High Temperature Creep Properties of Advanced Structural Materials: Modeling and Simulation of Creep in Advanced Structural Alloys
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee
Program Organizers: Gianmarco Sahragard-Monfared, University of California, Davis; Mingwei Zhang, Lawrence Berkeley National Lab; Jeffery Gibeling, University of California, Davis

Tuesday 8:00 AM
March 21, 2023
Room: Sapphire P
Location: Hilton

Session Chair: Gianmarco Sahragard-Monfared, University of California, Davis; Mingwei Zhang, Lawrence Berkeley National Laboratory; Jeffery Gibeling, University of California, Davis


8:00 AM Introductory Comments

8:05 AM  Invited
CALPHAD Alloy Design for Diffusion-mediated Plasticity-Induced Phase Transformations for Creep Resistant Multicomponent Principal Elemental Alloy: Jennifer Carter1; Sipei Li1; 1Case Western Reserve University
    All materials exhibit a reduction in strength as a function of temperature; this is inherently important for enabling thermo-mechanical manufacturing (>0.7Tm) but limits the subsequent creep resistance during applications (0.4Tm). It is hypothesized, that alloys in the Ni-Co-Cr MPEA space could exhibit a diffusion-mediated phase transformation induced plasticity (dm-TRIP) creep strengthening mechanism. The CALPHAD method was used to computationally suppress the stable FCC phase to explore the relative stability of the secondary unstable and metastable phases: Hexagonal Closed Packed (HCP) and the ordered sigma phase. Compositions where HCP (proxy for a stacking fault) is less stable than sigma, and sigma is metastable to FCC, could exhibit dm-TRIP. The stacking fault will be thermodynamically driven to form sigma prior, or instead of (if kinetics are right), FCC phase; thus strengthening the alloy. The motivation, computational approach, and proposed alloys are presented in this work.

8:35 AM  
Crystal Plasticity Creep Modeling in Cobalt Based Superalloys: Shahriyar Keshavarz1; Carelyn Campbell1; Andrew Reid1; 1NIST
    The current work centers on analyzing and predicting the creep responses of cobalt-based superalloys utilizing crystal plasticity finite element methods. The model captures the effects of composition and morphology including the average size, volume fraction, and shape of the precipitates. A homogenized composition-dependent activation energy-based crystal plasticity model is developed assimilating the detailed attributes of morphology. The model can significantly expedite the computational process due to the parameterized representation of the leading features while retaining accuracy. The glide and climb dislocation mechanisms are considered the key components of the constitutive model through which the thermo-mechanical behavior of cobalt-based superalloys is addressed for an extensive temperature spectrum. The method is validated for diverse compositions, temperatures, and load intensities via experimental data.

8:55 AM  
Effect of Alloying Additions on Twinning in Ni-based Superalloys: Valery Borovikov1; Mikhail Mendelev1; Timothy Smith1; John Lawson1; 1NASA
    Micro-twinning is the dominant creep deformation mechanism in Ni-based superalloys at temperatures above 700 °C. We use atomistic simulations to study two mechanisms of twin nucleation and growth that are characterized by qualitatively different rate limiting processes. In case of the mechanism proposed by Kolbe, the rate limiting process is diffusion-mediated atomic reshuffling. In case of the other mechanism, we proposed recently, the rate limiting process is nucleation of Shockley partial dislocation. We demonstrate the effects of alloying additions on functionality of these mechanisms.

9:15 AM Break

9:35 AM  Invited
Creep Simulations of Refractory High Entropy Alloys: Xin Chen1; Saro San2; Fei Wang1; Bai Cui1; Dongsheng Li3; Shanshan Hu4; Xingbo Liu4; David Alman2; Michael Gao2; 1University of Nebraska Lincoln; 2National Energy Technology Laboratory; 3Advanced Manufacturing LLC; 4West Virginia University
    To improve the efficiency and decrease CO2 emissions of aviation and land-based turbines, there is a need to develop novel refractory alloys that can be operated at temperature over 1300 Celsius. Besides room temperature ductility and fracture toughness, excellent creep performance and oxidation resistance at high temperatures are also required. In this talk, ongoing research on creep simulations of refractory high entropy alloys (RHEAs), supported by ARPA-E ULTIMATE program, will be presented. A crystal plasticity constitutive model has been developed at the length scale of polycrystalline microstructures, which utilizes the MOOSE multi-physics framework to predict the thermal-mechanical properties of RHEAs as a function of temperature and applied stress. Temperature-dependent elastic constants and coefficients of thermal expansion of select RHEAs are calculated using first-principles density functional theory. The simulated yield stress and creep strain are compared with experiments where available. Strategies in improving creep performance of RHEAs will be discussed.

10:05 AM  
Thermal Creep Models Derived from a Comprehensive Multiple Heat 9Cr Tempered Martensitic Steels Database: Md Ershadul Alam1; Takuya Yamamoto1; G.R. Odette1; 1University of California, Santa Barbara
    The dimensional stability of fusion structures must account for primary creep strains. Three new primary creep models have been developed for 9Cr TMS. The applied creep stress (σ) was the independent variable to be optimized for 0.2 to 2% strains at 375 to 550ºC. The models were calibrated to a TMS database for 17 heats, predict s from 160 to 420 MPa at times from ≈ 0.2 to 80,000h. The models include: 1) the Larson-Miller; 2) applied stress (σ) normalized to the temperature dependent σy [σ/σy(T)] or σu, [σ/σu(T)]; and 3) a threshold stress scaling with either σy(T) or σu(T), as [σ-Cσy/u(T)]. The [σ/σu(T)] model yields the best σ predictions with a SD ≈ 11 MPa, mean error ≈ 0 MPa and ≈1:1 measured vs predicted lines with at ≈ 0 MPa intercept. All other creep properties were modeled and the effects of irradiation softening were also assessed.