mechanical alloying

Microwave sintering has emerged as a promising technique for the fabrication of Ti-based alloys, offering unique advantages over conventional sintering methods. The selective and volumetric heating capabilities of microwaves can result in rapid densification, microstructural refinement, and enhanced properties in Ti-Cu alloy systems. Therefore, this study aimed to synthesize an intermetallic alloy of Ti-50 at. % Cu through high-energy mechanical milling and a microwave-assisted sintering method. The objective was to expedite the sintering process of the Ti-Cu alloy using microwave assistance and analyze how this method influences the phases formed and the properties of the alloy. A Ti-50 at. % Cu powder mixture was milled for 30 hours under an argon atmosphere, then uniaxially compacted to form green samples, which were subsequently sintered by microwave heating. This method allowed for rapid consolidation without significant grain growth within a short sintering period. The effects of the sintering method and temperature on microstructure and mechanical properties were studied. The density of the sintered samples increased with rising temperatures, with the highest density of 6.54 g/cm³ obtained at 900°C. Microstructural examination revealed that the Ti3Cu4 and TiCu phases primarily formed, with an average grain size of approximately 28 nm. A high micro-hardness of ~880 HV was achieved for the dense alloy prepared using this method.

The present study focuses on the phase and structural features of MnAl intermetallic compound during solid-state synthesis. In this regard, the milling process was done in differentMn50+xAl50-x (0<x<7.5)powder mixtures and the prepared samples were evaluated using X-ray diffractometer, scanning and transmission electron microscopy, differential thermal analysis and vibrating sample magnetometer. The results showed that the τ-MnAl magnetic phase with L10 structure could not be formed during the milling and low temperature annealing. During milling process, Al atoms dissolve in Mn network and a single β-Mn supersaturated solid solution (SSSS) form. The β-Mn (SSSS) phase is unstable and transforms into the icosahedral quasi-crystal as well as γ2-Al8Mn5 and β-Mn stable phases during subsequent annealing.

Mechanical alloying was employed to synthesize a nanostructured alloy with the chemical formula of (Fe80Ni20)1-xCrx (x= 0, 4). The microstructural and magnetic properties of the samples were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and a vibrating sample magnetometer (VSM). Additionally, theoretical calculations were performed using density functional theory (DFT) under the generalized gradient approximation (GGA). Simulations have demonstrated that an appropriate quantity of chromium (Cr) can dissolve within the BCC-Fe (Ni) structure, resulting in a favorable enhancement of the magnetic moment of the lattice. The XRD results indicated that after 96 hours of milling, Fe (Ni) and Fe (Ni, Cr) with a body-centered cubic (BCC) structure were formed. With increasing milling time, the grain size decreased while the microstrain increased. The saturation magnetization (Ms) of Fe80Ni20 composition increased up to 32 hours of milling, but further milling (up to 96 h) resulted in a decrease in the saturation magnetization However, for the (Fe80Ni20)96Cr4 powders, milling up to 64 h caused a reduction in Ms. The coercivity (Hc) trend was different and increased with longer milling times (up to 96 h) for both compositions.

Nearly two decades have passed since the introduction of high entropy alloys, which can be synthesized using solid, liquid, or gas methods. This study focuses on the solid-state method of mechanical alloying to create high entropy alloy AlCoCuFeNi and examines the properties of the material at various stages of synthesis. The solid-state method of mechanical alloying was utilized in this research to synthesize a high entropy alloy, with samples taken at regular intervals of 10, 20, 30, 40, and 50 hours. X-ray diffraction (XRD) was used to characterize the alloys, with further XRD analysis performed to determine crystallite size and lattice strain. In this study, high entropy alloys were successfully synthesized as two-phase solid solutions with a two-phase crystal (FCC) structure. The resulting alloy had a crystallite size of 8.4 nm and a residual strain of 1.7%. Elemental mapping image revealed that after 50 hours of mechanical alloying, all elements in the high entropy alloy were dissolved into each other with nearly identical atomic ratios, a finding confirmed by XRD analysis. The solid solution alloys synthesized in this research exhibited an intriguing phase separation phenomenon at the nano scale. The observation of two phases with different lattice constants highlights the versatility of high entropy alloys and their potential for diverse applications.

This study investigated the flowability and compactability of the milled Ti-Cu alloys as a new version of biomedical alloys used for fabrication via Additive Manufacturing. In this study, Ti- 50 at. % Cu powder was first milled for different durations, and the morphology, microhardness, size, flowability, and compactability of the powder were assessed. The results indicated that while flowability increased with prolonged milling time, compressibility decreased owing to a decrease in the plastic deformation capacity. The highest flowability level was obtained when hard TiCu phase was synthesized after 30 hours of milling. Different linear and nonlinear compaction equations were used to investigate the densification response of TiCu powder in a rigid mold during uniaxial compression. Cooper-Eaton nonlinear equation was found to be the best fit compared to the linear equation. The contribution of particle rearrangement to the densification behavior was high, and it increased upon increasing the applied pressure. At pressures below 1200 MPa, the contribution of plastic deformation to the powder densification was negligible.

Copper-based alloys are one of the most popular materials in the power distribution, welding industry, hydraulic equipment, industrial machinery, etc. Among different methods for the fabrication of Cu alloys, mechanical alloying (MA) is the major approach due to the fact that this approach is simple, inexpensive, suitable for mass production, and has a high capacity for homogeneous distribution of the second phase. However, the prediction of the hardness of products is very difficult in MA because of a lot of effective parameters. In this work, we designed a feed-forward back propagation neural network (FFBPNN) to predict the hardness of copper-based nanocomposites. First, some of the most common nanocomposites of copper including Cu-Al, Cu-Al2O3, Cu-Cr, and Cu-Ti were synthesized by mechanical alloying of copper at varying weight percentages (1, 3, and 6). Next, the alloyed powders were compacted by a cold press (12 tons) and subjected to heat treatment at 650˚C. Then, the strength of the alloys was measured by the Vickers microscopy test. Finally, to anticipate the micro-hardness of Cu nanocomposites, the significant variables in the ball milling process including hardness, size, and volume of the reinforcement material, vial speed, the ball-to-powder-weight-ratio (BPR), and milling time; were determined as the inputs, and hardness of nanocomposite was assumed as an output of the artificial neural network (ANN). For training the ANN, many different ANN architectures have been employed and the optimal structure of the model was obtained by regression of 0.9914. The network was designed with two hidden layers. The first and second hidden layer includes 12 and 8 neurons, respectively. The comparison between the predicted results of the network and the experimental values showed that the proposed model with a root mean square error (RMSE) of 3.7 % can predict the micro-hardness of the nanocomposites.

In this research, a high entropy alloy of AlCoCrFeNiMn is made through mechanical alloying and the spark plasma sintering processes. Ball milling was done at different times of 12 h, 36 h, and 48 h in a cup with a diameter of 20 cm. Ball to powder percent weight of 10:1 was selected. X-ray diffraction patterns indicate the formation of solid solution microstructure after 48 h. The crystal size decreases from 23 to 16 nm with increasing milling time. The lattice strain of the structure increments from 0.3 to 0.68% with increasing time up to 48 h. SEM images clearly show the phenomenon of powder agglomeration and the absence of intermetallic compounds or brittle, complex structures. It is observed that with increasing ball-milling time, homogenization of powders increases, and the body-centered cubic phase is formed in the structure. The mechanically alloyed powders were consolidated spark plasma sintered at 700, 900, and 1000 °C. 50 MPa pressure, argon gas as atmosphere, and ten minutes as sintering time were selected as the sintering process parameters. The X-ray diffraction pattern shows that the structure of consolidated high entropy alloy has face-centered cubic and body-centered cubic phases. After sintering by the spark plasma method, the density of powders was measured by Archimedes’ rules, and the value was determined as 99% of theoretical density. The structure was without porosity. The hardness was measured using the microhardness Vickers test. Loading force was 50 g and loading time was seven seconds. The highest hardness was about 649 HV0.05.

In the present study, the effects of boron on the structural and magnetic properties of AlCrFeNiMnSiBx high entropy alloys (HEAs) were investigated. In this regards, different percentages of boron element were added to the based composition and the samples were identified using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. Based on results, the tendency of Si element to formation of silicide phases prevents from the stabilization of single FCC and BCC solid solution phases in AlCrFeNiMnSi alloy. The boron element has significant effects on destabilization of silicide phases and by increasing in the percentage of this element, the simple BCC solid solution phase has been dominate phase. Of course, boron has distractive effects on magnetic properties of prepared alloys and the saturation of magnetization of AlCrFeNiMnSiBx HEAs decrease from 29.8 emu/g to about 6 emu/g by increasing the boron content.

Aluminum-based composites reinforced with ceramic particles have been used for many applications because of their high hardness, good wear resistance, low weight, and low thermal expansion coefficient. The Al-MgO/Mg composite was prepared in the present study. The effects of milling time and amounts of initial Mg and MgO were studied on the properties of the composite. The milled powder mixtures were subsequently analyzed by the XRD and SEM tests. Crystal sizes and internal strains were calculated using XRD data and the Williamson-Hall equa-tion. The hardness of samples was measured by the Vickers method. The results showed that the lattice parameter significantly increased by increasing the amount of Mg. During the milling, the crystallite size, and simultaneously internal strain and hardness increased by increasing amounts of Mg and MgO. The results also showed that the effects of Mg on the composite properties were higher than MgO particles.

The principles and magnetic properties of nanostructured high-entropy alloys (HEAs) processed by mechanical alloying are overviewed. Firstly, the general concepts of HEAs (multi-principal element alloys with ≥5 elements) and phase formation rules are briefly reviewed. Subsequently, the processing of nanocrystalline and amorphous HEAs by mechanical alloying and the effect of high-energy ball milling parameters are summarized. Finally, the magnetic properties of nanostructured HEAs are critically discussed to infer some general rules. In summary, a higher content of ferromagnetic elements (e.g. Fe, Co, and Ni) normally results in a higher saturation magnetization. The as-milled products with solid solution phases show better soft-magnetic properties compared to the fully amorphous phases, and increasing the amount of the amorphous phase decreases the saturation magnetization. The magnetic properties are also influenced by processing (such as sintering) and thermal history through the alteration of phases and crystallite size.

The change in the elastic modulus of mechanically alloyed MA754 Ni-based superalloy as a function of the porosity and fabricating method has been discussed in this study. A mixed powder of a nano-particle strengthened nickel alloy was prepared directly from its alloying elements via mechanical alloying. The mixture then consolidated using two different powder metallurgy methods, pressing was followed by sintering and as was hot extrusion followed by drawing. The powder and solid parts were characterized by XRD, XRF, and microscopic examination. The porosity content and the elastic modulus of the samples were measured via Archimedes, image analysis, tensile, and/or compression tests, respectively. The results indicated that two methods of porosity measurement provided different values for each specimen. In addition, results showed, while processing method has influences on porosity content, it also affects the elastic modulus of the alloy tremendously. Two different values of experimental modulus can be justified by the effect of texture. The different linear and polynomial models are given for different methods of the processing.