The constitutive relations and thermal deformation mechanism of nickel aluminum bronze

Abstract

A Gleeble3500 thermal simulator investigated the flow behavior of cast nickel aluminum bronze(NAB) with quasi-static test and a split Hopkinson pressure bar (SHBP) with strain rates of 2000–16000 s−1 and a temperature range of 298–1073 K. The relationship between the flow stress and the deformation temperature, strain, and strain rate was exhibited by Johson-Cook (JC) constitutive model. It's found that the strengthening and softening parameters were variables at the high strain rate and hot deformation. The modification was employed, and the modified JC model showed a more precise prediction demonstrated by the higher average absolute relative error. The coupling effect of strain rate strengthening and thermal softening mechanism resulted in the flow stress evolution under different strain rates and temperatures. The dislocation theory was used to explain the strain rate strengthening that under the high strain rate over 102 s−1, the main obstacle was the viscous damping mechanism. The quasi-static tests evaluated the thermal softening mechanism associated with the microstructure evolution. The dynamic recovery and recrystallization's synergistic effect dominated the thermal softening. During the thermal deformation, dense dislocations tangled around the κ phases, apt to be the nucleation of the dynamic recrystallization. The κIV phase dissolution contributed to the grain growth at 1073 K.

Keywords

• Nickel aluminum bronze
• Johson-Cook model
• Strain rate strengthening
• Thermal softening