Title

Effect Of Temperature On The Creep Of Polycrystalline Aluminum By The Cross-Sslip Mechanism

Description

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.

Date

1960

Index Abstract

Contrails and DTIC

Photo Quality

Incomplete

Report Number

WADD TR 60-53

Creator

Jaffe, N.

Dorn, J. E.

Corporate Author

University Of California

Laboratory

Materials Central

Extent

21

PB Number

PB171360

Identifier

ADA328524

ADA328524

Access Rights

OTS

Distribution Classification

1

Contract

AF 33(616)-3860

DoD Project

7360

DoD Task

73604

DTIC Record Exists

Yes

Distribution Change Authority Correspondence

None

Report Availability

Full text available

Date Issued

1960-06

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

Type

report

Format

1 online resource (iv, 17 pages) : ill.

Subject

Aluminum

Creep Tests

Polycrystalline

Activation Energy

Publisher

Wright-Patterson Air Force Base, OH : Wright Air Development Division, Air Research and Development Command, United States Air Force

Distribution Conflict

No