Hi,
Please assist me with the following,
I am working with aluminium silicon bronze components (small connectors). As part of their manufacturing process the parts are ink coded and require curing in an oven at 150 deg C for one hour. The oven atmosphere is not controlled.
Prior to the oven treatment the appearance of the parts is uniform, the parts have a gold like appearance. Following the treatment in the oven the parts have deep blue to purple hues appearing on all their surfaces.
I am looking for the cause of this change and to prevent it.
Thank you for reading my query,
Kind regards,
Elie
Article Effect of Heat Treatment on Microstructural Changes in Alumi...
https://www.copper.org/applications/marine/nickel_al_bronze/pub-222-nickel-al-bronze-guide-engineers.pdf
What is the percentage composition of alloy components in weight percent ?
Kind regards,
Jerzy
Thank you for your answer.
The composition is Cu rem, Al 6.0%, Fe 0.6%, Si 2.2% .
Kind regards,
Elie
downloaded this article: Effect of Heat Treatment on Microstructural Changes in Aluminium Bronze
Daer Elie,
I think there is a problem with transformation of beta to alpha phase.
The heating temperature of 850 °C changes the nature of the microstructure. Polyhedral grains contain annealing twins. Their interiors are not attacked by the etchant to any different extent. The colour of the discontinuous network suggests that there is increased iron content. Inside the grains, there are coarse globular κIV precipitates. The iron-rich κI precipitates are distributed uniformly. By changing the cooling rate partial proeutectoid transformation of β to α can be stopped. Moment transformation stopped by cooling, iron content is reduced and color may not change.
Heat treatment of aluminium bronze is somewhat analogical to heat treatment of steel. The fundamental difference lies in the type of the solid solution. In steels, interstitial solid solution is the key phase, whereas the aluminium bronze contains a substitutional solid solution. In the same way as TTT and CCT diagrams are used in heat treatment of steel, it would be appropriate to use diagrams of the β phase decomposition to describe the behaviour of aluminium bronzes.
Ashish
To determine the cause, the phase composition of the discolored zone must be determined .
Kind regards,
Jerzy
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