A Study on the Strain Softening and Anneal Hardening in Zn-22 wt％ Al Alloy
| Autor: | Yu-Sheng Yu, 余育陞 |
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| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 In this study thermomechanical processings were applied to a Zn-22 wt.% Al alloy to produce fine- and coarse-grained structures for the strain softening and anneal hardening studies. The microstructure, hardness and compression curve of Zn-22 wt.% Al alloy 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 the Zn-Al alloy in the temperature range from -10℃ to 250℃ and an anneal hardening behavior in the softened Zn-Al alloy upon high temperature annealing. The mechanism of the strain softening behavior was found to be the 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 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 mechanism of strain softening in the Zn-22 wt.％ Al alloy. By using this model detailed informations regarding to the deformation and the DRX (i.e. the strain softening behavior) in individual α and β phases were disclosed from the experimental compressive stress-strain curve. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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