Microstructure and deformation in the spray deposited Zn–22% Al alloy

✍ Scribed by Yuwei Xun; Farghalli A. Mohamed

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 700 KB
• Volume: 432
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2006.06.019

✦ Synopsis

Microstructure and deformation in Zn-22% Al that was prepared by spray atomization and deposition were investigated. The results show that the as-deposited alloy exhibits a non-uniform microstructure composed of coarse and fine lamellar eutectoid domains, and that elongations to failure in tensile samples having such a microstructure are less than 100%. When the lamellar structure is transformed into a fine equiaxed grain structure that is free of porosity as a result of heat treatment and extrusion, the alloy exhibits the characteristics of superplastic flow including: the attainment of elongations to failure in excess of 1600%, the observation of a sigmoidal relationship between stress and strain rate, and the presence of a threshold stress for superplastic flow that is sensitive to the presence of impurities. Microstructure characterization of the samples after creep deformation reveals a limited dislocation activity that is manifested in the presence of dislocation-particle interaction in some of the grains. A comparison in creep behavior between Zn-22% Al and 7 vol.% SiC p -Zn-22% Al composite that, like the alloy, was prepared by spray atomization and deposition shows the presence of a strengthening effect. This effect is explained in terms of the details of a deformation mechanism for superplastic flow that is based on dislocation accommodated boundary sliding.