Flow Behavior and Constitutive Equation of Metal Beryllium in the First Plastic Peak Zone
The true stress-true strain curves of the metal beryllium were obtained under deformation temperature of 250-450 ℃ and strain rate of 10-1-10-4 s-1 by the isothermal compression testing which was conducted on the Instron 5582 universal material testing machine,and thus flow behavior of the metal beryllium was studied in the first plastic peak zone.The results indicate that the flow stress of the metal beryllium increases with the increase in strain rate and decreases with the increase in deformation temperature under the experimental conditions.Furthermore,the flow stress is more sensitive to the variation of temperature.Under various deformation conditions,the true stress-true strain curves of the metal beryllium show the characteristic of dynamic recovery curve.Moreover,the compressed samples exhibit a typical pressure-working microstructure with elongated grains.These results indicate that dynamic recovery is the main softening mechanism of the metal beryllium during deformation in the first plastic peak zone.The deformation activation energy of the metal beryllium decreases from 244.95 kJ/mol to 166.82 kJ/mol as the strain increase.An Arrhenius strain compensated constitutive equation including strain variables was established.The equation can accurately predict the flow stress of the metal beryllium during compression deformation in the first plastic peak zone,and the maximum mean relative estimation error(MRE)is 5.0550％,and the minimum correlation coefficient(R)is 0.9899.
metal berylliumthe first plastic peak zoneconstitutive equationdeformation activation energy
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