THE NOTCH IMPACT BEHAVIOR OF TUNGSTEN
HONEYWELL RESEARCH CENTER HOPKINS MN
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This paper compare the fracture behavior of tungsten rods in three conditions, recrystallized, recovered, and wrought. Notched specimens subjected to a 50 in. lb. impact load showed ductile brittle transitions at 700 C, 490 C, and 440 C respectively. The recrystallized material had an equiaxed grain structure and fractured by simple cleavage from a grain boundary source at all temperatures up to 700 C. The wrought and recovered material had an elongated fiberous structure and at low temperatures fractured by cleavage originating from the notch. As the transition temperatures was approached cleavage was preceded by more and more intergranular splitting which deflected the crack front into planes parallel to the tensile axis. The enhanced toughness of wrought and recovered tungsten was attributed both to its inability to initiate cleavage because no grain boundaries were suitably oriented perpendicular to the tensile stress and its inability to maintain cleavage because of intergranular splitting ahead of the crack.
- Properties of Metals and Alloys