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Surface activation by trace elements

Surface activation by trace elements. Effect of Pb on activation of aluminium - ØS Effect of Mg on activation of aluminium - YY Effect of other trace elements (In, Sn, Misch, Zr) - BG. Summary of surface activation by trace elements in our investigated Al alloy systems.

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Surface activation by trace elements

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  1. Surface activation by trace elements • Effect of Pb on activation of aluminium - ØS • Effect of Mg on activation of aluminium - YY • Effect of other trace elements (In, Sn, Misch, Zr) - BG

  2. Summary of surface activation by trace elements in our investigated Al alloy systems Activation at lower Temperaturesmore fine oxidation peaks corresponding to the potential arrests Activation at higher Temperatures with Mg in alloy without Mg in alloy • 8006 Håkon • Al-Pb Øystein • 3102 Jan Tore • 3005 Andres • 5180 Andres • 1100 Håkon • “Alloy X” Håkon • 1200 Håkon

  3. An example of activation from 3102 without Mgfrom Jan Tore, PhD work at high T

  4. Surface activation from 8006 with Mgfrom the etched surfaces etched and desmutted at low T etched + 450oC 2h WQ Polarization measurements of AA8006 etched in10 wt% NaOH 10s for 60s and desmutted in HNO3

  5. GD-OES characterization as etched etched; 2h @ 450 C water quenched etched; 2h @ 550 C water quenched GD-OES depth profiles for 8006 alloys 10s etched in 5% NaOH and desmutted for 60s in concentrated HNO3; then with different annealing conditions.

  6. Anodic Behavior in 5% NaCl Anodic behavior of alloy 8006 as function of annealing temperature. All polarisation curves were recorded at least twice in order to ensure reproducibility of the plotted results. Potential, VSCE Current Density, mA/cm2

  7. GD-OES characterization as received fully annealed temper 2h @ 450 C water quenched 2h @ 600 C water quenched GD-OES depth profiles for 8006 alloys at different annealing conditions. Mg exhibits significant enrichment at the surface. Pb peak broadening with increasing annealing temperature.

  8. TEM bright-field micrographs of the stripped oxide film from 2h @ 500 and 600 C water quenched sample. TEM characterization of the stripped oxides At increasing annealing temperatures, more Mg segregated to the surface and formed the flake-shape Spinel (MgAl2O4) crystalline phases.

  9. Phase diagrams J.M. Eldridge et al., Trans., Metall. Soc. AIME, 236, p102, 1966 L.F. Mondolfo, Aluminium Alloy, p563, 1976

  10. Conclusion Remarks • Surface “passivation” effect by Mg-Spinel phase • Mass Mg diffusion would promote Pb surface segregation • possible to form a new low melting point phase, Mg2Pb • Particle size effect – lower the melting point • All of these seemed suggest 8006 activated at “a relative lower temperature” which motivated: • A ternary Al-Pb-Mg model alloy is investigating for getting a more clear understanding of the Mg effect. Nanomat trace element, http://www.nt.ntnu.no/users/yingday/NanoNFR

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