Bulk and Sheet Thermal-Deformation Processing and Microstructure Development in Metals – Characterization, Experiments and Modeling: Session II
Sponsored by: TMS Shaping and Forming Committee
Program Organizers: Daniel Coughlin, United States Steel Corp; Kester Clarke, Los Alamos National Laboratory; Piyush Upadhyay, Pacific Northwest National Laboratory
Tuesday 2:00 PM
November 3, 2020
Room: Virtual Meeting Room 34
Location: MS&T Virtual
Session Chair: Cody Miller, Los Alamos National Laboratory
2:00 PM
Probing Differences in Processing and Texture in FCC/BCC Nanolaminates Fabricated via Accumulative Roll Bonding: John Carpenter1; Thomas Nizolek1; Cody Miller1; Carl Osborne1; Rodney McCabe1; Daniel Coughlin1; 1Los Alamos National Laboratory
This talk will present our efforts to characterize the processing and microstructure of FCC/BCC metallic nanolaminates manufactured via accumulative roll bonding. Efforts behind achieving nanoscale layers in the Cu/Nb, Cu/Fe, and Ag/Fe systems will be presented in the form of material microstructure, texture, and detailed deformation processing history. This history will include in situ data from the rolling process such as material temperature, roll gap and deflection, roll load across the width of the rolls, and roll speed. This data is used to understand microstructural changes which could lead to material failure during the roll bonding process. The effect of intermittent heat treatments on the success of processing is also investigated. Texture as a function of strain and layer thickness will be explored and compared at the micron and nanoscales for these materials.
2:30 PM
Continuum Dislocation Dynamics-based Modeling of the Strain Hardening Behavior of ECAPed Aluminum Alloy: Ali Kobaissy1; Georges Ayoub2; Mu'Tasem Shehadeh1; 1American University of Beirut; 2University of Michigan
In this work, a multi-scale framework that couples a crystal plasticity (CP) scheme with a continuum dislocation dynamics (CDD) model is proposed to predict the material behavior, microstructure and texture during equal channel angular pressing (ECAP) processes. The strain hardening in the model is considered to result from both the increase in the dislocation density and the grain fragmentation. The grain fragmentation process is modeled by accounting for the grain-grain interaction and incorporating the concept of the geometrically necessary dislocations (GNDs) into the mean free path of the dislocations. GNDs result from grain boundaries restricting the free deformation of a grain, causing an internal plastic deformation gradient that subsequently leads to grain fragmentation. A commercial Al 1100 billet, with rolling texture, is ECAP processed under Route C for different numbers of passes. The ECAP-processed aluminum microstructure, texture and dislocation densities and then the mechanical properties are predicted.
2:50 PM
Austenite Stability and Strain Localization in Q&P Steels Deformed at Dynamic Strain Rates: Christopher Finfrock1; Trevor Ballard1; Gus Becker1; John Copley1; Benjamin Ellyson1; Melissa Thrun1; Jonah Klemm-Toole1; Amy Clarke1; Kester Clarke1; 1Colorado School of Mines
Successful application of the quenching and partitioning (Q&P) process using commercial production equipment has led to promising combinations of strength and ductility. This noteworthy mechanical performance is caused by the TRIP effect, whereby the deformation induced transformation of austenite to martensite suppresses strain localization. Predicting the deformation response of Q&P steels at the dynamic rates reached during stamping operations and crash scenarios remains a significant challenge, because the austenite transformation is inherently sensitive to temperature, strain rate, and strain path. Recent studies have reported variations in toughness at elevated strain rates and temperatures. To determine the cause of this behavior, interrupted mechanical testing and synchrotron experiments were performed, to quantify the extent of the austenite transformation over a range of strain rates and temperatures. In this talk, potential causes for the shift in deformation behavior, such as strain rate sensitivity and adiabatic heat accumulation, are evaluated in the context of the martensite transformation.