Determination of the work hardening exponent by the Hollomon and differential Crussard-Jaoul analyses of cold drawn ferrite-pearlite steels

This research work analyses the effect of cold working level produced by drawing, on the work hardening exponent of 0.18 and 0.43 % C ferrite-pearlite steels. Such analysis is carried out by means of true stress-true strain curves derived from uniaxial tension tests. The work hardening exponent behaviour was determined by using Hollorrion and differential Crussard-Jaoul models. It is found that the work hardening exponent decreases as a function of the applied cold-drawing level, and negative values were obtained when differential analysis is used. The results indicate that the Hollomon analysis shows some deviations from the experimentally determined true stress - true strain curves while the differential Crussard-Jaoul analysis fits better when two work hardening exponents are considered. This analysis establishes two exponents for different stages of plastic deformation which are determined by the sharp slope change in the plot of In (d sigma/d epsilon) - In epsilon.