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Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an Al-Zn-Mg-(Cu) Alloy.

DE2004820717

Publication Date	2002
Personal Author	Young, G. A.; Scully, J. R.
Page Count	24
Abstract	Precipitation hardenable Al-Zn-Mg alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are used to increase HEAC resistance at the expense of strength but overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). Results show that overaging the copper bearing alloys both inhibits hydrogen ingress from oxide covered surfaces and decreases the apparent hydrogen diffusion rates in the metal.
Keywords	Alloys Hydrogen Crack propagation Humidity Aluminum Copper Magnesium Zinc Aluminum alloys Copper alloys Ion beams Spectroscopy Mass spectroscopy Crack growth Crack initiation
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Virginia Univ., Charlottesville. Dept. of Materials Science.; Rensselaer Polytechnic Inst., Troy, NY. Dept. of Nuclear Engineering.; Department of Energy, Washington, DC.
Supplemental Notes	Prepared in cooperation with Rensselaer Polytechnic Inst., Troy, NY. Dept. of Nuclear Engineering. Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200413

Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an Al-Zn-Mg-(Cu) Alloy.

Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an Al-Zn-Mg-(Cu) Alloy.
DE2004820717

Publication Date	2002
Personal Author	Young, G. A.; Scully, J. R.
Page Count	24
Abstract	Precipitation hardenable Al-Zn-Mg alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are used to increase HEAC resistance at the expense of strength but overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). Results show that overaging the copper bearing alloys both inhibits hydrogen ingress from oxide covered surfaces and decreases the apparent hydrogen diffusion rates in the metal.
Keywords	Alloys Hydrogen Crack propagation Humidity Aluminum Copper Magnesium Zinc Aluminum alloys Copper alloys Ion beams Spectroscopy Mass spectroscopy Crack growth Crack initiation
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Virginia Univ., Charlottesville. Dept. of Materials Science.; Rensselaer Polytechnic Inst., Troy, NY. Dept. of Nuclear Engineering.; Department of Energy, Washington, DC.
Supplemental Notes	Prepared in cooperation with Rensselaer Polytechnic Inst., Troy, NY. Dept. of Nuclear Engineering. Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200413