Effect Of Temperature On The Creep Of Polycrystalline Aluminum By The Cross-Sslip Mechanism
Report Number: WADD TR 60-53
Author(s): Jaffe, N., Dorn, J. E.
Corporate Author(s): University Of California
Laboratory: Materials Central
Date of Publication: 1960-06
Pages: 21
Contract: AF 33(616)-3860
DoD Project: 7360
DoD Task: 73604
PB Number: PB171360
Identifier: ADA328524
Abstract:
The apparent activation energy for creep of polycrystalline aluminum was determined over the range of 273° to 350°K by the effect of small abrupt changes in temperature on the creep rate. A constant activation energy of 27,400 ± 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 10-5 to 29.5 x 10-5 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 ε during creep under a given stress should be a function of temperature compensated time Θ = 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.
Provenance: IIT
Author(s): Jaffe, N., Dorn, J. E.
Corporate Author(s): University Of California
Laboratory: Materials Central
Date of Publication: 1960-06
Pages: 21
Contract: AF 33(616)-3860
DoD Project: 7360
DoD Task: 73604
PB Number: PB171360
Identifier: ADA328524
Abstract:
The apparent activation energy for creep of polycrystalline aluminum was determined over the range of 273° to 350°K by the effect of small abrupt changes in temperature on the creep rate. A constant activation energy of 27,400 ± 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 10-5 to 29.5 x 10-5 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 ε during creep under a given stress should be a function of temperature compensated time Θ = 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.
Provenance: IIT