rdf-syntax-grammar
mods:
  schema location: http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
  title info:
    title: Controlling microstructure and texture in magnesium alloy sheet by shear-based deformation processing
  name:
    name part: Sagapuram, Dinakar
    role:
      role term: creator
    role:
      role term: author.
  type of resource: text
  genre: bibliography
  genre: Academic theses.
  origin info:
    place:
      place term: miu
    date issued: 2013
    copyright date: 2013
    issuance: monographic
  language:
    language term: eng
  physical description:
    extent: xviii, 138 pages : illustrations (some color) ; 28 cm
  abstract: Application of lightweight Mg sheet is limited by its low workability, both in production of sheet (typically by multistep hot and cold-rolling) and forming of sheet into components. Large strain extrusion machining (LSEM), a constrained chip formation process, is used to create Mg alloy AZ31B sheet in a single deformation step. The deformation in LSEM is shown to be intense simple shear that is confined to a narrow zone, which results in significant deformation-induced heating up to ~ 200C and reduces the need for pre-heating to realize continuous sheet forms. This study focuses on the texture and microstructure development in the sheet processed by LSEM. Interestingly, deep, highly twinned steady-state layer develops in the workpiece subsurface due to the compressive field ahead of the shear zone. The shear deformation, in conjunction with this pre-deformed twinned layer, results in tilted-basal textures in the sheet with basal planes tilted well away from the surface. These textures are significantly different from those in rolled sheet, where basal planes are nearly parallel to the surface. By controlling the strain path, the basal plane inclination from the surface could be varied in the range of 32-53. B-fiber (basal plane parallel to LSEM shear plane), associated with basal slip, is the major texture component in the sheet. An additional minor C2-fiber component appears above 250C due to the thermal activation of pyramidal slip. Together with these textures, microstructure ranges from severely cold-worked to (dynamically) recrystallized type, with the corresponding grain sizes varying from ultrafine- (~ 200 nm) to fine- (2 m) grained.
  abstract: Small-scale limiting dome height (LDH) confirmed enhanced formability (~ 50% increase in LDH) of LSEM sheet over the conventional rolled sheet. Premature, twinning-driven shear fractures are observed in the rolled sheet with the basal texture. In contrast, LSEM sheet with a tilted-basal texture favorably oriented for basal slip exhibits ductile tensile-type fracture. A two-fold increase in ductility is also observed for the LSEM sheet under uniaxial tensile testing without significant changes in the strength. Among texture and microstructure (grain size), texture is shown to be more critical for Mg sheet formability. However, in conjunction with a favorable texture, fine recrystallized microstructure provides for additional enhancement of strain-hardening capacity and formability.
  abstract: In-situ imaging of material flow during uniaxial tensile testing revealed new, interesting flow localization phenomena and fracture behavior. It is shown that the deformation behavior of Mg sheet is highly texture dependent, and also radically different from that of conventional ductile metals both in terms of necking and fracture. The implications of these observations for the LDH test results and formability of Mg sheet, in general, are briefly discussed.
  note: by Dinakar Sagapuram.
  note: Advisers: Kevin P. Trumble; Srinivasan Chandrasekar.
  note: Ph. D. Purdue University 2013
  note: Includes bibliographical references.
  subject:
    topic: Deformations (Mechanics)
  subject:
    topic: Shear (Mechanics)
  subject:
    topic: Magnesium alloys
    topic: Microstructure
  subject:
    topic: Magnesium alloys
    topic: Mechanical properties
  subject:
    topic: Mechanical engineering
  subject:
    topic: Mechanics, Applied
  classification: TA417.7.S5 S24 2013a
  identifier: 3605129 UMI Number
  record info:
    record content source: TXA
    record creation date: 260610
    record change date: 20260610175831.0
    record identifier: in00005781795
    language of cataloging:
      language term: eng