tension-compression asymmetry and orientation creep...

Tension-Compression Asymmetry and Orientation Creep Anisotropy of a Ni

Based Turbine Disk Alloy

Dan Butler

JHU Mechanical Engineering MEANS2 Update Meeting

April 4, 2007

Our Goals

• Through high temperature microsample testing we aim to:

• Determine creep anisotropy and tension-compression asymmetry.

• Measure activation energies and stress dependencies.

• Enhance fidelity of mechanism map for turbine disk alloys.

Analyzing Grain Size• 700-800µm thick circular slices were cut perpendicular to longitudinal axis of each rod using a wire EDM.

• Slices were polished to remove residual recast layer from the EDM process.

• Faces of the slices were polished to a mirror finish using 400 grit SiC through 0.05µm colloidal silica.

• A modified waterless Kalling's etch is applied to reveal grain structure. This etchantconsists of 4g CuCl2, 50mL methanol (95%), and 40mL HCl (37%) and is applied using a cotton swab for 30 seconds.

1 cm

One of four bars received from University of Michigan

Analyzing Grain Size in Crystals

2 mm

Polishing and etching show that the majority of each slice is single crystalline with typical slice containing two grains.

An Observed Grain Boundary

0.35 mm

Verifying Chemical AnalysisICP Results*

ElementNominal

compositionOriginal sample(R104)

“Single”crystal

(4-bar mold)

Single crystal

(Crystalox)

Ni 50.1 50.9 50.06 51.2

Co 20.6 20.76 21.40 20.84

Cr 13 12.65 12.55 12.52

Al 3.4 3.11 3.19 3.01

Ti 3.1 3.62 3.53 3.49

W 2.1 2.07 2.06 2.11

Ta 2.4 2.34 2.38 2.33

Nb 0.9 0.77 0.86 0.73

Mo 3.8 3.74 3.81 3.70

C - 0.044 0.04 0.055

Fe - 0.09 0.08 0.08

Zr - 0.05 0.04 0.05

* Analysis of 4-bar mold alloy conducted at Sherry Labs, Daleville, IN. All others after Mills.

Determining Crystal Orientation

Transmission

Back reflection

http://www.matter.org.uk/diffraction/x-ray/laue_method.htm

http://www.matter.org.uk/diffraction/x-ray/laue_method.htm

X-Ray Set-up at Hopkins

Replace photo multiplier tube with Polaroid cassette and film to capture Laue patterns.

Photo multiplier tubeX-

Ray

sou

rce

Sample

Collimator

Calibrating Laue Experiments using Si Wafer

LauePT simulation (5.1 cm image distance)

{100} Si

<011>

Si {100} Transmission Laue: Theory vs. Experiment

-60 -40 -20 0 20 40 60

-40

-30

-20

-10

0

10

20

30

40

Blue circles are from LauePt simulations, red stars are the diffraction spots taken from the image on the left. Measurements confirm image distance of 5.1cm.

Ni-Superalloy Transmission Laue

Sample A03Sample A01 Sample A02

Ni-Superalloy Transmission Laue Analysis

Spot ϕ δ

1 14 48

2 16 28

3 17 15

4 17 9

5 18 -1

6 19 -20

7 21 -39

8 23 -49

9 30 -64

1* 13 50

2* 17 40

3* 20 20

4* 80 -75

5* 55 -69

6* 48 -64

1

23

45

67

8

9

1*2*

3*

4*5*

6*

Data from Leonhardt ChartSample A02

Stereographic Projection

Poles θ

P to P* ~45

Planes θ

(100) to (110) 45

(130) to (210) 45

(211) to (113) 42

(111) to (171) 43

P

P*

Example Sample Layout

4mm

Tension-Compression Sample Geometry

Original Sample Geometry – 5mm

New Sample Geometry – 4.25mmshorter length saves material and allows one to test even smaller volumes of material

Courtesy of Dan Gianola

Elastic Buckling Analysis

2

22

12LEt

APcr

crπσ ==The Euler buckling load, is given by: , then

2

2

LEIPcr

π=

3

121 wtI = wtA =where

oldcrnewcr __ 0625.3 σσ ∗=mmLnew 0.1=mmLold 75.1=

GPa

GPa

oldcr

newcr

36.3

28.10

_

_

=

=

σ

σLet: and then:mmt 250.0=GPaE 200=

A Study of T-C Yield Asymmetry in Ti-6Al

• Orient single crystal samples for a-type basal slip (hcp).

• Expect tension-compression asymmetry based on observed asymmetry in polycrystalline material even at very small strains.

Courtesy of Matt Brandes

Capacitance Strain (%)

Stre

ss (M

Pa)

764 MPa

-504 MPa

Video rate = 90x testing rate

Measuring T-C Asymmetry in Ti-6Al

With Matt Brandes Sample 005a


-50 0 50 100-1000

-500

0

500

1000


Stre

ss (M

Pa)

679 MPa

-575 MPa


With Matt Brandes Sample 005e


Stre

ss (M

Pa)



With Matt Brandes Sample 005c

Using Image Analysis to Measure Strain

Sample 005eWith Matt Brandes, Chris Eberl

Stress-Strain Response from Image Analysis

-0.035 -0.03 -0.025 -0.02 -0.015 -0.01 -0.005 0 0.005-600

-500

-400

-300

-200

-100

0

100

Eng. strain [ ]

Eng

. stre

ss [M

Pa]

Image analysis clearly shows a plastic strain has occurred in compression of the sample.

Extending the Technique to Elevated Temperature

Tension test of RuNiAl at 900oC

Maintaining Constant Temperature vs. Time

Action Items

• Heat treatment:• What temperature?• How long?• Under what conditions?• When?• Where?

• Precise long-term temperature control of resistive heating set-up:• Have EuroTherm feedback controller• Working out bugs• Need to synchronize timing with optical pyrometer

• Start testing• Orient• Cut samples• Polish

Questions?

tension-compression asymmetry and orientation creep...

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