Texture determinations on pure thorium and a range of cerium-thorium alloys indicated that thorium had a stacking fault energy higher than that of copper (γ∼- 70mJ/m2). It was found, also, from texture determinations, that upon high deformation in rolling at room temperature, the γ(face-centered cubic) to β(hexagonal) transformation occurred in pure cerium. This indicated a stacking fault energy for cerium approaching zero. As little as 10% thorium added to the cerium was sufficient to raise its stacking fault energy to about 40mJ/m2.

The Rolling Texture and Stacking-Fault Energy of Thorium, Cerium and Thorium-Cerium Alloys. I.L.Dillamore, I.R.Harris, R.E.Smallman: Acta Metallurgica, 1964, 12[2], 155-8