Development of zinc-based superplastic alloys and investigation of structural, mechanical and damping behaviors

In this study, Zn-22Al, Zn-5Al and Zn-0.3Al alloys in different phase structures were subjected to some thermal and/or thermomechanical processes from simple to complex types, and the effects of these processes on the microstructure, room temperature (RT) superplastic behavior and elastic deformation induced damping capacity were investigated in detail. In general, equal-channel angular extrusion/pressing (ECAE/P) remarkably refined microstructures as compared to aging and rolling processes. While the lowest grain size was obtained from Zn-22Al alloy as 200 nm, the minimum grain sizes of Zn-5Al and Zn-0.3Al alloys were measured to be ~540 nm and 2 µm, respectively, after ECAP. After the formation of fine/ultrafine grained (F/UFG) microstructures, all three Zn-Al alloys showed superplastic behavior at RT and at high strain rates. The maximum superplastic elongations were obtained as 400 %, 520 % and 1000 % for Zn-22Al, Zn-5Al and Zn-0.3Al alloys, respectively. Thus, RT superplasticity of Zn-22Al was improved, and Zn-5Al showed superplastic behavior at RT for the first time. Besides the superplastic properties, Zn-Al alloys also showed high damping capacity (tanδ) at RT. The maximum tanδ of 0.256 (the highest one achieved in Zn-Al alloys in the literature) was obtained from Zn-0.3Al alloy at 1 Hz frequency and 2x10-3 strain amplitude. The tanδ values of Zn-22Al and Zn-5Al alloys were measured as 0.211 and 0.170, respectively, at the same frequency and strain amlitude. Thus, damping capacity of Zn-22Al alloy was further improved, and new high damping capacity Zn-Al alloys (Zn-5Al and Zn-0.3Al) were developed with this study.