Practical Tools for Integration and Analysis in Materials Engineering: Poster Session
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Titanium Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Integrated Computational Materials Engineering Committee
Program Organizers: Adam Pilchak, Pratt & Whitney; Michael Gram, Pratt & Whitney; William Joost; Raymundo Arroyave, Texas A&M University; Charles Ward, AFRL/RXM
Monday 5:30 PM
March 15, 2021
Room: RM 34
Location: TMS2021 Virtual
An Automated Procedure for Reconstructing Deformation Twin Hierarchies in Heavily Twinned Microstructures Implemented Using MTEX: Daniel Savage1; Rodney McCabe2; Marko Knezevic3; 1University of New Hampshire/Los Alamos National Lab; 2Los Alamos National Laboratory; 3University of New Hampshire
Approaches for automated reconstruction of deformation twin hierarchies from orientation raster maps have historically not performed well for highly twinned microstructures due to: 1) mischaracterized orientation relationships that arise from reorientation by slip or high levels of segmentation, 2) misidentification of non-twinned grain fragments when most or all of an initial grain is twinned, and 3) nonflexible selection of the twin hierarchy when multiple generations exist. In this work, a general twin analysis code is implemented using MTEX and the MATLAB graph toolbox to address each issue. Highlights of the novel algorithms developed include grouping methodologies that mitigate slip artifacts and problematic twin relationships, incorporation of texture in determining non-twin grain fragments, and a minimum spanning tree approach to determining twin hierarchies. To demonstrate the utility of the algorithms, highly twinned α-Ti is investigated and the level of automation is demonstrated to largely improve over approaches in literature.
Application of Prolate Spheroid Stereology to Microtexture Regions in Ti-6Al-4V: Jaylen James1; Adam Pilchak2; Sushant Jha3; Raymundo Arroyave1; Eric Payton2; 1Texas A&M University; 2AFRL; 3AFRL/UDRI
The fatigue life of near-alpha titanium alloys in service is a function of dwell time and microstructure. Clusters of alpha phase with similar c-axis orientations, known as micro-textured regions (MTRs), provide a local environment which facilitates initiation and growth of sub-surface cracks. Models exist for prediction of fatigue crack growth rate taking into account both dwell time and microtextured region parameters such as size; however, to date only 2-dimensional measurements have been used as inputs to this inherently 3-dimensional problem. In the present work, the MTR regions are assumed to be in the shape of prolate spheroids and the major and minor axis lengths are measured in cross-section. Then, the 3D size and shape distributions are estimated using the expectation-maximization and the Cruz-Orive spheroid unfolding algorithm. The magnitude of uncertainty in the unfolding results and implications for 2D fatigue life models for Ti-6Al-4V will be discussed.
Crystal Plasticity Model for Single Crystal Ni-based Superalloys: Capturing Orientation and Temperature Dependence of Flow Stress: Satyapriya Gupta1; Curt Bronkhorst1; 1University of Wisconsin, Madison
We develop a dislocation density based crystal plasticity model to capture the micromechanical behavior of γ' strengthening nickel-based superalloys. The model presented here accounts for elasticity, plastic deformation, and hardening behavior of both γ and γ'. The model includes multiple strengthening mechanisms such as Orowan stress, evolving slip resistance caused by dislocation interactions, and γ' structural contribution to initial slip resistance. Interaction between γ and γ', a key feature of these alloys has been modelled in terms of back stress induced by dislocation pileup or looping around the large γ' precipitates. Antiphase boundary (APB) shearing is considered as the dominant deformation mechanism for shearable γ' precipitates. In addition to octahedral {111}<110> slip, the model also accounts for cube slip systems {100}<110> which are known to be instrumental in γ' shearing. The model is tested against an independent set of single crystal experimental data available for CMSX-4 and MD2.