Twinning during β → α slow cooling in a zirconium alloy

Twinning is frequently reported in Zr alloys during deformation and martensitic phase transformation. In the present work, however, we report {101¯2} and {112¯1} twinning after furnace cooling form β phase domain to room temperature in a Zr alloy. Intergranular thermal residual stresses produced during cooling due to anisotropic coefficients of thermal expansion, combined with the extraordinarily large grain size of the transformed α-Zr, are believed to be the reasons accounting for the formation of these twins.