| Summary: | 碩士 === 大同大學 === 材料工程研究所 === 90 === The effects of room temperature rolling and room temperature aging on the phase transformation and strain induced superplasticity in an eutectoid Zinc-22wt.% Aluminum alloy were studied. Phase composition analysis, damping capacity measurement, elongation and micro-hardness measurements, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were carried out to examine the phase transformation and the room temperature rolling effects on the Zn-Al alloy. The results show that after solution treatment, quench, room temperature aging for 1440 minutes, the phase compositions of α and β precipitates and the chemical free energy of the Zn-Al alloy reach a stable stage. Further aging or rolling treatment did not alter the phase compositions nor its chemical equilibrium state. Upon room temperature rolling to various extent from 50% ~ 90% reduction in thickness, the microstructure of the Zn-Al alloy changed to a lamellar structure via a discontinuous precipitation and a subsequent discontinuous coarsening reaction. It was found that during the subsequent room temperature aging after rolling the hardness decreased, ductility increased and damping factor decreased with aging time for the rolled Zn-Al alloy specimens. These behaviors can be readily understood using the theory of room temperature annealing of the Zn-Al alloy.
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