, MPa

Em

dyn. stress at 10% strain

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Formation of ASB in high-strength steels

MARS 300 45NCD16

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0

500

1000

1500

2000

2500

0 0,1 0,2 0,3 0,4 0,5 0,6TRUE STRAIN

TRU

E ST

RES

S

MPa armour steel

rail steel(lower bainit)

Bainitic steels (lower bainit)

dyn compression tests

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0,00,20,40,60,81,01,21,41,61,82,02,2

200 300 400 500 600 700 800 900Hardness HV30

Fm

armour steel

cold working steel

rail steellower bainit

Bainitic steel

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Lower bainit is brittle

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0

500

1000

1500

2000

2500

0,0 0,1 0,2 0,3 0,4 0,5 0,6TRUE STRAIN

TRU

E ST

RES

S

lamellar, quasistaticlamellar, 4000 - 3000 1/sglobular, quasistaticglobular, 4000 - 2500 1/s

MPaTiAl

γ-TiAlCompression test

x 100

lamellar micro

structurex 500

globular micro

structure

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0,00,20,40,60,81,01,21,41,61,82,02,2

200 300 400 500 600 700 800 900Vickershardness HV30

Fm

armour steel

cold working steel

γ -TiAl

globularlamellar

γ-TiAl

After the ballistic test

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0,00,20,40,60,81,01,21,41,61,82,02,22,4

100 200 300 400 500 600 700 800 900

Vickershardness HV30

Fm

Armour steel

Cold working steel

Ti 6 4

Ti 6 4

low cost Ti 6 4

rolled

forged

Ti alloy Ti 6 4

rolled, lamellar micro structure

slow cooling rate

forged, globular micro structure

recrystallisation

x 100 x 500

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Ti 17 alloy (thermomechanical treatment)

specimen 26: ϕ

= 0.7 solution annealing T = 820 °C 4 htempern T = 680 °C 8 h, hardness: 391 HV30

specimen 27: ϕ

= 0.7 solution annealing T = 820 °C 4 h tempern T = 580 °C 8 h, hardness: 463 HV30

specimen 28: ϕ

= 0.9 solution annealing T = 910 °C 1 h tempern T = 560 °C 8 h, hardness: 507 HV30

specimen 29: ϕ

= 0.9 solution annealing T = 910 °C 1 h tempern T = 680 °C 8 h, hardness: 387 HV30

Al Sn Zr Cr Mo O N C H

4.9 2 2.04 4 3.94 0.47 0.004 0.016 0.006

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Different treated Ti 17

x50

initial micro structure specimen 26

x200

x1000

specimen 27

x100 x500

specimen 28 specimen 29

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0

200

400

600

800

1000

1200

1400

1600

0,00 0,02 0,04 0,06 0,08 0,10 0,12TRUE STRAIN

TRU

E ST

RES

S

specimen 26specimen 29specimen 27specimen 28

MPa

Quasistatic tensile test

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0

400

800

1200

1600

2000

2400

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40True Strain

True

Str

ess

26: 391 HV30 27: 463 HV30 28: 507 HV30 29: 387 HV30

MPa

Dyn. Compression Test

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0,00,20,40,60,81,01,21,41,61,82,02,22,4

100 200 300 400 500 600 700 800 900

Vickershardness HV30

Fm

2 9

2 6

2 72 8

armour steels

cold working steels

T i 17 fo rgedinitial status

Ballistic Tests

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Specimen 28

ASB: width = 4 µm

Initial status

ASB: width = 30 µm

Ti alloy Ti17

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Ti 17 specimen 28

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0,0

0,4

0,8

1,2

1,6

2,0

2,4

2,8

0 100 200 300 400 500 600 700 800 900Vickershardness H V30

Fm

Al-Cu5/25% SiCAlSi9M g/20%SiCAlSi7M g0,5/55%SiCAlCu4M g1Ag/55%SiC316L/15%TiB2

armour steel

cold working steelmechanically alloyed

cast

squeeze cast ing

H IP ped

Al-Cu5/25% SiC 316L/15%TiB2

cast AlSi9Mg/20%SiC

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0

100

200

300

400

500

600

700

800

900

AlSi7Mg AlCu5Mg

TRU

E ST

RES

S

20% SiC

55% SiC 25% SiC

MPa

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AlSi7Mg reinforced by 55 - 60 % SiC of size:

F100

106 – 150 µm

F500

5 – 25 µm

F1200

1 – 5 µm

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0

200

400

600

800

0 0,05 0,1 0,15 0,2 0,25TRUE STRAIN

TRU

E ST

RES

S

F100F500F1200

MPa

Matrix: AlSi7Mg

SiCP:

Dynamic Compression Tests

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1,0

1,2

1,4

1,6

1,8

2,0

0 200 400 600 800 1000 1200 1400Particle Size F

EmAlSi7Mg / SiC

F100ρ= 3.0 g/cm3

F500ρ = 3.0 g/cm 3

F1200ρ = 2.7 g/cm 3

Ballistic Tests

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AlSi7Mg reinforced by SiC- particles of size F1200

Gaspressure infiltration

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Submicro Ceramic

Al2 O3 , grain size: 0.6 µm - 9.82 µm

grain-Ø: 0.6 µm grain-Ø: 0.91 µm

grain-Ø: 3.76 µm grain-Ø: 9.82 µm

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Ballistic Test and Materials Properties

grain-Ø yaw

a 0,6 0°

b 3,76 0°

c 9,82 1,8°

d 0,91 0,2°

grain-Øhardness strength

4-point bending test

µm HV10 MPa

a 0,6 1977 ± 32 557 ± 35

b 3,76 1725 ± 22 470 ± 31

c 9,82 1543 ± 46 350 ± 16

d 0,91 1908 ± 15 345 ± 30

Al2 O3

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yaw 1,8 °

Ballistic Tests

hardness / strength

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Ballistic Tests