BSE	Backscattered electron
CJ	Joint of as-cast alloy
CLSM	Confocal laser microscope
DP	Duplex
EDM	Electrical discharge machining
FJ	Joint of as-forged alloy
LCr	Fine recrystallized lamellar colonies
LCc	Lamellar colonies in as-cast alloy
NL	Nearly lamellar
PE	Plastic elongation at fracture
PM	Parent metal
PWHT	Post-welding heat treatments
RFW	Rotary friction welding
SDZ	Severely deformation zone
SEM	Scanning electron microscope
TZ	Transition zone
TEM	Transmission electron microscope
UTS	Ultimate tensile strength
ω	Rotation speed
Pf	Friction pressure
δL	Friction burn-off distance
dL	Upset distance
ΔL	Size reduction of the specimen
Pu	Upset pressure
$\dot{\epsilon }$	Upset rate