Optimization of RT superplasticity of UFG Zn-22Al alloy by applying ECAP at different temperatures and phase regions

7th International Conference on Nanomaterials by Severe Plastic Deformation

Demirtas, M.^1,2 ; Yanar, H.^2 ; Purcek, G.^2

Bayburt University, Faculty of Engineering, Department of Mechanical Engineering, Bayburt

69000, Turkey^1

Karadeniz Technical University, Faculty of Engineering, Department of Mechanical Engineering, Trabzon

61080, Turkey^2

关键词: ECAP processing;    Equal-channel;    High strain rates;    Phase region;    Processing temperature;    Single phase region;    Superplastic elongation;    Two-phase region;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/194/1/012033/pdf
DOI  :  10.1088/1757-899X/194/1/012033

来源: IOP

【 摘 要 】

Zn-22Al alloy was subjected to either one-step or two-step equal channel pressing (ECAP) to investigate the effect of processing temperature on its microstructure and room temperature (RT) superplasticity. In one-step ECAP processes, 4 passes ECAP were applied to the alloy at different temperatures: RT, 100°C and 250°C in two-phase region below eutectoid temperature and 350°C in single-phase region above eutectoid temperature. In two-step ECAP processes, one-step ECAP-processed samples were subjected to four more passes ECAP at RT. Considering the one-step ECAP processing, RT superplasticity increased with decreasing ECAP temperature as expected, and the highest RT superplasticity was achieved as 350% after 4 passes ECAP at RT. On the other hand, application of 4 more passes ECAP at RT to the sample showing the lowest superplastic elongation after one-step ECAP (the sample processed at 350°C) resulted in the maximum RT elongation of 400% at a high strain rate of 5×10-2s-1. These results suggest that first step temperature of two-step ECAP process is needed to increase above the eutectoid point of Zn-22Al alloy to achieve high RT superplasticity. These results were attributed to the changes in microstructure inside the single-phase and two-phase regions during the processes.