Microstructural characterization of Mg-SiC nanocomposite synthesized by high energy ball milling

Effect of Milling Time and Reinforcement Volume Fraction on Microstructure and Mechanical Properties of SiCp-Reinforced AA2017 Composite Powder Produced by High-Energy Ball Milling

The influence of milling time and volume fraction of reinforcement on the morphology, microstructure, and mechanical behaviors of SiCp-reinforced AA2017 composite powder produced by high-energy ball milling (HEBM) was investigated. AA2017 + SiCp composite powder with different amounts of SiC particles (5, 10, and 15 vol%) was successfully prepared from gas-atomized AA2017 aluminum alloy powder with a particle size of <100 μm and silicon carbide (SiC) powder particles with an average particle size of <1 μm. An optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscope (SEM) were utilized to characterize the microstructure of the milled composite powder at different milling periods. The results indicated that the SiC particles were homogeneously distributed in the AA2017 matrix after 5 h of HEBM time. The morphology of the particles transformed from a laminar to a nearly spherical shape, and the size of the milled powder particles reduced with increasing the content of SiC particles. The XRD analysis was carried out to characterize the phase constituents, crystallite size, and lattice strain of the composite powders at different milling periods. It was found that with increasing milling time and SiC volume fraction, the crystallite size of the aluminum alloy matrix decreased while the lattice strain increased. The average crystallite sizes were reduced from >300 nm to 68 nm, 64 nm, and 64 nm after 5 h of milling, corresponding to SiC contents of 5, 10, and 15 vol%, respectively. As a result, the lattice strain increased from 0.15% to 0.5%, which is due to significant plastic deformation during the ball milling process. XRD results showed a rapid decrease in crystallite size during the early milling phase, and the minimum grain size was achieved at a higher volume fraction of SiC particles. Microhardness tests revealed that the milling time has a greater influence on the hardness than the amount of SiC reinforcements. Therefore, the composite powder milled for 5 h showed an average microhardness three times higher than that of the unmilled powder particles.

Producing Metal Powder from Machining Chips Using Ball Milling Process: A Review

In the pursuit of achieving zero emissions, exploring the concept of recycling metal waste from industries and workshops (i.e., waste-free) is essential. This is because metal recycling not only helps conserve natural resources but also requires less energy as compared to the production of new products from virgin raw materials. The use of metal scrap in rapid tooling (RT) for injection molding is an interesting and viable approach. Recycling methods enable the recovery of valuable metal powders from various sources, such as electronic, industrial, and automobile scrap. Mechanical alloying is a potential opportunity for sustainable powder production as it has the capability to convert various starting materials with different initial sizes into powder particles through the ball milling process. Nevertheless, parameter factors, such as the type of ball milling, ball-to-powder ratio (BPR), rotation speed, grinding period, size and shape of the milling media, and process control agent (PCA), can influence the quality and characteristics of the metal powders produced. Despite potential drawbacks and environmental impacts, this process can still be a valuable method for recycling metals into powders. Further research is required to optimize the process. Furthermore, ball milling has been widely used in various industries, including recycling and metal mold production, to improve product properties in an environmentally friendly way. This review found that ball milling is the best tool for reducing the particle size of recycled metal chips and creating new metal powders to enhance mechanical properties and novelty for mold additive manufacturing (MAM) applications. Therefore, it is necessary to conduct further research on various parameters associated with ball milling to optimize the process of converting recycled copper chips into powder. This research will assist in attaining the highest level of efficiency and effectiveness in particle size reduction and powder quality. Lastly, this review also presents potential avenues for future research by exploring the application of RT in the ball milling technique.

Mechanochemically synthesized Al-Fe (oxide) composite with superior reductive performance: Solid-state kinetic processes during ball milling

Recently, mechanical ball milling (BM), a simple and green powder processing method, has been successfully applied to improve the performance of zero-valent metals (ZVMs) for efficient water treatment. However, until now BM is still regarded as a "black box" in which the processes of the solid-state reaction during activation remain unclear. In this paper, firstly, FeSO₄·7H₂O crystal was used to activate and modify inert microscale zero-valent aluminum (mZVAl) by BM to synthesize Al-Fe (oxide)^bm composite that showed superior reactivity in reductive removal of various contaminants and excellent reusability, which may be mainly ascribed to the newly formed iron oxide layer on mZVAl by mechanochemical reaction. At the same time, the formation of iron oxides on mZVAl was closely related to BM parameters. Further kinematic analysis revealed that the occurrence of mechanochemical reaction depended on the impact energy and input energy, which BM speed and BM time were two main factors determining reaction extent on the premise that the precursors were full dose. Moreover, kinetic fitting uncovered the solid-state reaction mechanism between mZVAl and FeSO₄·7H₂O conformed to three-dimensional diffusion and phase boundary reaction models. This study ponders deeply upon the mechanochemical process and solid reaction mechanism during the preparation of Al-Fe (oxide)^bm composite, which deepens comprehensions of material synthesis procedures by BM and promotes applications of ZVM-based composite in polluted water or wastewater treatment.

Influencing the Size and Shape of High-Energy Ball Milled Particle Reinforced Aluminum Alloy Powder

High-energy ball milling represents an efficient process for producing composite powders consisting of ceramic particles dispersed in a metallic matrix. However, collision events, plastic deformations, and cold welding during the milling lead to a flake or block-like shape of the resulting composite powders. Further consolidation of such irregularly shaped powders by powder bed-based additive manufacturing technologies can be challenging because of their low flowability and low bulk density. In this work, different approaches, including milling process parameters (speed, process control agent atmosphere) and post-treatments (mechanical and thermal), are investigated on their suitability to influence the particle shape, especially concerning the roundness of the composite powders consisting of the aluminum alloy AlSi10Mg with 5 vol% SiC and Al₂O₃ reinforcement. It is found that milling with menthol as a process control agent leads to the finest composite powder compared to other milling parameters, with the lowest particle roundness of 0.39 (initial powders 0.84). No success in rounding the milled composite powder could be achieved through mechanical post-treatment in a planetary ball mill. On the other side, the thermal spraying of, e.g., SiC reinforced AlSi10Mg powder resulted in a 77–82% relative roundness. A remarkable change in the microstructure and the shape of the composite powders could also be observed after heat treatment in tube furnaces at a temperature above the melting point of AlSi10Mg. The best result in terms of improved roundness (relative to around 85%) was obtained for Al₂O₃ reinforced at 600 °C. A further increase of the temperature to 700 °C resulted in a moderate coarsening of powders with Al₂O₃ and extensive sintering of powders with SiC, presumably due to a different distribution inside the matrix.

Effect of Ball Size on the Microstructure and Morphology of Mg Powders Processed by High-Energy Ball Milling

Commercial powders of pure magnesium were processed by high-energy ball milling. The microstructural and morphological evolution of the powders was studied using scanning electron microscopy (SEM), energy dispersive spectrometry (EDX) and X-ray diffraction (XRD). From the results obtained, it was determined that the ball size is the most influential milling parameter. This was because balls of 1 mm diameter were used after a previous stage of milling with larger balls (i.e., 10 and 3 mm). The powder particles presented an unusual morphology with respect to those observed in the Mg-milling literature and recrystallization phenomena. Moreover, the result strongly varied depending on the ball-to-powder weight ratio (BPR) used during the milling process.

Enhanced Strength and Ductility in Magnesium Matrix Composites Reinforced by a High Volume Fraction of Nano- and Submicron-Sized SiC Particles Produced by Mechanical Milling and Hot Extrusion

In the present study, Mg nanocomposites with a high volume fraction (10 vol %) of SiC particles were fabricated by two approaches: mechanical milling and mixing, followed by the powder consolidation steps, including isostatic cold pressing, sintering, and extrusion. A uniform distribution of the high content SiC particles in a fully dense Mg matrix with ultrafine microstructure was successfully achieved in the mechanically milled composites. The effect of nano- and submicron-sized SiC particles on the microstructure and mechanical properties of the nanocomposites was evaluated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffractometry (XRD) were used to characterize microstructures of the milled and mixed composites. Mechanical behavior of the Mg composites was studied under nanoindentation and compressive loading to understand the effects the microstructural modification on the strength and ductility of the Mg/SiC composites. The mechanical properties of the composites showed a significant difference regarding the size and distribution of SiC particles in the Mg matrix. The enhanced strength and superior ductility achieved in the mechanically milled Mg composites are mainly ascribed to the effective load transfer between matrix and SiC particles, grain refinement of the matrix, and strengthening effects of the nano- and submicron-sized SiC particles.