High fracture toughness in a hierarchical nanostructured zirconium

Nanocrystalline metals usually exhibit a high strength but a disappointingly low ductility and toughness, which limit their practical utility. Here, we report a high fracture toughness (K-IC similar to 117 MPa m(1/2)) in a hierarchical nanostructured Zr that consists of nano-, sub-micrometer- and micrometer-sized grains, which is much larger than that K-IC similar to 78 MPa m(1/2) in coarse-grained Zr. This hierarchical nanostructured Zr shows a good combination of yield strength (sigma(s)similar to 550 MPa) and fracture toughness as compared with its coarse-grained counterpart. We expect that these results will have implications in the enhancement of fracture toughness of nanocrystalline materials and in the design of high-performance structural materials. (C) 2014 Elsevier B.V. All rights reserved.