Mg Alloys for Improved Corrosion Resistance Presenter: Michael A. - - PowerPoint PPT Presentation

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Mg Alloys for Improved Corrosion Resistance Presenter: Michael A. - - PowerPoint PPT Presentation

Mar 18, 2024 12 likes •328 views

Excimer Laser Processing of Al containing Mg Alloys for Improved Corrosion Resistance Presenter: Michael A. Melia Co-Authors: M.L. Serron a , D.C. Florian a , J.P. Weiler b , J.R. Scully a , J.M. Fitz-Gerald a a University of Virginia b Meridian

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SLIDE 1

Excimer Laser Processing of Al containing Mg Alloys for Improved Corrosion Resistance

Presenter: Michael A. Melia

Co-Authors: M.L. Serrona, D.C. Floriana, J.P. Weilerb, J.R. Scullya, J.M. Fitz-Geralda

a University of Virginia b Meridian Lightweight Technologies, Inc.

March 2nd, 2017

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SLIDE 2

Motivation: Need for Light-Weight Vehicles

Maupin (2010) Picture from: bp3.ford.com

Mg alloys used in Ford F-150

2

Mg sacrificial anodes.

http://www.williammaloney.com/aviation/USNavyMuseum/SwiftBoat/images/06SwiftBoatSacrificialAnode.jpg http://www.cathodicme.com/sacp.html

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SLIDE 3

A Closer Look at Mg-Al Alloys: AZ31B

3

1 μm

Φ-Mg6(Al,Zn)5

γ-Al8Mn5 IMPs

10 μm

Large γ-Al8Mn5 IMPs

Mg has low solid solubility with alloying elements.

  • K. Schlüter et al. / Corrosion Science 52 (2010) 3973–3977
  • F. H. Froes et al. / Materials Science and Engineering, A 117 (1989) 19 – 32

http://www.himikatus.ru/art/phase-diagr1/Al-Mg.php

Binary System Equilibrium Terminal Solid Solubility Range (at. %) <0.1 0.1-1 1-5 5-25 >25 Mg - X As, Ba, Ce, Co, Cu, Eu, Fe, Ge, La, Na, Ni, Pd, Pr, Sb, Si, Sr Au, Ca, Ir, Nd, Th, Mn, Ti Ag, Bi, Dy, Ga, Gd, Hg, Pu, Sn, Y, Yb, Zn, Zr Al, Er, Ho, Li, Lu, Pb, Tl, Tm, In, Sc Cd

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SLIDE 4

Issues with Mg: Corrosion

4

Heterogeneous Mg alloy Microstructure

Cathodic Reaction (H2 Evolution): 2H2O + 2e- H2 (gas) + 2OH- Anodic Reaction (Mg Dissolution): Mg  Mg+2 + 2e- e-

Mg+2 H2

Corrosion potential of phases present in 0.6 M NaCl: α-Mg = -1.65 VSCE β-Mg17Al12 = -1.20 VSCE γ-Al8Mn5 = -1.25 VSCE

http://iarjset.com/upload/2015/december-15/IARJSET%2012.pdf

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SLIDE 5

Composition of AZ31B-H24, AZ91D, and AM60B alloys. Element (wt%) Al Zn Mn Fe Mg AZ31B-H24 3.0 1.0 0.33 0.005 Bal. AZ91D 7.2 0.79 0.19 0.02 Bal. AM60B 5.9 0.02 0.28 0.01 Bal.

Alloys Under Investigation

AZ31B-H24 AZ91D AM60B

Increasing amount of β-Mg17Al12 phase.

10 μm 10 μm 10 μm

Decreasing size of Al8Mn5 particles.

5

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SLIDE 6

Excimer Laser Processing

5 mm

Polished surface Laser processed

6

Key Parameters:

  • Laser source: pulsed excimer laser

(λ = 248 nm and FWHM = 25 ns).

  • Laser fluence.
  • Pulse per area (PPA) and overlap.
  • Spot size: cylindrical lens.
  • Ar backfill gas.
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SLIDE 7

7

20 40 60 80 100 120 140 300 600 900 1200 1500 1800

1.5 J/cm

2

Temperature (K)

Time (ns)

Pure Mg boiling Pure Mg melting

γ-Al8Mn5 β-Mg17Al12

Surface Temperature

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SLIDE 8

Solution to Micro-galvanic Corrosion of Mg alloys

8

Heterogeneous Mg alloy Microstructure

Homogenized top layer Cathodic Reaction (H2 Evolution): 2H2O + 2e- H2 (gas) + 2OH- Anodic Reaction (Mg Dissolution): Mg  Mg+2 + 2e-

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SLIDE 9

Base 2 PPA 10 PPA 20 PPA 100 PPA 200 PPA

9

Fiduciary Backscatter Micrographs of AZ31B-H24

10 μm

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SLIDE 10

AZ91D Base AZ91D 100 PPA

10

10 μm

Fiduciary Backscatter Micrographs

AM60B Base AM60B 100 PPA

10

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SLIDE 11

Grazing Incident X-ray Diffraction

AM60B Laser Processed.

30 35 40 45 50 55 60 65

Intensity (Arb.)

Angle (2)

Mg peaks  - Mg17Al12 MgO

Grazing angle of 0.5 degrees using Cu-Kα radiation, ~2.5 μm x-ray penetration. AM60B Base. AZ91D Laser Processed. AZ91D Base. AZ31B Laser Processed. AZ31B Base.

11

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SLIDE 12

12

Grazing Incident X-ray Diffraction

35 40 45 50

Intensity (Arb.)

Angle (2)

Laser processed Base material β-Mg17Al12 Laser processing results in β-Mg17Al12 phase below XRD detection limit for AM60B and AZ91D.

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SLIDE 13

Laser Processed Cross-section of AZ31B

13

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SLIDE 14

Cross-section with EDS line-scan of AM60B

2 4 6 8 10 5 10 15 80 90 100 Weight Percent Distance (m) Mg Al Mn

14

The cast alloys revealed a uniform distribution of Al throughout the processed region.

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SLIDE 15

1 10 100 1000 10000 100000

  • 2.00
  • 1.95
  • 1.90
  • 1.85
  • 1.80
  • 1.75
  • 1.70
  • 1.65
  • 1.60
  • 1.55
  • 1.50

Base AZ91D Laser Processed AZ91D

V vs. SCE Time (seconds)

1 10 100 1000 10000 100000

  • 2.00
  • 1.95
  • 1.90
  • 1.85
  • 1.80
  • 1.75
  • 1.70
  • 1.65
  • 1.60
  • 1.55
  • 1.50

Base AM60B Laser Processed AM60B

V vs. SCE Time (seconds)

1 10 100 1000 10000 100000

  • 2.0
  • 1.9
  • 1.8
  • 1.7
  • 1.6
  • 1.5

V vs. SCE Time (seconds) Base AZ31B-H24 Laser Processed AZ31B-H24

Corrosion of the specimens were performed in quiescent 0.6 M NaCl (pH = 5.5). AZ31B was measured for 24 hours, AM60B and AZ91D OCP measured for 72 hours with EIS.

15

Open Circuit Potential (OCP) Measurements

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SLIDE 16

The Cathodic E-log(i) Measurement

16

Log (Current Density)

V vs. SCE

ECorr

Expected result of reduced micro- galvanic

Anodic branch Cathodic branch

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SLIDE 17

17

The Cathodic E-log(i) Measurements

10

  • 8

10

  • 7

10

  • 6

10

  • 5

10

  • 4

10

  • 3

10

  • 2
  • 2.3
  • 2.2
  • 2.1
  • 2.0
  • 1.9
  • 1.8
  • 1.7
  • 1.6
  • 1.5

AZ91D Base AZ91D Processed AM60B Base AM60B Processed AZ31B-H24 Base AZ31B-H24 Processed

E(V vs. SCE)

i (A/cm

2)

Performed in quiescent 0.6 M NaCl (pH = 5.5) after 30 min. at OCP.

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SLIDE 18

Rs C1 C2 R1 R2 R3 L

1 Rp = 1 R1+R2 + 1 R3 EIS measurement conditions:

  • Frequency range: 100,000 Hz to 0.005 Hz at 3 points per decade.
  • Frequency amplitude: ±10 mV.
  • At OCP

At low frequencies reduces to

Bland (2015) and King (2014)

18

Electrochemical Impedance Measurements

20 40 60 80 100 120 140 60 40 20

  • 20
  • 40
  • 60

Measured data Simulated with equivalent circuit

Z" (-cm

2)

Z' (-cm

2)

Rs+Rct Rs+Rp Rs freq0 freq∞

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SLIDE 19

10000 20000 30000 15000 10000 5000

  • 5000
  • 10000
  • 15000

AM60B Base 1 Hr AM60B Base 60 Hr AM60B Processed 1 Hr AM60B Processed 60 Hr

Z' (-cm

2)

Z'' (-cm

2)

10000 20000 30000 15000 10000 5000

  • 5000
  • 10000
  • 15000

AZ91D Base 1 Hr AZ91D Base 60 Hr AZ91D Processed 1 Hr AZ91D Processed 60 Hr

Z' (-cm

2)

Z'' (-cm

2)

Electrochemical Impedance Measurements

5000 10000 15000 20000 25000 30000 15000 10000 5000

  • 5000
  • 10000
  • 15000

200 400 600 800 400 200

  • 200
  • 400

Z" (cm

2)

Z' (cm

2)

AZ31B Base - 12 Hr AZ31B Laser processed - 12 Hr

Z" (cm

2)

Z' (cm

2)

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SLIDE 20

20

Summary of Impedance Measurements – Corrosion per year

Corrosion rate (thickness per year) based on EIS estimated anodic charge consumed after 24 hours for base and laser processed Mg alloy samples (AZ31B, AM60B, and AZ91D).

0.01 0.1 1 10

Thickness Loss (mm/year)

AZ31B

Laser Processed Base Alloy

AZ91D AM60B

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SLIDE 21

Conclusions

  • Dissolution and complete homogenization of the cast

alloys was easier.

– lower melting temperature and more uniform distribution

  • f secondary phases.
  • Less MgO on alloys with more Al present.
  • Benefits to corrosion are evident but less pronounced

for cast alloys.

  • Control over the ablation environment is critical

to reduction of the large γ-Al8Mn5 phase due to plasma induced pressure wave effects.

21

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SLIDE 22

Acknowledgements

  • U.S. Army Research Laboratory under agreement number

W911NF-14-2-0005 with Joe Labukas as project manager.

  • Students: Michael Serron, David Florian, Fritz Steuer,

Patrick Steiner, Bruce Briglia, Michael Purzycki, Michael Serron, Philip Grudier, Chase Weaverling, Ethan Keyser, Bailey Kraft, and Liam Agnew.

22

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SLIDE 23

Questions?

23

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SLIDE 24

Backup Slides

24

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SLIDE 25

Plasma Induced Pressure Wave

40 μm

  • M. Von Allmen, A. Blatter, Laser-Beam Interactions with Materials, 2nd ed., Springer Series in Materials Science 1987.
  • P. Schaaf, Laser nitriding of metals, Progress in Materials Science, 47 (2002) 1-161.
  • M. Han, K.P. Lieb, E. Carpene, and P. Schaaf, Laser-plume dynamics during excimer laser nitriding of iron, J. Appl. Phys., 93 (2003).

25

The effective pressure at surface during irradiation is approximately 40 MPa. Potential to move material 10’s of μm per pulse.

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SLIDE 26

Plasma Induced Pressure Wave

26

After 2 PPA Base Material

5 μm

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SLIDE 27

Plasma Induced Pressure Wave

10 μm

27

After 2 PPA Base Material

  • Laser fluence: 1.5 J/cm2.
  • 1.2 mm x 27 mm spot size

(cylindrical shape).

  • 95% pulse overlap.
  • Ar backing pressure (Torr): 810.
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SLIDE 28

Secondary Electron Micrograph of Laser Processed Surface

28

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SLIDE 29

Laser Processing Cross-section of AZ31B

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SLIDE 30

Table 5: Melting temperatures for common phases found in Mg-Al-Zn- Mn alloys Melting Temp. (K) Phase 923 α-Mg 728 β-Al12Mg17 1,253 Al11Mn4 1,321 γ-Al8Mn5

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SLIDE 31

Current Mg Alloy Applications

31

Transfer Cover (Drive Train) Seat Cushion and Frame Rear Door Liftgate Rolls Royce RB211 New, highly efficient turboprop engines incorporate these alloys in many structural parts and in integrated reduction gearboxes

Pictures from: http://www.meridian-mag.com/ bp3.ford.com http://www.airteamimages.com/bo eing-747__saudi-arabian- airlines_90395.html http://www.autoblog.com/2010/09 /13/first-drive-2011-lincoln-mkx/