| dc.description.abstract | Commerical avaiable 5083 Al alloy is well known for its good weldability, corrosion resistance and medium strength with ductility. It was one of the few aluminum alloys that had been targeted for developing fine-grained superplasticity for structural applications through rolling type thermo-mechanical process. In recent years, a new technique for refining grain sizes, equal channel angular extrusion (ECAE) has been emerged and imposed on many magnesium and some aluminum alloys. Surprisingly, it is seemingly not involving the Al-5083. In this study, billets extruded by ECAE using four kinds of process parameters will be prepared for microstructure observations and mechanical property tests. Furthermore, two batches of 5083 Al alloys containing slightly different on composition will also be compared after ECAE.
The microstructure of 5083 Al alloy processed by 90°-200℃-Bc8 condition is consisted of equaxied subgrain structure, and grain size is small than 1μm. The elongations of 5083 alloy containing lower Fe that tested at initial strain rate 1×10-3 s-1 are 266.7% and 350% at 250℃ and 450℃, respectively. The restult shows that 5083 Al alloy reveals low and high temperatures superplasticity simultaneously. After ECAE, the initial texture of 〈110〉// ND of materials disappeared completely and were translated into 〈111〉// ND shear texture which was also formed in torsion processed material. Besides extrusion temperatures, the amount of shear planes and an included angle between them also affect the intensity of shear texture. The intensity of shear texture at die angle Φ=120° is higher than Φ=90°, and Route C＞Route A＞Route Bc.
Using different process parameters, such as Routes, temperatures and number of passes, which will lead to microstructure having different grain shapes, grain boundary properties and texture components. These characteristics will control whether dynamic recrystallization occurs or not during low temperature superplasticity. During high temperature superplasticity, the second phase particles consist of Mn, Fe and Si elements, which play an important part for tensile testing. The 5083 Al alloy containing fewer Fe which represents higher m-value and optimum elongation at 450℃. | en_US |