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Minimizing fracturing to EN on aluminum

Will a high-phosphorous content in the nickel reduce or minimize the stresses associated with bending aluminum with an EN finish? I am seeing fracturing occurring in and around the bend radii with an EN finish call-out of AMS2404, .0002"-.0003" thick, heat-treated. No temperature is called-out, specifically. I know exposure to heat will improve adhesion, but will it harden the nickel so much that it will cause fracturing when subjected to a bend of 60°? If exposure to temperature improves the stresses, what is the ideal temperature? The temperatures given in the AMS2404 spec are +375°C or +191°C.

Michael Pitchell
Product designer - Manteca, California, USA
2007

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2007

EN is not suitable for parts that will see deformation. It is considered a metallic glass with a very low elastic limit of around 2-3%. Like other fragile materials, it shows very little or no permanent deformation and fractures suddenly when it reaches its limit. As plated, it is an amorphous solid solution of Ni and P without crystal structure. Any heat treatment above some 220-260oC (400-500oF) promotes formation of a nickel phosphide phase which will further reduce its mechanical properties. Higher P content will accentuate this situation.

Guillermo Marrufo
Monterrey, NL, Mexico

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