Recent Developments in High-Strength Near-Beta Titanium ... · A380 Landing Gear Upper Stay Upper...

Recent Developments in High-Strength

Near-Beta Titanium Alloys

John Fanning

TIMET

http://www.titanium.org/Category.cfm?CategoryID=262

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


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



Production Scale-Up



Outline



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.


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.


1m

REF: R. Panza-Giosa – Ph.D. Thesis – Dept. of Materials

Science and Engineering, McMaster University (2009)

Historical Overview



Production Scale-Up



Outline



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.


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


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.


Historical Overview



Production Scale-Up



Outline



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.


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


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



Production Scale-Up



Outline



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


1341 (192) 1276 (183) 9


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.


1246 (181) 1184 (172) 7



1341 (192) 1276 (183) 9


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



Production Scale-Up



Outline



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.

Recent Developments in High-Strength Near-Beta Titanium ... · A380 Landing Gear Upper Stay Upper...

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