Comparison of Prediction Capabilities of Flow Stress by Various Constitutive Equation Models for Hot Deformation of Aluminum Matrix Composites

One of the important objectives of studies on the hot deformation of materials is the development of constitutive equations that represent the flow stress of the material as a function of strain, strain rate, and temperature useful for the structural designers in finite element analysis. While the constitutive analysis is fairly simple for pure metals and dilute alloys at high temperatures and low strain rates (low flow stresses), it can get complicated at high stresses and with the presence of a second phase, such as those in metal matrix composites. In the present work, the hot deformation behavior of aluminum matrix composites was studied by developing constitutive equations using Johnson–Cook (JC), modified JC (m-JC), Arrhenius, and modified Zerilli and Armstrong (m-ZA) models, and the prediction capability of these models was compared based on average absolute error (Δ). Further, the effect of reinforcement on activation energy of these composites was studied by varying parameters, viz., nature of reinforcement, volume fraction, and size. Out of the four constitutive models studied, the average absolute error is lowest for m-JC and Arrhenius models, and the flow stress values predicted by these two models compare well with the experimental data. Material constants of all the constitutive models for silicon carbide particulate (SiCp)-reinforced AA2124 composites with various volume fractions (5–30 %) were evaluated and provided as a database for the numerical simulations of hot deformation of these composites. To validate the constitutive equations, power dissipation maps have been developed for AA2124-15 vol % SiCp-reinforced composites, and it was found that the predicted flow stress data obtained from m-JC and Arrhenius equations could successfully reproduce the efficiency of power dissipation, indicating their better predictability of flow stress over JC and m-ZA models. Constitutive equations are quantified for 28 aluminum alloys and their composites, and physical interpretation of the constants of Arrhenius equation was provided.