Lecture 9 - Characterization of AM Materials Flashcards
What is neutron diffraction?
nondestructive evaluation of macro-residual stresses, phase, deformation behavior
what is x-ray computed tomography (CT)?
nondestructive evaluation of porosity/defects, geometry/dimension, deformation, surface roughness, particle size
what is synchrotron x-ray diffraction?
nondestructive evaluation of macro and micro residual stresses, phases, pores, deformation behavior
what techniques can be used to analyze prints during 3d printing?
thermal imaging, x-rays, and high-speed camera
what is optical imaging?
large scale imaging
what two processes measure grain orientation, dislocations, and phases?
scanning electron microscopy
electron back scatter diffraction
what is transmission electron micrscopy?
length scale <1 micrometer
What neutron facility is at Los Alamos National Lab?
Spectrometer for Materials Research at Temperature and Stress
What is the wavelength of LANSCE generated neutrons?
0.5 to 7.5 Å
What is the minimum size of samples at LANSCE?
one millimeter
What are four characteristics of cell/grain boundaries?
are imperfections
are more susceptible to etching
may be revealed as dark lines
change in crystal orientation across boundary
What is the optical light resolution?
0.1 µm
What wavelengths do the human eye detect?
380nm-700nm
What are three characteristics of electron microscopy?
wavelength ~ 0.003nm
atomic resolution possible
focused by magnetic lenses
What does electron backscatter diffraction depend on?
beam size, scan step size
What does transmission electron microscopy require of its samples?
sophisticated preparation (thickness <0.25 µm)
Which technique is the most indispensable for characterization of printing defects?
x-ray computed tomography
What do neutron or x-ray diffraction techniques characterize?
residual stresses
pores
other microstructures
What do in operando characterizations do?
understand the fundamental sciences of laser-material interactions
What properties are not investigated using these means?
mechanical, thermal, electrical properties
What destructive evaluations are also used?
electron backscatter diffraction
multiscale characterizations
what are the neutron diffraction facilities?
Los Alamos
Oak Ridge
what is the best way to ensure that your image pops up on ct?
use elements with low attenuation coefficient
how do you take a ct scan?
rotate part 360 degrees and take sample
combine samples into 3d image
What is the typical resolution of CT scan?
1 µm
What is CT scan based on?
absorption
What is synchrotron based on?
transmission
What can synchrotron x-rays pick up?
texture, dislocation
which planes are parallel to incident beam in TEM?
diffracting atomic planes
What does deformation measure?
lattice strain and stresses
What does elastic modulus depend on?
grain boundary direction
how do you measure the stress?
measure the strain and convert using elastic modulus
what is pyrometry?
determination of temperature by analyzing wavelengths of thermal radiation emissions
What does EBSD show?
grain orientation
what are the three different modes of TEM?
bright-field, dark-field, weak-beam
What does “in operando” mean?
Machine has measurement tools in situ
