Controlling Particle/Metal Interactions in Metal Matrix Composites During Solidification: The Role of Melt Viscosity and
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LIGHTWEIGHT materials have shown increasing applications for energy efficiency[1] in the aerospace[2] and automotive[3,4] industries. Advanced light alloys, such as Al alloys[5,6] and Mg alloys,[7,8] have been developed by optimizing alloy compositions and manufacturing processes with computational and experimental approaches.[9] One effective approach to further improve the performance of light alloys is to introduce ceramic reinforcements (e.g., particles and fibers) to produce metal matrix composites (MMCs).[10–16] In order to obtain a homogeneous distribution of ceramic reinforcements in a MMC, there are two required conditions. First, the ceramic particles/fibers must be uniformly dispersed in the liquid metal.[17–19] Second, the particles/fibers must be captured and engulfed by the solidification front during processing.[20–22] RENHAI SHI and JANET M. MEIER are with the Department of Materials Science and Engineering, The Ohio State University, Columbus, OH, 43210. ALAN A. LUO is with the Department of Materials Science and Engineering, The Ohio State University and also with the Department of Integrated Systems Engineering, The Ohio State University, Columbus, OH, 43210. Contact e-mail: [email protected] Manuscript submitted January 21, 2019. Article published online June 5, 2019 3736—VOLUME 50A, AUGUST 2019
It is particularly challenging to capture particles of small size, such as micron to nano-scale, during solidification in conventional casting conditions. For example, the solidification cooling rate in MMC casting is often not high enough to capture particles within the grain/dendrite interiors and the particles are pushed to grain boundaries or inter-dendritic regions. One way to improve capture is to increase the solidification cooling rate so the velocity of the solidification front is higher than the moving velocity of the particles.[20–22] In this paper, we propose an approach to increase the melt viscosity to decrease the moving velocity of particles so capture can occur at lower cooling rates. The benefit of this approach is that the viscosity of a MMC melt can be modified via microalloying. However, one important gap in understanding the influence of microalloying on the particle/metal interactions during solidification is the lack of composition/temperature-dependent thermo-physical parameters, such as viscosity, for multi-component alloy systems. So far, theoretical models[20–22] dealing with such influences only used viscosity values for pure metals due to the complexity and difficulty of measurements for multi-component alloy systems. It is critical to construct a theoretical model for the viscosity of multi-component alloy systems to understand and optimize the solidification processing of MMCs. However, previous theoretical viscosity METALLURGICAL AND MATERIALS TRANSACTIONS A
models[23–25] for multi-component alloy systems only include thermodynamic parameters, but not the nonideal mixing behavior corresponding to chemical shortrange order. In this work, we first developed a new theoretical particle-ca
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