Yazarlar

• Demirtas, M.(2)
• Purcek, G.(2)
• Yanar, H.(2)
• Zhang, Z.F.(2)
• Zhang, Z.J.(2)
• Demirtas, Muhammet(1)
• Department of Mechanical Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, 316-8511(1)
• Graduate School of System Design, Tokyo Metropolitan University, 6-6 Asahigaoka, Hino,Tokyo, 191-0065(1)
• Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa, 252-5210(1)
• Itoh, G.(1)
• Itoi, T.(1)
• Kitazono, K.(1)
• Kobayashi, J.(1)
• Morita, K.(1)
• National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047(1)
• Purcek, Gencaga(1)
• Sato, E.(1)
• Takayama, Y.(1)
• Yanar, Harun(1)
• Zhang, Zhe-Feng(1)
• Zhang, Zhenjun(1)

• BildiriAçık Erişim2016Scopus SJRQ3/r/bayburt/13869
  Effect of natural aging on RT and HSR superplasticity of ultrafine grained Zn-22Al alloy

  Demirtas, Muhammet; Purcek, Gencaga; Yanar, Harun; Zhang, Zhenjun; Zhang, Zhe-Feng; Sato, E.; Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa, 252-5210; Itoh, G.; Kobayashi, J.; Department of Mechanical Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, 316-8511

  Zn–22Al alloy was processed using a well-designed two-step equal channel angular extrusion/pressing (ECAE/P), and ultrafine-grained (UFG) microstructure with 200 nm grain size was achieved. UFG Zn-22Al was subjected to long-term (up to 60 days) aging at room temperature (RT) and it was seen that natural aging caused limited grain growth in the microstructure. Grain sizes of about 300 nm, 350 nm and 350 nm were measured after 15, 30 and 60 days aging, which mean that UFG Zn-22Al alloy has a good microstructural stability at RT up to 60 days. ECAPed Zn-22Al alloy showed a maximum elongation of about 400% at a high strain rate of 5×10-2 s-1 and maximum elongation decreased with increasing grain size. Elongation to failures of ~375% and ~350% were obtained with the samples having 300 nm and 350 nm grain sizes, respectively. In addition, natural aging slightly decreased the strain rate at which superplastic region formed. While the maximum elongation occurred at the strain rate of 5×10-2 s-1 in ECAPed UFG alloy, it took place at lower strain rate of 1×10-2 s-1 after aging for all time periods. Also, flow stress of the alloy increased with increasing grain size during natural aging.

  AtıfScopus7·OpenAlex8

  İncele
• MakaleAçık Erişim2015Scopus SJRQ1/r/bayburt/12532
  Improvement of high strain rate and room temperature superplasticity in Zn-22Al alloy by two-step equal-channel angular pressing

  Demirtas, M.; Purcek, G.; Yanar, H.; Zhang, Z.J.; Zhang, Z.F.

  The Zn-22Al alloy was subjected to equal-channel angular pressing (ECAP) to improve its high strain rate (HSR) superplasticity at room temperature (RT). A well-designed two-step ECAP process formed an ultrafine-grained (UFG) microstructure with an average grain size of 200nm as the lowest one obtained so far after ECAP processing of this alloy. Also, agglomerate- and texture-free microstructure with UFG Al-rich α- and Zn-rich η-grains separated mostly by high-angle grain boundaries (HAGBs) was produced by this process. The maximum RT elongation was achieved to be 400% with a strain rate sensitivity of 0.30 at a very high strain rate of 5×10-2s-1 after the two-step ECAP process. This elongation value is the highest one obtained at RT and at all strain rates for this alloy up to now. The current results demonstrate that such an improvement in superplasticity of Zn-22Al alloy after the two-step ECAP process can enhance its applications where RT and HSR superplasticity are strongly needed.

  AtıfScopus48·OpenAlex48

  İncele
• MakaleAçık Erişim2015Scopus SJRQ1/r/bayburt/12329
  Achieving room temperature superplasticity in Zn-5Al alloy at high strain rates by equal-channel angular extrusion

  Demirtas, M.; Purcek, G.; Yanar, H.; Zhang, Z.J.; Zhang, Z.F.

  Multi-pass equal-channel angular extrusion/pressing (ECAE/P) was applied to the eutectic Zn-5Al alloy to achieve high strain-rate (HSR) superplasticity in that alloy at room temperature (RT) by producing ultrafine-grained (UFG) microstructure. ECAE processing transformed the coarse-grained lamellar/spherical microstructure into a unique bimodal structure having equiaxed Zn-rich η-phase with a mean grain size of 540 nm and spherical Al-rich α-phase with an average grain size of 110 nm. The α-phase particles accumulated mainly along the η-phase boundaries. This unique microstructure brought about an extraordinary improvement in HSR superplasticity of the alloy even at RT. While the strength values decreased after ECAE, the elongation to failure increased substantially. The maximum elongation was 520% at the strain rate of 10-3 s-1, still high elongation of about 400% was achieved at a high strain rate of 10-2 s-1. This extraordinary improvement in HSR superplasticity of Zn-5Al alloy was attributed to the morphologically unique bimodal microstructure in UFG regime formed after ECAE. The grain boundary sliding (GBS) was found to be the main deformation mechanism for this alloy in superplastic regime.

  AtıfScopus33·WoS35·OpenAlex34

  İncele