Accession Number : ADA328524

Title :   Effect of Temperature on the Creep of Polycrystalline Aluminum by the Cross-Slip Mechanism

Descriptive Note : Technical rept. 1 Apr 59-31 Mar 60

Corporate Author : CALIFORNIA UNIV BERKELEY INST OF ENGINEERING RESEARCH

Personal Author(s) : Jaffe, N. ; Dorn, J. E.

PDF Url : ADA328524

Report Date : JUN 1960

Pagination or Media Count : 25

Abstract : The apparent activation energy for creep of polycrystalline aluminum was determined over the range of 273 deg to 350 deg K by the effect of small abrupt changes in temperature on the creep rate. A constant activation energy of 27,400 + or - 1000 cal/mole was obtained over strains of 0.003 to 0.23, stresses ranging from 2250 to 6000 p. s. i. and strain rates varying from 0.1145 x l0(exp -5) to 29.5 x l0(exp -5) per minute. Metallographic studies and comparison with theory suggested that creep in this range is controlled by the rate of cross-slip of dislocations. Both X-ray diffraction analyses and room temperature tensile stress-strain data following precreep revealed that the substructure produced in this range by creep under a given stress depended only on the total creep strain being independent of the actual test temperature. As a result it was deduced that the total strain Epsilon during creep under a given stress should be a function of temperature compensated time Theta = te - Q/RT where t is the duration of the test, Q the apparent activation energy, R the gas constant and T the absolute temperature. A number of creep tests conducted at two different temperatures verified the validity of this conclusion.

Descriptors :   *ALUMINUM, *CREEP TESTS, *POLYCRYSTALLINE, ACTIVATION ENERGY.

Subject Categories : Inorganic Chemistry
      Crystallography
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE