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Variation of low temperature heat capacity with hardness in an aluminum alloy. Technical report No. 15

Technical Report ·
OSTI ID:6215074
The specific heat of a dilute alloy of Mg (0.7%) and Si (0.3%) in aluminum has been measured down to 1.8/sup 0/K. The hardness and mechanical strength of this alloy varied with the degree of precipitation of Mg/sub 2/Si from supersaturated solution and can be controlled by heat treatment. Measurements have been made in the annealed and fully hardened conditions. From 1.8 to 4.2/sup 0/K, the specific heats of hard or annealed specimens can be represented by C = ..gamma.. T +- 1.944 x 10/sup 6/ (T/THETA/sub D/)/sup 3/ mj/mol-deg with ..gamma.. = 1.33 +- 0.02 mj/mol-deg/sup 2/ and THETA/sub D/ = 430 +- 4/sup 0/K for the case of the annealed specimen. For the hard specimens, ..gamma.. = 1.35 +- 0.02 mj/mol-deg/sup 2/, and THETA/sub D/ = 436 +- 4/sup 0/K. In this temperature range, ..gamma.. and THETA/sub D/ increase for the alloy in the hardened condition. The changes are d ..gamma../..gamma.. = 1.1 +- 0.5% and d THETA/THETA/sub D/ = 1.3 +- 0.6%. No change in THETA/sub D/ was observed from 10 to 20/sup 0/K. These results are compared to the change in the superconducting critical temperature found for the same alloy (dT/sub c//T/sub c/ = -4.6%) by Mould in 1954. The discussion is based on the recent theory of superconductivity of Bardeen, Cooper, and Schrieffer and on Morel's calculation of the quantity N/sub 0/V which appears in that theory. The experimental results seem consistent with this treatment and with the experimental correlation between ..gamma.., T/sub c/, H/sub 0/, and THETA/sub D/ that exists among superconductors and which was recently published by Goodman.
Research Organization:
Illinois Univ., Urbana (USA). Dept. of Physics
OSTI ID:
6215074
Report Number(s):
NP-5900332; ON: DE85900332
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
HARDNESS
MAGNESIUM ADDITIONS
MAGNESIUM ALLOYS
MECHANICAL PROPERTIES
PHYSICAL PROPERTIES
SILICON ADDITIONS
SILICON ALLOYS
SPECIFIC HEAT
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
ULTRALOW TEMPERATURE