MICROYIELDING IN IRON AT LOW TEMPERATURES,
Abstract
The micro and macro yielding of zone refined polycrystalline iron was investigated between 298 and 5K. The elastic limit became temperature sensitive below 50K so that its value at 0K was about twice its 5,000 psi tensile value at 298K. The stress to produce a permanent strain of about 10 to minus 6th power was more temperature sensitive with an increase of 8,000 to 14,000 psi between 298 and 0K. The stress for macro yielding increased about 120,000 psi between 298 and 0K. The results have been interpreted in terms of three PeierlsNabarro forces, one for existing kinks another for the motion of screw dislocations on a constant slip plane, and the third for motion onto another slip plane. Impurities play a role with the Peierls-Nabarro force in determining the microyield points. The large 120,000 psi increase in macroyield point between 298 and 0K is attributed to the P-N-F for cross-slip which causes a high internal stress field to be built up prior to macro-yielding. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 30, 1965
- Accession Number
- AD0615757
Entities
People
- Norman Brown
- Ram Kossowsky
Organizations
- University of Pennsylvania