The Design and Application of Titanium Alloys to U.S. Army Platforms - 2007

Abstract

Titanium alloys have long been used for reducing system weight in airframe structure and jet engine components. The high cost of titanium, however, has historically prevented the application to military ground vehicles. In recent years, the cost of titanium has fallen relative to the cost of composite and ceramic armors and titanium is now a valid option for some armor applications. As early as 1950, Pitler and Hurlich [1] noted that titanium alloys showed promise as armors against small arms projectiles. By the early 1960's, Sliney [2] presented ballistic performance data for Ti-6Al-4V alloy that demonstrated significant weight reductions over steel armors for small arms threats. Little work with larger threats was conducted due to the then prohibitive cost of the titanium. Since the early 1990's, ARL has undertaken a research effort to develop baseline titanium ballistic performance data against a range of penetrators and fragments.

Full text

The Design and Application of Titanium Alloys to U.S. Army Platforms
William A. Gooch and Matthew Burkins
U.S. Army Research Laboratory, Weapons and Materials Research Directorate,
Aberdeen Proving Ground, Maryland 21005-5066, USA
INTRODUCTION
Titanium alloys have long been used for reducing system weight in airframe structure and jet engine components.
The high cost of titanium, however, has historically prevented the application to military ground vehicles. In recent
years, the cost of titanium has fallen relative to the cost of composite and ceramic armors and titanium is now a valid
option for some armor applications.
As early as 1950, Pitler and Hurlich [1] noted that titanium alloys showed promise as armors against small arms
projectiles. By the early 1960's, Sliney [2] presented ballistic performance data for Ti-6Al-4V alloy that
demonstrated significant weight reductions over steel armors for small arms threats. Little work with larger threats
was conducted due to the then prohibitive cost of the titanium. Since the early 1990’s, ARL has undertaken a
research effort to develop baseline titanium ballistic performance data against a range of penetrators and fragments.
BACKGROUND
Titanium can exist in a hexagonal close-packed crystal structure (known as the alpha phase) and a body-centered
cubic structure (known as the beta phase). In unalloyed titanium, the alpha phase is stable at all temperatures up to
882o C, where transformation to the beta phase occurs. This transformation temperature is known as the beta transus
temperature. The beta phase is stable from 882o C to the melting point. As alloying elements are added to pure
titanium, the phase transformation temperature and the amount of each phase change. Alloy additions to titanium,
except tin and zirconium, tend to stabilize either the alpha or beta phase. Ti-6Al-4V, the most common titanium
alloy, contains mixtures of alpha and beta phases and is therefore classified as an alpha-beta alloy. The aluminum is
an alpha stabilizer, which stabilizes the alpha phase to higher temperatures, and the vanadium is a beta stabilizer,
which stabilizes the beta phase to lower temperatures. The addition of these alloying elements raises the beta transus
temperature to approximately 996o C. Alpha-beta alloys, such as Ti-6Al-4V, are of interest for armor applications
because the alloys are generally weldable, can be heat treated, and offer moderate to high strength [3]. Ti-6Al-4V
alloy can be ordered to a variety of commercial and military specifications. Extra Low Interstitial (ELI) grade plates,
simultaneously conforming to MIL-T-9046J, AB-2 (aerospace) and MIL-A-46077G (armor) specifications are used
in these ballistic tests. The specifications define alloy chemistry ranges, minimum mechanical properties, and, in the
case of MIL-A-46077G, ballistic requirements. Typical chemical compositions of titanium plate are listed in Table 1
for a Class 1 ELI alloy; mechanical property data for a typical MIL-T-9046J, AB-2 (aerospace) plate are found in
Table 2. The hardness values are representative of the plates tested; hardness is not specified in MIL-T-9046J.
Titanium alloys have long been used for reducing system weight in airframe structure and jet engine
components. The high cost of titanium, however, has historically prevented their application to military
ground vehicles. In recent years, the cost of titanium has fallen relative to the cost of composite and
ceramic armors and titanium is now a valid option for some Army applications, whether for weight
reduction or improved ballistic performance. The distinct advantages of low density, high strength, a
large competitive industrial base, and well established forming and shaping techniques establishes
titanium as an excellent material for many military applications. The U.S. Army Research Laboratory
(ARL) has invested significant research efforts in understanding the material processing requirements
for ground versus aerospace applications and this paper will provide an overview of that research. A
major concurrent effort has been the amending existing military specifications to allow the use of lower
cost, higher oxygen content titanium alloys that meet specific ground applications. The paper will end
with a review of some of the current applications of titanium on US Army platforms.
Preprint
International Titanium Association
Titanium 2007
Orlando, Florida
7-9 October 2007

U.S. rolled homogeneous armor (RHA) steel is used as the baseline for most ballistic comparisons. RHA mechanical
properties are also provided in Table 2 for plate thicknesses ranging from 38-mm to 152-mm; the mechanical
properties of RHA vary as a function of plate thickness due to differences in thermomechanical processing. A 38-
mm RHA plate has higher strength and hardness than a 152-mm plate. Titanium has poor hardenability in thick
sections and cannot be rapidly quenched. However, excellent mechanical properties can be developed in wrought
plate through thermomechanical working (rolling). Titanium mechanical properties are very uniform across the plate
thickness that increases the relative ballistic performance when compared to an equivalent thickness of RHA. In
thick sections, titanium has significantly better mechanical properties for ballistic application than RHA.
Table 1. Typical Chemical Compositions for Class 1 Titanium Plates by Weight-Percent
Al
V
C
O
N
H
Fe
Ti
5.50-
6.50
3.50-
4.50
0.04
Max
0.14
Max
0.02
Max
0.0125
Max
0.25
Max
Balance
Table 2. Typical Titanium and RHA Mechanical Properties
MATERIAL
SOURCE
DENSITY
g/cm3
TENSILE
STRENGTH
HARDNESS
ELONGATION
%
Ti-6Al-4V
MIL-T-9046J
4.45
>896 MPa
302-364HB
>10
RHA
MIL-A-12560
7.85
794-951 MPa
241-331HB
11-21
TITANIUM MILITARY SPECIFICATION MIL-DTL-46077G
An important factor in the use of titanium alloys for military applications is Military Specification MIL-DTL-
46077G that defines different classes of titanium that can be used as armor [4]. While commercial specifications
such as SAE-AMS-T-9046, SAE-AMS4911 or ASTM-B265 maintain quality control through mechanical
properties, chemistry and processing, MIL-DTL-46077G emphasizes ballistic response to maintain quality control;
no process is specified. This specification covers the thickness ranges of 0.125”- 4.000” and was revised last on 28
September 2006. The main change from the previous specification is the expansion of the thickness range in thin
sections down to 0.125”; the ballistic acceptance tables for this range have not been finalized to date.
The emphasis in recent amendments to the specification has been to incorporate new classes of titanium armor that
utilize lower cost titanium processing and alternate alloys. Table 3 provides the current four classes of titanium that
can be specified under the MIL-DTL-46077G. While all four classes have the same strength and ballistic
requirements, the direction has been to increase the oxygen content to a maximum of 0.30% that has allowed the use
of lower cost processing technologies such as Electron Beam or Plasma Melt for both Class 3 and 4. Armor grade
titanium has a greater tolerance to oxygen content than other applications. Class 4 titanium, unlike Class 1-3, allows
alternate alloys to be utilized for armor applications.
Table 3. MIL-DTL-46077G Titanium Armor Specification
Chemistry
Max. O2
Content
Comments
Class 1
6AL- 4V
0.14%
ELI-
10% Elongation Min.
Class 2
6AL- 4V
0.20%
Common Armor
6% Elongation Min.
Class 3
6AL- 4V
0.30%
High Scrap Content
Weld & cold temp issues
Class 4
Not Limited
0.30%
For future developments

0
50
100
150
200
250
300
0 0.5 1.0 1.5 2.0 2.5 3.0
Ti: P=348.8*exp(-(1.486/V)2)
131W-Ti
RHA: P=292.6*exp(-(1.404/V)2)
131W-RHA
IMPACT VELOCITY (km/s)
PENETRATION (mm)
BALLISTIC RESPONSE OF TITANIUM TO FRAGMENTS AND PROJECTILES
ARL has conducted extensive analysis of the ballistic response of titanium to both projectiles and fragment
simulators [5-12] and more details can be found in the references. As seen in Table 2, titanium has similar strength,
hardness and elongation to ballistic steel, but the density is 43% less. This strength to density ratio is the primary
factor in the greater performance of titanium over ballistic steel. Figure 1 illustrates the penetration of a Ti-6Al-V
alpha-beta titanium and RHA steel by a long rod penetrator at velocities from 500 m/s up to 2600 m/s. The
penetration into both metals is approximately equal up to about 1700 m/s and has a mass efficiency compared to
steel of 1.87 at 1000 m/s dropping off to 1.44 at 2000 m/s when the densities are considered. Even when the impact
velocities approach the hydrodynamic limit where material strengths can be ignored, the penetration density law
results in a theoretical performance of 1.3 times that of steel.
Figure 1. Penetration of a Tungsten Long Rod Penetrator into RHA and Titanium
Microstructure and processing technology can still have a significant effect on the performance at Ordnance
velocities. Figures 2 and 3 show two Ti-6Al-4V ELI plates that were beta- and alpha-beta-processed and then
impacted by a 20mm fragment simulating projectile. The large difference noted in the ballistic performance between
the plates tends to indicate that the failure mechanisms were in some way different. Observation of the rear plate
surface failures for perforating and near-perforating impacts showed this to be the case. The beta processed plates
failed by adiabatic shear plugging. This low-energy failure mode caused a titanium plug to be ejected from the rear
surface of plate after the FSP penetrated approximately 6-mm into the plate and has been described in previous ARL
work [12-14]. The plates that were alpha-beta processed failed by a mixed process of bulging, delamination,
shearing, and spalling. However, this failure occurred only after the FSP had penetrated approximately 15-mm into
the plate, requiring the FSP to penetrate significantly deeper into the armor than for the beta-processed plates.
Rolling or annealing at temperatures above the beta transus significantly reduced the performance.
Adiabatic shear plugging is inherent in titanium due to shear-induced strain localizations due to the low heat transfer
properties of titanium. Figure 4 shows the deep penetration of a long rod tungsten penetrator into a titanium plate.
The adiabatic shear bands in the sectioned plate are visible parallel to the penetration channel. The shear banding
happens all along the circular penetration channel and then the titanium fragments mix with the tungsten rod
fragments. In a complete perforation of the plate, the adiabatic titanium chips and penetrator debris are ejected and

the penetration cavity wall appears very smooth. When an eroded penetrator comes within approximately one
penetrator diameter of the rear free surface, the plate will eject a shear plug that has a larger diameter than the
penetrator. This spall plug is generally not penetrated during the interaction and decreases performance. Figure 5
shows a large spall plug induced in a four inch plate that resulted in an approximate 20% loss in penetrator/target
interaction. For this reason, titanium is not recommended for standalone use and low density backings, such as
aluminum or composites, increase performance as the spall plug is held in place and contribute to erosion of the
penetrator.
Figure 4. Deep Penetration of a Tungsten Long Rod Penetrator into
Titanium showing Adiabatic Shear Bands

Figure 5. Spall Plug Breakout of a 100mm (4.0”) Titanium Plate after Perforation by a Long Rod Penetrator
EFFECT OF MECHANICAL PROPERTIES ON BALLISTIC PERFORMANCE
The quasi-static mechanical properties of titanium are very important for most engineering applications and were
included in the property requirements in MIL-DTL-46077G for Class 1 and 2 titanium. However, for armor
applications, the impact of varying the mechanical properties is not apparent and processing history is more
important. The most complete analysis of these effects were conducted by Burkins, Love and Wood where a set of
Ti-6Al-4V ELI plates were subjected to a series of annealing temperatures and the effects on the mechanical
properties were determined [13]. The results on the samples from the original single 28.5mm plate are summarized
in Figure 6 where the effect of heat treating or working the plates over the beta transus temperature is obvious. The
initial vacuum creep flatten process produced ballistic plate with a performance similar to plates subjected to
SHEAR BANDS AND
DELAMINATION
PENETRATOR
CHANNEL
SPALL RING
BREAKOUT
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, No Anneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 Min Anneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, No Anneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 Min Anneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
Figure 6. Effect of Annealing Temperature on Ballistic Performance

700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, No Anneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 Min Anneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
831 MPa
704 MPa
826 MPa
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, No Anneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 Min Anneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, No Anneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 Min Anneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
831 MPa
704 MPa704 MPa
826 MPa826 MPa
additional annealing below the beta transus. Plates annealed above the beta transus have a microstructure change to
a Widmanstätten alpha-beta structure as seen in Figure 7. The effect on ballistic performance compared to transverse
yield strength, transverse elongation and Charpy impact data are shown in Figures 8-10. The annealing step could be
omitted to reduce cost or the anneal temperature could be increased to 900oC to obtain the highest performance.
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly,NoAnneal
30MinAnneal,AC
30MinAnneal,WQ
30MinAnneal,FC
120MinAnneal,AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
200x
Partially
recrystallized a +
intergranular ß
200x
Coarse prior ß
transformed to
Widmanstatten a-ß
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly,NoAnneal
30MinAnneal,AC
30MinAnneal,WQ
30MinAnneal,FC
120MinAnneal,AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly,NoAnneal
30MinAnneal,AC
30MinAnneal,WQ
30MinAnneal,FC
120MinAnneal,AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
200x
Partially
recrystallized a +
intergranular ß
200x
Coarse prior ß
transformed to
Widmanstatten a-ß
Figure 8. Change in Transverse Yield Strength with Annealing Temperature
Figure 7. Change in Microstructure for Annealing over the Beta Transus Temperature

Figure 9. Effect of Transverse Elongation with Annealing Temperature
Figure 10. Effect on Charpy Impact Results with Annealing Temperature
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, NoAnneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 MinAnneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
Below 12%
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, NoAnneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 MinAnneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, NoAnneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 MinAnneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
Below 12%
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, NoAnneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 MinAnneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
L- 27J
T- 29J
L- 22J
T- 20J L- 46J
T- 45J
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, NoAnneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 MinAnneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
700
800
900
1000
1100
1200
700 800 900 1000 1100
VCFOnly, NoAnneal
30Min Anneal, AC
30Min Anneal, WQ
30Min Anneal, FC
120 MinAnneal, AC
Duplex(1038+788)
ANNEALINGTEMPERATURE (C)
V50 LIMIT VELOCITY (m/s)
Beta Transus
L- 27J
T- 29J
L- 22J
T- 20J
L- 22J
T- 20J L- 46J
T- 45J
L- 46J
T- 45J

EFFECT OF THERMOMECHANICAL PROCESSING ON BALLISTIC PERFORMA NCE
In an effort to provide further data on processing of titanium armor plate, ARL and the U.S. Department of Energy
Albany Research Center (ALRC) performed a joint research program to evaluate the effect of thermomechanical
processing on the ballistic limit velocity of an ELI grade of Ti-6Al-4V [14-15]. ALRC obtained MIL-T-9046J, AB-2
plates from RMI Titanium Company, rolled these plates to final thickness, performed the annealing, and collected
mechanical and microstructural information. ARL then tested the plates with 20-mm fragment-simulating projectiles
(FSPs) and 12.7-mm armor-piercing (AP) M2 bullets in order to determine the ballistic limit velocity of each plate.
The ballistic limit velocities were then compared to assess the effect of changes in rolling and heat treatment.
The starting material was commercially produced 127-mm-thick Ti-6Al-4V ELI alloy plate product. Each plate was
coated with a silica-based material to reduce oxygen contamination, placed into the furnace, and soaked for two
hours at either 1,066o C (beta) or 954o C (alpha-beta), and step forged to 108-mm first and then 89-mm. The step
forging was done without reheating. Upon completion, the plates were returned to the furnace and reheated for 20
minutes. The plates were then, either unidirectionally (straight) rolled or cross-rolled at the same temperature used in
the forging operation (1,066o C or 954o C). The rolling schedule consisted of two passes at 12% reduction in
thickness, two passes at 15% reduction in thickness, three passes at 20% reduction in thickness, and one final pass at
the final mill setting of 25.4 mm. Each plate was reheated for 20 minutes after every second pass through the mill.
Following the final pass, the plates were placed on a rack and air cooled to room temperature.
Four different annealing heat treatments were used at the completion of rolling and air cooling: (1) a beta anneal at
1,038o C for 30 minutes with an air cool (AC); (2) a beta plus alpha-beta anneal at 1,038o C for 30 minutes with an
AC, followed by 788o C for 30 minutes with an AC; (3) an alpha-beta anneal at 788o C for 30 minutes with an AC;
and (4) a solution treat and age (STA) at 927o C for 30 minutes with a water quench (WQ), followed by 538o C for 6
hours with an AC. As an experimental control, the final heat treatment was omitted for some of the plates.
Following heat treatment, all the plates were sand-blasted to remove any remaining protective coating. All plates
forged, rolled, or annealed in the beta region had a typical structure of plate-like alpha and intergranular beta with
alpha at the prior beta grain boundaries. All plates forged, rolled, and annealed in the alpha-beta region had a typical
structure of equiaxed alpha grains and intergranular beta.
V50 limit velocities were obtained for all eleven plate conditions, tested with both the 20-mm FSP and 12.7-mm
APM2 projectiles. Figure 11 shows graphically the V50 difference for the eleven plate conditions. The required V50
values were derived from the acceptance tables in MIL-A-46077D. Regardless of the penetrator used, only three
plates (S1, C1, and C4) passed the ballistic requirements of MIL-A-46077D, even though these three plates also
failed to meet the elongation requirements of MIL-A-46077D. Beta-processed plates, either rolled or annealed at
temperatures above the beta transus, had lower V50 ballistic limit velocities for both the 20-mm FSP and the 12.7-
mm APM2. The magnitude of the effect was much greater for the 20-mm FSP (~200 m/s) than for the APM2 (~40
m/s), confirming a trend that had been indicated in prior data [12]. The plates that received no additional anneal
treatment (C4 and S5) gave a ballistic performance comparable to similarly processed plates that received an alpha-
beta anneal treatment (C1 and S2). For the APM2 tests, cross rolling provided no significant difference in V50 as
compared to straight rolling (S1 vs. C1 and C5 vs. S2). For the 20-mm FSP tests, cross rolling seemed to provide a
slightly higher V50 than straight rolling in the alpha-beta region (S1 vs. C1); however, straight rolling seemed to be
slightly better than cross rolling in the beta region (C5 vs. S2). The beta-processed plates failed by a process of
adiabatic shear plugging. The alpha-beta-processed plates failed by a mixed process of bulging, delamination,
shearing, and spalling, which required more energy because the FSP had to burrow much deeper into the armor plate
before rear surface failure occurred. The failure mode for beta and alpha-beta processed plates appeared to be the
same for the 12.7-mm APM2. This observation is consistent with the relatively small differences in V50 performance
between the beta- and alpha-beta-processed plates.

TITANIUM WROUGHT PLATE VS CASTINGS
The advantages of utilizing net shape cast titanium components for armor applications and other ballistic uses led to
an examination of the ballistic performance of cast titanium as compared to wrought plate [16]. The main issue from
the US Army standpoint is cost reduction by eliminating unnecessary processing. The ballistic evaluation of cast
titanium utilized ASTM 367-87 Grade 5 alloy and was compared to wrought Ti-6Al-4V plate as defined in Tables 4
and 5. The mechanical properties for the cast material are lower than the wrought plate, except for hardness and the
compositions are similar. The cast titanium was also subjected to post processing procedures to include hot isostatic
pressing to reduce porosity and pickling to reduce the case hardened layer and surface imperfections. The samples
were impacted with armor-piercing and FSP projectiles and the results for the 20mm FSP are shown in Figure 12.
The baseline wrought data are plotted in Figure 12 as a dashed red line and the cast titanium is plotted as a solid
black line. These data show the cast titanium performance to be, at best, 75% of wrought titanium and results from
the reduced strengths as compared to the rolled wrought plate. The effects of post processing procedures are
minimal with some possible improvement in the ballistic performance due to pickling; but the data are scattered.
Conjecture would be that any post process that homogenizes the surface, particularly the back of the casting could
decrease crack initiation points when in tension. The use of cast components will require 20-25% thicker cross-
sections over wrought plate. In complex shapes, casting may be advantageous when compared to steel castings that
suffer the same issues.
Titanium Forgings
Figure 13 shows a single application of the forging of the titanium for military application for ground vehicles. The
commander’s hatch for the M2A2 Bradley is a very intricate shape and a titanium forging resulted in providing a
lower weight and ballistically equivalent hatch.
Beta processed
No beta processing
S= straight rolled C= cross rolled
Beta processed
No beta processing
S= straight rolled C= cross rolled
Beta processed
No beta processing
S= straight rolled C= cross rolled
Figure 11. Beta processed Ti-6Al-4V Plate Compared to Alpha-Beta Processed Plate

Heat
#Part
ID # Nominal
Thickness
(mm)
Al
(%)
V
(%)
Fe
(%)
O
(%)
C
(%)
N
(%)
H
(%)
970139 970181 25.4 6.27 3.8 0.15 0.21 0.02 0.01 0.002
970179 12.7
970140
970179 12.7
6.27 3.8 0.17 0.23 0.02 0.01 0.004970180 19.1
970183 38.1
970138 970182 31.8 6.28 3.8 0.16 0.21 0.02 0.01 0.002
970183 38.1
ASTM 367-87
Grade C5 5.5-
6.75 3.5-
4.5 0.40
max 0.25
max 0.10
max 0.05
max 0.015
max
Heat
#Part
ID # Nominal
Thickness
(mm)
Al
(%)
V
(%)
Fe
(%)
O
(%)
C
(%)
N
(%)
H
(%)
970139 970181 25.4 6.27 3.8 0.15 0.21 0.02 0.01 0.002
970179 12.7
970140
970179 12.7
6.27 3.8 0.17 0.23 0.02 0.01 0.004970180 19.1
970183 38.1
970138 970182 31.8 6.28 3.8 0.16 0.21 0.02 0.01 0.002
970183 38.1
ASTM 367-87
Grade C5 5.5-
6.75 3.5-
4.5 0.40
max 0.25
max 0.10
max 0.05
max 0.015
max
Table 4. Comparison of Wrought and Cast Titanium Compositions
Heat
#Part
ID #
Nominal
Thickness
(mm)
Tensile Properties Hardness
(BHN)
0.2%YS
(MPa) UTS
(MPa) Elong
(%)
970139 970181 25.4 885 989 10.0 318
970179 12.7
970140
970179 12.7
900 1024 11.0 315970180 19.1
970183 38.1
970138 970182 31.8 879 981 10.0 299
970183 38.1
ASTM 367-87 Grade C5 825 min. 895 min. 6 min. 365 max.
Heat
#Part
ID #
Nominal
Thickness
(mm)
Tensile Properties Hardness
(BHN)
0.2%YS
(MPa) UTS
(MPa) Elong
(%)
970139 970181 25.4 885 989 10.0 318
970179 12.7
970140
970179 12.7
900 1024 11.0 315970180 19.1
970183 38.1
970138 970182 31.8 879 981 10.0 299
970183 38.1
ASTM 367-87 Grade C5 825 min. 895 min. 6 min. 365 max.
Table 5. Mechanical Properties of Cast and Wrought Titanium

450
500
550
600
650
700
750
800
850
900
950
1000
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
MIL-DTL-46077F (Wrought Ti-6Al-4V)
Cast Ti-6Al-4V (1997-HIP)
No HIP - No Pickle
No HIP - Light Pickle
No HIP - Heavy Pickle
HIP - No Pickle
HIP - Light Pickle
HIP - Heavy Pickle
THICKNESS (mm)
V50 LIMIT VELOCITY (m/s)
Figure 12. Ballistic Performance of 20mm FSP vs Wrought and Cast Titanium
Figure 13. Titanium Forging of Bradley M2A2 Commanders Hatch

TITANIUM COMPOSITES/LAMINATES
The use of titanium as a standalone armor material has ballistic disadvantages due the breakout effects of adiabatic
shearing. Similar effects are found with high hard steels. For this reason, these types of metals can be backed with
ductile or compliant materials as a laminate to create a much higher ballistic performance than the individual
materials. This is shown in Figure 14 where a titanium plate is mechanically attached to an aluminum back plate.
The backing could also be fiber composites such as S2 glass, Kevlar Aramids, or polyethylene
Dyneema/Spectrashield composites. The harder front face erodes the projectile and the rear ductile layer captures
the fragment. Figure 15 conceptually shows a titanium dual hard metallurgically bonded laminate similar in concept
to dual hard steel. These type of laminates would take advantage of mechanical properties and ballistic response of
the individual components to make a superior ballistic material that could be fabricated as a single plate.
The development of functionally graded materials (FGM) using ceramics and metals offers higher performance than
metal laminates or even dual hardness metal laminates. BAE Advanced Materials, under contract to ARL, has
developed a process to hot-press large near net-shape FGM tiles in a single stage utilizing titanium and
titanium/titanium diboride (TiB2) powder mixtures, forming a titanium monoboride (TiB) hard face/titanium metal
substrate that grades through intermediate layers [17]. As seen in Figure 16, the TiB ceramic is formed through a
reaction sintering process between the TiB2 and titanium powders during the hot-press phase. TiB is densified as a
cermet (ceramic in a metal matrix) to aid in fabrication. A major development in the process was overcoming the
inherent thermoelastic properties of the constituent layers and the resultant stresses that arise from the differences in
thermal expansion coefficients and elastic moduli of the layers. Analytical and finite element modeling techniques
Figure 14. Titanium Wrought Plate Bolted to an
Aluminum Rear Plate
Ti-6Al-4V CP Ti Gr 2
Beta Alloy Ti-6Al-4V
Ti-6Al-4V CP Ti Gr 2
Beta Alloy Ti-6Al-4V
Figure 15. Dual Hard Titanium Concepts
Figure 16. Functionally Graded Titanium Monoboride/Titanium Plate

were used to determine the residual stresses and modify the processing parameters. The resultant tiles produced to
date are among the largest functionally gradient materials produced in the world by a practical process and represent
advancement in this technology area.
Another more advanced ceramic laminate is hot isostatically pressed ceramic tiles in titanium matrices. The titanium
matrix maintains a compressive load on the ceramic, thereby allowing full advantage of the large dynamic
compressive strengths of ceramics [18]. The left image of Figure 17 shows the defeat of a long rod tungsten alloy
penetrator by a defeat mechanism called “interface dwell; the projectile is being totally consumed at the metal
ceramic interface with little damage to the ceramic. One fabrication method for incapsulation in a metallic structure
is to hot isostatically press the titanium around the ceramic as seen in the right two images.
CURRENT APPLICATIONS OF TITANIUM IN GROUND SYSTEMS
The use of titanium in military platforms has been driven by two related requirements, increased ballistic
performance when used as an armor or weight reduction to increase mobility or meet tactical requirements. Either
application takes advantage of the unique density and strength properties of this metal. As an armor, the
performance has been documented in previous sections; however, the use of titanium as a weight reduction
technique is also employed. The earliest use of titanium in a combat vehicle is shown in Figure 18 of a 1960 Detroit
Arsenal prototype of a titanium cab on an ONTOS tracked vehicle [19]. While the research on titanium armors
Figure 17. Hot Isostatically Pressed Ceramic in Titanium Matrices
Figure 18. 1960 Detroit Arsenal Titanium Cab on an ONTOS Tracked Vehicle

continued with periodic armor designs, the main drawback to the use of titanium remained the relative cost to other
metals. Until very recently, the majority of the structure and armor components for the worlds combat vehicles
remained steel based. The advent of low cost titanium grades and increased cost of more advanced materials such as
composites and ceramics has allowed the use of titanium alloys as cost effective alternatives. The following
paragraphs will illustrate some applications of titanium to currently field combat vehicles and weapon systems; the
discussion is not comprehensive and some applications cannot be discussed in this forum.
One of the best illustrations of titanium on a current legacy system is shown in Figure 19 on the M1A2 Abrams tank
where a concerted effort was made to reduce weight of components on the chassis [20-21]. While this weight
reduction program envisioned a larger replacement of components, these four areas reduced combat weight by over
1500 lbs without loss of function or protection. Figure 20 shows the M2A2 Bradley Fighting Vehicle and two uses
Figure 19. Titanium Weight Reduction Program for M1A2 Abrams Battle Tank
Figure 20. Titanium Commanders Hatch and Roof Applique on M2A2 Bradley Fighting Vehicle
Commander’s Hatch
Turret Roof Applique

of titanium have been incorporated into design. The drivers hatch is a titanium forging and a titanium roof appliqué
was added for increased protection. The Reactive Armor Boxes on the sides were also designed to utilize titanium
sheet as a replacement for sheet metal in the box construction. The Ultra-light weight Field Howitzer, designated
M777A1 in the USA, shown in Figure 21,was selected in 1997 by a joint US Army / Marine Corps initiative to
replace the existing inventory of M198 155mm towed howitzers [22]. The construction of the M777A1 makes
extensive use of titanium and titanium castings, enabling a weight reduction of 3,175kg (7,000lb) compared to the
M198 howitzer which it replaces in the US Army and USMC inventory.
Future platforms will utilize a range of advanced light weight materials and low cost titanium has a role in providing
high strength, low weight structures and components. These can be seen in a number of prototypes developed by the
US Army and their contractors. Figure 22 shows the Pegasus electric drive wheeled prototype developed by BAE
Systems that utilized both a lower and upper titanium welded structure [23]. The vehicle incorporated a composite
rear space frame armor as well as the capability to mount a composite appliqué. This was the first full titanium
vehicle prototype since the ONTOS vehicle in 1960. The latest prototype titanium vehicle structure was an early
Future Combat Vehicle hull section that was used to test composite armors (Figure 23) [19]. The lower body and
nose sections were fabricated from Military Specification 46077G Class 3 low cost titanium and were mated to a
composite and space frame composite upper hull section. The vehicle was subjected to extensive ballistic testing and
shock loading to measure the vehicle response.
CONCLUSIONS
This paper has provided an overview on the use of titanium in military ground systems. The emphasis has been to
examine the design and processing aspects in the application of this lightweight, high strength metal. With major
emphasis on lightening future ground platforms, low cost grades of titanium can provide both structural and ballistic
solutions. The biggest issues are cost tradeoffs versus ballistic and structural performance and continued
advancements in titanium processing are important to maintain titanium as a metal choice for future military
systems.
Figure 21. Ultra-light Weight M777A1 Towed Howitzer Utilizes Extensive Titanium
Castings

Figure 23. Future Combat Vehicle Titanium Hull Prototype
Figure 22. BAE Pegasus Titanium Wheeled Prototype

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