Mechanical properties and thermal stability of gradient structured Zr via cyclic skin-pass cryorolling

Abstract Gradient-structured Zr sheets were fabricated by cyclic skin-pass cryorolling and cyclic skin-pass rolling. The mechanical properties and microstructural evolution of the gradient-structured Zr after rolling and annealing were investigated. The results indicated that the cyclic skin-pass cryorolled samples exhibited higher tensile strengths (σb = 557 MPa) and slightly lower fracture elongations (eu = 17.1%) than the cyclic skin-pass rolled samples due to high dislocation storage. After annealing at 150 °C–450 °C for 1 h, high-resolution transmission electron microscopy results showed that the ultrafine-grained layer of the cyclic skin-pass cryorolled samples exhibited better thermal stability, which was attributed to the formation of nanoscale twins and incomplete recovery of dislocations.