tension-compression asymmetry and orientation creep...
TRANSCRIPT
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?