Recent Developments in High-Strength Near

Recent Developments in High-Strength
Near-Beta Titanium Alloys
John Fanning
TIMET
High-Strength Near-Beta Titanium Alloys
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.
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:
Historical Overview
Example Applications
New Alloy Development [TIMETAL 18]
Production Scale-Up
Comparative Tensile Properties
Die Forging Observations
Near-Beta High Strength Ti Alloys
Nominal Compositions of Current and Historical
Near-Beta Titanium Alloys
History High Strength Ti Applications
Listed by 1st Flight Date
B757
B777
‘70
1960
C-17
‘80
B787
‘90
A380
‘00
New Alloys
For New
Programs?
‘10
A350
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
High Strength Ti Applications
Side Strut
Upper
Lower
Lower
Torque
Link
Steering
Walking
Beam
Drag Strut
Upper
Lower
Truck
Beam
Brake
Rods
Truck Beam and other TIMETAL 10-2-3 forging
applications on the Boeing 777 Main Landing Gear.
High Strength Ti Applications
TIMETAL 555 die forging evaluated for Boeing 777 Main Landing Gear [4].
Inset: Schematic diagram of Wyman Gordon forging.
A380 Landing Gear
Upper Stay
Upper Panel
Lower Stay
Lower Panel
Upper Torque Arm
Bogie Beams
Lower Torque
Arm
Brake Rods
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)
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
Ti555 vs. Ti-10-2-3
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.
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 . . .
Binary Ti Alloy Phases and Periodic Table
b-isomorphous (V, Mo)
b-eutectoid (Fe, Cr)
Beta Stabilizers
b-peritectoid (Al)
Simple Peritectic (O, N)
Alpha Stabilizers
Ti18 (wt%): Ti – 5.5Al – 5Mo – 5V – 2.3Cr – 0.8Fe – 0.15O
TIMETAL 18 Alloy Development
V
Cr
Fe
Moeq  Mo 


1.5 0.65 0.35
For TIMETAL 18, the Mo equivalent has been set
at about 14.2 and ranges from about 12.8 to 15.2
b ISO
b EUT
V
Mo 
1.5

Cr
Fe

0.65 0.35
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.
TIMETAL 18 Alloy Development
The down-selected composition has been named TIMETAL 18.
Patent Number GB2470613 granted 25 May 2011.
Nominal Metallic Compositions of Near-Beta Titanium Alloys
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
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
Location
Tb, calc
Element, wt%
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
Excellent uniformity. Beta transus range = 11F [6C]
TIMETAL 18 Production Scale-Up
Product Analysis Results for Top Slice [worst case]
Location
Tb, calc
Element, wt%
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 . . .
TIMETAL 18 Billet Microstructure
Photomicrograph at center of TIMETAL 18 10in (254mm) Diameter Billet
TIMETAL 18 (Ti-5.5Al-5V-5Mo-2.3Cr-0.8Fe)
High-Strength Forging Alloy
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.
120
220
UTS
110
200
TYS
100
180
90
160
80
140
70
120
60
100
50
RA
80
40
60
30
ELONG
40
20
20
10
0
0
1000
1050
1100
1150
1200
Age Temperature, F
TIMET PROPRIETARY
1250
1300
1350
Ductility, %
Strength, ksi
240
Ti18 Subtransus STA Microstructures
Age
Temperature
Nominal
UTS
1100F
[593C]
205 ksi
[1435 MPa]
Optical
Backscattered Electron
5mm
1200F
[649C]
185 ksi
[1295 MPa]
5mm
1300F
[704C]
165 ksi
[1155 MPa]
5mm
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
Comparative Tensile Property Evaluation of
Ti18 and Ti555 Billet
Experimental Approach
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.
TIMETAL 18 Billet Evaluation
Product chemical analysis results for billet used in heat treat study.
Product
Sample
Fe
0.73
0.74
0.73
0.74
0.75
0.74
0.73
0.75
0.75
0.74
0.74
0.75
0.75
0.75
0.76
O
0.15
0.16
0.15
0.15
0.15
0.15
0.16
0.16
0.16
0.16
0.15
0.16
0.14
0.15
0.15
Ti18 Avg. 5.56 5.01 4.96 2.39 0.74
0.15
T2A-OS
T2A-OS180
T2A-MR
T2A-MR180
T2A-CTR
T2C-OS
T2C-OS180
Ti18 5.9in
T2C-MR
Rnd.
T2C-MR180
T2C-CTR
T2CU-OS
T2CU-OS180
T2CU-MR
T2CU-MR180
T2CU-CTR
Al
5.58
5.58
5.56
5.57
5.57
5.56
5.52
5.58
5.55
5.55
5.50
5.56
5.56
5.56
5.57
Mo
5.04
5.04
5.03
5.03
5.01
5.00
4.98
5.02
4.99
4.98
4.94
5.00
5.00
5.01
5.01
Element, wt%
V
Cr
4.98
2.39
4.96
2.39
4.96
2.38
4.96
2.38
4.98
2.40
4.94
2.38
4.89
2.36
4.96
2.39
4.93
2.39
4.92
2.38
4.96
2.39
4.98
2.41
4.97
2.40
4.97
2.40
5.00
2.42
Product
Ti555 7in
Rnd.
Sample
Mo
5.11
5.09
5.09
5.08
5.09
5.09
5.09
5.07
5.08
5.11
5.07
5.10
Element, wt%
V
Cr
5.05
3.00
5.04
3.00
5.08
3.04
5.05
3.01
5.07
3.03
5.06
3.02
5.06
3.02
5.04
3.01
5.07
3.04
5.08
3.03
5.05
3.03
5.07
3.03
Fe
0.361
0.365
0.373
0.365
0.422
0.368
0.367
0.367
0.371
0.368
0.371
0.371
O
0.141
0.135
0.138
0.135
0.132
0.136
0.146
0.134
0.133
0.133
0.142
0.138
Ti555 Avg. 5.45 5.09 5.06 3.02 0.37
0.14
Edge
Mid-Rad
Center
Edge
Mid-Rad
Center
Edge
Mid-Rad
Center
Edge
Mid-Rad
Center
Al
5.44
5.42
5.46
5.44
5.45
5.45
5.44
5.44
5.46
5.47
5.45
5.48
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
Tensile Specimen Arrangement for
Billet Heat Treat Study
X
LONG
OD
MR
C
C
MR
OD
OD
MR
C
C
MR
OD
O
MR
C
C
MR
O
Side View
~1in
Top 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
220
55
200
50
180
45
160
40
140
35
120
100
UTS - Ti18
UTS - Ti555
TYS - Ti18
TYS - Ti555
Elong - Ti18
Elong - Ti555
30
25
80
20
60
15
40
10
20
5
0
1050
1100
1150
1200
1250
Age Temperature, F
1300
0
1350
Elongation, %
Strength, ksi
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.
Experimental Approach
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:
Tensile Specimen Arrangement for
10in [250mm] Diam. Billet Heat Treat Study
X
LONG
O
OD
MR
C
C
MR
MR
C
C
MR
O
OD
Side View
Top View
Solution heat treated and aged as full billet section.
~2in
Tensile Properties vs. Radial Position for
10in [250mm] Diam. Ti Billet
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.
Position
UTS, MPa (ksi) TYS, MPa (ksi)
Elong, RA,
%
%
Outer
Mid-Radius
1338 (191.4)
1340 (191.7)
1277 (182.7)
1285 (183.8)
8.7
7.2
20
17
Center
Center
1345 (192.4)
1356 (194.0)
1274 (182.2)
1276 (182.5)
9.6
9.3
21
18
Mid-Radius
Outer
1335 (190.9)
1331 (190.4)
1274 (182.3)
1271 (181.9)
8.9
8.6
18
21
Comparison of Ti18 and Ti555 Strength-Ductility
Combinations for 250mm Diameter Billet
1500
Ultimate Tensile Strength, MPa
Ultimate Tensile Strength, ksi
210
Ti18
200
Ti555
190
180
170
160
Ti18
1400
Ti555
1300
1200
1100
1000
150
0
2
4
6
8
Elongation, %
10
12
0
2
4
6
8
10
Elongation, %
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.
12
Microstructure of 10in Ti18 and Ti555 Billet
Solution Treated at Tb - 80F, AC, then aged.
Ti18
Ti555
2mm
Average Tensile Properties
2mm
Average Tensile Properties
UTS, MPa (ksi)
TYS, MPa (ksi)
Elong, %
UTS, MPa (ksi)
TYS, MPa (ksi)
Elong, %
1341 (192)
1276 (183)
9
1246 (181)
1184 (172)
7
Generalized Reaction: bo b  b’  b  b’  a  b  a
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:
bo b  b’  b  b’  a  b  a
(The above reactions may or may not involve w at an intermediate stage.)
Microstructure of 10in Ti18 and Ti555 Billet
Solution Treated at Tb - 80F, AC, then aged.
Ti18
Ti555
Average Tensile Properties
Average Tensile Properties
UTS, MPa (ksi)
TYS, MPa (ksi)
Elong, %
UTS, MPa (ksi)
TYS, MPa (ksi)
Elong, %
1341 (192)
1276 (183)
9
1246 (181)
1184 (172)
7
Low Cycle Fatigue of Ti18 100mm [4in] Bar
160
1.0
Max. Strain, %
0.8
UTS=
140ksi
UTS=
161ksi
140
UTS=
191ksi
Alternating Pseudostress, ksi
0.9
0.7
0.6
0.5
0.4
0.3
0.2
Ti18 Aged 621C
Ti18 Aged 704C
Ti64 Annealed
0.1
0.0
1.E+02
1.E+04
1.E+06
Ni or Nf, cycles
120
100
80
60
40
20
0
1.E+02
Ti18 Aged 1150F (621C)
Ti18 Aged 1300F (704C)
Ti64 Annealed
1.E+04
Ni or Nf
1.E+06
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.
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.
1.E+07
1.E+06
Cycles to Failure
1.E+05
1.E+04
1.E+03
1.E+02
Ti18- Globular
1.E+01
VT22-Globular
VT22-Lamellar
1.E+00
1000
1100
1200
1300
1400
1500
Ultimate Tensile Strength, MPa
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.
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
Ti18 Die Forging Observations
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.
Concluding Remarks
TIMETAL 18 is expected to provide
incremental property improvements
over current near-beta alloys.
Evaluation of production-scale material
continues.