Recent Developments in High-Strength Near-Beta Titanium ... · A380 Landing Gear Upper Stay Upper Panel Lower Panel Bogie Beams Brake Rods Lower Torque Arm Upper Torque Arm Lower
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Recent Developments in High-Strength
Near-Beta Titanium Alloys
John Fanning
TIMET
Use of high strength titanium alloys in lieu of steels
reduces weight, avoids problematic coatings, and lowers
maintenance requirements.
Ti555 (also known as Ti555-3) is capable of favorable
combinations of properties that have enabled the
expanded use of titanium in aerospace applications.
Newer alloys, such as Ti-5.5Al-5Mo-5V-2.3Cr-0.8Fe-0.14O
[Ti18] have been designed to provide similar benefits, but
with incremental improvements in properties.
This presentation provides comparative data for selected
high strength titanium alloys ins the subtransus solution
heat treated plus aged condition.
High-Strength Near-Beta Titanium Alloys
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Outline
Recent Developments in High-Strength
Near-Beta Titanium Alloys:
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Outline
Recent Developments in High-Strength
Near-Beta Titanium Alloys:
Nominal Compositions of Current and Historical
Near-Beta Titanium Alloys
Near-Beta High Strength Ti Alloys
‘10 ‘00 ‘90 ‘80 ‘70 1960
New Alloys
For New
Programs?
C-17
B757 B777 B787
History High Strength Ti Applications Listed by 1st Flight Date
A350 A380
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Outline
Recent Developments in High-Strength
Near-Beta Titanium Alloys:
High Strength Ti Applications
Truck Beam and other TIMETAL 10-2-3 forging
applications on the Boeing 777 Main Landing Gear.
Truck
Beam
Brake
Rods
Upper
Lower
Drag Strut
Upper
Lower
Side Strut Lower
Torque
Link Steering
Walking
Beam
TIMETAL 555 die forging evaluated for Boeing 777 Main Landing Gear [4].
Inset: Schematic diagram of Wyman Gordon forging.
High Strength Ti Applications
A380 Landing Gear
Upper Stay
Upper Panel
Lower Panel
Bogie Beams
Brake Rods
Lower Torque
Arm
Upper Torque Arm
Lower Stay
REF: R.R. Boyer, K.T. Slattery, D.J.
Chellman and H.R. Phelps, Ti-2007
Science and Technology, ed. by N.
Niinomi, et al, (Japan Inst. of Metals,
Sendai, Japan, 2007) pp1255-1262.
High Strength Ti Applications
1m
REF: R. Panza-Giosa – Ph.D. Thesis – Dept. of Materials
Science and Engineering, McMaster University (2009)
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Outline
Recent Developments in High-Strength
Near-Beta Titanium Alloys:
Ti555 has evolved into the baseline alloy
for numerous high strength applications.
The main advantages of 555 vs. Ti-10-2-3
are:
Not as prone to segregation.
- Lower Fe
Less sensitive to forging and heat
treatment parameters. - Processed further below Tb.
Air-hardenable in large sections. - Avoids the need for WQ.
Ti555 vs. Ti-10-2-3
TIMETAL 18 Alloy Development
Ti64 Ti10-2-3 Ti-555 ???
What alloy comes next?
The R&D goal was to achieve incremental
property improvements over the incumbent
near-beta alloys.
TIMETAL 18 Alloy Development
The ultimate goal was to identify and characterize new
allow compositions that offer advantages with regards
to mechanical properties, cost or processing (i.e., less
sensitivity to variations in heat treatment parameters).
An investigation of new titanium alloys (with Mo, V, Cr,
Fe and Al) was performed for production of high
strength structural aerospace components.
Main constraint on alloy development is the periodic
table of the elements . . .
Beta Stabilizers Alpha Stabilizers
b-isomorphous (V, Mo) b-eutectoid (Fe, Cr) b-peritectoid (Al) Simple Peritectic (O, N)
Binary Ti Alloy Phases and Periodic Table
Ti18 (wt%): Ti – 5.5Al – 5Mo – 5V – 2.3Cr – 0.8Fe – 0.15O
TIMETAL 18 Alloy Development
For TIMETAL 18, the Mo equivalent has been set
at about 14.2 and ranges from about 12.8 to 15.2
35.065.05.1
FeCrVMoMoeq
35.065.0
5.1FeCr
VMo
EUT
ISO
b
b
The beta stabilizer ratio has been set at about 1.4
The above equations refer to equilibrium conditions, but
the kinetics are affected by the relative amounts of bEUT.
Nominal Metallic Compositions of Near-Beta Titanium Alloys
The down-selected composition has been named TIMETAL 18.
Patent Number GB2470613 granted 25 May 2011.
TIMETAL 18 Alloy Development
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Outline
Recent Developments in High-Strength
Near-Beta Titanium Alloys:
TIMETAL 18 Production Scale-Up
First production-scale heat launched in
2010 to confirm lab observations.
A 32in diameter 10.7klbs ingot was melted
at TIMET Henderson.
The heat was converted at TIMET Toronto
OH and is under evaluation.
TIMETAL 18 Production Scale-Up
Ingot Analysis Results for Heat H14634
Excellent uniformity. Beta transus range = 11F [6C]
Location Element, wt% Tb, calc
Al C Cr Fe Mo N O V F C
TOP 5.56 0.012 2.30 0.71 5.12 0.007 0.15 5.03 1596 869
TOP-MIDDLE 5.65 0.014 2.35 0.72 5.17 0.006 0.15 5.10 1597 870
MIDDLE 5.55 0.012 2.33 0.73 5.07 0.006 0.15 5.03 1595 868
BOT-MIDDLE 5.60 0.012 2.36 0.75 5.08 0.006 0.15 5.09 1594 868
BOTTOM 5.50 0.011 2.38 0.79 4.94 0.005 0.14 5.03 1586 863
Ingot Min 5.50 0.011 2.30 0.71 4.94 0.005 0.14 5.03 1586 863.2
Ingot Max 5.65 0.014 2.38 0.79 5.17 0.007 0.15 5.10 1597 869.8
Ingot Range 0.15 0.003 0.08 0.08 0.23 0.002 0.01 0.07 11 6
Ingot Average 5.57 0.012 2.34 0.740 5.08 0.006 0.148 5.06 1594 868
TIMETAL 18 Production Scale-Up
Product Analysis Results for Top Slice [worst case]
Location Element, wt% Tb, calc
Al C Cr Fe Mo N O V F C
T1-OS 5.51 0.012 2.36 0.72 4.99 0.005 0.14 5.02 1589 865
T1-OS-180 5.53 0.013 2.35 0.72 5.04 0.007 0.15 5.02 1596 869
T1-MR 5.50 0.014 2.40 0.77 4.94 0.006 0.15 5.06 1593 867
T1-MR-180 5.50 0.014 2.40 0.76 4.95 0.006 0.15 5.05 1593 867
T1-CTR 5.39 0.013 2.43 0.82 4.80 0.005 0.14 5.07 1583 861
T1 Min 5.39 0.012 2.35 0.72 4.80 0.005 0.14 5.02 1583 861.5
T1 Max 5.53 0.014 2.43 0.82 5.04 0.007 0.15 5.07 1596 868.8
T1 Range 0.14 0.002 0.08 0.10 0.24 0.002 0.01 0.05 13 7
T1 Average 5.49 0.013 2.39 0.758 4.94 0.006 0.146 5.04 1591 866
T1 (and all other slices) exhibited no beta flecks at Tb – 40F [Tb – 22C]
Production-Scale Evaluation Interim Summary
Product chemical analysis shows excellent chemical homogeneity.
All beta fleck check evaluations passed.
Capability testing showed good strength-ductility combinations were achievable.
10in and 5.9in round successfully ultrasonic inspected to #2 FBH.
Immediately available product:
Evaluation of Forged Products is Underway . . .
Photomicrograph at center of TIMETAL 18 10in (254mm) Diameter Billet
TIMETAL 18 Billet Microstructure
TIMETAL 18 (Ti-5.5Al-5V-5Mo-2.3Cr-0.8Fe)
High-Strength Forging Alloy
0
10
20
30
40
50
60
70
80
90
100
110
120
0
20
40
60
80
100
120
140
160
180
200
220
240
1000 1050 1100 1150 1200 1250 1300 1350
Du
cti
lity
, %
Str
en
gth
, ksi
Age Temperature, F
General Trends for Tensile Properties of TIMETAL 18 Billet and Bar 10in, 5.9in, 4in, and 0.5in diameter. Tested at radial positions of center, mid and outer.
Solution Treated at Tb - 80F, Air Cooled. Room Temperature. Longitudinal.
TIMET PROPRIETARY
UTS
TYS
RA
ELONG
1100F
[593C]
1200F
[649C]
1300F
[704C]
Optical
5mm
5mm
5mm
Backscattered Electron
Ti18 Subtransus STA Microstructures
Age
Temperature
205 ksi
[1435 MPa]
185 ksi
[1295 MPa]
165 ksi
[1155 MPa]
Nominal
UTS
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Outline
Recent Developments in High-Strength
Near-Beta Titanium Alloys:
Comparative Tensile Property Evaluation of
Ti18 and Ti555 Billet
The purpose was to obtain a meaningful direct
comparison of tensile properties of Ti18 and Ti555.
Each alloy sample was:
• The product of production-scale material.
• Melted to its preferred composition.
• Converted by similar TMP.
• Heat treated at similar size.
• Systematically tensile tested across diameter.
Experiments were performed on two sizes.
Experimental Approach
Product chemical analysis results for billet used in heat treat study.
Product Sample
Al Mo V Cr Fe O
T2A-OS 5.58 5.04 4.98 2.39 0.73 0.15
T2A-OS180 5.58 5.04 4.96 2.39 0.74 0.16
T2A-MR 5.56 5.03 4.96 2.38 0.73 0.15
T2A-MR180 5.57 5.03 4.96 2.38 0.74 0.15
T2A-CTR 5.57 5.01 4.98 2.40 0.75 0.15
T2C-OS 5.56 5.00 4.94 2.38 0.74 0.15
T2C-OS180 5.52 4.98 4.89 2.36 0.73 0.16
T2C-MR 5.58 5.02 4.96 2.39 0.75 0.16
T2C-MR180 5.55 4.99 4.93 2.39 0.75 0.16
T2C-CTR 5.55 4.98 4.92 2.38 0.74 0.16
T2CU-OS 5.50 4.94 4.96 2.39 0.74 0.15
T2CU-OS180 5.56 5.00 4.98 2.41 0.75 0.16
T2CU-MR 5.56 5.00 4.97 2.40 0.75 0.14
T2CU-MR180 5.56 5.01 4.97 2.40 0.75 0.15
T2CU-CTR 5.57 5.01 5.00 2.42 0.76 0.15
Ti18 Avg. 5.56 5.01 4.96 2.39 0.74 0.15
Ti18 5.9in
Rnd.
Element, wt%
Product Sample
Al Mo V Cr Fe O
Edge 5.44 5.11 5.05 3.00 0.361 0.141
Mid-Rad 5.42 5.09 5.04 3.00 0.365 0.135
Center 5.46 5.09 5.08 3.04 0.373 0.138
Edge 5.44 5.08 5.05 3.01 0.365 0.135
Mid-Rad 5.45 5.09 5.07 3.03 0.422 0.132
Center 5.45 5.09 5.06 3.02 0.368 0.136
Edge 5.44 5.09 5.06 3.02 0.367 0.146
Mid-Rad 5.44 5.07 5.04 3.01 0.367 0.134
Center 5.46 5.08 5.07 3.04 0.371 0.133
Edge 5.47 5.11 5.08 3.03 0.368 0.133
Mid-Rad 5.45 5.07 5.05 3.03 0.371 0.142
Center 5.48 5.10 5.07 3.03 0.371 0.138
Ti555 Avg. 5.45 5.09 5.06 3.02 0.37 0.14
Ti555 7in
Rnd.
Element, wt%
Ti18: Ti-5.6Al-5.0Mo-5.0V-2.4Cr-0.74Fe-0.15O
Ti555: Ti-5.5Al-5.1Mo-5.1V-3.0Cr-0.37Fe-0.14O
TIMETAL 18 Billet Evaluation
~1in
Tensile Specimen Arrangement for
Billet Heat Treat Study
Top View
X LONG
C OD MR
C OD MR
C
C
OD
OD
MR
MR
O MR O MR C C
Side View
Solution heat treated as full billet section, then cut into quarters for aging and tensile testing.
TIMET Background Proprietary Information
Tensile Properties of Ti18 and Ti555 Billet
Solution Treated at Tb - 80F
0
5
10
15
20
25
30
35
40
45
50
55
0
20
40
60
80
100
120
140
160
180
200
220
1050 1100 1150 1200 1250 1300 1350
Elo
ng
ati
on
, %
Str
en
gth
, ksi
Age Temperature, F
Solution Treated Size: 6in diam. X 3.75in long for Ti18 and 7in diam. X 3.5in long for Ti555 Each observation represents the average of the center, mid-radius, and OD L results.
UTS - Ti18 UTS - Ti555
TYS - Ti18 TYS - Ti555
Elong - Ti18 Elong - Ti555
The purpose was to obtain a meaningful direct
comparison of tensile properties of Ti18 and Ti555.
Each alloy sample was:
• The product of production-scale material.
• Melted to its preferred composition.
• Converted by similar TMP.
• Heat treated at same size.
• Systematically tensile tested across diameter.
Experiments were performed on two sizes.
Results for 10in Diameter:
Experimental Approach
~2in
Tensile Specimen Arrangement for
10in [250mm] Diam. Billet Heat Treat Study
Top View
X LONG
C OD MR C OD MR
O MR O MR C C
Side View
Solution heat treated and aged as full billet section.
Tensile Properties vs. Radial Position for
10in [250mm] Diam. Ti Billet
Position UTS, MPa (ksi) TYS, MPa (ksi) Elong,
%
RA,
%
Outer 1338 (191.4) 1277 (182.7) 8.7 20
Mid-Radius 1340 (191.7) 1285 (183.8) 7.2 17
Center 1345 (192.4) 1274 (182.2) 9.6 21
Center 1356 (194.0) 1276 (182.5) 9.3 18
Mid-Radius 1335 (190.9) 1274 (182.3) 8.9 18
Outer 1331 (190.4) 1271 (181.9) 8.6 21
Long. tensile properties vs. radial position for 250mm (10in)
diam.Ti18 billet solution treated at 816C (1505F), 2hrs, air
cooled, then aged at 621C (1150F) for 8 hrs, air cooled.
150
160
170
180
190
200
210
0 2 4 6 8 10 12
Ult
imate
Ten
sil
e S
tren
gth
, ksi
Elongation, %
Ti18
Ti555
Comparison of Ti18 and Ti555 L strength-ductility combinations for
250mm diameter billet solution treated at Tb-44C (Tb-80F), 2hrs, air
cooled, then aged at 621C (1150F) for 8 hrs, air cooled.
Comparison of Ti18 and Ti555 Strength-Ductility
Combinations for 250mm Diameter Billet
1000
1100
1200
1300
1400
1500
0 2 4 6 8 10 12 U
ltim
ate
Te
ns
ile
Str
en
gth
, M
Pa
Elongation, %
Ti18
Ti555
2mm
Ti18 Ti555
Microstructure of 10in Ti18 and Ti555 Billet
Solution Treated at Tb - 80F, AC, then aged.
2mm
UTS, MPa (ksi) TYS, MPa (ksi) Elong, %
1246 (181) 1184 (172) 7
Average Tensile Properties
UTS, MPa (ksi) TYS, MPa (ksi) Elong, %
1341 (192) 1276 (183) 9
Average Tensile Properties
Generalized Reaction: bo b b’ b b’ a b a
bo b b’ b b’ a b a
(The above reactions may or may not involve w at an intermediate stage.)
Comparison of Ti18 and Ti555 Strength-Ductility
Combinations for 250mm Diameter Billet
Observations:
Similar macrostructure.
Similar volume fraction and morphology of primary a.
∴ Differences in tensile properties are likely related to
effect of different Fe and Cr levels on the kinetics of
bo decomposition and subsequent a precipitation:
Ti18 Ti555
Microstructure of 10in Ti18 and Ti555 Billet
Solution Treated at Tb - 80F, AC, then aged.
UTS, MPa (ksi) TYS, MPa (ksi) Elong, %
1246 (181) 1184 (172) 7
Average Tensile Properties
UTS, MPa (ksi) TYS, MPa (ksi) Elong, %
1341 (192) 1276 (183) 9
Average Tensile Properties
0
20
40
60
80
100
120
140
160
1.E+02 1.E+04 1.E+06 A
lte
rna
tin
g P
se
ud
ostr
ess, ksi
Ni or Nf
Ti18 Aged 1150F (621C)
Ti18 Aged 1300F (704C)
Ti64 Annealed
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.E+02 1.E+04 1.E+06
Ma
x. S
tra
in, %
Ni or Nf, cycles
Ti18 Aged 621C
Ti18 Aged 704C
Ti64 Annealed
Low cycle fatigue life for Ti18 100mm (4in) bar at two strength levels as noted.
Tested at room temperature using unnotched longitudinal specimens at R= -1.0.
Data for Ti64 plate is included for general reference.
UTS=
191ksi UTS=
161ksi UTS=
140ksi
Low Cycle Fatigue of Ti18 100mm [4in] Bar
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1000 1100 1200 1300 1400 1500
Cycle
s to
Fa
ilure
Ultimate Tensile Strength, MPa
Ti18- Globular
VT22-Globular
VT22-Lamellar
Fatigue life vs. UTS for unnotched specimens tested at smax = 0.5*UTS at
R= -1.0. Comparison of Ti18 to VT-22 as reported by Polkin et al.
I.S. Polkin et al., “Structure and Mechanical Properties
of VT22 High Strength Titanium Alloy Semiproducts”,
Proceedings 7th World Conference on Titanium, TMS,
San Diego, CA, 1992, v. II, p.1569-1578.
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Outline
Recent Developments in High-Strength
Near-Beta Titanium Alloys:
Biggest challenge is always scaling from lab material to
production—scale parts.
Melts, converts, and forges without difficulty.
Lab scale and basic mill products are capable of
achieving excellent properties.
Preliminary die forging results indicated excellent
forgeability at both ab and b temperatures.
Scale-Up Challenges:
Optimization of Heat Treatment
Balancing initial work with subsequent work in part.
Affects overall properties.
Affects directionality.
Ti18 Die Forging Observations
Concluding Remarks
TIMETAL 18 is expected to provide incremental property improvements over current near-beta alloys.
Evaluation of production-scale material continues.
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