Microstructure of additive manufactured materials for plasma-facing components of future fusion reactors

Two metallic materials considered for the divertor in fusion reactors are
manufactured by powder bed fusion through electron beam melting: tungsten as
armor of plasma-facing components and an age-hardenable CuCrZr alloy as heat
sink material for the divertor. Cuboids are additively manufactured from both
materials, and cross sections containing the build direction are characterized by
electron backscatter diffraction. A peculiar heterogeneity is observed in the
microstructure of tungsten and traced to the scanning strategy. Large columnar
grains along the building direction with slight outward inclination are seen on
both sides of the cross section i.e. where grains are observed in viewing planes
perpendicular to the printing direction. Grains appear only slightly elongated in
the center; neither their entire length nor their inclination is detected when the
plane of view contains the printing direction. Many incidental twin boundaries are
identiied in the CuCrZr alloy; their occurrence is rationalized by the presence of
an almost perfect <110> iber texture. Additionally, X-ray computed tomography
conirmed the low porosity of the CuCrZr specimen.