Two methods of the TEM specimen preparation used in
the present work allowed to characterize the microstructure of the WHA. Argon ion milling at −50 ◦C was
used to prepare foils for the observation of the WHA
matrix microstructure, whereas an electrochemical polishing
method have been used for the preparation of
thin foils for characterizing the microstructure of the
tungsten particles. A relatively high density of dislocations
in the tungsten particles and a low density of
dislocations in the matrix characterize the as-sintered
WHA. The material annealed after cold rolling reveals
a refinement of the microstructure. The grain size locally
decreases down to about 100 nm in the tungsten
particles and in the matrix region located near the
particles.