Constitutive modeling for elevated temperature flow behavior of 42CrMo steel

in order to study the workability and establish the optimum hot formation processing parameters for 42CrMo steel, the compressive deformation behavior of 42CrMo steel was investigated at the temperatures from 850 to 1150 degrees C and strain rates from 0.01 to 50 s(-1) on Gleeble-1500 thermo-simulation machine. The results show that the true stress-true strain curves exhibit a peak stress at a small strain, after which the flow stresses decrease monotonically until high strains, showing a dynamic flow softening. The flow stress obtained from experiments consists of four different stage, i.e., Stage I (Work hardening stage), Stage II (Stable stage), Stage III (Softening stage) and Stage IV (Steady stage). The stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in an exponent-type equation. A revised model describing the relationships of the flow stress, strain rate and temperature of 42CrMo steel at elevated temperatures is proposed by compensation of strain and strain rate. The stress-strain values of 42CrMo steel predicted by the proposed model well agree with experimental results, which confirmed that the revised deformation constitutive equation gives an accurate and precise estimate for the flow stress of 42CrMo steel. (C) 2007 Elsevier B.V. All rights reserved.