Announcement for Downloading full text filePlease respect the Copyright Act.
All digital full text dissertation and theses from this website are authorized the copyright owners. These copyrighted full-text dissertation and theses can be only used for academic, research and non-commercial purposes. Users of this website can search, read, and print for personal usage. In respect of the Copyright Act of the Republic of China, please do not reproduce, distribute, change, or edit the content of these dissertations and theses without any permission. Please do not create any work based upon a pre-existing work by reproduction, Adaptation, Distribution or other means.
URN etd-0802106-162003 Statistics This thesis had been viewed 2506 times. Download 406 times. Author Yu-Shuo Chan Author's Email Address No Public. Department Materials Engineering Year 2005 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 143 Title A Study on the Strain Softening and Anneal Hardening in Pseudo-single- and Dual-phase Zn-Al Alloys Keyword dynamic recrystallization (DRX) Zn-Al alloy work softening anneal hardening anneal hardening work softening Zn-Al alloy dynamic recrystallization (DRX) Abstract In this study thermomechanical processings were applied to three Zn-Al alloys, namely the micro-duplex Zn-22 wt.% Al alloy, pseudo-single α phase Zn-95 wt.% Al and pseudo-single β phase Zn-1wt.% Al for the strain softening and anneal hardening studies. The microstructure, hardness and compression S-S curves of these Zn-Al alloys were studied by using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), microhardness measurements and compression tester. The results showed the occurrence of a strain softening phenomenon in Zn-Al alloys containing a substantial amount of β phase in the temperature range from -10℃ to 250℃ and an anneal hardening behavior in the strain softened Zn-Al alloys upon high temperature annealing. The mechanism of the strain softening behavior was found to be a DRX-induced softening during hot working, which can be facilitated by the formation of ultra-fine β grains with high-angle-boundaries; the mechanism of the anneal hardening behavior, on the other hand, was found to be the annihilation of the ultra-fine β grains by a high temperature grain coarsening treatment to retard the occurrence of the DRX-induced softening and to restore the “normal strength” of the alloy.
A composite stress-strain curve model was proposed in this study to resolve the strain softening and anneal hardening behaviors in the dual-phase Zn-22 wt.％ Al alloy. By using this model detailed informations regarding to the deformation, the DRX (i.e. the strain softening) and the grain coarsening (i.e. the anneal hardening) behaviors in the β phase can be disclosed.
Advisor Committee Chih-Fu Yang - advisor
Jien-Wei Yeh - co-chair
Lui-Ho Chiu - co-chair
Shu-Chun Lin - co-chair
Files Date of Defense 2006-06-30 Date of Submission 2006-08-02