Softening of Young's modulus of polycrystalline Nb/sub 3/Sn

Conference · Fri Jun 01 00:00:00 EDT 1979

OSTI ID:6061085

Welch, D O; Bussiere, J F; Suenaga, M

Ultrasonic measurements show that the shear modulus (C/sub 11/-C/sub 12/)/2 softens dramatically as single crystals of Nb/sub 3/Sn approach the martensitic transition near 50K. It is expected that Young's modulus of polycrystals will olso soften, but previous ultrasonic measurements, which suffer from severe damping, fail to show the expected effect. We have measured Young's modulus of polycrystalline Nb/sub 3/Sn between 4.2K and 300K by static beam deflection methods, and observe marked softening. A value of 14.3 +- .5 x 10/sup 11/ dyne cm/sup -2/ was obtained at 300K by the deflection of thin Nb/sub 3/Sn-Nb-Nb/sub 3/Sn composite strips by external stress. The variation of the modulus with T was obtained from the change in the radius of curvature of internally stressed Nb/sub 3/Sn-Nb composite strips. (This method is made possible by the near perfect match between the thermal expansion coefficients of Nb and Nb/sub 3/Sn.) The modulus is found to be proportional to 1nT between 50K and 300K and is temperature independent below the superconducting T/sub c/, resulting in a decrease by a factor of approx. 2 between 300K and 18K. The observed softening is somewhat less than that predicted by a polycrystalline average of the experimental single crystal elastic constants, but is much larger than that observed with ultrasonic measurements.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: EY-76-C-02-0016
• OSTI ID: 6061085
• Report Number(s): BNL-25949; CONF-7906103-2; TRN: 79-019384
• Resource Relation: Conference: International conference on martensitic transformation, Boston, MA, USA, 24 Jun 1979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
NIOBIUM ALLOYS
YOUNG MODULUS
TIN ALLOYS
TEMPERATURE DEPENDENCE
LOW TEMPERATURE
MEDIUM TEMPERATURE
SUPERCONDUCTORS
ULTRALOW TEMPERATURE
ALLOYS
ELASTICITY
MECHANICAL PROPERTIES
TENSILE PROPERTIES
360104* - Metals & Alloys- Physical Properties
656102 - Solid State Physics- Superconductivity- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)