recent developments in high-strength titanium fasteners for aerospace applications

Mission Critical Metallics

2013 ATI. All Rights Reserved.

Gavin Garside Greg Vignoul, John Foltz, Walter Vernitsky, Leonard Nowak, Corey Smith

April 3, 2013

ATI 2013. All Rights Reserved. MISSION CRITICAL METALLICS 2


Background

Supply Chain and Processing

ATI 425 Alloy

Heading Trials

Mechanical Properties

Direct Age Experiments

Minimum Mechanical Properties of Fastener Alloys

ATI 6-4

Quenching Study

Summary

Outline



ATI has vast experience with titanium and titanium alloys

Long Products Ingot, billet, round & rectangle bar, shapes, rod, wire & coil, extrusions, seamless

tube & pipe, fastener stock

Flat Products Plate, sheet, coil, foil & precision rolled strip

Alloys ATI 6-4 Alloy, ATI 425 Alloy, ATI 45Nb Alloy, ATI 3-2.5 Alloy, ATI 3510, ATI

6-2-4-2, ATI 6-2-4-6, and many more

Until recently, ATI has not targeted fastener markets

But has supplied ATI 45Nb Alloy for over 20 years for aerospace applications including rivets

New to the market, not the materials

Focus on ATI 425 Alloy and ATI 6-4 Alloy

Background



Titanium for fastener applications

Similar strength of medium alloy steel

Half the weight of steel

Much more corrosion resistant than steel

Often with no coating

Wide operating temperature range

-350oF to 800oF

Background



ATI Titanium Fastener Stock Processing Double Melting

(Primary + VAR)

Forging

Drawing

Hot Rolling

Finishing



Reliable, Secure, and Redundant Supply Chain

Lebanon

Louisville

Richland

Albany

Rowley

La Porte

Portland

Bolingbrook

Northbrook

Houston

Grant, Gurley, Huntsville, Madison

Richburg

Monroe

Bakers

La Vergne

Pittsburgh, PA

(ATI Headquarters)

Waterbury

Wallingford

Windsor

S Windsor

New Bedford

Bagdad, Latrobe, Brackenridge,

Houston, Midland, Washington,

Vandergrift, Oakdale, Waynesboro

Primary & Melting

Manufacturing & Fabricating

Monaca, Rochester, Zelienople

R&D

Service Centers

Pico Rivera

Walterboro

Lockport

Frackville

Cudahy

La Crosse

Irvine

*Facilities Worldwide*



Specifications

AMS 6946, AMS 6947, AMS 6948

MMPDS design allowables

MIL-DTL-46077 class 4

ASTM Ti Grade 38

Advantages

Typical alpha/beta processing

Lower flow stress than Ti-6Al-4V

High Strength

Cold deformable

Beta Transus = 1778oF

ATI 425 Alloy Composition



Heading trials Mill Annealed Material

Trials with no process adjustments

14.6mm bar

ATI 425 Alloy

Warm headed

ATI 425 Alloy

Warm thread

rolled

ATI 425 Alloy

Warm thread

rolled

Ti 6-4 Alloy

Rolled and headed just as well as Ti 6-4 Alloy

8



Thread macros Cold formed Warm formed

Thread appearance

similar to ATI 6-4 Alloy

Fine thread details were

reproduced in ATI 425 Alloy

9



ATI 425 Alloy Solution Treated and Aged

Both ATI 6-4TM Alloy and ATI 425 Alloy hold the relationship:

UTSDS 6.0Min. Properties Condition UTS (ksi)

A-286 STA 130

A-286 DA 180

Standard solution treatment and ageing conditions

Good correlation between UTS and double shear



Material Condition UTS (ksi) Yield (ksi) Density (lb/in3)

ATI 425 Alloy MA 145 135 0.162

ATI 425 Alloy (Typical) STA 193 171 0.162

STA = Solution Treat and Age; DA = Direct Age; MA = Mill Anneal

ATI 425 Alloy Elevated

Temperature

Testing



ATI 425 Alloy Direct Age Experiments




140

150

160

170

180

190

200

210

220

Yie

ld S

tre

ngt

h, k

si

Increasing Temperature

Yield Strength vs. Increasing Temperature

Low Reduction - 3 Hours


Medium Reduction - 3 Hours


High Reduction - 3 Hours


Straightened - 3 Hours


180

185

190

195

200

205

210

215

220

225

230

Ult

imat

e T

en

sile

Str

en

gth

, ksi


Ultimate Tensile vs. Increasing Temperature









5

6

7

8

9

10

11

12

13

14

% E

lon

gati

on


% El vs. Increasing Temperature

25

27

29

31

33

35

37

39

41

43

45

Re

du

ctio

n o

f A

rea,

%


% RA vs. Increasing Temperature



Parameters chosen for comparison

Medium Reduction Draw

There is a happy medium that needs to be found


7

8

9

10

11

12

13

14

160

170

180

190

200

210

220

230

% E

lon

gati

on

Stre

ngt

h, k

si


Strength - % Elongation Comparison

26

31

36

41

160

170

180

190

200

210

220

230

% R

ed

uct

ion

of

Are

a

Stre

ngt

h, k

si


Strength - % Reduction of Area Comparison

Yield Strength

Ultimate TensileStrength



Minimum Mechanical Properties Material Condition UTS (ksi) Yield (ksi) Elong (%) RA (%) Density (lb/in3)

A-286 STA 130 85 15 20 0.286

A-286 DA 180 150 10 18 0.286

Alloy 718 STA 180 150 12 15 0.296

Alloy 718 DA 220 200 8 15 0.296

MP35N DA 260 230 8 35 0.304

MP159 DA 260 250 6 22 0.301

ATI 6-4 Alloy MA 130 120 10 25 0.160

ATI 6-4 Alloy STA 165 155 10 20 0.160

ATI 425 Alloy MA 145 135 15 30 0.162

ATI 425 Alloy STA 170 150 10 20 0.162

ATI 425 Alloy (Typical)

STA 193 171 12 44 0.162

ATI 425 Alloy (Experimental Results)

DA 213 195 10 34 0.162

STA = Solution Treat and Age; DA = Direct Age; MA = Mill Anneal



ATI 425 Alloy meets or exceeds A-286 values

ATI 425 Alloy is almost half the density of A-286

Minimum Mechanical Properties Material Condition UTS (ksi) Yield (Ksi) Elong (%) RA (%) Density (lb/in3)

A-286# STA 130 85 15 20 0.286

A-286# DA 180 150 10 18 0.286

ATI 6-4 Alloy MA 130 120 10 25 0.160

ATI 6-4 Alloy STA 165 155 10 20 0.160

ATI 425 Alloy MA 145 135 15 30 0.162

ATI 425 Alloy STA 170 150 10 20 0.162

ATI 425 Alloy (Typical Results)

STA 193 171 12 44 0.162

ATI 425 Alloy (Experimental Results)

DA 213 195 10 34 0.162

STA = Solution Treat and Age; DA = Cold Work and Age; MA = Mill Anneal

#Source: Roach, Thomas SPS Technologies, Inc. Alloy 718 Fasteners: Versatility and Reliability for Aerospace Design



ATI 6-4 Alloy

ATI 425

Alloy

Solution Treated and Aged Mill Annealed

Transverse



Heading trials

Difficulty of the process

Trials with no process adjustments

Cold, low

heading

strain

Cold, high

heading

strain

Warm, high

heading strain Standard Ti 6-4 Alloy Process

18



0.248 fastener stock

Parameters

Time to quench

As fast as possible, 5 second delay, 10 second delay

Water agitation

Agitated and unagitated

Solution treatment time

30, 60, and 90 minutes at temperature (1700oF)

Samples then aged 900oF for 4 hours

Air cooled

Double shear testing

Quench Study ATI 6-4 Alloy



Time to quench had a drastic effect on double shear properties

Water agitation and solution treatment time did not significantly affect double shear properties

Quench Study ATI 6-4 Alloy Time to Quench

Solution Treatment Time ASAP 5 sec 10 sec

30 min 105.2 102.3 99.6

30 min with water agitation during quench 104.6 101.5 99.7

60 min 104.8 102.7 101.1


90 min 104.8 103.5 100.5


(Double shear - values in ksi)



ATI 6-4 Alloy has a great combination of properties for aerospace fastener applications

o High strength to weight ratio with good corrosion resistance

o ATI produces fastener stock to meet industrial applications

o Our material has a uniform fine grain microstructure well suited for aerospace

fasteners

ATI 425 Alloy is a highly versatile / titanium alloy with:

o Higher mill annealed strengths than ATI 6-4 Alloy

o Excellent formability and ductility

o Higher solution treated and aged double shear and ultimate tensile strengths

than ATI 6-4 Alloy

o Greater strength especially at >0.5 diameter than ATI 6-4 Alloy

o Capability to replace A286 for cold applications

o Direct age experiments show potential for higher mechanical properties than

STA treatment

Summary

recent developments in high-strength titanium fasteners for aerospace applications

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