forming {HEAD ~ a cavity} in the root portion of {TAIL ~ at least one single crystal superalloy blade} 
forming { HEAD ~ a cavity } in the root portion of { TAIL ~ at least one single crystal superalloy blade }
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL