Hot Formability Studies on 359/SiC/20p and Their Application in Forging Optimisation

Hot formability of 359/SiC/20p was investigated in temperature and strain rate ranges from 375 to 500°C and from 0.003 to 10 s-1, respectively. Flow stress and ductility were studied as a function of deforming conditions. A microstructural damage analysis showed that, at higher strain rates and lower temperatures, stress concentrations at the matrix-particle interfaces strongly affect the cavitation process: stresses become large enough that the interface can separate or particles can crack. Conversely, when temperature increases and strain rate decreases, diffusional processes and grain boundary sliding become the preferential mechanisms for void nucleation and growth. A damage criterion is proposed, based on both FEM simulations and ductility data. The criterion results in very good agreement with the experimental damage measurements performed on an H-section component forged under similar conditions. The criterion was used in the optimisation of forging conditions.