Titanium Structures for Army Systems

Titanium Structures for Army Systems

W. M. MullinsUS Army Research Office

PO Box 12211Research Triangle Park, NC 27709-2211

[email protected]

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1. REPORT DATE 11 MAY 2001

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4. TITLE AND SUBTITLE Titanium Structures for Army Systems

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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

RTA-AVT Specialists Meeting07-11MAY01

MechanizedMechanizedForcesForces

20002000

Cap

abili

tyC

apab

ility

TimeTime

LightForces

Follow-OnHeavy Forces

Enemy Force Build Up

FCS• Multi-mission• Rapidly deployed• Light logistically• Variable lethality

Allows U.S. to set conditionson the battlefield

TODAY

THE GOAL

Red overmatch sets theconditions of battle

SOF

Cap

abili

tyC

apab

ility

TimeTimeSOF

MechanizedMechanizedForcesForces

FCS / Medium Forces

Follow-OnHeavy Forces(if Necessary)

Enem

y Fo

rce

Bui

ld U

p

• Robotics• Mobile C3

• Networked Fires• Organic 3D

Targeting

The Challenge: Lethal, EffectiveEarly Entry Forces

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Current System54-64 Tonnes18.5 m3 Internal Volume

Future Concept - FCS & FSCS18 +/- Tonnes8.5-11.5 m3 Internal Volume

C130C17/C5

Up to:70% Lighter50% Smaller

Technology Challenges• Survivability • Lethality• C4I• Supportability

• HumanFactors

• Mobility• Training

Lighten the force, notjust lighten the platform

Science&

Technology

Operational Challenge - Moving the Full Spectrum Force

Objective Force Drivers

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Notes for Slide 3

A key parameter that we will have to look at in arming theFull Spectrum Brigade is the available space within ourairborne transportation assets. The best projections fromour Army Staff studies on Strategic Maneuver indicate thatwe will probably not have a new transportation aircraftavailable for inter or intra-theatre lift in the 2010-2020timeframe. Therefore, we will have to use existing airtransportation assets to move the Full Spectrum Brigade -which drives us in size to a 20 ton/400 cubic foot vehiclethat will fit in both a C130 and in commercial 747-classcargo aircraft. I echo the VCSA’s comment that aiming forC-130 transportability is an excellent way to keep the FCVsize and weight manageable.

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Technology Driver: Lethality

• Impulse of ammunition isincreasing for lethality overmatch.

•Problem:• Trunnion Force = Impulse2 / 2 M X• Lighting and reducing size to

increase mobility.•Techniques under development tomitigate recoil:• High strength trunnion and carriage

materials.• Benign muzzle brakes.• Fire-out-of-Battery• Sonic Rarefaction Wave GunWave front of the sonic

rarefaction wave

The back of the gun may be uncorkedwhen the projectile has traveled aboutone third the way down the gun with NONEGATIVE EFFECT ON THE PROJECTILEPROPULSION. Can reduce recoil up to75%.

• Gun Pre-Acceleratedforward from RearPosition to one half ofthe normal recoilspeed.

• Firing reverses forwardvelocity.

• Gun Decelerated to restat out of batteryposition.

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XM777

•Active procurementprogramme.

•No “revolutionary” changes inbasic howitzer design.• Novel transport configuration• Carriage constructed from Ti-

alloy weldments.

Auto-Primer FeedPrimer Mechanism

9,000lbsWeight

2 HowitzersC-130 Capacity**Investigating C130 Capability toTransport Both the M1083 and XM777

2 MinDisplacement Time3 MinEmplacement Time

5 Rds/minMax Rate of Fire

XM777

Manual Single Round

16,000lbs

1 Howitzer

11 Min8 Min

4 Rds/min

M198

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LWT 81mm Mortar System

•Man-portable design:– ~32 kg weight, 30% lighter than

the M252 mortar system.– replace the M252 81-mm or

even the M224 60-mm mortar.•Features

• Redesigned graphite-compositeand titanium bipod.

• A new baseplate featureingintegrated aluminum and fiber-reinforced composite.

• Bi-metallic steel and titanium tube.– will undergo firings to validate its

structural integrity androbustness.

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Survive first round engagement … don’t be hit

Achieving the paradigm requires innovative thinking

Signaturereduction

Jammers DecoysActive Protection

Passive armorReactive armorEM armorSmart armor

ObscurantsJammers

Don’t Be ...

CompartmentingSpall reductionFire suppression

Killed

DetectedAcquired

Hit

Penetrated

New Battle ConceptsNew Battle ConceptsTechnology BreakthroughsTechnology Breakthroughs

Novel System Design(s)Novel System Design(s)

Requires:

Momentumtransfer issue

Technology Driver: Survivability

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Composite Armoured Vehicle

• S2-Glass Epoxy Structure• High Alumina Ceramic

Armour plates• Entire Structure Integrally

Resin-Transfer Moulded

FCSNeed

ARMORReqt’s

200 mm RHA Equivalent Protection

Arm

or W

eigh

t (to

ns)

0

2.5

5

7.5

Mass Efficiency1 102 3 4 5 6 7 8 9

100 ft2

(9.3 m2)

50 ft2

(4.65 m2)

III

III

IV

3.3 6.6

Composite Armoured Vehicle

•Completed ATD Programme•Best “off-the-shelf” armour systemavailable now.

•System of choice for Crusader andcandidate for FCS vehicles.

•Problems:• Expensive, long lead-times and etc.• Still heavy!

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An Example: Cu-Cu Joint

Rx Foil

Copper

Thin Braze

SiC Plate

Ti-6-4 Plate

100µm Reacting Foil

Tin Coating (6µm)

Tin WettingLayer (2µm)

Tin Coating (6µm)

T. Weihs, E. Chin, S. Schoenfeld (ARL-WMRD)

Joining Armor Materials withReactive Multilayer Foils

• Goal: join armor materials usingreactive multilayer foils as local heatsources as shown schematically

• A Cu to Cu joint with a thick reactivefoil (~150µm) and thin braze layers.The outer Cu layers are approximately40µm thick, and the joints have shearstrengths greater than 30 MPa

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Ti - Al Composites

Ti - Al - Ceramic Particulate CompositesK. Vecchio (UC San Diego)

Ti-Al Metallic-IntermetallicComposites

•Fabrication• Alternating stack of Ti and Al foils• Reaction to form intermetallic layer

structure• Final structure set by stacking

– Ti + TiAl– Al + Al3Ti

• Automated processing for reducedprocessing time and reactioncontrol

• Additional particle reinforcementpossible

•Structure-property correlation forstrength and toughnessoptimization

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Laminated Armor Plates

•Hard intermetallic layers break upand erode projectile.

•Metallic layers provideinterlamellar failure mode, stillbinding the hard phase.

•Properties must be balanced foroptimal ballistic performance

Ballistic test showinginterlamellar failure mode incomposite.

Simulation showing defeat mechanism ofhard/soft layers. Note lamella failurebeneath projectile. Metallic layers bindhard phase to prevent ejection. Too softof a metallic binder provides a“lubrication” effect though.

K. Vecchio (UC San Diego)

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Transformation Plasticity

•OBJECTIVE: Increaseplasticity Ti and Ti-matrixcomposite materials.

•APPROACH: Induce anallotropic transformation(∆V) in one phase.• Cycle about the transition

while under external stress.• Transformation stresses

induce local plasticity andallow accelerateddeformation.

• Results in enhanced “creepforming” of alloys.

α→β transformation via ∆T or ∆[H]

D.C. Dunand (NWU/MIT)

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Tota

l Stra

in, %

TIME [sec]

Titanium

Transformation Plasticity

•ACCOMPLISHMENTS• Demonstrated TP in Ti/TiC

MMC (matrix ∆T)• Demonstrated TP in Titanium

(chemically driven ∆[H])• Theory of Transformation

Plasticity extended from lowstress linear regime to high-stress levels near the yieldstrength

• IMPACT• Enhanced creep formability for

TiMC• Enhanced superplastic forming

of Ti D.C. Dunand (NWU/MIT)

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20µm

300

400

500

600

700

800

900

0.1 1 10 100Time (hrs)

Tem

pera

ture

(C) β

β

α+β

20µmβ-quench microstructure

β-annealed microstructure

TTT Curve, Ti-64 (30 at.% H)

Thermohydrogen Processing

•APPROACH• Cast & HIP’d (890°C) Ti-6Al-4V plate• Hydrogenated 780°C 24 hrs to 30 at.% Hydrogen

•RESULTS• Reduction in grain size from 30-60mm to 1-3mm• Temperature decrease of 100°C to 200°C for hot

working• Improved processability and machinability• Improved final mechanical properties.F.H. Froes et al. (U. Idaho)

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Pressureless sinteredat 900ºC for 4 hrs.Final density ~89%

Effect of Hydrogen on PowderSinterability

•OBJECTIVE: Hydrogen effect asTemporary Alloying Element on theSinterability of Ti Powders.

•RESULTS• Preliminary Results to date.• Higher hardness for hydrogen-charged

sample.• Higher sintered density for hydrogen

charged sample.•APPLICATIONS

• Sinter-forged Ti-6Al-4V commander’shatch on M1 Abrams (SBIR projectfrom ARL-WMRD)

• Jet engine compressor rotors(possible)

CP-Ti Powder, Cold-Compacted to ~74%density.

F.H. Froes et al. (U. Idaho)(SM2) KN4-16


0.5cm

100µm

50µm

Scrap Conversion

•Commercial turnings and scrap readilyavailable for low cost.

•Clean and hydrogenate to brittle solid.•Grind to form powder.•Powder process with or withoutdehydrogenation to form components.

•Good microstructures and propertiesobserved.

Microstructureafter HIPing.

TiH powder after grinding

Scrap Ti turnings fromaerospace fabricator.

Ti

F.H. Froes et al. (U. Idaho)(SM2) KN4-17


0

70

60

50

40

30

20

10

0 100 200 300 400 500 600 700Specific Ultimate Strength (MPa/g/cm3)

Spec

ific

Stiff

ness

(GPa

/g/cm

3 )

Al, Mg, Ni, Steel,α/β-Ti

β-Ti

Gr/epoxy X-ply

DRADRTi

Amorphous AlAmorphous Ti

Specific Properties

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Ti-based Amorphous Alloys

G

X→

β1β2

amor.

CoherentSystem

•Amorphous powders formed bystrong mechanical alloying.

•Amorphous bulk formed byspontaneous “melting” ofcrystalline phases.• Immiscible system, ie. Ti-Cr• Melt solidified to form single

crystalline phase.• Once cooled deep into miscibility

gap, two-phases spontaneouslyemerge.

• Coherency strains of two phasesincrease free energy of system, tohigher than amorphous phase.

• System metastability maintained bydiffusion-limited kinetics.

G. Schiflet (UVa)DCS measured Free-Energydifference between β phaseand glass

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Conclusions

•Long history of Ti R&D in the U.S. Army.•Cost has been a major barrier to Ti usage.•Ti-alloys are finding application in developmental gunsystems.• Light weight overrides cost issues.• Significant design challenges posed in gun applications.

•Current Ti research looks at reducing processing costs.•New Ti alloys (and metallic glasses) promise to revolutionizeTi applications.

•Future looks good for including structural Ti in U.S. Armyground systems.

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Titanium Structures for Army Systems

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