Helmholtz Free Energy and the Activation Volume of Steady-State Creep in FGH96 Superalloy

2021 ◽  
Vol 1035 ◽  
pp. 206-211
Author(s):  
Zi Chao Peng ◽  
Jin Wen Zou ◽  
Lei Zhou ◽  
Xu Qing Wang
Keyword(s):  
Free Energy ◽  
Steady State ◽  
Helmholtz Free Energy ◽  
Activation Volume ◽  
Steady State Creep ◽  
Creep Life ◽  
Creep Properties ◽  
Model Base ◽  
Creep Life Prediction ◽  
Crystal Plasticity Theory

The creep properties of FGH96 superalloy were studied in the temperature range of 650 °C to 750 °C and stress range of 690MPa to 897MPa. The results show that the creep life of the alloy decreased significantly with the increase of stress and temperature. However, the temperature produced more effects than that of stress. The most suitable service temperature and stress were also obtained based on the creep results. A physical model base on crystal-plasticity theory was established, but the simplification of the Helmholtz free energy and the activation volume might reduce the accuracy of strain rate prediction. Based on the results of creep at different stresses and temperatures, the Helmholtz free energy and the activation volume of steady-state creep were obtained, which would play a key role in creep life prediction.

scholarly journals Verification of Equation for Evaluating Dislocation Density during Steady-state Creep of Metals

2017 ◽  
Vol 6 (2) ◽  
pp. 20 ◽  
Author(s):  
Manabu Tamura
Keyword(s):  
Free Energy ◽  
Steady State ◽  
Dislocation Density ◽  
Shear Modulus ◽  
Strain Rate ◽  
Gibbs Free Energy ◽  
Steady State Creep ◽  
Austenitic Steels ◽  
Exponential Factor ◽  
Delta G

Ninety-two sets of observed dislocation densities for crept specimens of 21 types of ferritic/martensitic and austenitic steels, Al, W, Mo, and Mg alloys, Cu, and Ti including germanium single crystals were collected to verify an equation for evaluating the dislocation density during steady-state creep proposed by Tamura and Abe (2015). The activation energy, Qex, activation volume, Vex, and Larson–Miller constant, Cex, were calculated from the creep data. Using these parameter constants, the strain rate, and the temperature dependence of the shear modulus, a correction term, Gamma, was back-calculated from the observed dislocation density for each material. Gamma is defined in the present paper as a function of the temperature dependences of both the shear modulus and pre-exponential factor of the strain rate. The values of Gamma range from −394 to 233  and average 2.1 KJmol-1, which is a value considerably lower than the average value of Qex (410.4 KJmol-1), and values of Gamma are mainly within the range from 0 to 50 KJmol-1. The change in Gibbs free energy, Delta G, for creep deformation is obtained using the calculated value of , and the empirical relation Delta G~Delta GD is found, where Delta GD is the change in Gibbs free energy for self-diffusion of the main componential element of each material. Experimental data confirm the validity of the evaluation equation for the dislocation density.

The effect of thickness on the steady-state creep properties of freestanding aluminum nano-films

2012 ◽  
Vol 60 (11) ◽  
pp. 4438-4447 ◽  
Author(s):  
Hiroyuki Hirakata ◽  
Naomichi Fukuhara ◽  
Shoichi Ajioka ◽  
Akio Yonezu ◽  
Masayuki Sakihara ◽  
...  
Keyword(s):  
Steady State ◽  
Steady State Creep ◽  
Creep Properties

Improved tensile creep properties of yttrium- and lanthanum-doped alumina: a solid solution effect

2001 ◽  
Vol 16 (2) ◽  
pp. 425-429 ◽  
Author(s):  
Junghyun Cho ◽  
Chong Min Wang ◽  
Helen M. Chan ◽  
J. M. Rickman ◽  
Martin P. Harmer
Keyword(s):  
Solid Solution ◽  
Steady State ◽  
Creep Behavior ◽  
Solubility Limit ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Properties ◽  
Uniform Microstructure ◽  
Equiaxed Grains ◽  
Rare Earth Doped

The tensile creep behavior of yttrium- and lanthanum-doped alumina (at dopant levels below the solubility limit) was examined. Both compositions (100 ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains. The creep resistance of both doped aluminas was enhanced, compared with undoped alumina, by about two orders of magnitude, which was almost the same degree of improvement as for materials with higher dopant levels (in excess of the solubility limit). In addition, measured creep rupture curves exhibited predominantly steady-state creep behavior. Our results, therefore, verified that the creep improvement in these rare-earth doped aluminas was primarily a solid-solution effect.

scholarly journals ɤ-TiAl Alloy: Tensile Creep Deformation Behaviour and Creep Life at 832 °C

2021 ◽  
Author(s):  
Mainak Saha
Keyword(s):  
Steady State ◽  
Creep Deformation ◽  
Original Work ◽  
Single Phase ◽  
Tial Alloy ◽  
Deformation Behaviour ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Life ◽  
Processing Techniques

Creep deformation in single phase ɤ-TiAl alloy manufactured using different processing techniques has been an extensively studied topic since the late 1970s. The present work revisits the original work on understanding the tensile creep deformation behaviour of wrought single-phase ɤ-TiAl alloy by Hayes and Martin [1] and is aimed to develop an understanding of steady state creep. Besides, it is also aimed to investigate the creep life for stress levels of 69.4 and 103.4 MPa at 832 ⁰C using Monkman-Grant [2] approach.

Effects of Si3N4 Additions on Creep Resistance of Al-Al2O3 Composites

2016 ◽  
Vol 697 ◽  
pp. 644-647
Author(s):  
Hao Ning Shi ◽  
Yong Li ◽  
Chuan Jing Li ◽  
Hai Xia Qin ◽  
Jia Lin Sun
Keyword(s):  
Steady State ◽  
Creep Resistance ◽  
Phenolic Resin ◽  
Steady State Creep ◽  
Creep Properties ◽  
Creep Stage ◽  
Properties Of Composites

Si3N4 (0 and 6 mass%) were added to Al-Al2O3 composite respectively, with phenolic resin as binder, to make Al-Si3N4-Al2O3 unfired composites, which were dried at 200°C for 24h.The creep properties of composites were tested researched under 0.2MPa×50h at 1300°C. The results indicated that the samples put up the features of steady-state creep stage from 25h to 50h; Al4O4C appeared in the corundum matrix with the addition of Al,which improve its creep resistance; when Al and Si3N4 were both existed, sialon phase was formed while Al4O4C was disappeared.

scholarly journals ɤ-TiAl alloy: Tensile creep deformation behaviour and creep life at 832 °C

2021 ◽  
Author(s):  
Mainak Saha
Keyword(s):  
Steady State ◽  
Creep Deformation ◽  
Original Work ◽  
Single Phase ◽  
Tial Alloy ◽  
Deformation Behaviour ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Life ◽  
Processing Techniques

Abstract Creep deformation in single phase ɤ-TiAl alloy manufactured using different processing techniques has been an extensively studied topic since the late 1970s. The present work revisits the original work on understanding the tensile creep deformation behaviour of wrought single-phase ɤ-TiAl alloy by Hayes and Martin [1] and is aimed to develop an understanding of steady state creep. Besides, it is also aimed to investigate the creep life for stress levels of 69.4 and 103.4 MPa at 832 ⁰C using Monkman-Grant [2] approach.

Mismatch Effect of Creep Properties on Steady-State Stresses for Welded Straight Pipes: Quantification and Application

2013 ◽  
Author(s):  
Jae-Jun Han ◽  
Sang-Hyun Kim ◽  
Yun-Jae Kim ◽  
Kamran Nikbin ◽  
David Dean
Keyword(s):  
Steady State ◽  
Steady State Creep ◽  
Two Dimensional ◽  
Finite Element Analyses ◽  
Creep Properties ◽  
Loading Mode ◽  
Parametric Studies ◽  
Match Effect ◽  
Match Factor ◽  
Mismatch Effect

This paper describes steady-state stresses on welded straight pipes with the heat-affected zone (HAZ) using detailed two dimensional elastic creep finite element analyses. In our previous studies [9,10], it was found that the mis-match effect in creep on steady-state stresses within the weld metal for a various branch junction could be uniquely quantified by the mis-match factor, defined as a function of creep exponent and constants. The present study expands the findings to be applicable for welded straight pipes, not only the most widely used but also relatively simple compared to branch junctions. To see the effects of mis-match in creep properties and weld configuration, the parametric studies have been performed for various mismatched creep properties and three different groove angles, respectively. Internal pressure, tension and its combined cases are applied to investigate the effect of the loading mode. It is found that steady-state creep stresses can be quantified as mis-match factor and creep exponent. In conclusion, validation of the findings is presented and discussed through an application to the CMV pipe.

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