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A processing map for hot deformation of an ultrafine-grained aluminum-magnesium-silicon alloy prepared by mechanical milling and hot extrusion

Asgharzadeh, H ; Sharif University of Technology | 2015

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  1. Type of Document: Article
  2. DOI: 10.1007/s11661-015-3162-3
  3. Publisher: Springer Boston , 2015
  4. Abstract:
  5. Uniaxial compression test at different temperatures [573 K to 723 K (300 °C to 450 °C)] and strain rates (0.01 to 1 s−1) was employed to study the hot deformation behavior of an ultrafine-grained (UFG) Al6063 alloy prepared by the powder metallurgy route. The UFG alloy with an average grain size of ~0.3 µm was prepared by mechanical milling of a gas-atomized aluminum alloy powder for 20 hours followed by hot powder extrusion at 723 K (450 °C). To elaborate the effect of grain size, the aluminum alloy powder was extruded without mechanical milling to attain a coarse-grained (CG) structure with an average grain size of about 2.2 µm. By employing the dynamic materials model, processing maps for the hot deformation of the UFG and CG Al alloy were constructed. For investigation of microstructural evolutions and deformation instability occurring upon hot working, optical microscopy, scanning electron microscopy coupled with electron backscattered diffraction and transmission electron microscopy were utilized. It is shown that the grain refinement increases the deformation flow stress while reducing the strain hardening and power dissipation efficiency during the deformation process at the elevated temperatures. Restoration mechanisms, including dynamic recovery and recrystallization are demonstrated to control microstructural evolutions and thus the deformation behavior. Coarsening of the grain structure in the UFG alloy is illustrated, particularly when the deformation is performed at high temperatures and low strain rates. The manifestations of instability are observed in the form of cracking and void formation
  6. Keywords:
  7. Aluminum ; Compression testing ; Crystal microstructure ; Deformation ; Dynamic recrystallization ; Dynamics ; Electron microscopy ; Extrusion ; Grain refinement ; Grain size and shape ; High resolution transmission electron microscopy ; Hot working ; Magnesium alloys ; Mechanical alloying ; Microstructural evolution ; Milling (machining) ; Powder metallurgy ; Scanning electron microscopy ; Silicon alloys ; Strain hardening ; Strain rate ; Transmission electron microscopy ; Aluminum magnesium silicon alloys ; Deformation instabilities ; Dynamic materials model ; Dynamic recovery and recrystallization ; Electron back-scattered diffraction ; Hot deformation behaviors ; Ultra-fine grained ( UFG) ; Uni-axial compression tests ; Aluminum alloys
  8. Source: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 46, Issue 12 , December , 2015 , pp 5900–5908 ; 10735623 (ISSN)
  9. URL: http://link.springer.com/article/10.1007%2Fs11661-015-3162-3