VISCOUS CREEP OF ALUMINUM NEAR ITS MELTING TEMPERATURE. Technical Report No. 48

Abstract The creep of pure polycrystalline aluminum was studied at low stresses, and temperatures near the melting point. It was found that at stresses between 3 and 13 lb/in2 the secondary creep rate varied linearly with the stress, whereas at slightly higher stresses, the creep rate increased with the fourth power of the stress. The activation energy for creep was determined to be about 35,500 calories per mole over the entire stress range. The low stress creep results in the range of “viscous” creep were analysed from the viewpoint of the Nabarro-Herring model for stress directed self-diffusion of vacancies, and it was found that the experimental creep rates were about one thousandfold greater than those predicted theoretically. This factor plus additional experimental observations on the displacements of markers at grain boundaries, and on creep recovery upon removal of the stress led to the conclusion that the Nabarro-Herring model does not apply to the case of aluminum, and that creep occurs by a dislocation climb mechanism at all stresses considered.

[1]  J. Weertman,et al.  Theory of Steady‐State Creep Based on Dislocation Climb , 1955 .

[2]  Conyers Herring,et al.  Diffusional Viscosity of a Polycrystalline Solid , 1950 .

[3]  H. Udin.  Surface tension of solid copper , 1949 .

[4]  A. P. Greenough.  CVIII. The deformation of silver at high temperature , 1952 .

[5]  J. E. Dorn,et al.  Activation energies for creep of high-purity aluminum , 1957 .

[6]  J. E. Dorn,et al.  EFFECT OF STRESS ON CREEP AT HIGH TEMPERATURES , 1954 .

[7]  E. N. da C. Andrade,et al.  Über das zähe Fließen in Metallen und verwandte Erscheinungen = On the viscous flow in metals, and allied phenomena , 1910 .

[8]  G. M. Pound,et al.  Viscous Flow of Copper at High Temperatures , 1955 .

[9]  F. Buttner,et al.  Viscous Creep of Gold Wires Near the Melting Point , 1952 .

[10]  J. E. Dorn.  Some fundamental experiments on high temperature creep , 1955 .

[11]  J. E. Dorn,et al.  Creep correlations of metals at elevated temperatures , 1954 .

[12]  J. Frenkel.  XXX. On the surface electric double-layer of solid and liquid bodies , 1917 .

[13]  F. N. Rhines,et al.  Behavior of pores during the sintering of copper compacts , 1950 .

[14]  J. E. Dorn,et al.  Creep of Copper at Intermediate Temperatures , 1956 .

[15]  G. Kuczynski.  Study of the Sintering of Glass , 1949 .

[16]  A. Shaler.  Seminar on the kinetics of sintering , 1949 .

[17]  W. Johnston,et al.  Observations of Dislocation Glide and Climb in Lithium Fluoride Crystals , 1956 .

[18]  C. Zener.  Theory of Do for Atomic Diffusion in Metals , 1951 .