Title page for etd-0523112-110630


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URN etd-0523112-110630
Author Hong-Kun Yan
Author's Email Address No Public.
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Department Materials and Optoelectronic Science
Year 2011
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title The influence of Zn on the mechanical property of Al-Zn alloy
Date of Defense 2012-05-04
Page Count 110
Keyword
  • friction stir processing
  • dynamic recovery
  • Strain rate sensitivity
  • Hall-Petch equation
  • solid solute softening
  • Abstract   In this study, mechanical properties of Al-Zn alloys were conducted, with various parameters including Zn contents, grain size, and tensile strain rate. Experimental samples were all manufactured with friction stir processing method. Samples of Al-Zn alloys with the grain size of 1.5μm, 1μm, or 0.5μm and five Zn concentration were pulled in tension at strain rate of 10-3s-1,10-4s-1 and 10-5s-1 . 
       The data set were then used to draw engineering and true tensile stress vs. strain curves , flowing stress vs. Zn contents curves, Hall-Petch equation curves, m vs. Zn contents curves and m vs. grain size curves. Quantitative analysis were conducted to discover that solid solute softening and inverse Hall-Petch relation were present in Al-Zn alloys, which were more prominent at slower tensile strain rate when grain size was less than 1μm and the Zn contents was higher than 10wt%.
      Quantitative analysis of strain rate sensitivity (m) showed the trends of increasing value of m with higher Zn contents and smaller grain sizes when solid solute softening and inverse Hall-Petch relation were present. The high grain-boundary diffusion coefficient of Zn which accelerates the efficiency of dynamic recovery are considered the main reason. The effect gets more prominent with increasing Zn contents , smaller grain size , and slower tensile strain rate. For Zn concentration higher than 10wt%, dynamic recovery may drive inverse Hall-Petch relation to appear when grain size is about 1μm large.
    Advisory Committee
  • none - chair
  • none - co-chair
  • none - co-chair
  • none - advisor
  • Files
  • etd-0523112-110630.pdf
  • Indicate in-campus at 5 year and off-campus access at 99 year.
    Date of Submission 2012-05-23

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