An ultrasonic clad steel buffer rod sensor embedded in the die has been use
d to in-line monitor the die casting process using aluminium alloy billets
with semi-solid (thixotropic) and dendritic microstructures as feedstocks.
This clad steel buffer rod provided better performance than the previously
reported clad zirconium buffer rod. A multiple recording technique was used
for the fast data acquisition with a rate up to 0.003 s per acquisition. T
his single ultrasonic probe monitored the completion of the die fining, the
release of the pressure, the opening of the die, part detachment and solid
ification of the part. The change of the ultrasonic travel time in the clad
buffer rod and cast part relates to the variation of the average temperatu
re in the die and part, respectively. The measured amplitude profile of the
reflected echo at the probe end/cast part interface can be used to monitor
the cold shot and complete filling. The variation of the ultrasonic attenu
ation coefficient in the cast part may also relate to the change of the com
position, microstructure and porosity.