Modeling the Effect of Active Fiber Cooling on the Microstructure of Fiber-Reinforced Metal Matrix Composites

Abstract

A modified pressure infiltration process was recently developed to synthesize carbon-fiberreinforced aluminum matrix composites. In the modified process, the ends of carbon fibers are extended out of the crucible to induce selective cooling. The process is found to be effective in improving the quality of composites. The present work is focused on determining the effect of the induced conductive heat transfer on the composite system through numerical methods. Due to the axisymmetry of the system, a two-dimensional (2-D) model is studied that can be expanded into three dimensions. The variables in this transient analysis include the fiber radius, fiber length, and melt superheat temperature. The results show that the composite system can be tailored to have a temperature on the fiber surface that is lower than the melt, to promote nucleation on the fiber surface. It is also observed that there is a point of inflection in the temperature profile along the particle/melt interface at which there is no temperature gradient in the radial direction. The information about the inflection point can be used to control the diffusion of solute atoms in the system. The result can be used in determining the optimum fiber volume fraction in metal matrix composite (MMC) materials to obtain the desired microstructure.

Analysis of active cooling through nickel coated carbon fibers in the solidification processing of aluminum matrix composites

“…However, due to the complexity in developing a two-dimensional analytical heat transfer model for such systems, most studies are based on finite element analysis (FEA) [22]. In our previous study the system was modeled without the presence of nickel coating [23]. The present study extends the analysis to understand the role of nickel coating on the cooling mechanism.…”

“…In our previous study, the cooling mechanism through fibers was modeled without having the nickel coating present in the model [23]. It is shown that an inflection point exists along the fiber length, where the net heat transfer between the melt and the fiber is zero.…”

“…Contacts between carbon fiber, nickel coating, and aluminum melt are assumed to be thermal and mechanical bonding. Conduction is considered as the primary heat transfer mode and convective effects are neglected because they are not significant in the system as described previously [23].…”

“…It is noted that although the rate of heat removed from the system is nearly the same, presence of coating causes significant differences in the temperature profile in the material when the results presented in Figs. 6 and 7 are compared with the previously published data [23].…”

Numerical Simulation on Thermal Stresses and Solidification Microstructure for Making Fiber-Reinforced Aluminum Matrix Composites

“…This method is referred to as the thermal management of fibers, which can significantly change the nature of the interface and the surrounding matrix and, therefore, the properties of the composite. Such an active fiber cooling method has also been used by researchers [30,31] to prevent damage to the nickel coating during the infiltration process. Rohatgi et al [32] used the squeeze infiltration process to synthesize an MMC of Al-2014 reinforced with nickel-coated carbon fibers.…”