Looking at several cores from failed motors some will have a filler-type material that is inside the stack of laminates. This material is almost always silvery, and it does melt relatively low, leading me to believe it is aluminum (and thus recoverable for casting parts purposes). However I haven't found anything to indicate what it is, other than not Magnesium for obvious fire-testing reasons.

In the found photo below, the metal in question is at the top and bottom of the core; runs through the core (thin lines), and can be extracted through application of heat. It is not extremely shiny nor is it extremely dense (like zinc might be), and I'm unfamiliar with the different grades of 'pot metal' if I could determine that with testing.


enter image description here

  • \$\begingroup\$ so, what is your question? \$\endgroup\$
    – jsotola
    Jun 1, 2020 at 19:11

1 Answer 1


That is the rotor of a squirrel-cage induction motor. The aluminum makes the shape of a squirrel cage to form the electrical conductors in the rotor. The material must be pure enough so that the resistance is not too high. However it may contain something to increase the strength.

Here is a specification that I found:

enter image description here

Malcolm Burwell et al, Improving the High Speed Efficiency of xEV Induction Motors, Society of Automotive Engineers of Japan, Inc.

  • \$\begingroup\$ Nice find... I've always wondered what the alloy configuration was, pure aluminum is way too soft.I've had two different instances of a motor getting so hot that the rotor bars and end rings melted and in one, flowed into the air gap so when the motor eventually stopped, the aluminum cooled and welded it all into a solid mass. \$\endgroup\$
    – JRaef
    Jun 1, 2020 at 21:21
  • \$\begingroup\$ @JRaef The cited paper seems to be mostly about copper rotors. I saw another one about adding Boron to the aluminum alloy to reduce resistivity, but I don't have access to more than the abstract. \$\endgroup\$
    – user80875
    Jun 1, 2020 at 21:30

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