Significance of Low Copper Content on Grain Boundary Nanostructure and Intergranular Corrosion of AlMgSi(Cu) Model Alloys

Magnus Hurlen Larsen; John Charles Walmsley; Otto Lunder; Kemal Nisancioglu

doi:10.4028/www.scientific.net/MSF.519-521.667

Paper Titles

Intergranular Corrosion and Stress Corrosion Cracking of Sensitised AA5182
p.641

Corrosion of Painted Aluminium Sheet
p.647

Fracture Mechanical Testing of Adhesion of Organic Coatings on Aluminium
p.655

Protection of Aluminium Alloys via Hybrid Sol-Gel Coatings with Encapsulated Organic Corrosion Inhibitors
p.661

Significance of Low Copper Content on Grain Boundary Nanostructure and Intergranular Corrosion of AlMgSi(Cu) Model Alloys
p.667

Surface Segregation of Indium by Heat Treatment of Aluminium
p.673

Scanning Kelvin Probe Studies of Cosmetic (Filiform) Corrosion on AA6016
p.679

Consequences of Hot Rolling of Recycled AA5050 on Filiform Corrosion
p.687

Exfoliation Corrosion Mechanism: Interplay between Intergranular Corrosion and Stress Corrosion Cracking during Exfoliation Corrosion of AA7449
p.693

HomeMaterials Science ForumMaterials Science Forum Vols. 519-521Significance of Low Copper Content on Grain...

Significance of Low Copper Content on Grain Boundary Nanostructure and Intergranular Corrosion of AlMgSi(Cu) Model Alloys

Abstract:

Intergranular corrosion (IGC) of model alloys in the 6000-series, with and without 0.2 wt% Cu, was studied using an accelerated corrosion test (BS ISO 11846 B), FE-SEM and FE-TEM. Low Cu alloys (0.02wt%) did not exhibit IGC even though they contained excess Si. The high-Cu, naturally aged material (T4) was susceptible to severe superficial etching. In the underaged state (below peak strength), the Cu-containing material was highly susceptible to IGC. Materials aged to peak strength (T6) or overaged were only slightly susceptible to IGC, with localized, shallow attacks. FE-TEM investigation of the underaged material revealed scattered, small AlMgSiCu-type precipitates, as well as a Cu-enriched film along the grain boundaries. The overaged material showed more extensive, coarse grain boundary precipitation. However, the Cu-enriched film was still present at localized sites. The reduced susceptibility to IGC upon artificial ageing was attributed to breaking of the continuity of the grain boundary film. The possible role of matrix precipitation is also discussed.