Anodisation of aluminium alloy AA7075 – Influence of intermetallic particles on anodic oxide growth

• Microstructure and Volta-potential analyses were conducted to characterise intermetallic-particles (IMPs) in AA7075-T5. EIS and AFM were applied under operando-conditions to investigate anodisation processes. IMPs have pronounced influence on the growth of anodic aluminium oxide (AAO) films resulting in low charge-transfer resistance. Cu-bearing constituents show cathodic-character, whereas Mg2Si and MgZn2 particles show anodic-character. During anodisation, Al7Cu2Fe remain stable with peripheral-dissolution around boundary. De-alloying of S-phase particles leads to the detachment. Mg2Si undergoes de-alloying at low potential, and re-passivation at high potential. MgZn2 dissolves entirely upon anodization. Localised-dissolution in large-IMPs boundaries or nanometre-sized IMPs facilitates bubble evolution, confirming local breakdown of barrier-layer.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Anodization

In-situ EC-AFM

Intermetallic particles

Localised dissolution

Operando EIS

SKPFM

Alloying

Alumina

Aluminum alloys

Aluminum oxide

Anodic oxidation

Binary alloys

Charge transfer

Dealloying

Dissolution

Intermetallics

Iron alloys

Oxide films

Silicon alloys

Ternary alloys

Anodizations

Inter-metallic particle

Localised

Operando

Magnesium alloys

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