  The heat-treatment of a number of gas atomised aluminium alloys prior to cold
spraying recently showed that the resultant microstructural modification was
accompanied by an improvement in deposition; however, the relationship between
the microstructural homogenisation occurring after recrystallisation and the
increase in deposition efficiency and particle-particle bonding had not been
investigated. In this study, AL 6061 gas atomised feedstock powder, before and
after solution heat-treatment, was cold sprayed and these materials were
charaterised using electron backscatter diffraction. The solution heat-treated
Al 6061 powder showed large stress-free grains as opposed to the as-atomised
feedstock powder which exhibited a homogeneous distribution of misorientation
and lattice defects throughout the particles, whereas the coating produced from
solution heat-treated powder showed an accumulation of dislocations in the
interfacial zones. For the first time, a mechanism was proposed where this
phenomenon was attributed to localised deformation of the heat-treated
particle's exterior due to the dissolution of precipitates in the intermetallic
network. The accumulation of dislocations in the interfacial area enhanced the
rotation of subgrains to accomodate the plastic deformation, thus improving the
particle-particle bonding.
