Tailoring Microstructure and Properties of Hierarchical Aluminum Metal Matrix Composites Through Friction Stir Processing

    Authors

    Y. H. Sohn; T. Patterson; C. Hofmeister; C. Kammerer; W. Mohr; M. Van Den Bergh; M. Shaeffer; J. Seaman;K. Cho

    Comments

    Authors: contact us about adding a copy of your work at STARS@ucf.edu

    Abbreviated Journal Title

    Jom

    Keywords

    NANOSTRUCTURED MATERIALS; STRENGTH; BEHAVIOR; Materials Science, Multidisciplinary; Metallurgy & Metallurgical; Engineering; Mineralogy; Mining & Mineral Processing

    Abstract

    The fabrication of hierarchical aluminum metal matrix composites (MMCs) begins with the cryomilling of inert gas-atomized AA5083 Al powders with B4C particles, which yields agglomerates of nanocrystalline (NC) Al grains containing a uniform dispersion of solidly bonded, submicron B4C particles. The cryomilled agglomerates are size classified, blended with coarse-grain Al (CG-Al) powders, vacuum degassed at an elevated temperature, and consolidated to form the bulk composite. This hierarchical Al MMCs have low weight and high strength/stiffness attributable to the (A) Hall-Petch strengthening from NC-Al (5083) grains, (B) Zener pinning effects from B4C particulate reinforcement and dispersoids in both the NC-Al and CG-Al, (C) the interface characteristics between the three constituents, and (D) a high dislocation density. The hierarchical Al MMCs exhibit good thermal stability and microstructural characteristics that deflect or blunt crack propagation. A significant change in the microstructure of the composite was observed after friction stir processing (FSP) in the thermomechanically affected zone (TMAZ) due to the mechanical mixing, particularly in the advancing side of the stir zone (SZ). The NC-Al grains in the TMAZ grew during FSP. Evidence of CG-Al size reduction was also documented since CG-Al domain was absent by optical observation. Given the proper control of the microstructure, FSP has demonstrated its potential to increase both strength and ductility, and to create functionally tailored hierarchical MMCs through surface modification, graded structures, and other hybrid microstructural design.

    Journal Title

    Jom

    Volume

    64

    Issue/Number

    2

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    234

    Last Page

    238

    WOS Identifier

    WOS:000301040000008

    ISSN

    1047-4838

    Share

    COinS