INVESTIGATION OF THE RELATIONSHIP OF TWINNING TO BRITTLE FRACTURE OF REFRACTORY METALS.
Rept. for 1 Jan 63-15 Feb 64
BATTELLE MEMORIAL INST COLUMBUS OHIO
Pagination or Media Count:
Tension, compression, and bend tests were used to investigate brittle fracture in both single-crystal and polycrystalline molybdenum samples of three contrasting compositions. Although in compression, twins were observed frequently to be responsible for transcrystalline and intercrystalline crack nucleation, during tension or bend tests, no failures were observed whose initiation could be ascribed to twinning. Even in single crystals stressed along 001, the fractures were not twin-induced. It is concluded that twins are just one of several heterogeneities competing in the formation of cracks and that in the material examined other heterogeneities were always dominant. Experiments were conducted on Mo-35Re in which the strain was recorded as a function of time during the formation of twinning bursts. The results indicate that twinning in this situation is essentially a sonic phenomenon. Dislocation arrangements were revealed in Fe-3Si by etchpitting, and it was observed that the propensity for twinning under given conditions was identical in both the presence and absence of a strongly polygonized substructure. Author