Microstructure modeling of high-temperature microcrack initiation and evolution in a welded 9Cr martensitic steel

2019 ◽  
Vol 233 (10) ◽  
pp. 2160-2174
Author(s):  
M Li ◽  
PE O'Donoghue ◽  
SB Leen
Keyword(s):  
High Temperature ◽  
Crystal Plasticity ◽  
Heat Affected Zone ◽  
Elevated Temperatures ◽  
Element Model ◽  
Plasticity Model ◽  
Welded Steel ◽  
Premature Failure ◽  
Crystal Plasticity Model ◽  
Microcrack Initiation

Welded joints in tempered 9Cr–1Mo operating at elevated temperatures are well known to be prone to premature failure due to cracking in the heat-affected zone. This paper describes a crystal plasticity model to predict the microcrack initiation and evolution in the inter-critical heat-affected zone of 9Cr–1Mo welded steel at elevated temperature. A crystal plasticity finite element model indicates that the micro-cracks of 9Cr–1Mo steel mostly nucleate at prior austenite grain boundaries and boundary clustered regions. Inter-granular and trans-granular microcracking are shown to be the key predicted microdamage mechanisms from the current crystal plasticity model. A small amount of ferrite in the inter-critical heat-affected zone is shown to not only influence the microcrack initiation and evolution, but also significantly accentuate material degradation for a given applied load leading to premature failure at high temperature.

Development of a model for simulation of micro-twin and corresponding asymmetry in high temperature deformation behavior of nickel-based superalloy single crystals using crystal plasticity-based framework

2016 ◽  
Vol 231 (14) ◽  
pp. 2621-2635 ◽  
Author(s):  
MK Samal
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Crystal Plasticity ◽  
Deformation Behavior ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Plasticity Model ◽  
Multi Scale ◽  
Nickel Based Superalloy ◽  
Crystal Plasticity Model

Development of reliable computational models to predict the high temperature deformation behavior of nickel-based superalloys is in the forefront of materials research. These alloys find wide applications in manufacturing of turbine blades and discs of aircraft engines. The microstructure of these alloys consists of the primary γ′-phase, and the secondary and tertiary precipitates (of Ni3Al type) are dispersed as γ′-phases in the gamma matrix. It is computationally expensive to incorporate the explicit finite element model of the γ-γ′ microstructure in a crystal plasticity-based constitutive framework to simulate the response of the polycrystalline microstructure. Existing models in literature do not account for these underlying micro-structural features which are important for simulation of polycrystalline response. The aim of this work is to develop a physically motivated multi-scale approach for simulation of high temperature response of nickel-based superalloys. At the lower length scale, a dislocation density-based crystal plasticity model is developed which simulates the response of various types of microstructures. The microstructures are designed with various shapes and volume fractions of γ′-precipitates. A new model for simulation of the mechanism of anti-phase boundary shearing of the γ′-precipitates, by the matrix dislocations, is developed in this work. The lower scale model is homogenized as a function of various micro-structural parameters, and the homogenized model is used in the next scale of multi-scale simulation. In addition, a new criterion for initiation of micro-twin and a constitutive model for twin strain accumulation are developed. This new micro-twin model along with the homogenized crystal plasticity model has been used to simulate the creep response of a single crystal nickel-based superalloy, and the results have been compared with those of experiment from literature. It was observed that the new model has been able to model the tension–compression asymmetry as observed in single crystal experiments.

scholarly journals Crystal Plasticity Modeling of Creep in Alloys with Lamellar Microstructures at the Example of Fully Lamellar TiAl

2021 ◽  
Vol 7 ◽  
Author(s):  
Jan E. Schnabel ◽  
Ingo Scheider
Keyword(s):  
Dislocation Density ◽  
Crystal Plasticity ◽  
Creep Behavior ◽  
Elevated Temperatures ◽  
Secondary Creep ◽  
Plasticity Model ◽  
Crystal Plasticity Model ◽  
Path Lengths ◽  
Experimental Findings ◽  
Fully Lamellar

A crystal plasticity model of the creep behavior of alloys with lamellar microstructures is presented. The model is based on the additive decomposition of the plastic strain into a part that describes the instantaneous (i.e., high strain rate) plastic response due to loading above the yield point, and a part that captures the viscoplastic deformation at elevated temperatures. In order to reproduce the transition from the primary to the secondary creep stage in a physically meaningful way, the competition between work hardening and recovery is modeled in terms of the evolving dislocation density. The evolution model for the dislocation density is designed to account for the significantly different free path lengths of slip systems in lamellar microstructures depending on their orientation with respect to the lamella interface. The established model is applied to reproduce and critically discuss experimental findings on the creep behavior of polysynthetically twinned TiAl crystals. Although the presented crystal plasticity model is designed with the creep behavior of fully lamellar TiAl in mind, it is by no means limited to these specific alloys. The constitutive model and many of the discussed assumptions also apply to the creep behavior of other crystalline materials with lamellar microstructures.

Multi-level direct crystal plasticity model of polycrystalline specimen: Grains generation

2021 ◽  
Author(s):  
Artyom A. Tokarev ◽  
Anton Yu. Yants ◽  
Alexey I. Shveykin ◽  
Nikita S. Kondratiev
Keyword(s):  
Crystal Plasticity ◽  
Plasticity Model ◽  
Polycrystalline Specimen ◽  
Crystal Plasticity Model ◽  
Multi Level

Crystal Plasticity Predictions of Forward-Reverse Simple Shear Flow Stress

2011 ◽  
Vol 702-703 ◽  
pp. 204-207 ◽  
Author(s):  
Young Ung Jeong ◽  
Frédéric Barlat ◽  
Myoung Gyu Lee
Keyword(s):  
Flow Stress ◽  
Crystal Plasticity ◽  
Simple Shear ◽  
Bauschinger Effect ◽  
Texture Evolution ◽  
Simple Shear Flow ◽  
Plasticity Model ◽  
Lower Yield Stress ◽  
Crystal Plasticity Model ◽  
Stress Reversals

The flow stress behavior of a bake-hardenable steel during a few simple shear cycles is investigated using a crystal plasticity model. The simple shear test provides a stable way to reverse the loading direction. Stress reversals were accompanied with a lower yield stress, i.e., the Bauschinger effect, followed by a transient hardening stage with a plateau region and, permanent softening. The origins of these three distinct stages are discussed using a crystal plasticity model. To this end, the representative discrete grain set is tuned to capture such behavior by coupling slip system hardening appropriately. The simulated results are compared with experimental forward-reverse simple shear stress-strain curves. It is shown that the characteristic flow stress stages are linked to texture evolution and to the Bauschinger effect acting on the different slip systems.

Sign in / Sign up

Export Citation Format

Share Document