NIST MaterialsData
https://materialsdata.nist.gov:443
The Materials Data digital repository system captures, stores, indexes, preserves, and distributes digital research material.2019-02-01T20:10:01ZMaterials Informatics Approach to Material Extrusion Additive Manufacturing
http://hdl.handle.net/11256/983
Materials Informatics Approach to Material Extrusion Additive Manufacturing
Braconnier, Daniel; Peterson, Amy; Jensen, Robert
Processing-structure-property relationships in material extrusion additive manufacturing are complex, non-linear, and poorly understood. In this work, we designed an informatics workflow for the collection of high pedigree data from each stage of the fused filament fabrication (FFF) printing process. In conjunction with a design of experiments, we applied the workflow to investigate the influences of processing parameters on weld strength across three commercially available FFF printers. Environmental, material, and print conditions that may impact performance were monitored to ensure that relevant data was collected in a consistent manner. Acrylonitrile butadiene styrene (ABS) filament was used to print ASTM D638-14 Type V tensile bars. Data was analyzed using multivariate statistical techniques, including principal component analysis. The magnitude of effect of extrusion temperature, layer thickness, print bed temperature, and print speed on the tensile properties of the final print were determined. The results demonstrated that printer selection is important and changes the impacts of print parameters.
Impact of solutes on the lattice parameters and elastic stiffness coefficients of hcp Fe from first-principles calculations
http://hdl.handle.net/11256/982
Impact of solutes on the lattice parameters and elastic stiffness coefficients of hcp Fe from first-principles calculations
Fellinger, Michael R.; Hector Jr., Louis G.; Trinkle, Dallas R.
The hexagonal close-packed (hcp) $\epsilon$-martensite phase in steels nucleates from the austenite parent phase during plastic straining and can be stabilized by solute additions. We compute the lattice parameters and elastic stiffness coefficients $C_{ij}$ of single-crystal hcp Fe as functions of solute concentration in the dilute limit for the substitutional solutes Al, B, Cu, Mn, and Si, and the octahedral interstitial solutes C and N. Solute strain misfit tensors determine the solute dependence of the lattice parameters, as well as the strain contributions to the solute-induced changes in the $C_{ij}$. We also compute chemical contributions to the changes in the $C_{ij}$ for each solute, and show that the sum of the strain and chemical contributions agrees with more computationally expensive direct calculations that simultaneously incorporate both effects. The computed data can be used to estimate solute-induced changes in polycrystalline elastic moduli and changes in mechanical properties such as strength and ductility, and can be directly incorporated into mesoscale simulations of multiphase steels to model solute effects on the $\epsilon$-martensite phase.
2018-12-16T00:00:00ZUTC time
http://hdl.handle.net/11256/981
UTC time
Wong, T
Geometries of edge and mixed dislocations in bcc Fe from first principles calculations
http://hdl.handle.net/11256/978
Geometries of edge and mixed dislocations in bcc Fe from first principles calculations
Fellinger, Michael R.; Tan, Anne Marie Z.; Hector Jr., Louis G.; Trinkle, Dallas R.
We use density functional theory (DFT) to compute the core structures of a_0[100](010) edge, a_0[100](011) edge, a_0/2[-1-11](1-10) edge, and a_0/2[111](1-10) 71 degree mixed dislocations in body-centered cubic (bcc) Fe. The calculations are performed using flexible boundary conditions (FBC), which effectively allow the dislocations to relax as isolated defects by coupling the DFT core to an infinite harmonic lattice through the lattice Green function (LGF). We use the LGFs of the dislocated geometries in contrast to most previous FBC-based dislocation calculations that use the LGF of the bulk crystal. The dislocation LGFs account for changes in the topology of the crystal in the core as well as local strain throughout the crystal lattice. The standard deviations of the dislocation Nye tensor distributions quantify the widths of the dislocation cores. The relaxed cores are compact, and the local magnetic moments on the Fe atoms closely follow the volumetric strain distributions in the cores. We also compute the core structures of these dislocations using eight different classical interatomic potentials, and quantify symmetry differences between the cores using the Fourier coefficients of their Nye tensor distributions. Most of the core structures computed using the classical potentials agree well with the DFT results. The DFT core geometries provide substitutional and interstitial sites for computing solute-dislocation interactions and can serve as inputs for mesoscale models of solute diffusion near dislocations.