<p>The over-aging of a polycrystalline <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}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>γ</mi> <mo>′</mo> </mrow> </math></EquationSource> </InlineEquation> nickel-based superalloy can alter numerous microstructural features that are known to be critical for the mechanical properties of these alloys. The aim of this study is to decouple the impact of different microstructural modifications on the monotonic and viscoplastic properties of the René 65 superalloy, produced by conventional cast-and-wrought processing, after various thermal exposures. Over-aging treatments were carried out at 700 °C, 725 °C, 750 °C, 775 °C, 800 °C, and 850 °C for durations of up to 4 000 h. The evolution of <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\gamma {\prime}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>γ</mi> <mo>′</mo> </mrow> </math></EquationSource> </InlineEquation> precipitates and the formation of TCP phases during these treatments were quantified. These microstructural changes were identified as being responsible for either the degradation or the improvement of specific monotonic and viscoplastic properties of the alloy. It was shown that the dissolution or progressive transformation of the smallest <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\gamma {\prime}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>γ</mi> <mo>′</mo> </mrow> </math></EquationSource> </InlineEquation> precipitates, within grains or at grain boundaries, governs the evolution of several properties in tension (20 °C and 700 °C), creep (700 °C), and stress relaxation (700 °C). The wide range of treatments applied allowed, at least partially, to decouple the effects of fine <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\gamma {\prime}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>γ</mi> <mo>′</mo> </mrow> </math></EquationSource> </InlineEquation> precipitates evolution from those of TCP phase formation. In particular, the stress relaxation tests provided insights into the deformation mechanisms controlling the evolution of the creep rate after over-aging.</p>

Mechanical Properties of the Polycrystalline γ/γ′ Nickel-Based Superalloy René 65 After Long-Term Aging

期刊论文
发表日期：

2026年2月3日

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Julien Prouteau,
Florence Hamon,
Patrick Villechaise,
Anchal Goyal,
Jonathan Cormier

摘要

The over-aging of a polycrystalline $\gamma $ $γ$ / $\gamma {\prime}$ $γ'$ nickel-based superalloy can alter numerous microstructural features that are known to be critical for the mechanical properties of these alloys. The aim of this study is to decouple the impact of different microstructural modifications on the monotonic and viscoplastic properties of the René 65 superalloy, produced by conventional cast-and-wrought processing, after various thermal exposures. Over-aging treatments were carried out at 700 °C, 725 °C, 750 °C, 775 °C, 800 °C, and 850 °C for durations of up to 4 000 h. The evolution of $\gamma {\prime}$ $γ'$ precipitates and the formation of TCP phases during these treatments were quantified. These microstructural changes were identified as being responsible for either the degradation or the improvement of specific monotonic and viscoplastic properties of the alloy. It was shown that the dissolution or progressive transformation of the smallest $\gamma {\prime}$ $γ'$ precipitates, within grains or at grain boundaries, governs the evolution of several properties in tension (20 °C and 700 °C), creep (700 °C), and stress relaxation (700 °C). The wide range of treatments applied allowed, at least partially, to decouple the effects of fine $\gamma {\prime}$ $γ'$ precipitates evolution from those of TCP phase formation. In particular, the stress relaxation tests provided insights into the deformation mechanisms controlling the evolution of the creep rate after over-aging.