The hypothesis that {HEAD ~ the retention} of Al and O at {TAIL ~ grain boundaries} and triple points would result in high fracture toughness was not correct 
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The hypothesis that { HEAD ~ the retention } of Al and O at { TAIL ~ grain boundaries } and triple points would result in high fracture toughness was not correct
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH