Abstract
Hot compression tests for 2219/TiB2 Al-matrix composite were conducted on a Gleeble-3500 isothermal simulator in the temperature range of 300~500°C and strain rates of 0.01, 0.1, 1, 10s-1 to obtain true stress strain curves. The original Johnson-Cook model was calculated and used to describe the constitutive relationship of hot deformation behavior of this composite. After precision evaluation and analysis, a new modified Johnson-Cook model was proposed. Comparing with the original model, the new model has a lower absolute average relative error (AARE) of 6.4415% and a higher relative error (R) of 0.9852, which indicates better prediction precision. Meanwhile, to understand the intrinsic workability of this composite, processing map based on dynamic materials model was constructed. Two stable regions locating at 300~400°C&0.01~0.1s-1 and 420~500°C &0.01~1s-1 were identified by the processing map and the instable microstructure in the instability region validated the reliability of the processing map. Furthermore, the microstructure evolution was analyzed and the results revealed that the θ-phase reduced with the increasing temperature.
Highlights
Aluminum matrix composites (AMCs) are increasingly used in aerospace, aircraft, automotive industries due to the advantages such as light weight, good wear resistance, high specific strength and low thermal expansion coefficient[1,2,3]
Higher deformation temperature and lower strain rate will result in lower true stress, a conventional explain for this phenomenon is that the nucleation of dynamic recrystallization is easier to process under higher temperature and lower strain rate[22,23,24]
The true stress increases dramatically at the initial stage of deformation and decreases with the increasing strain, which is caused by the predomination of work hardening at the beginning of deformation and the subsequent effect of dynamic recovery and dynamic recrystallization becoming stronger with the increasing strain
Summary
Aluminum matrix composites (AMCs) are increasingly used in aerospace, aircraft, automotive industries due to the advantages such as light weight, good wear resistance, high specific strength and low thermal expansion coefficient[1,2,3]. The main widely used reinforcing particles for AMCs are Ni2O34, Al2O33, ZrB25, SiC1,6 and TiB27 etc Among these strengthened Al-matrix composites, the main research goals of previous research reports were at obtaining good adhesion property at the interface of particles and matrix and mature fabrication processes. Hot deformation behaviors of alloys were normally studied using constitutive models and processing maps[8,9,10]. The original Johnson-Cook constitutive model for 2219/TiB2 Al-matrix composite was firstly constructed and the prediction precision was evaluated. After analyzing the main factors limiting the precision of the model, a modified Johnson-Cook model was proposed to better describing the flow behavior of this composite. The microstructure evolution was analyzed by optical microscopy and used to verify the processing map, at the same time, the microstructure evolution during hot deformation was studied
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