Constitutive Modelling and Hot Workability Analysis by Microstructure Examination of GH4169 Alloy

The relationships between hot deformation parameters and flow behaviour have attracted many researchers' attention for the past few decades, whilst precise constitutive modelling of GH4169 remained a problem, which seriously affected the process and microstructure control of alloys. In this work, a modified Arrhenius type model was introduced to describe the flow stresses of various compression conditions. The model showed high precision in flow stress prediction. In order to facilitate workability evaluation for engineering applications, the hot processing maps were established at the strain of 0.4 similar to 0.6. The processing maps revealed an instability domain at 900 similar to 950 degrees C and 0.1 similar to 1 s(-1), a high dissipation efficiency domain at 1060 similar to 1100 degrees C and 0.001 similar to 0.01 s(-1), and a stable deformation domain for the rest of processing parameters. Microstructures of each domain were observed via optical microscope (OM) and electron backscattered diffraction (EBSD). The intriguing finding was that the microstructures morphology agreed well with the descriptions in discontinuous mechanism, and incompletely recrystallized microstructures were found in the instability domain. Fully recrystallized microstructures were found in the stable deformation domain, and grain coarsen in the high dissipation efficiency domain. Optimal hot working conditions were suggested based on the microstructure analysis. This investigation contributed to a comprehensive understanding of the workability of GH4169.