Creep Data Research Articles

Creep data sheet for Nickel-based 19Cr-18Fe-3Mo-5Nb-ti-al superalloy

Creep data sheet for Nickel-based 19Cr-18Fe-3Mo-5Nb-ti-al superalloy

Creep Lifetime Prediction of Alloy 617 Using Black Box Machine Learning Approach

Abstract This study explored the application of black box machine learning (ML) to build high throughput models that predict the creep response of Ni-based Alloy 617. Black box ML refers to highly complex machine learning algorithms that generate outputs from inputs without an interpretable internal process. The rapid implementation of suitable heat of alloys into targeted service is impeded by the extended qualification process involving chemistry-processing-structure-performance assessment. The ASME B&PV Code III outlines the requirement of 10,000 h of creep testing before each heat can be qualified for service and 30,000 h for heats that exhibit metastable phases. There is a critical need to shorten the development-to-deployment timeline for heats of an alloy at specific applications. Recent advancement in ML offers the ability to identify correlations in data which is difficult to elucidate by other approaches. To that end, black box ML is employed to expedite the HEAT qualification of Alloy 617 and predict performance from HEAT chemistry out to an unprecedented timescale. In this study, creep data for Ni-based Alloy 617—a solid solution strengthened material is gathered from a wide range of data sources. The alloy chemistry, phases, precipitates, and microstructural features are analyzed to obtain the key strengthening mechanism. Service conditions, mechanical properties, chemistry, and chemical ratios are provided as potential input features. The Pearson correlation coefficient with a 95% confidence bound is employed for input feature screening where poorly correlated inputs are eliminated to speed up the ML process and prevent under- and/or over-fitting of predictions. In the ML algorithm, the selected input features are regarded as predictors, and rupture is regarded as the response. An algorithm evaluation is performed where 20 ML algorithms are trained with the training set. The three-layered neural network (NN) was observed to be the best algorithm for the given data based on statistical rationale. The NN accurately predicts rupture across a range of isotherms and data sources. The interpolative and extrapolative predictions are in compliance with ECCC V5 guidelines. A post-audit validation exhibits neither under- nor over-fitting and confirms the applicability of NN algorithms to unseen data. The black box ML provides a pathway to predict the performance directly from chemistry and opens avenues to rapid heat qualification.

A probabilistic evaluation method on temperature and time-dependent stress intensity limit St in creep assessment of components at elevated temperatures

Abstract Creep is an important damage mode of components at elevated temperatures, and the temperature and time-dependent stress intensity limit St is an essential indicator in creep assessment of components. In general, the safety factors are directly applied to three criteria in stress intensity limit St in ASME code, but a quantitative evaluation on the failure probability covered in this indicator is rarely reported. Based on this, a probabilistic evaluation method on stress intensity limit St is proposed by correlating each criterion with mean creep rupture life data. The failure probability of three criteria in stress intensity limit St of 316 and 304 stainless steels is calculated, and the effect of safety factors on failure probability results is discussed. A probabilistic evaluation on stress intensity limit St is conducted. Results indicate that the stress intensity limit St presents a low failure probability or high conservativeness, and the minimum stress to creep rupture is the governing role in stress intensity limit St for cases involved. The failure probability of stress intensity limit St of 316 stainless steel is much lower than that of 304 stainless steel, attributed to the differences of creep deformation features and data scatter of the two stainless steels.

Understanding the deformation creep and role of intermetallic compound-microstructure in Sn-Ag-Cu solders

Tin-based alloys are commonly used in lead-free solder joints in electronic interconnection applications, where creep can limit joint reliability. In this work, directionally solidified bulk solder alloys of different compositions (pure tin, SAC105 and SAC305) are mechanically tested under a constant load for each composition at room temperature to understand mechanical creep performance and quantify the role of different content of Ag3Sn and Cu6Sn5 intermetallic compounds (IMCs) in terms of secondary creep strain rate, microstructural evolution, and total amount of accumulated strain. In this work, microstructures are fabricated using directional solidification to promote a systematic variation in IMC sizes, shapes, and distributions within similar crystal orientations of the primary β-Sn matrix. Analysis of creep data indicates that secondary creep is dominated by obstacle-controlled dislocation motion. This is further confirmed by electron backscatter diffraction (EBSD) analysis, which reveals that the formation of subgrains and internal structure, correlating to the initial microstructure of the sample, i.e. changes in secondary dendrite arm spacing (λ2) and eutectic intermetallic spacing (λe). The experimental observations are supported further by crystal plasticity simulations that explicitly model the presence of IMCs within the Sn-based samples and show the dependence of the secondary creep rate upon the IMC content, and therefore be beneficial for the possible future composition design in solders.

Dynamic creep of Al2O3 whisker-reinforced ZrO2 ceramic composite

Previous studies on the creep behavior of ceramic materials were primarily conducted under static loads. However, the majority of applications for ceramic materials are subject to dynamic loads, and there is a paucity of research conducted in this area. In this work, we report for the first time the creep behavior of Al2O3 whisker-reinforced ZrO2 composites under dynamic pressure. The results showed that the sample crept under dynamic pressure produced higher creep rate and lower activation energy compared to static pressure. By analyzing the creep data and microstructures, we showed that the dynamic pressure can enhance dislocation motion and transform the creep mechanism from diffusion-controlled grain-boundary sliding to dislocation-controlled grain-boundary sliding. This work provides a foundation for subsequent detailed studies of the creep behavior of ceramic materials under dynamic pressure.

An Advanced Sine-Hyperbolic Creep-Damage Model Incorporating Threshold Strength

Abstract This study aims at improving the classic Sine-Hyperbolic (Sinh) creep-damage model to predict minimum-creep-strain-rate (MCSR), rupture, damage, and creep deformation. The Sinh model employs a continuum-damage-mechanics-based framework to model secondary and tertiary creep regimes. In Sinh, the creep strain and damage rate equations exhibit an implicit threshold stress that arises during numerical optimization. Herein, the Sinh model is modified to include an explicit threshold strength as a material property and the tensile strength. Threshold strength is defined as the lower limit for creep activation at a given temperature. Stresses are applied below the threshold, resulting in infinite life. The advanced Sinh offers several advantages including a physical significance of stress ratios, a closed-form solution, and adaptability in finite element analysis. Experimental creep data of 304SS at multiple isotherms are gathered. The advanced Sinh is calibrated to the MCSR and SR data of 304SS. The calibration of threshold strength follows a standard procedure from literature and is observed to be realistic for stainless steel at elevated temperatures. The MCSR and SR predictions illustrate the Sigmoidal bend and demonstrate zero creep rate and infinite life at or below threshold strength. The creep deformation and damage predictions exhibit agreement with experimental data. The advanced Sinh is validated by employing finite element simulation to ensure the applicability of the model across a range of applications. The advanced Sinh improved creep response prediction and added physical realism to the model?s framework

Load transfer behavior in semisolid formed hypereutectic Al-Fe-based alloys during tensile creep

The tensile creep behavior of semisolid formed hypereutectic Al-Fe-based alloys (for short Al-5Fe-based alloys) is investigated at temperatures ranging from 200 °C to 350 °C and stresses ranging from 30 MPa to 100 MPa. A power law model incorporating the “generalized” load transfer term is employed to rationalize creep data for Al-5Fe-based alloys with respect to that of the pure aluminum as a corresponding matrix without second phases and/or reinforcements. This expression proves more suitable for describing the creep characteristics of Al-5Fe-based alloys. The AlFe phases in the alloys transfer and bear load, and have no interaction with dislocations practically, which is the main reason for the creep strengthening of Al-5Fe-based alloys. The results obtained in this study are validated by creep data for Al-Fe alloys obtained by a thorough literature review.

A unified model of tensile and creep deformation for use in niobium alloy materials selection and design for high-temperature applications

There is renewed interest in refractory alloys that possess higher service temperatures than incumbent Ni-based superalloys (e.g., ⪆1100 °C). This study provides a review of the high-temperature constitutive responses of Nb-alloys measured over a wide range of temperatures (≈860 °C < T < ≈1760 °C) and strain rates (≈10–9 s-1< ε˙ < ≈10–1 s-1). Nevertheless, the extant data is sparse and informed materials selection decisions require constitutive expressions to interpolate and reliably extrapolate. The Larson-Miller parameter approach to describe creep-life provides a conservative estimate of material response at the highest temperatures and lowest strain rates, whereas the Sellars-Tegart model describes both steady-state creep and high-temperature tensile test data with a single, universal equation. A minimum flow stress based on the combination of these two models is proposed for design considerations to address the overprediction of strength that can arise from applying one or the other independently. This effort highlights the fact that refractory alloys exhibit strain rate sensitive flow strengths in the temperature range of interest for applications. The roles of alloying, thermomechanical processing, and impurity levels are discussed, and highlight the fact that these advanced Nb-alloys evidence Class 1 (Class A) solute drag controlled creep behavior, except the carbide precipitation strengthened alloy, D-43. In addition, the high-temperature strengths are confirmed to be strongly correlated with alloy melting point.

Influence of powder particle size distribution on the creep performance of Ti-48Al-2Cr-2Nb alloy fabricated via electron beam-powder bed fusion

The effects of particle size distributions (PSDs) on the microstructure and creep behavior of Ti-48Al-2Cr-2 Nb fabricated via electron beam-powder bed fusion (EB-PBF) were investigated. Three PSDs of 45–150 (PSD-A), 38–150 (PSD-B), and 38–180 µm (PSD-C) were used as powder feedstock. Widening the PSD range decreased the relative density of fabricated parts and promoted the formation of banding microstructure. Moreover, samples fabricated with wider PSDs had a higher volume of lack-of-fusion (LoF) defects; however, the content of gas pores decreased significantly in PSD-C, which was related to the presence of coarse powder particles. The volume of the LoF defects in PSD-C was approximately 2.8 times of the same defects in PSD-A, which influenced the creep performance (at 750℃) and failure mechanism of Ti-48Al-2Cr-2 Nb. A longer steady-state creep period at different stress levels was identified for the samples fabricated with the narrowest PSD (45–150 µm). Widening the PSD span also caused weakness in the creep properties and data scattering at higher stress levels of 300 and 350 MPa. The LoF defects and coarse grains accelerated the crack initiation and propagation in Ti-48Al-2Cr-2 Nb during creep. This study represents the first report on the impact of PSD on the creep properties of TiAl alloys fabricated via EB-PBF, which offers new insights and enhances understanding of the powder-process-microstructure-property relationship.

A unified creep and fatigue life prediction approach for 316 austenitic stainless steel using machine and deep learning

Abstract316 Austenitic stainless steel (AusSS) is extensively utilized in high‐temperature industrial applications such as boiler tubes and nuclear reactor pressure vessels. These components commonly experience failure under high‐temperature and high‐pressure conditions, attributed to either creep or fatigue. Existing classical models for creep and fatigue life prediction focus on a singular failure mode (either creep or fatigue) and consider physical features only. This study aims to develop a unified life prediction model for both creep and fatigue phenomena. It synthesizes information from 12 additional unexplored chemical and microstructural features from the National Institute of Materials Science (NIMS), Japan database, and previously published literature. Machine learning (such as decision tree, random forest, and XGBoost) and deep learning (like deep neural network) algorithms are employed in the modeling process. The trained models have been cross‐validated against unseen creep and fatigue life data, demonstrating superior prediction accuracy of 96.1% for deep neural network compared with classical models.

A comparison of hyperbolic sine creep life equations and data correlation methods for these equations

ABSTRACT Hyperbolic sine (HS) minimum creep rate equations combined with the Monkman-Grant equation are attractive for correlating time to rupture data because of their physical basis in dislocation creep theory, numerical stability, and conformance to physical boundary conditions at zero and infinite stress. In this study, uniaxial creep life data of Sanicro 25 and HR6W alloys were correlated to two recently published HS creep life equations with three commonly used objective functions. For each alloy, the correlation results (fit to the data and predicted strength at 100,000 h time to rupture) were essentially the same using either HS equation. Multiple equivalent solutions (same goodness of fit but different values of the fitting constants) were obtained with the HR6W data set. A discussion on obtaining initial estimates of fitting constants is provided as an Appendix.

Uniaxial compressive creep tests by spark plasma sintering of 70% theoretical density α-uranium and U-10Zr

Metallic fuels hold numerous advantages over conventional uranium dioxide fuels and are a key component of several liquid metal-cooled advanced reactor concepts including sodium fast reactors. These fuels undergo rapid swelling during early burnup; consequently, they spend most of their reactor lifetime in a porous state. The presence of this porosity alters many of the mechanical properties of the fuel including creep impacting fuel deformation during axial swelling. This work investigates the creep behavior of the porous fuel using a spark plasma sintering technique. Creep tests were performed for the first time on porous α-phase uranium and uranium with 10 wt. % zirconium (U-10Zr) samples. The samples of α-phase uranium and U-10Zr were fabricated from depleted uranium by spark plasma sintering and subjected to uniaxial compressive creep testing. Calculated stress exponents were found to be 2.6±1.6 and 5.7±1.4 for α-U and U-10Zr, respectively, and calculated activation energies were found to be 61.6±1.1kJ/mol for α-U. The creep data were also used to evaluate existing porosity inclusive in creep models.

Reliability and thermal fatigue life prediction of solder joints using nanoindentation

The construction of accurate constitutive equations is critical for the reliability analysis of the solder joints in high-density interconnect. However, there are some distinct differences between the actual solder joints and conventional bulk solder in determining the parameters for constitutive equations. In this work, the Young's modulus and hardness of various grain regions are experimentally investigated using electron backscatter diffraction and nanoindentation for the Sn-3.0Ag-0.5Cu polycrystalline and single-grain solder joints. The disparities in the Young's modulus and hardness of different grain regions in the polycrystalline solder joint are up to 25.11% and 28.34%, respectively, while those of the single-grain solder joint exhibit stability. It indicates the anisotropy of β-Sn grains and the size effects between actual solder joints and bulk solder materials. Furthermore, a method is proposed to determine the parameters of the Anand constitutive equations using high-temperature nanoindentation creep data. A flip-chip assembly in thermal shock conditions is numerically investigated. The Darveaux model is employed to predict the thermal fatigue life of the critical solder joint. Compared to experimental results, the life prediction of the solder joint using nanoindentation is found to be accurate. A concept of life correction factor n has been proposed to improve the accuracy of the predicted life.

A thermodynamically consistent creep constitutive model considering damage mechanisms

This paper derives a physically-based creep-damage and life prediction model through the basic laws of thermodynamics. The model divides creep damage into two parts: one corresponding to high temperature and low stress, related to cavity nucleation and cavity growth, and the other corresponding to high stress, related to dislocation movement. The creep strain rate consists of two components: diffusion creep, which is assumed to occur in all stress ranges, and dislocation-related creep, which activates when the external stress exceeds a certain threshold. The proposed model characterizes damage by the degradation of creep free energy. It accurately describes creep behavior over a wide stress range, including the transition phenomena observed in creep strain rate curves and creep life curves. This provides a constitutive reference for simulating long-term creep damage and life based on short-term creep data.

Thermal creep properties of virgin and irradiated cladding tubes made of Ti-stabilised DIN 1.4970 (15-15Ti) austenitic stainless steel

ABSTRACT This paper presents assessments performed on a large database of virgin material and irradiated material thermal creep data from uniaxial and pressurised DIN 1.4970 Ti-stabilised austenitic stainless steel i.e. EN X10NiCrMoTiB15–15 or ‘15-15Ti’ cladding tubes. The data base incorporates multi-heat data from uniaxial and bi-axial (internal pressure) creep tests conducted during the fast reactor R&D program of the DeBeNe (Deutschland-Belgium-Netherlands) consortium between the 1960s to the late 1980s together with more recent data, for example, from the European projects MATTER and PATRICIA and the EERA JPNM pilot project TASTE. The data comprises of a virgin material data base and a data base with irradiated creep data. The virgin material data comprises of time-to-rupture and time-to-0.2% creep strain in a temperature range of 600–800°C and covers a large range of stresses. The irradiated data base has less data and does not cover all material heats tested for the virgin material properties. The irradiation conditions are also different depending on the test reactor specifics and the irradiation campaign targets. The attained ‘irradiation damage’ in displacements per atom (DPA) for the irradiated materials range from 0.1 up to 38.1. Un-irradiated ‘reference material’ models for tensile strength and creep strength are constructed from the current-state of the art literature data and more recent results from the Sandvik 24% cold worked 1515–Ti cladding tube currently used as the main material batch studied at SCK CEN. The tensile strength model is used throughout the paper for normalizing creep strengths by the tensile properties, needed when applying the Wilshire (WE) creep model. Time factors (TF), stress factors (SF) and temperature ratio factors (TRF) are calculated for different material states for describing the impact of heat treatments, (virgin and irradiated) and irradiation conditions. This initial study targets to give estimates for the thermal creep properties of cladding tubes with a cold work range of 16–24% in a non-annealed state, as it is the preferred option for future designs according to the state-of-the art knowledge base. However, the main bulk of the available data on irradiated material is on claddings with a cold work range of 0-16% with and without annealing and at various levels of irradiation damage, thus leading to the need for estimation by interpolation and extrapolation assuming that irradiation damage levels and trends, e.g. time reduction factors found on a lower cold worked material can also be applied on materials with higher cold work levels. The results of the assessments clearly show relative strength differences between chosen material heats and heat treatments and has enabled constructing simple multilinear models for estimating the life of irradiated material. The models show that low creep test temperatures (and irradiation temperatures), low stress levels, low levels of cold work and high irradiation doses are increasing the detrimental difference between the specific material condition and the reference material. Also, it was found that the general level of life reduction (time factor TF and stress factor SF) for irradiation damaged material failure, in relation to the reference material failure, roughly coincides the corresponding values of time to 0.2% creep strain for virgin material. The estimated ‘failure creep temperature limits’ for 30 000 hours of service are studied and compared for both virgin and irradiated materials at a reference stress level of 1/3 of the tensile strength (at temperature).

Creep strength breakdown and the change in back stress strengthening in 10 % Cr martensitic steels during creep at 923 K

The creep strength breakdown in 10 % Cr martensitic steels appeared under creep conditions at a temperature of 923 K and the applied stresses below 120 MPa as a declination from linear regression obtained using short-term creep data. To reveal the origin of creep strength breakdown, the back stress strengthening conception was used. In the initial state, both 10 % Cr martensitic steels had a tempered martensite lath structure with a high dislocation density in the lath interiors and in the lath boundaries, which was stabilized by M23C6 carbides, NbX carbonitrides, and M6C carbides. The shear internal back stresses of 57.5–68.5 MPa and 35–37 MPa were obtained from the creep rate – stress relationship for the regions of high applied stress (above 120 MPa) and low applied stress (below 120 MPa), respectively. The transition from the high stress region to the low stress one in both steels was accompanied by a significant decrease in the dislocation density by an order of magnitude as well as a decrease in particle number density and an increase in the inter-particle spacing in the M23C6 carbide and Laves phase particles located at the low-angle boundaries of the martensitic laths/subgrains. The root mean square superposition of the dislocation and particle contributions to the shear internal back stresses gave the best coincidence with the values obtained from the creep data. The stability of the M23C6 carbide and Laves phase particles located at the low-angle boundaries was concluded to be the key factor suppressing the creep strength breakdown in the 10 % Cr martensitic steels.

3D printing of rice starch incorporated peanut protein isolate paste: Rheological characterization and simulation of flow properties

This study investigates the viscosity and creep behavior of peanut protein isolate (PPI) paste incorporated with rice starch (RS) for potential applications in 3D printing. The change in flow properties during the 3D printing was also studied by numerical simulation. The paste exhibited shear-thinning behavior with yield stress. The pressure predicted from the Herschel-Bulkley model showed higher values than those derived from the Power-Law model. The PPI and RS levels had negligible influence on velocity and shear rate; however, they showed greater dependence on the inflow rate. The fractional element model described the creep data well (R2 > 0.9). The addition of PPI resulted in increased viscosity, simulated pressure, and mean extrusion force, with similar effects observed for RS, except at higher PPI levels. Furthermore, the 3D-printed objects revealed that deformations were pronounced at low concentrations of PPI and RS, while resolution suffered when employing higher concentrations of PPI and RS. Industrial relevanceUsing peanut protein isolate, a plant-based high protein ingredient in 3D printing, reduces energy consumption, thereby reducing carbon footprints, offers improved functional properties, and diversifies dietary options by offering an alternative protein source from peanuts. The printing is influenced by the rheological properties of food ink. Thus, knowing the rheological properties of food ink can help researchers and industries to prepare food inks with desired properties. The observations of numerical simulation of this work have the potential to offer practical insights for designing 3D printing systems. In summary, this work has the potential to aid in improving and developing food ink for 3D printing, hence enhancing the performance of extrusion-based 3D food printers.

Study on Viscoelastic Poisson's Ratio of Nonwovens

Abstract Combined with Laplace transform and creep stress conditions, an accurate expression of the viscoelastic Poisson's ratio calculated from the transverse strain and relax modulus is derived. From creep and relax tests data, Prony series of the transverse strain and relax modulus of nonwovens with time were obtained, and the time-varying curve of the viscoelastic Poisson's ratio of nonwovens was simulated by 1stOpt software. The method proposed can effectively obtain the viscoelastic Poisson's ratio of nonwovens and provide a reference value for calculating mechanical indexes involved in its subsequent production and processing.

On creep of trapped flux near [formula omitted] in MgB2 and CaKFe4As4

We present flux creep data taken at different temperatures on single crystals of known, ambient pressure, superconductors, CaKFe4As4 and MgB2, taken using the protocol that is common for trapped flux measurements. Using our results, we show that the time dependence of the magnetic moment in H3S is remarkably similar to the magnetization relaxation rates observed in established superconductors at ambient pressure, where in the latter cases this can be unambiguously assigned to flux creep.

Constant Strain-Rate Garofalo Creep Behavior of Intermediate 83Pb/10Sb/5Sn/2Ag and 91.5Sn/8.5Sb Solder Materials

Abstract Modern electronics reliability prediction models require materials-specific failure data across a range of conditions. Garofalo models are preferred due to their ability to accurately predict performance over a wide temperature range. However, data on intermediate solders are sparse, especially regarding performance at cold temperatures. We report Garofalo creep data for 83Pb/10Sb/5Sn/2Ag (Indalloy 236) and 91.5Sn/8.5Sb (Indalloy 264). Indalloy 236 exhibits an activation energy of 54.5 kJ/mol, n = 4.5, and α = 0.043 while Indalloy 264 exhibits an activation energy of 70.04 kJ/mol, n = 2.705, and α = 0.099 from −20 °C to 175 °C. We show that modern curve-fitting analysis should be utilized for Garofalo analysis rather than traditional linearization methods. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to characterize the changes in the alloy phases during testing. Microstructural analysis indicates that Indalloy 236 can experience void coalescence at high temperatures while Indalloy 264 precipitates antimony-rich phases on the grain boundaries.