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: CoNiGa high temperature shape memory alloys
  name:
    name part: Dogan, Ebubekir.
    role:
      role term: creator
  name:
    name part: Karaman, Ibrahim
    role:
      role term: thesis advisor.
  type of resource: text
  genre: bibliography
  origin info:
    place:
      place term: txu
    date issued: 2011
    issuance: monographic
  language:
    language term: eng
  physical description:
    form: remote
    extent: 1 online resource.
  abstract: Shape memory alloys (SMAs) are an important class of smart materials that have the ability to remember a shape. Current practical uses of SMAs are limited to below 100°C which is the limit for the transformation temperatures of most commercially successful SMAs such as NiTi and Cu-based alloys. In recent years, the CoNiGa system has emerged as a new ferromagnetic shape memory alloy with some compositions exhibiting high martensitic transformation temperatures which makes CoNiGa a potential high temperature shape memory alloy (HTSMA). In this study, the microstructural evolution and martensitic transformation characteristics of CoNiGa (mainly Co₄₆Ni₂₇Ga₂₇ and Co₄₄Ni₂₆Ga₃₀ in at.%) HTSMAs were investigated in as-cast and hot-rolled conditions as a function of different heat treatments. Heat treatment conditions were selected to introduce single, two, and three phase structures, where two precipitate phases (ductile Y and hard Y') do not martensitically transform. Calorimetry, X-ray analysis, scanning and transmission electron microscopy, thermo-mechanical process and cycling techniques are applied to understand the structural and chemical factors influencing the thermal stability and transformation characteristics. The main findings include improvement of ductility, most cyclically stable compositions with narrow transformation hysteresis (<40°C) and transformation temperatures in the range of 100°C to 250°C, formation of new phases and their effects, and associated compositional changes in the matrix, on the transformation temperatures and on the microstructural evolution. In addition, Ms temperature depends linearly on the valence electron concentration (e/a) of the matrix, only if the Ga content is constant, and the samples with narrow transformation hysteresis demonstrate reversible martensitic transformation in constant-stress thermal cycling experiments.
  note: by Ebubekir Dogan.
  note: "Major Subject: Mechanical Engineering"
  note: Title from author supplied metadata (automated record created 2011-11-01 09:04:20).
  note: Electronic resource.
  note: Master of Science Texas A&M University 2010 http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8544
  note: Includes bibliographical references.
  note: Text (Thesis)
  subject:
    topic: Major mechanical engineering
  subject:
    topic: e/a ratio
  subject:
    topic: Martensitic Transformation
  subject:
    topic: Thermal Cyclic Stability
  subject:
    topic: CoNiGa
  subject:
    topic: High Temperature Shape Memory Alloys
  identifier: http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8544
  record info:
    record content source: TXA
    record creation date: 111116
    record change date: 20151202144305.0
    record identifier: in00002721231