회귀기반의 동적재료모델을 이용한 Inconel 718 합금의 고온 변형 거동 분석 및 Ring rolling 공정의 적용 = Hot Deformation Behavior of Inconel 718 Alloy Using Regression-based Dynamic Material Model and Applications in Ring Rolling Manufacturing

다국어 초록 (Multilingual Abstract)

Inconel 718 nickel-based alloy is extensively used in the aerospace industry (e.g., gas turbine enginecomponents) because of its excellent corrosion resistance and high mechanical properties at elevatedtemperatures. However, there is a certain limit to manufacturing the alloy through plastic deformation dueto its high deformation resistance and complicated deformation behaviors. In this study, the hot deformationbehavior of Inconel 718 alloy was investigated to establish how processing conditions of flow stress-strain, atstrain rates from 0.001 to 10 s-1, and temperatures from 850 to 1200oC, affected dynamic recrystallization.
The regression-based material model was utilized to calculate the strain-rate sensitivity, and subsequentlydepict the efficiency of the power dissipation and instability criterion of hot deformation. The processing mapand instability criterion predicted by the developed 3rd-order polynomial regression model corresponded withthe experimental results and in particular, showed a better prediction for instability regime compared to theexisting discrete derivative approach. Predicting the strain-rate sensitivity values on a continuous scale withregression analysis covered the additional instability region of the high strain rate near 10 s-1. The dynamicrecrystallization deformation was also characterized by microstructural analysis along with the processingmap. Consequently, ring-rolled aviation parts were manufactured with the optimum processing parameters,which conform to the AMS 5663 standard (Aerospace material specifications for Inconel 718).