Fine‐structure superplasticity in materials

Nieh, T.G.; Wadsworth, J.

doi:10.1080/02533839.1998.9670427

Cited by 4 publications

(3 citation statements)

References 152 publications

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“…Thus, grain boundary sliding occurred much more effectively at the η/α and η/η phase boundaries in all three Zn-Al alloys, and thus high superplastic elongations were achieved at RT and high strain rates. Besides the F/UFG microstructures, equiaxed grainy morphology and homogeneously distributed phases in the microstructures, presence of second phase in Zn-22Al and Zn-5Al alloys and second phase particles in Zn-0.3Al alloy prevent the excessive grain growth during the RT deformation of the alloys and promotes to high superplastic elongation in these alloys [11,12]. More detailed analysis on the RT superplasticy and main reason of high superplastic elongation achieved in Zn-22Al, Zn-5Al and Zn-0.3Al alloys can be found in previously published papers [3,5,6].…”

Section: Discussionmentioning

confidence: 99%

Room Temperature Superplasticity in Fine/Ultrafine-Grained Zn-Al Alloys with Different Phase Compositions

Demirtas

Yanar

Saray

et al. 2018

DDF

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Three Zn-Al alloys, namely Zn-22Al, Zn-5Al and Zn-0.3Al, were subjected to equal-channel angular pressing (ECAP), and the effect of ECAP on their microstructure and room temperature (RT) superplastic behavior were investigated in detail referring to previous studies reported by the authors of the current study. ECAP remarkably refined the microstructures of three alloys as compared to their pre-processed conditions. While the lowest grain size was achieved in Zn-22Al alloy as 200 nm, the grain sizes of Zn-5Al and Zn-0.3Al alloys were ~540 nm and 2 µm, respectively, after ECAP. After the formation of fine/ultrafine-grained (F/UFG) microstructures, all Zn-Al alloys exhibited superplastic behavior at RT and high strain rates. The maximum superplastic elongations were 400%, 520% and 1000% for Zn-22Al, Zn-5Al and Zn-0.3Al alloys, respectively. It is interesting to point out that the highest RT superplastic elongation was obtained in Zn-0.3Al alloy with the largest grain size, while Zn-22Al alloy having the lowest grain size showed the minimum superplastic elongation. This paradox was attributed to the different phase compositions of these alloys. The formation of Al-rich α/α phase boundaries, where grain boundary sliding is minimum comparing to Zn-rich η/η and η/α phase boundaries of Zn-Al alloys, is the lowest level in Zn-0.3Al alloy among all the alloys. Therefore, it can be concluded that if it is desired to achieve high superplastic elongation in Zn-Al alloys at RT, keeping Al content at a possibly minimum level seems to be the most suitable way.

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Section: Discussionmentioning

confidence: 99%

Room Temperature Superplasticity in Fine/Ultrafine-Grained Zn-Al Alloys with Different Phase Compositions

Demirtas

Yanar

Saray

et al. 2018

DDF

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“…[16] Phase-boundary migration promoted by the grain-boundary sliding restores the damage introduced near boundary by grain-boundary sliding. [16] Phase-boundary migration promoted by the grain-boundary sliding restores the damage introduced near boundary by grain-boundary sliding.…”

Section: B Grain-boundary Sliding and Grain-boundary Migrationmentioning

confidence: 99%

“…[11][12][13][14][15] The volume fraction of a soft ␤ phase always increases by dynamic phase transformation of titanium alloys. [16] However, there is no available information about the possible role of dynamic phase transformation in superplastic deformation accompanied by grain-boundary sliding in Nb ss /Nb 3 Al in-situ composite. In contrast to the titanium alloys, the volume fraction of the hard Nb 3 Al phase was found to increase during superplastic deformation in Nb ss /Nb 3 Al in-situ composite.…”

Section: Introductionmentioning

confidence: 99%

Dynamic phase transformation during superplastic deformation of Nb/Nb3Al in-situ composite

Murayama

Fang

2004

Metall Mater Trans A

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YONOSUKE MURAYAMA and FANG WEINb ss /Nb 3 Al in-situ composite with the nominal composition of Nb-16 mol pct Al-1 mol pct B, consisting of bcc niobium solid solution (Nb ss ) and A15 ordered Nb 3 Al, was synthesized by arc melting, homogenization annealing, and isothermal forging, and their superplastic deformation behavior was investigated by tensile tests and microstructure observations. Maximum superplastic elongation over 750 pct was obtained at 1573 K and at a strain rate of 1.6 ϫ 10 Ϫ4 s Ϫ1 for as-forged specimens. Phase transformation from Nb ss to Nb 3 Al was observed to occur during superplastic deformation. Dynamic phase transformation during superplastic deformation progresses more quickly than static phase transformation during annealing without applied stress. Dynamic phase transformation is accompanied by phase-boundary migration, which operates as an accommodation process of grain-boundary sliding. Dislocation creep dominates deformation and grain-boundary sliding is inhibited at a high strain rate, while grain-boundary sliding and cavity formation are promoted at a low strain rate because of insufficient accommodation of grain-boundary sliding arising from sluggish dynamic phase transformation. It is concluded that there exists an optimum strain rate that guarantees the grain-boundary sliding and the rapid dynamic phase transformation to achieve maximum superplastic elongation.

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