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

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

Measuring T-C Asymmetry in Ti-6Al

-50 0 50 100-1000

-500

0

500

1000

Capacitance Strain (%)

Stre

ss (M

Pa)

679 MPa

-575 MPa

Video rate = 90x testing rate

With Matt Brandes Sample 005e

Capacitance Strain (%)

Stre

ss (M

Pa)

Video rate = 30x testing rate

Measuring T-C Asymmetry in Ti-6Al

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

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?