THE TENSILE DUCTILITY-TRANSITION IN MOLYBDENUM
Abstract
An investigation was carried out to determine the nature of the tensile ductility transition in recrystallized molybdenum strip of three interstitialal contents. For a fine grain size, the tensile ductility transition temperature (T sub d) and the brittleness transition temperature (T sub b) were found to approximately coincide; whereas with increase in grain size T sub d is raised and T sub b is lowered. The occurrence of a minimum in the fracture stress (sigma sub F) at T sub d appears to be associated with the temperature dependence of the necking stress (Sigma sub n). Prestraining above T sub d, was found to result in as much as a 20% increase in (sigma sub F) as determined at temperature below T sub d. In general, the mode of fracture initiation was found to be intergranular at T sub d or below and cleavage above T sub d. For a test temperature above as well as below T sub d, crack initiation appears to be the controlling step in fracture. Considering (sigma sub F) as a flow stress corresponding to the fracture strain (epsilon sub F), the variation of (sigma sub F) with temperature above T sub d was predicted within about 15%. Based on a modification of the Cottrell relation for crack initiation, the increase in (sigma sub F) above T sub d is associated with a decrease in both the flow locking parameter (k sub f) and the effective grain size.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1964
- Accession Number
- AD0603698
Entities
People
- B. S. Lement
- K. Kreder