  The creep behaviour and microstructural evolution of a Sn-3Ag-0.5Cu wt.%
sample with a columnar microstructure have been investigated through in-situ
creep testing under constant stress of 30 MPa at 298 K. This is important, as
298 K is high temperature within the solder system and in-situ observations of
microstructure evolutions confirm the mechanisms involved in deformation and
ultimately failure of the material. The sample has been observed in-situ using
repeat and automatic forescatter diode and auto electron backscatter
diffraction imaging. During deformation, polygonisation and recrystallisation
are observed heterogeneously with increasing strain, and these correlate with
local lattice rotations near matrix-intermetallic compound interfaces.
Recrystallised grains have either twin or special boundary relationships to
their parent grains. The combination of these two imaging methods reveal one
grain (loading direction, LD, 10.4 {\deg} from [100]) deforms less than the
neighbour grain 2 (LD 18.8{\deg} from [110]), with slip traces in the strain
localised regions. In grain 1, (1-10)[001] slip system are observed and in
grain 2, (1-10)[-1-11]/2 and (110)[-111]/2 slip systems are observed. Lattice
orientation gradients build up with increasing plastic strain and near fracture
recrystallisation is observed concurrent with fracture.
