Study On Deformation Behavior Of Aermet100 Ultra High Strength Steel During Hot Compression Deformation At Elevated Temperature

Aer Met100 ultra-high strength steel is used in the manufacture of aircraft critical parts of support strength due to its excellent comprehensive performance. It’s very important to control the grain evolution in the forging forming process because the forging grain size has a decisive impact on performance of tensile strength, fracture toughness, fatigue resistance and so on which the aircraft parts have strict requirements on. The hot deformation behavior of Aer Met100 steel must be studied in order to predict the grain evolution in forging process and control the performance of plastic deformation.The relationship between the flow stress and deformation condition and the variation of microstructure can be reflected by the constitutive model in the deformation process of Aer Met100 ultra high strength steel. In addition, the validity and accuracy of simulation technology of plastic forming can also be determined by the degree of precision of the constitutive model. So the establishment of accurate material constitutive model has important significance to the optimization of forming process parameters and the improvement of products quality. The constitutive model containing dynamic recrystallization of Aer Met100 steel was established based on the study of hot deformation behavior and microstructure evolution by the hot compression deformation experiment of Aer Met100 steel in this paper. The research results obtained are as follows:(1) The flow stress decreases significantly with deformation temperature T increasing and strain rate e& decreasing through the analysis of hot deformation behavior of Aer Met100 steel. Combined with the analysis of the microstructure of Aer Met100 steel, the true stress-strain curves appeares peak stresses apparently when T>950 and℃ e& <0.1s-1. The degree of dynamic recrystallization and recrystallized grain increases with deformation temperature T increasing and strain rate e& decreasing, which shows that it’s helpful to obtain the complete and small dynamic recrystallization microstructure with the deformation temperature in the range 1000~1050 and the strain rate higher than 0.01s℃-1.(2) The instability region which was obtained according to establish the hot processing map of Aer Met100 steel based on the flow stress contains the deformation temperature around 900~1000 ℃and 1100~1200℃ with the strain rate e& around 1s-1~10s-1.Combining the analysis of power dissipation map with the effect of deformation parameters on microstructure, the hot deformation conditions of Aer Met100 steel are estimated that the deformation temperature is around 900~1000 ℃and the strain rate around 0.01~0.1s-1(3) In this paper, constitutive equations were established by using the Arrhenius equation which could describe characteristics of stress values in deformation behavior. In order to describe all the rheological behavior of Aer Met100 steel during hot deformation, the paper established the constitutive model containing dynamic recrystallization. Compared with the constitutive model considering the strain compensation, the paper analyzes their accuracy and shows that the predicted stress deviations of the constitutive model considering the strain compensation are larger in the intital stage of deformation, while the the predicted stress of the constitutive model containing dynamic recrystallization deviates easily in the rapid rise of stress. Overall, the constitutive model containing dynamic recrystallization is more accurate than the other one.