Analysis of Mechanical Milling in Simoloyer: An Energy Modeling Approach
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INTRODUCTION
HIGH-ENERGY ball milling is an established route to reduce the size of the coarse grains to nanosizes.[1–3] It involves impact/shear of balls with powder, which subsequently results in the deformation and fracture of particles leading to nanostructures through dynamic recrystallization. Collision regime is considered to be the main form of grain refinement during high-energy ball milling. The energy imparted to the powder during impact/shear is responsible for crack propagation and the fracture of particles.[2,3] Modeling of high-energy ball milling has received Renewed attention,[4] primarily to develop novel alloys by lesser use of energy. In that context, Abdelloui and Gaffet[5] established a mathematical approach to illustrate the mechanics of planetary milling, which was used for the development of milling maps by Murty and coworkers.[6,7] Similarly, an ab initio mathematical model was developed by Chattopadhyay et al.[8] to demonstrate mechanics of planetary milling. Dallimore and McCormick[9] worked on the dynamics of milling media motion in planetary mills. There were also attempts to understand the energy transfer in the vibratory ball mills. Zhong et al.[10] analyzed the mechanics of a high-energy vibrator mill. An attempt to measure the impact velocities of balls in Spex mills was done by Basset et al.[11] The communition process of the Spex mill was studied by Concas et al.[12] and Ward et al.[13] Maurice and Courtney[14] developed a model based on Hertzian collisions, which was used by Magini and Iasonna[15] to calculate the energy transferred to the powder per collision. Similar work has been done by Joardar et al.,[16] who formulated a model to determine the temperature of the entrapped powder particle between balls. Sasikumar et al.[17] analyzed the distribution of the energy in various forms during the course of milling.
Recently, a horizontal attritor mill (Simoloyer mill) has gained popularity because of its high energy and faster milling kinetics. The Zoz Group[18–20] worked on the mechanism of milling and the fundamentals of energetics in the simoloyer. However, extensive calculations on the energetics of the simoloyer were not reported so far. This work is an attempt to understand the energy transfer mechanisms occurring in the simoloyer mill and to predict the milling duration required to achieve a particular nanocrystalline grain size.
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EXPERIMENTAL PROCEDURE
Simoloyer CM01 (Zoz GmbH, Wenden, Germany), having double-walled stainless steel vial and stainless steel impeller (10 arms) was employed in the current work. In all, 1 kg of high-chrome steel balls (100Cr6) of 5 mm in diameter were used with a ball-to-powder ratio of 10:1. Commercial pure iron powder (325 mesh, 99 pct) and aluminum powder (325 mesh, 99 pct) were subjected to milling in the current study. The mass flow rate of the cooling water was maintained at 28 g/s. The temperature difference between the inlet and the outlet pipes was measured using a thermometer with a resolution of 0.1 K (0.1 °C). Care was taken
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