<p>This study proposes that creep-induced segregation to planar faults reflects the dynamic establishment of a new compositional steady state within the two-phase <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\gamma $</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation>/<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\gamma ^{\prime }$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>γ</mi> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation> single-crystal Ni-base superalloy during creep. The temperature difference between the alloy’s aging condition and the creep-experiment temperature drives a creep-induced partitioning flux, causing elements to redistribute within the <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\gamma ^{\prime }$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>γ</mi> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation> phase and accumulate at planar faults. In this work, the single-crystal Ni-base superalloy ERBO-1 (SX) was creep-deformed using double-shear creep testing at 250 MPa and 750 °C, which is 120 °C below the preceding aging treatment temperature. At 1 and 2 pct strain, the interrupted creep states show planar faults with solute segregation as commonly observed in this low-temperature, high-stress regime. Solute segregation at superlattice extrinsic stacking faults (SESF), anti-phase boundaries (APB), and microtwins in the <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\gamma ^{\prime }$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>γ</mi> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation> phase reveals systematic depletion of Ni and Al, accompanied by enrichment of Re, Co, Cr, Mo, and Ti. Thermodynamic calculations predict the temperature-dependent <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\gamma $</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation>/<InlineEquation ID="IEq6"> <EquationSource Format="TEX">$\gamma ^{\prime }$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>γ</mi> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation> compositions. Under the present experimental conditions, this results in increased uptake of Ni and Al and rejection of Re, Co, and Cr by the <InlineEquation ID="IEq7"> <EquationSource Format="TEX">$\gamma ^{\prime }$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>γ</mi> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation> phase. Consequently, depletion of Ni and Al and enrichment of Re, Co, and Cr are detected at planar defect sites. In contrast, Ti, Mo, Ta, and W segregation at microtwins and SESFs cannot be explained by bulk <InlineEquation ID="IEq8"> <EquationSource Format="TEX">$\gamma ^{\prime }$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>γ</mi> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation> partitioning and is instead attributed to localized phase transformations in the vicinity of the defects.</p>

Creep-Driven Solute Segregation to Planar Faults in Ni-Base Single-Crystal Superalloys

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2026年4月10日

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Zhongmin Long,
David Bürger,
Lukas Grünewald,
Vamshi Krishna Rao,
K. V. Vamsi,
Yolita M. Eggeler

摘要

This study proposes that creep-induced segregation to planar faults reflects the dynamic establishment of a new compositional steady state within the two-phase $\gamma $ $γ$ / $\gamma ^{\prime }$ $γ^{'}$ single-crystal Ni-base superalloy during creep. The temperature difference between the alloy’s aging condition and the creep-experiment temperature drives a creep-induced partitioning flux, causing elements to redistribute within the $\gamma ^{\prime }$ $γ^{'}$ phase and accumulate at planar faults. In this work, the single-crystal Ni-base superalloy ERBO-1 (SX) was creep-deformed using double-shear creep testing at 250 MPa and 750 °C, which is 120 °C below the preceding aging treatment temperature. At 1 and 2 pct strain, the interrupted creep states show planar faults with solute segregation as commonly observed in this low-temperature, high-stress regime. Solute segregation at superlattice extrinsic stacking faults (SESF), anti-phase boundaries (APB), and microtwins in the $\gamma ^{\prime }$ $γ^{'}$ phase reveals systematic depletion of Ni and Al, accompanied by enrichment of Re, Co, Cr, Mo, and Ti. Thermodynamic calculations predict the temperature-dependent $\gamma $ $γ$ / $\gamma ^{\prime }$ $γ^{'}$ compositions. Under the present experimental conditions, this results in increased uptake of Ni and Al and rejection of Re, Co, and Cr by the $\gamma ^{\prime }$ $γ^{'}$ phase. Consequently, depletion of Ni and Al and enrichment of Re, Co, and Cr are detected at planar defect sites. In contrast, Ti, Mo, Ta, and W segregation at microtwins and SESFs cannot be explained by bulk $\gamma ^{\prime }$ $γ^{'}$ partitioning and is instead attributed to localized phase transformations in the vicinity of the defects.