The present work studied the dislocation densities in cold-rolled stainless steel by measuring the doppler broadening of the annihilation line. The specific trapping rate of dislocation for positron was given.

The γ-rays due to annihilation were detected by a pure germanium detector with the sensitive volume being 0.1cm

3

. The resolution of the system for 514keV γ-rays of

85

Sr was 1.2keV.

Dislocation densities were calculated according to the formulae for F. C. C. pure metal. Results showed that they increased from 9×10

8

cm

-2

to 5.7×10

11

cm

-2

as percent thickless reduced from 1% to 25%. The specific trapping rate for positrons was obtained: μ

d

=0.58cm

2

·s

-1

.

The results of present work made it clear that positron annihilation technique could be used to measure the densities of dislocation in alloys. However

the upper limit of dislocation density was about 10

-12

cm

-2

due to the saturation effect of the annihilation parameters.