Material Properties & Characterization Flashcards

Which characterization technique uses X-rays to determine the crystal structure and phase composition of a metal AM part?

Answer: X-ray diffraction (XRD)

XRD identifies crystal phases by measuring diffraction angles caused by lattice spacing in the material's crystal structure.

Residual stress in metal AM parts is primarily caused by:

Answer: Rapid thermal cycling and non-uniform temperature gradients during solidification

The rapid heating and cooling cycles create steep thermal gradients that cause differential expansion/contraction, leaving residual stresses locked in the part.

The tensile strength of a FDM part is generally highest when the applied load is oriented:

Answer: Parallel to the build layers (XY-direction)

FDM inter-layer bonds are the weakest link, so loads applied parallel to the layers avoid stressing those bonds, yielding higher strength.

Which material characterization method uses a focused electron beam to image surface morphology at high magnification?

Answer: Scanning electron microscopy (SEM)

SEM uses a focused electron beam to produce high-resolution images of surface topography and microstructure.

Differential Scanning Calorimetry (DSC) is used in AM material characterization to measure:

Answer: Thermal transitions such as melting point, crystallization, and Tg

DSC measures heat flow into or out of a material as a function of temperature, identifying phase transitions like melting, crystallization, and glass transition.

Titanium alloys are widely used in metal AM for aerospace applications primarily because of their:

Answer: High strength-to-weight ratio and excellent corrosion resistance

Titanium alloys offer exceptional strength relative to their density along with corrosion resistance, making them ideal for lightweight aerospace structures.

In SLS (selective laser sintering) of nylons, the 'refresh rate' of powder refers to:

Answer: The ratio of new powder mixed with recycled powder to maintain consistent material properties

Recycled powder degrades with repeated thermal cycling, so blending it with fresh powder at a controlled ratio maintains consistent flowability and mechanical properties.