Yazarlar
Yayınlar
- MakaleAçık Erişim2018Scopus SJRQ2Effect of grain refinement and phase composition on room temperature superplasticity and damping capacity of dual-phase Zn-Al alloys
Demirtas, Muhammet; Atli, Kadri C.; Yanar, Harun; Purcek, Gencaga
The effects of grain refinement and phase composition on superplasticity and damping capacity of eutectic Zn-5Al and eutectoid Zn-22Al alloys were investigated. For grain refinement, equal-channel angular pressing (ECAP) was applied to these alloys. ECAP completely eliminated the as-cast lamellar microstructures of both alloys and resulted in ultrafine-grained structures along with room temperature superplasticity. Furthermore, these microstructural changes with ECAP increased the damping capacity of both alloys in the dynamic hysteresis region, where damping arises from viscous sliding of phase/grain boundaries. Dynamic recrystallization at the surface and thermally activated viscous motion of grain/phase boundaries at the subsurface of the samples of both alloys were proposed as the damping mechanisms in the region where the alloys showed combined aspects of static/dynamic hysteresis damping behavior. Although the grain size is larger in Zn-5Al compared to Zn-22Al, it showed higher damping capacity due to the different sliding characteristics of its phase boundaries.
AtıfScopus14WoS11OpenAlex14
İncele - MakaleYalnız künye2018Scopus SJRQ1High temperature superplasticity and deformation behavior of naturally aged Zn-Al alloys with different phase compositions
Demirtas, M.; Kawasaki, M.; Yanar, H.; Purcek, G.
Two Zn-Al alloys, eutectoid Zn-22Al and dilute Zn-0.3Al, were processed through equal-channel angular pressing (ECAP). The ECAP-processed alloys were subjected to long-term natural aging at room temperature for 120 days in order to investigate the effect of long-term natural aging on high-temperature superplasticity and the deformation behavior of these alloys. The grain size of the Zn-22Al alloy increased from 200 nm after ECAP to 400 nm after the natural aging process. The Zn-0.3Al alloy with a grain size of 1.3 µm after ECAP demonstrated a reasonably stable microstructure with the grain size of ~ 1.7 µm after long-term natural aging. The naturally aged ultrafine-grained (UFG) Zn-22Al alloy showed an excellent superplastic elongation of about 1800% at 200 °C. Grain boundary sliding was determined as the dominant deformation mechanism in this alloy. On the contrary, a considerably low elongation to failure of 230% was recorded in the naturally aged fine-grained (FG) Zn-0.3Al alloy at 150 °C, and dislocation creep was evaluated as the main deformation mechanism for this alloy. Detailed microstructural analyses showed that the FG Zn-0.3Al alloy was exposed to grain boundary corrosion during the natural aging process due to the presence of Al precipitates at grain boundaries whereas such formation was not observed in the UFG Zn-22% Al alloy. Grain boundary sliding was hindered by grain boundary corrosion and the cavity nucleation at the corroded grain boundaries caused a premature failure leading to such a low elongation in the Zn-0.3Al alloy.
AtıfScopus30WoS30OpenAlex33İncele - MakaleAçık Erişim2016Scopus SJRQ1Effect of different processes on lamellar-free ultrafine grain formation, room temperature superplasticity and fracture mode of Zn-22Al alloy
Demirtas, M.; Purcek, G.; Yanar, H.; Zhang, Z.J.; Zhang, Z.F.
The Zn-22 wt.%Al was processed using five different selected routes including thermal, thermo-mechanical and severe plastic deformation (SPD) techniques in order to produce ultrafine grained (UFG) microstructure for achieving room temperature (RT) and high strain rate (HSR) superplasticity, and to compare the same set of the results. After all routes, the microstructural evolutions and RT uniaxial tensile tests at different strain rates ranging from 1 × 10-3 to 1 × 100 s-1 were investigated. The smallest grain size was achieved to be 300 nm after the thermo-mechanical process including conventional hot and cold rolling steps. However, the lamellar microstructure of the alloy was not completely eliminated during that process. On the other hand, equal-channel angular pressing (ECAP) as one of the SPD techniques decreased the grain size down to 400 nm with a lamellar-free microstructure. The maximum elongation value was achieved to be 330% with the sample tested at 1 × 10-3 s-1 after a thermo-mechanical process including conventional hot and cold rolling, and an aging stage between these rolling steps. It was found that lamellar-free microstructure causes higher superplastic elongation even if it has higher grain size compared to the sample having partially lamellar structure.
AtıfScopus40WoS39İncele