FEM Analysis of Defects and Microstructure Evolution during Hot Working of Specialty Alloys

摘要

The main goals of process simulation in manufacturing are to reduce manufacturing/part development time and cost as well as increasing quality and productivity. In this study, porosity evolution is modeled by introducing a porosity evolution parameter, which is function of strain rate and stress triaxiality factor. Applicability is shown by simulating the first two stages of an ingot conversion process; variables are die geometry and bite size. Moreover, application is extended to hot shape rolling, where the geometry of the oval passes is the variable. Validation is carried out through evaluation of samples from final products. Also, surface defects in hot shape rolling are tracked by studying the instability during the rolling of the material. Plastic work approach was used to judge the occurrence of instability during the process. The effect of number of passes and roll gap was examined to predict the occurrence of surface cracking. On the other hand, unrecrystallized grains and coarse grain problem are other significant problems in the metalworking industry. A recrystallization model is implemented in a finite element framework, to study the effect of forging parameters on the microstructure evolution during ingot conversion process of a superalloy.