Microscale and Mesoscale Crystallographic Textures of Nanocrystalline Ni-Based Electrodeposits
- PDF / 2,088,447 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 28 Downloads / 220 Views
ANOCRYSTALLINE metals, characterized by grain sizes smaller than 100 nm, exhibit a range of superior properties compared to their microcrystalline counterparts (e.g., Reference 1). One of the effective methods to produce such materials is pulsed electrodeposition.[2] It has been frequently observed that electrodeposits exhibit a nodular surface morphology with a size scale that can be several orders of magnitude greater than the grain size.[3,4] It has been postulated that each nodule represents a ‘‘colony’’ of nanosized grains, as schematically shown in Figure 1, and that these grain colonies form and grow competitively during deposition.[4] Although properties such as yield strength and hardness of electrodeposited nanocrystalline alloys may be primarily dictated by grain size, it can be expected that many other properties, such as corrosion resistance, toughness or ductility, coefficient of friction, and wear resistance, will be affected by the characteristics of the mesoscale colonies.[2,4] Thus, the thorough understanding of these characteristics is of immediate practical importance. It has recently been suggested that the colonies might represent crystallographically related groups of grains.[4] P. CIZEK, Senior Research Academic, M.R. BARNETT, Professor, and M.D. NAVE, Research Engineer, are with the Centre for Material and Fibre Innovation, Deakin University, Geelong, VIC 3217, Australia. Contact e-mail: [email protected] E.F. RAUCH, Professor, is with the Ge´nie Physique et Me´canique des Mate´riaux, (CNRS-UMR5010) – INPG, BP 46, 38402 Saint Martin d’He`res Cedex, France. R. BALASUBRAMANIAM, formerly Professor, Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur 208016, India, is deceased. Manuscript submitted March 16, 2010. Article published online December 15, 2010 2048—VOLUME 42A, JULY 2011
Although the overall crystallographic texture of the nanocrystalline Ni-based electrodeposits is known to be generally characterized by h001i and h111i fiber axes parallel to the deposition direction (DD), with the h001i//DD texture being dominant more frequently,[5–8] information on the crystallographic nature of the mesoscale colonies is at present rather limited. It has recently been proposed by a number of the present authors[9] that the colonies in a nanocrystalline Ni-20 pct Fe electrodeposit might display a distinct ‘‘cobblestone’’ mesotexture characterized by a h001i fiber axis approximately perpendicular to the local curvature of the colony growth surface. Nevertheless, this suggestion was largely based on the orientation measurements performed in the vicinity of the boundaries separating two neighbouring colonies, and it was brought to the authors’ attention during the review process that there might be an alternative explanation to the measured data (Figure 2). This article presents further work that has been conducted in order to verify the possible presence of the cobblestone mesotexture in Ni-based electrodeposits. In particular, transmission electron microsco
Data Loading...
