The Mechanical Properties of Tantalum with Special Reference to the Ductile-Brittle Transition

Item

Title
The Mechanical Properties of Tantalum with Special Reference to the Ductile-Brittle Transition
Description
The lower yield stress-grain size relationship was studied in tantalum for two compositions; one consisting of a total interstitial content of 72 ppm with the major constituent being oxygen, and the other containing primarily carbon (116 ppm) in which part of the carbon existed in the form of a finely dispersed carbide precipitate. These results were compared to those obtained earlier (1) on commercial tantalum containing a total interstitial content of about 200 ppm. The parameters σi and ky in the Petch equationσy=σi + kyd-1/2
were of primary interest. The commercial tantalum exhibited significantly higher yield and flow stresses and correspondingly higher σi values. The carbon containing material showed the lowest yield stresses primarily because of its lower oxygen content. It was concluded that oxygen is much more effective than carbon in restricting dislocation movement. The effect of the flow stresses, however, even in the presence of the carbide phase were lower than those observed for commercial tantalum.The ky values obtained on the 72 ppm solute content materials for a strain rate of 10-1/sec. were found to be approximately 2 x 107 c.g.s. units and thus about a factor of two larger than those found on commercial tantalum. For both materials ky did not vary with test temperature at a strain rate of 10-3/sec., however at a strain rate of 10-1/sec. ky for the 72 ppm solute material was found to vary from about 1 to 3 x 107 c.g.s. with the larger values being measured at the lower test temperature. ky values for the carbon containing material were found to be very small (~0.5 x 107 c.g.s) and did not vary appreciably with test temperature or strain rate. It was suggested that this small ky may be due to a large number of unlocked dislocations as a result of the carbide particles acting as sources.ky and σi values were also computed by the Lüders strain technique for the room temperature tests and found to agree reasonably well with those obtained by the grain size method.
Date
1963
Index Abstract
Contrails only
Photo Quality
Incomplete
Report Number
ASD TR 61-203 Part II
Creator
Murray, G. T.
Burn, R. A.
Corporate Author
Materials Research Corporation
Extent
45
Identifier
AD0403074
AD0403074
Distribution Classification
1
DTIC Record Exists
Yes
Distribution Change Authority Correspondence
None
Report Availability
Full text available by request
Date Issued
1963-03
Abstract
The lower yield stress-grain size relationship was studied in tantalum for two compositions; one consisting of a total interstitial content of 72 ppm with the major constituent being oxygen, and the other containing primarily carbon (116 ppm) in which part of the carbon existed in the form of a finely dispersed carbide precipitate. These results were compared to those obtained earlier (1) on commercial tantalum containing a total interstitial content of about 200 ppm. The parameters σi and ky in the Petch equationσy=σi + kyd-1/2
were of primary interest. The commercial tantalum exhibited significantly higher yield and flow stresses and correspondingly higher σi values. The carbon containing material showed the lowest yield stresses primarily because of its lower oxygen content. It was concluded that oxygen is much more effective than carbon in restricting dislocation movement. The effect of the flow stresses, however, even in the presence of the carbide phase were lower than those observed for commercial tantalum.The ky values obtained on the 72 ppm solute content materials for a strain rate of 10-1/sec. were found to be approximately 2 x 107 c.g.s. units and thus about a factor of two larger than those found on commercial tantalum. For both materials ky did not vary with test temperature at a strain rate of 10-3/sec., however at a strain rate of 10-1/sec. ky for the 72 ppm solute material was found to vary from about 1 to 3 x 107 c.g.s. with the larger values being measured at the lower test temperature. ky values for the carbon containing material were found to be very small (~0.5 x 107 c.g.s) and did not vary appreciably with test temperature or strain rate. It was suggested that this small ky may be due to a large number of unlocked dislocations as a result of the carbide particles acting as sources.ky and σi values were also computed by the Lüders strain technique for the room temperature tests and found to agree reasonably well with those obtained by the grain size method.
Type
report
Provenance
Lockheed Martin Missiles & Fire Control
Format
vii, 45 pages : ill. ; 28 cm.
Subject
Ductile Brittle Transition
Tantalum
Mathematical Models
Temperature
Microstructure
Tensile Properties
Carbon
Crystal Defects
Cryogenics
Grain Structures (Metallurgy)
Ductility
Shear Stresses
Transition Temperature
Impurities
Fracture (Mechanics)
Oxygen
Brittleness
Publisher
Wright-Patterson Air Force Base, OH : Directorate of Materials and Processes, Aeronautical Systems Division, Air Force Systems Command,
Laboratory
Metals and Ceramics Laboratory
DoD Project
7351
DoD Task
735106
Distribution Conflict
No
Access Rights
OTS
Contract
AF 33(616)-7173