This paper presents a new microstructural model of the metastable eutectoid transformation in spheroidal graphite cast irons. The model takes into account the nucleation and growth of pearlite nodules. The nucleation is assumed to be continuous and dependent on the metastable undercooling associated with the upper limit of the three-phase field, while the growth rate is considered to be ruled by the silicon partitioning between ferrite and cementite at the pearlite/austenite front. The initial conditions for the metastable transformation are obtained from a microstructural simulation of solidification, graphite growth, and stable eutectoid transformation. These microstructural models are coupled with the thermal balance solved at a macroscopic level via the finite element method. The experimental validation of the metastable eutectoid model achieved by comparison with measured values of ferrite, graphite, and pearlite fractions at the end of the cooling process demonstrates the sound predictive capabilities of the proposed model.

This paper presents an analysis of the test and simulation of the equal channel angular extrusion (ECAE) of a commercial Al 6061-T6 alloy previously extruded. Special emphasis is given to the analysis and comparison of the simulated values and distribution of equivalent plastic strain with those calculated with analytical models across the height of the middle section of the deformed billet. The results reveal the limitations of the analytical models when the effects of the inner die corner and curvature of the outer wall on the material response during the test are considered for the ECAE device used in this work. Specifically, in the simulations performed in this work, the plastic deformation zone, far from being uniform, extends along with the height of the billet where, in particular, near the inner wall over the inlet and outlet channels, even in the central region of the billet, the equivalent plastic strain is not homogeneous or discontinuous, varying mainly due to the effect of the curvature of the outer channel.