Heterostructured and Gradient Materials (HGM V): New Mechanistic Discoveries Enabling Superior Properties: Poster Session
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Shaping and Forming Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Yuntian Zhu, City University of Hong Kong; Kei Ameyama, Ritsumeikan University; Irene Beyerlein, University of California, Santa Barbara; Yuri Estrin, Monash University; Huajian Gao, Nanyang Technological University; Ke Lu, Institute of Metal Research; Suveen Mathaudhu, Colorado School of Mines; Xiaolei Wu, State Institute of Mechanics, Chinese Academy of Sciences
Tuesday 5:30 PM
March 21, 2023
Room: Exhibit Hall G
Location: SDCC
L-47-Invited Poster: Chemically-induced Gradient Nanostructures: Brad Boyce1; Alejandro Barrios1; James Nathaniel1; Joseph Monti1; Khalid Hattar1; Douglas Medlin1; Remi Dingreville1; 1Sandia National Laboratories
Nanocrystalline metals are usually highly unstable and exhibit poor ductility. Common strategies to overcome these two challenges are to introduce an alloying element, stabilizing the microstructure via kinetic and thermodynamic mechanisms, and to develop gradient nanostructured films. In this work, we combine both strategies and introduce a methodology to fabricate gradient nanostructured films via chemical compositional means. We demonstrate that annealing an alloyed PtAu thin film, fabricated with a compositional gradient, results in a film with a microstructural gradient. We employ phase-field modeling to further explore the competing mechanisms of Au diffusion and thermally induced grain growth. We additionally investigate the mechanical behavior of these gradient films and compare its behavior to microstructurally homogeneous films. This new fabrication method offers an alternative for the development of the next generation of thin films with increased mechanical performance. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
L-48: Mechanical Properties and Microstructural Evolution of High-pressure Torsion-processed Al7068 Alloy: Juhee Oh1; Sujung Son2; Hyoung Seop Kim2; Jae Bok Seol1; Hyokyung Sung1; Jung Gi Kim1; 1Gyeongsang National University; 2Pohang University of Science and Technology(POSTECH)
The combination of severe plastic deformation, deformational heat, and frictional heat generated during the high-pressure torsion process has a great effect on microstructural evolutions including a grain refinement, dynamic recrystallization and recovery. In this study, the mechanical properties and microstructural evolution of high-pressure torsion-processed aluminum 7068 alloy at room temperature are investigated. In the early deformation stage, both grain refinement and nano-precipitates are formed that increase the strength of ultrafine-grained aluminum alloy, and maximum strength of 844 MPa was obtained at 5T. However, in the later deformation stage, strength decreases due to the grain growth, and coarse precipitates act as crack initiation sites during plastic deformation. This result shows severe plastic deformation of the HPT process positively contributes to the mechanical properties of the Aluminum alloy.
L-49: Microstructures and Nanomechanical Behavior of Laser Processed Sr-modified Al-Si Eutectic: Arkajit Ghosh1; Bibhu Sahu1; Jian Wang2; Amit Misra1; 1University of Michigan; 2University of Nebraska-Lincoln
Laser surface remelting of Al-20Si and Al-20Si-0.2Sr (wt.%) alloys was used to produce nanoscale eutectics. Sr-modification was observed to increase the volume fraction of the fully eutectic morphology within the melt pool as compared to the unmodified alloy. A wide range of orientations of the eutectic nano fibers are prevalent and can be broadly classified as vertical and inclined eutectic morphologies with respect to the laser scan direction. Apart from the fully eutectic domains, presence of hypo-eutectic morphology was seen along the edge of the melt pool. Nanoindentation experiments indicate strong hardness and modulus gradients from the melt pool to as-cast region as well as within the melt pool between different eutectic orientations. HRTEM micrographs have been used to draw a comparison between deformation behaviors of the as-cast and different melt pool eutectics. Laser-refined heterostructured morphologies in eutectic alloys are shown to simultaneously improve flow strength and ductility.
L-50: Towards a Novel Approach for Integrating Tungsten and Reduced Activation Ferritic Martensitic Steel for Fusion Reactors: Ishtiaque Robin1; Tim Graening2; Ying Yang2; Yutai Katoh2; Steven Zinkle1; 1University of Tennessee; 2Oak Ridge National Laboratory
Joining plasma-facing material tungsten and structural material ferritic/martensitic (FM) steel for fusion reactors is challenging. A novel transition layer design is proposed here to integrate tungsten and FM steel with the insertion of interlayers VCrTi, VCrAl, and FeCrAl which would minimize the coefficient of thermal expansion gradient and avoid formation of brittle intermetallic phases. Preliminary data confirms the existence of fully body-centered cubic structure throughout the spark plasma sintering (SPS)-produced diffusion-bonded transition structure. Upon annealing at fusion relevant temperature 620 °C for up to 1000 hours, formation of brittle intermetallic and delamination are avoided. Results from first annealing tests were used to optimize chemical composition for second set of experiments. After subjecting to different annealing conditions, extensive microstructure characterization was performed on SPS-produced transition structure with modified composition. Experimental diffusion profiles are used to modify mobility database which was used for diffusion simulation to design this novel transition structure.