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A New Piecewise Dynamic Constitutive Equation of Powder Metallurgy High Speed Steel

Xi Chen, LIU Yan-hui and Ning Yong-quan

In order to optimize the hot working technology of powder metallurgy high speed steel, The hot deformation behavior of powder metallurgy (PM) high speed steel was investigated by Gleeble-1500D simulation at the temperature range of 1000-1150°C, strain rates between 0.001 s-1 and 1.0 s-1 and deformation rate of 60% of the samples. The flow stress under different temperatures and strain rates were analyzed. The results show that the flow stress is influenced strikingly by deformation temperature and strain rate. Both the peak stress and the corresponding strain decrease with the increase of temperature and the decrease of strain rate. Deformation temperature, strain rate and deformation activation energy have a great affect on the microstructure. The value of deformation activation energy is 750.67 kJ/mol. The mathematical model of the strain corresponding to the peak stress was set up. The relationship between the strain corresponding to the peak stress and the strain corresponding to the critical stress can be described as: εc=0.606 εp. The segmental dynamic constitutive equation under different strain was established based on the idea of subsection.