2017 Technical Division Student Poster Competition: Structural Materials Division (SMD) Undergraduate Students
Sponsored by: TMS Extraction and Processing Division, TMS Functional Materials Division, TMS Light Metals Division, TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division
Program Organizers: TMS Administration
Monday 5:00 PM
February 27, 2017
Room: Hall B1
Location: San Diego Convention Ctr
SPU-13: Austenite Stability Dependence of the Mechanical Properties in medium-Mn Steels: Neil Krichi1; Binhan Sun1; Stephen Yue1; 1McGill University
The present study focuses on three medium-Mn steels containing 7-10 wt.% Mn and 0-1 wt.% Si. Each composition was subjected to varying cold rolling schedule, in order to produce different initial structures. The steel samples were intercritically annealed at various temperatures for different holding times. The microstructures, tensile properties, and strain-induced martensite transformation of the annealed sample are herein investigated, in an attempt to understand the dependence of the tensile behavior on the austenite stability, which is in turn highly influenced by alloying and processing parameters. The results showed that retained austenite characteristics after intercritical annealing can be well controlled by the cold rolling schedule. Different combinations of tensile properties can be achieved to fulfill a wide range of requirements by the automotive industry. Strengths as high as 1500 MPa were observed, with 20% elongation, and excellent elongations of 40% were reached with a UTS value of 1150 MPa.
SPU-15: Lifetime Prediction of FeCrAl Alloys through Statistical Modeling and High-Temperature Cycling Testing: Christina Cox1; Sebastien Dryepondt1; Josh Turan1; 1Oak Ridge National Laboratory
FeCrAl alloys are widely used at high temperatures in aggressive environments due to their exceptional resistance to oxidation, and the growth of the protective alumina at 800-1400ºC has been extensively studied. Less is known about the cyclic oxidation behavior of these alloys, and three cast FeCrAlY(Hf) and two oxide-dispersion-strengthened (ODS) FeCrAlY alloys have been tested at 1200°C for 1000 h. The effects of alloy composition, cycling period, and grain microstructure on deformation during thermal cycling were determined using a Keyence 3D optical microscope. Oxide formation, cracking, and spallation were characterized through mass change measurement, scanning electron microscopy, and image analysis. Frequent (1h) thermal cycling greatly increased scale spallation and crack formation in the alloy, leading to a decrease of the alloy predicted lifetime. These results were used to improve cyclic lifetime models developed for Ni-based alumina forming alloys.
SPU-16: Optimizing Electron Tomography of Bone and Bone-implant Specimens: Madeline Perrin1; Xiaoyue Wang2; Kathryn Grandfield2; 1McMaster University and McGill University; 2McMaster University
Electron tomography can be used for the visualization of bone nanostructure in three-dimensions. It is essential to reduce electron beam exposure for biological specimens such as bone and bone-implant samples. Here we explore reconstruction parameters for High-Angle Annular Dark-Field (HAADF) Scanning Transmission Electron Microscopy (STEM) tomography on bone. HAADF-STEM images of bone-implant interfaces were collected on an FEI Titan operated at 300kV, with image acquisition every 2°, up to ± 75°. Images were aligned by cross-correlation in FEI’s Inspect 3D. Simultaneous iterative reconstructions were performed by varying parameters, including angular tilt ranges from ±10° to ±75°, projections every 2° to 10°, and reconstruction iterations. The resulting reconstructions were compared through orthogonal slices and volume rendering. A set of parameters were established to produce optimal reconstructions, with the least number of projections and iterations, for the specific application of bone-implant interfaces for a high resolution understanding of its complex hierarchical structure.
SPU-17: Stacking Fault Energies of Complex Alloys Calculated from Special Quasirandom Structures: Jonas Kaufman1; Greg Pomrehn2; Aurora Pribram-Jones3; Michael Ferry4; Kevin Laws4; Lori Bassman1; 1Harvey Mudd College; 2The Boeing Company; 3Lawrence Livermore National Laboratory; 4School of Materials Science and Engineering, UNSW Australia
Ductility in metallic alloys is determined by which deformation modes are available to the lattice. Stacking fault energy is an indicator of deformation mode in alloys, as it controls dislocation mobility. A generalized stacking fault energy (GSFE) curve contains not only stable stacking fault energies, but also energy barriers to stacking fault formation, which partly determine an alloy’s tendency toward twinning. This study adapts a new method of calculating GSFE using density functional theory and special quasirandom structures for complex alloys such as high entropy alloys. A planar averaging approach is used to account for variation between different fault planes within the disordered structure. Special attention is paid to interlayer pair correlations around fault planes and their effect on the uncertainty in GSFE. The method is validated against literature for non-dilute binary alloys and results are compared to experimentally observed deformation behavior of ternary alloys in the Ag-Au-Pd system.