| Summary: | 碩士 === 遠東科技大學 === 機械研究所 === 97 === Al-Cu-Mg alloys are extensively used in industries . Due to high strength and difficulty for manufacturing, the complicated work of Al-Cu-Mg alloys need numerous manufacturing processes. Previous efforts were mainly focused on powder metallurgy processing, multi-step thermo mechanical processing, composition modification and severe plastic deformation technique. This research tried to process the 2017 Al alloy of Al-Cu-Mg alloys through an easy and effective annealing heat treatment followed by a compression test to estimate the re-formability. Once the materials attend better deformability, it would contribute to the manufacturing of complicated work pieces.
The experimental results show that the annealing temperature increase would reduce the hardness, the ultimate tensile strength and compressive strength of extrusion while there is a better malleability. In addition, it attain the best recrystallization when the annealing temperature reaches up to 325℃. The microstrucutre appear complete recrystallization, malleability increases obviously, and the height reduction ratio can reach 93.3%. However, as the annealing temperature is higher than 325℃, grain growth appear and the ultimate tensile strength and compressive strength get higher, but the malleability drops. The causes are the higher temperature makes the solute atoms solid back to matrix, and then precipitation hardening is formed gradually during the cooling process at room temperature. Precipitation hardening increases the strength and reduces the ductility and the height reduction ratio.
Samples were quenched after being processed by various annealing heat treatment temperature, and then were placed at room temperature for 96 hours followed by the tensile test. The tensile stress-strain curves show the serration phenomenon which is resulted in the phenomenon of dynamic strain aging, but not for the extrusion and 400 ℃.
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