THE EFFECT OF IMPURITIES ON MECHANICAL TWINNING AND DISLOCATION BEHAVIOR IN BODY-CENTERED CUBIC METALS
Dislocation substructures, as observed by transmission electron microscopy, are reported for materials that twin during deformation and are contrasted with substructures in materials that fail to twin. Differences are interpreted in terms of an increased lattice frictional stress and a reduced ability of dislocations to cross slip in high alloys or during low-temperature deformation. Mechanisms by which the effects alter the twinning behavior are discussed. There is evidence that the stacking fault energy is not lowered by the alloying action. It is further argued that stress concentrations resulting from the altered dislocation configuration are responsible for the enhanced twinning in the alloys. In addition, a raised cleavage strength and increased ability to hold interstitials in solution may act to prevent brittle fracture. The inhibiting effect which interstitials exert on twinning, is explained in terms of interstitial precipitates providing sites where dislocation tangles may form and thus break up potential centers of stress concentration. Transmission electron microscope observations of a Nb-40 wt% V alloy are described that show that the twins generally run entirely across the grains in lightly deformed materials. The observations suggest that solid solution alloys of the refractory metals can be developed that have superior strength to the pure metals, and, because of their ability to twin, may be fabricated readily at room temperature. (P.C.H.)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-17-023961
- OSTI ID:
- 4686607
- Report Number(s):
- ORNL-TM-542
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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