Ductile near Birmingham

Ductile has been a word for which I've seen different definitions over the years. One was that it meant that a material could be pulled into a wire. Another was that it could undergo plastic deformation before breaking, which is important in enginnering because the material can absorb quite a bit of energy before breaking. There is some warning. https://en.wikipedia.org/wiki/Ductility mentions that this is due to metallic bonds and the way that atoms can slide past each other. But cast iron is brittle for that reason and steel has carbon inserted so that the layers can't slide over each other as easily. https://www.reliance-foundry.com/blog/difference-cast-iron-wrought#gref talks about cast iron having a heterogeneous internal structure which creates stress points. It talks about it having a high carbon content. So I've learned somehting new. Cast iron has more carbon in it than steel.