High Temperature Flow Behavior and Microstructure of Al-Cu/Mg2Si Metal Matrix Composite

Abstract

The present work deals with the high temperature flow behavior and the microstructure of the AI-Cu/Mg2Si metal matrix composite. Toward this end, a set of hot compression tests was pet formed in a wide range of temperature (573-773 K) and strain rate (O.OOI-O. I s ). The results indicated that the temperature and strain rate have a signifi cant effect on the flow softening and hardening behavior of the material. The work hard ening rate may be offset due to the occurrence of the restoration processes, the dynamic coarsening, and spheroidization of the second phase particles. In this regard, two phe nomenological constitutive models, Johnson-Cook (JC) and Arrhenius-type equations, were employed to describe the high temperature deformation behavior o f the composite. The JC equation diverged from experimental curves mainly in conditions which are far from its reference temperature and reference strain rate. This was justified considering the fact that JC model considers thermal softening, strain rate hardening, and strain hardening as three independent phenomena. In contrast, the Arrhenius-type model was more accurate in modeling of the flow behavior in wide range of temperature and strain rate. The minor deviation at some specified conditions was attributed to the negative strain rate sensitivity of the alloys at low temperature deformation regime

Optimum Deformation Criteria and Flow Behavior Description of Boron-Alloyed Steel through Numerical Approach

“…At the final stage, DRX becomes slower so that the rate of energy consumption by softening would be balanced by strain hardening and a steady state flow level is being achieved. The consumption of strain energy provides the dislocation free path for further plastic deformation accommodation and so the stress to apply the strain . The flow curves obtained at relatively higher strain rate, i.e., 0.3 s −1 , on the other hand, show a significant work hardening up to a stress peak followed by a stress plateau (Figure c).…”

“…Among the phenomenological models, many researchers have successfully employed the Arrhenius equation to describe the flow stress of a number of alloys during TMP . In the case of boron steels, Li et al have investigated the capability of two phenomenological constitutive models, the modified Arrhenius and Johnson–Cook models, in predicting the hot tensile flow behavior of a hot stamping boron steel with 35 ppm boron and 0.22 wt% carbon over wide ranges of strain rates and temperatures.…”

The Mg2Si phase evolution during thermomechanical processing of in-situ aluminum matrix macro-composite

“…It is believed that the dynamic agglomeration and the formation of larger particles with the lower population may assist the dynamic decrease of the flow stress level which has been observed before in the flow curves [22].…”

“…1a) consists of the coarse polygonal-shape primary Mg 2 Si particles (defined as [Mg 2 Si] P ) surrounded by pseudo-eutectic lamellar structure of secondary Mg 2 Si/α Al (defined as [Mg 2 Si] S ). In addition, the presence of θ phases (CuAl 2 ) can be recognized specifically at the cell boundaries, which form during the final steps of solidification due to the copper addition [22]. Also, the electron backscattered diffraction (EBSD) image of as-received material is shown in Fig.…”