What metals or alloys become magnetic when heated, if any?
If I remember correctly, heating a metal which displays magnetic properties will de-magnetise it. The temperature needs to be quite high, but not close to melting point. The theory is that heating causes the magnetic particles within the metallic structure to lose their alignment with each other and so weakens their magnetic effect. Iron and its alloys display magnetic properties. Any non-magnetic metal, aluminium or copper for example, unless alloyed with iron in substantial proportion will remain non-magnetic at any temperature. There is no elevated temperature at which non-magnetic materials become magnetic, although I believe that, for some materials, the reverse is true. They can display magnetic properties when cooled to a very low temperature.
