Mechanical Properties of High Purity Niobium Novel ... · SRF 2003 3 September ‘03 WC Reactor Grade stress-strain End Group Reactor Grade Niobium 0 2 4 6 8 10 12 14 16 18 20 0 0.002

Thomas Jefferson National Accelerator FacilityInstitute for SRF Science and Technology

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

SRF 2003 3 September ‘03

Mechanical Properties of High Purity Niobium Novel Measurements

11th Workshop on RF SuperconductivitySeptember 8-12, 2003

G. R. Myneni, S. Agnew, G. Ciovati, P. Kneisel,

W. A. Lanford, R. L. Paul, and R. E. Ricker




Overview

. Why is an interest in mechanical properties of RRR niobium again?

. What are the Novel Measurements!!

. Where are we going from here?




SNS Cavity Field Profile

SNS β =0.61 cavity #3

0

1

2

3

4

5

6

7

8

9

0 5 10 15 2 0 2 5 3 0

Time [ s ]

Before heat treatment After heat treatment at 800C for 6hr.

FPC s id e

Before heat treatmentFrequency = 804.200 MHz

After heat treatmentFrequency = 803.179 MHzFF 26%

Gianluigi Ciovati




Cavity Tuning Sensitivity

SNS β =0.61 cavity #4 heat treated at 600C for 10 hr - Longitudinal tuning sensitivity

-100

0

100

2 00

3 00

4 00

500

6 00

700

8 00

9 00

0 20 4 0 6 0 80 100 120

C o mp re s s io n [ mils ]

lbs/mils lbs/mils 800C 6hr

Gianluigi Ciovati




Qo Vs Eacc

061SNS004Q0 vs. Eacc

1.00E+08

1.00E+09

1.00E+10

1.00E+11

0 2 4 6 8 10 12 14 16 18

Eacc [MV/m]

Q0

T=2.17K - Before warm up T=2.17K - After warm up at 120K for 24hrT=2.1K - After heat treatment at 600C for 10hr T=2.1K - After heat treatment and warm up to 120K for 24hr

Design Goal

Gianluigi Ciovati




Tensile sample

Does not meet ASTM standards but not required since used at very low strain rates




Tensile apparatus

Unique SystemWide temperature range down to 4.2 KStrain rate variation – six orders




Measurement Accuracies

. Strain Measurement Accuracy ± 2%

Strain rate can be varied from 1.e-6 s-1 to 10 s-1

. Accuracy of the Stress Measurement ± 1%

. Accuracy of the Percentage of Elongation ± 1%

. Measurements can be made from 4.2 K to ambient temperature




0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.0080

20

40

60

80

100

120

as-received 10 hrs at 600oC 6 hrs at 700oC 6 hrs at 800oC

stre

ss (M

Pa)

strain

Apparent YM Issue




TD RRR niobium heat treted at 1250 C for 6 hours

0

2

4

6

8

10

12

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014

Strain

Stre

ss (K

SI)

TDA-2-12CTDA-2-27-CTDA-2-35CTDA-2-36CTDA-2-48CTDA-3-60CTDA-4-20CTDA-5-12CTDA-5-41CTDA-5-56CTDA-1-36CTDA-1-139C

RRR=375

TD375 stress-strain




TD data summary

Summary of the TD niobium mechanical properties

Niobium Yield Strength (KSI) Tensile Strength (KSI) % Elongation RRR Hv SSR FSR SSR FSR SSR FSR

ASR 7.4 7.9 21 24 44 48 260 52

600 C 7.0 7.5 21 22 48 49 300 47

800 C 5.7 -- 19 -- 47 -- 350 43

1250 C 4.5 6.3 15 19 32 33 375 36

SSR ~ 5.5E-5

FSR ~ 2.0e-4 up to Yield point and 1.0e-3 until break




WC Reactor Grade stress-strainEnd Group Reactor Grade Niobium

0

2

4

6

8

10

12

14

16

18

20

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016

Strain

Stre

ss (K

SI)

RGACCELASR1200Ti6h1250T6hi

RRR=70

RRR=120

RRR=210




Re la tionship be tween RRR and inte rs titia l impuritie s of Niobium

0

10

20

30

40

50

60

70

80

0 50 100 150 200 250 300 350 400RRR

Inte

rstit

ial i

mpu

ritie

s co

ncen

tratio

n [w

t ppm

ONHC

Interstitials vs RRR




Ultrasonic Velocity Measurements (University of Va)

. Elastic properties may be accurately measured by the pulse-echo technique. Avoid potential problems of tensile tests (anelasticity, microyielding,

etc.). Assess anisotropy directly by changing the direction of shear wave

polarization (RD,TD)

2155

2244

2333

s

s

l

vC

vC

vC

ρ

ρ

ρ

=

=

=

transducer

pulseecho

pulser

0 2 4 6 8 10 12 14

-4

-3

-2

-1

0

1

2

3

4

2nd reflection

Volta

ge (V

)

Time (µs)

Incident Pulse

Front surface reflection

1st Back-surfacereflection

Delaytime, τ

d




. Elastic behavior normal for niobium (E = 110 ± 3 GPa). Anisotropy small (β ≤ 1.03). Reproducible trend with annealing in all lots

20' 600' 700' 750' 800'4000

4400

4800

5200

5600

6000

N P

Velo

city

(m/s

)

Temperature (C)

K

Longitudinal

Shear

20' 600' 700' 750' 800'1800

1900

2000

2100

2200

2300

2400

2500

20' 600' 700' 750' 800' 20' 600' 700' 750' 800'

Velo

city

(m/s

)

Temperature (C)

TD

RD

K

Temperature (C)

TD

RD

N

Temperature (C)

TD

RD

P

450

Velocities (UVa)




RRR Niobium Rolled Sheet Textured

. Due to deformation processing and recrystalization

. Anisotropy of single crystal manifest in textured polycrystal. Nb Zener anisotropy parameter, Z = 0.55,

is low (many cubic metals Z>1)

. May predict response of polycrystal response if single crystal behavior and texture are known.. Using averaging schemes such as Voigt, Ruess, Hill

. Initial studies using x-ray diffraction of the sheet surface showed no change in the texture with annealing.

1211

442CC

CZ−

=




Electron Backscattered Diffraction (EBSD)Utilizes automated indexing diffraction patterns

Provides a method for examining crystallography and crystallographic orientation at a single point in materials

grain boundary crystallography

intragranular substructure (mosaic)

microtexture




Schematic of EBSD




Rolling Direction

NormalDirection

100 µm

As-received P sample exhibits bands of fine and coarse grains typical of these samples. Different colors represent orientations as shown in the legend, where the Euler

angles are according to Bunge’s convention

White spots represent positions were surface roughness obscured the EBSD detector

EBSD maps through sheet thickness (UVa)




EBSD maps of sheet cross-section provide bulk texture (UVa)

Pole figures from as-received and annealed (800C) samples (lot P) reveal two facts:

Less cube component than in surface (x-ray).

Strengthening of texture with annealing




BGO Compton suppressor

Ge gamma detector

Neutron guide (end view)

Lead shielding

Sample

Gamma collimator

γ

γγ

γ

Cold neutron PGAA spectrometer at the NIST Center for Neutron Research




Schematic drawing for the NIS measurement setup

Cd aperture 9 mm diameter

45°

Neutron beam

Be filter

sample

3He detector

Cd sleeve




Treatment of niobium samples measuredSample Measured as

received?Measured following:

Measured following:

Measured following:

(No heating) Vacuum heating 1

Acid treatment 1 duration (min)

Vacuum heating 2

Acid treatment 2 duration (min)

Nb 2 No 800 °C / 6 h 1 --- ---

Nb 3 No 700 °C / 6 h 2 --- ---

Nb 4 No 750 °C / 6 h 3 800 °C / 6 h ---

Nb 5 No 600 °C / 10 h 0.5 800 °C / 6 h 5

Nb 6 Yes ---- 4 --- ---

P1 Yes 800 °C / > 48 h ---- ---- ----

P2 Yes 800 °C / > 48 h ---- ---- ----

K1 Yes 800 °C / > 48 h ---- ---- ----

K2 Yes 800 °C / > 48 h ---- ---- ----




Hydrogen fractions measured in the niobium samplesSample % atom fraction hydrogen

(determined relative blank)

As received After vacuum

heating #1

After acid treatment #1 After vacuum heating #2 (Nb 4) and acid treatment #2 (Nb 5)

PGAA PGAA NIS PGAA NIS

Nb 2 --- 0.138 ±0.025

0.257 ±0.041

0.153 ±0.032

--- ---

Nb 3 --- 0.156 ±0.026

0.169 ±0.028

0.167 ±0.034

--- ---

Nb 4 --- 0.122 ±0.028

0.114 ±0.027

0.083 ±0.020

< 0.03 < 0.03

Nb 5 --- 0.107 ±0.025

0.107 ±0.025

0.113 ±0.024

0.396 ± 0.037 0.352 ±0.070

Nb 6 0.126 ±0.027

--- 0.140 ±0.028

0.150 ±0.032

--- ---

P1 0.03 ± 0.02 < 0.03 --- --- --- ---

P2 0.03 ± 0.02 < 0.03 --- --- --- ---

K1 < 0.04 < 0.03 --- --- --- ---

K2 0.03 ± 0.02 < 0.03 --- --- --- ---




NRA Hydrogen depth profilesHydrogen Depth Profile in Niobium

-0.5

0

0.5

1

1.5

2

2.5

3

-0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Depth (microns)

H C

once

ntra

tion

(1.e

22/c

m3 )

Vacuum degassed @ 800 C for 6 hHydrogen Charged after vacuum degassingAs received - K TypeAs received - P TypeAs processedVacuum Baked @ 90 C for 48 h




Hydrogen and Other Interstitials can HaveFour Different Types of Interactions:1. Snoek - Dislocation drag (diffusion)2. Precipitation - Hydrides, etc.3. Pairing Effects - solute-solvent or solute-solute pair

interactions (e.g. Zener effect)4. Gorsky - Large scale diffusion effects

Note diagram shows tensile grip.The measurements of this study were

conducted in 3 point bend.

Dynamic Mechanical Analysis

(Internal Friction)Measures the phase

shift between stress and strain as a function of temperature

Other Peaks:1. Bordoni - Cold work and dislocation

density related2. Grain Boundary - Interface sliding




Dynamic Mechanical Analysis (Contd.)

Temperature - Relaxation Mechanism KineticsMagnitude - Proportional to Concentration

Peak Temperature = f(Frequency)

Comparison of peaks predicted from diffusion data for two frequencies to measurements.

Peak Magnitude = f(Concentration)

Comparison of the oxygen Snoek peak in two samples of Nb indicated a difference in the oxygen concentration




Dynamic Mechanical Analysis (Contd.)

Example of other types of interactions and peaks

H-O Interaction Peak

A peak was found at a temperature between that expected for the H and O Snoek peaks. Previous investigators postulated this peak to be due to H-O interstitial interaction.




Loss Modulus Peaks for NbDynamic Mechanical Analysis (Contd.)

Peak Ratios

Oxygen: P/K ≈ 1.94

Nitrogen: P/K ≈ 1.6

Carbon: P/K NA




Tensile Deformation andStress Fluctuations During Plastic Flow




Distribution of Stress FluctuationsDuring Plastic Flow

Standard Deviations

Nb, P = 0.1427 MPaNb, K = 0.0907 MPaRatio P/K = 1.57

Loss Modulus Peak Ratios

Oxygen: P/K ≈ 1.94Nitrogen: P/K ≈ 1.6Carbon: P/K NA




Analysis of Periodicity of theStress Fluctuations During Plastic Flow

SPD Peak

Nb, P = 2.49Nb, K = 0.56Ratio P/K = 4.44 (2.11)

Standard Deviations

Nb, P = 0.1427 MPaNb, K = 0.0907 MPaRatio P/K = 1.57

Loss Modulus Peak Ratios

Oxygen: P/K ≈ 1.94Nitrogen: P/K ≈ 1.6Carbon: P/K NA




2002 Hydrogen in Materials and Vacuum Systems Intl. Workshop

. This International Meeting, the First of its Kind, was Jointly Sponsored by. The Mid-Atlantic Chapter of the American Vacuum Society, . The Old Dominion University (Physics Department),. Deutsches Electronen – Synchrotron (DESY), . The College of William and Mary, . Reference Metals Company Inc., . Tokyo Denkai Co., Ltd. (Japan), . Wah Chang (USA) and. The Jefferson Lab.

. Success Lead to the Formation of International Hydrogen in Matter Symposia Board (ISOHIM): Chair – Dr. Jim Miller, ANL; Co-Chair – Dr. G. MyneniJLAB

. Second International Symposium on Hydrogen in Matter 2005 – Uppsala University, Sweden

. AIP Published the Proceedings of the workshop as CP #671 in July 2003




High RRR Nb–Hydrogen Research Collaborations

JLAB – ODU Physics Hydrogen Interactions in Materials – Theory. JLAB – UVa Physics H in Nb Grain Boundaries – SQUID Magnetic

Microscope. JLAB – NIST H–PGAA–Neutron Scattering Studies of high RRR

Niobium. JLAB – NIST Internal Friction Measurements of H and Interstitial

Content in High RRR Niobium. JLAB – SUNY Albany Hydrogen Depth Profile with Nuclear Reactions & Oxide

Thickness in High RRR Niobium. JLAB – DESY, Germany Thermal and Mechanical Properties of Niobium

With Heat Treatments – H Degassing Affects. JLAB – FZK, Germany Extreme High Vacuum Science & Technology – H. JLAB – William & Mary Hydrogen in Semiconductors. JLAB–LANL–UVa – High RRR Niobium Microstructure – Tuning with H

Reference Metals – MOUJLAB – Uppsala Univ. Fundamental Understanding of H-Matter Interactions




Conclusions

. High purity niobium mechanical properties vary from batch to batch and are very sensitive to various treatments and handling

. Elastic behavior of high purity niobium is normal and is unaffected by heat treatments

. Hydrogen bulk content and depth profile studies are yielding interesting results

. Internal Friction measurements are expected to provide quantitative interstitial concentrations

. Stress-Strain curves may provide the high RRR Nb purity

. Fundamental hydrogen-matter interactions knowledge from various communities will enhance the understanding and improve the SRF Technology




References. High RRR Niobium Material Studies. Jlab-TN-02-001 Ganapati Myneni and Peter Kneisel

. Requalification of Tokyo Denkai RRR Niobium

. JLAB-TN-02-011 Ganapati Myneni, Peter Kneisel

. Determination of Hydrogen in Niobium by Cold Neutron Prompt Gamma-Ray

. Activation Analysis and Neutron Incoherent Scattering, R. L. Paul, H. H.

. Chen-Mayer, and G. R. Myneni in Hydrogen in Materials and Vacuum

. Systems AIP CP 671, Melville, New York, 2003, pp. 151-161

. Elasto-Plastic Behavior of High RRR Niobium: Effects of Crystallographic

. Texture, Microstructure and Hydrogen Concentration, G.R. Myneni and S.R. Agnew in

. Hydrogen in Materials and Vacuum Systems, AIP CP 671, Melville, New

. York, 2003, pp. 227-242

. Variation of Mechanical Properties of High RRR And Reactor Grade Niobium

. With Heat Treatments, Ganapati Myneni, H. Umezawa in Materiaux & Techniques, Vol

. 7-8, 2003

Ultrasonic Velocity and Texture of High RRR Niobium,. S Agnew, F Zeng, G.R. Myneni in Materiaux & Techniques, Vol 7-8, 2003

. Hydrogen Uptake by High Purity Niobium Studied by Nuclear Analytical

. Methods Rick L. Paul, Heather H. Chen-Mayer, Ganapati Myneni William A. Lanford,

. and Richard E. Ricker in Materiaux & Techniques, Vol 7-8, 2003

Documents

Mechanical Properties of High Purity Niobium Novel ... · SRF 2003 3 September ‘03 WC Reactor Grade stress-strain End Group Reactor Grade Niobium 0 2 4 6 8 10 12 14 16 18 20 0 0.002