Magnesium Chips Research Articles

Solid-state recycling of magnesium and its alloys via plastic deformation: An overview of processing and properties

The increasing demand for primary magnesium production poses significant environmental challenges, aggravated by the limited availability of raw materials, which can hinder supply. Consequently, the recycling of magnesium chips and waste is gaining importance. While conventional remelting techniques are prevalent as they suffer from drawbacks including high energy consumption, material loss, low purity, and inferior mechanical properties. Solid-state recycling (SSR) via plastic deformation processes has been introduced as a promising alternative for producing ultrafine-grained (UFG) magnesium materials with outstanding properties. Despite the absence of any reviews on SSR using plastic deformation methods for magnesium, this paper offers a detailed examination of SSR techniques. The mechanisms of bonding and grain refinement, crucial for determining the final properties of recycled magnesium, are explored. Furthermore, the discussion delves into corrosion, an essential aspect concerning magnesium and its alloys. Ultimately, the impact of various parameters such as process temperature, level of shear strain, chips size, and hydrostatic pressure on the quality of the final sample, to be used as guidance for the production of better-qualified specimens was examined.

Improvement of the Hydrogen Storage Characteristics of MgH2 with Al Nano-Catalyst Produced by the Method of Electric Explosion of Wires.

A new composite with a core-shell structure based on magnesium hydride and finely dispersed aluminum powder with an aluminum oxide shell was mechanically synthesized. We used magnesium chips to produce magnesium hydride and aluminum wire after exploitation to produce nano-sized aluminum powder. The beginning of the hydrogen release from the composite occurred at the temperature of 117 °C. The maximum desorption temperature from the MgH2-EEWAl composite (10 wt.%) was 336 °C, compared to pure magnesium hydride-417 °C. The mass content of hydrogen in the composite was 5.5 wt.%. The positive effect of the aluminum powder produced by the electric explosion of wires method on reducing the activation energy of desorption was demonstrated. The composite's desorption activation energy was found to be 109 ± 1 kJ/mol, while pure magnesium hydride had an activation energy of 161 ± 2 kJ/mol. The results obtained make it possible to expand the possibility of using magnesium and aluminum waste for hydrogen energy.

Effect of CaF2 Additions on the Yield of AZ63 Magnesium Chips during Remelting

Magnesium is one of the metals listed in European Union’s critical raw materials list. Primary production of magnesium is a high energy demanding process which raised the necessity of recycling the magnesium alloys in an efficient way. Remelting those scraps under a salt flux consist of chlorides (NaCl, KCl, and MgCl2) and fluorides (CaF2) are a common process however, different alloys might behave differently when it comes to salt-metal-metal oxide interactions. Furthermore, the condition of the salt flux such as dry-mixed or pre-melted (fused) affects the coagulation and metal yield. This work presents results on the effect of CaF2 concentration and pre-melting the salt flux on metal yield during remelting of chips. A yield up to 75% was observed in the case of remelting of chips under a fused salt flux with 5.5% CaF2 concentration.

Effect of compaction and fluoride content on the remelting efficiency of pure magnesium chips

ABSTRACT Magnesium is widely used in industries, such as automotive, aerospace, and medical fields. The demand on magnesium has been growing, although the production and melt treatment is complex due to strong oxidation tendency. Recycling of magnesium scraps is crucial due to the criticality of magnesium-containing raw materials in Europe as well as increasing environmental concerns. Remelting of magnesium is typically conducted under a salt flux which absorbs the impurities and protects the melt against oxidation. This study investigates the effect of compaction, fused salt flux, and salt composition on remelting behavior of magnesium chips. Metal yield and coagulation efficiency were calculated after remelting, and samples were characterized by using Scanning Electron Microscope and X-ray Diffraction. The liquidus temperature and density of fluxes were analyzed by FactSage software. Remelting of compacted chips under a fused salt flux with 5 wt.% CaF2 showed the highest magnesium recovery with a yield of 97.7%.

Effect of Silicon Addition on Microstructure, Hardness and Young’s Modulus of Injection Molded AZ91D Alloy

Magnesium chips were coated with silicon powder using a binder, and thixomolding was attempted using the silicon-coated chips as the raw material. The microstructures of the products exhibited that all the added silicon was precipitated as Mg2Si particles. No voids were observed at the interfaces between the Mg2Si particles and the matrix. The hardness and Young's modulus of the products increased with the amount of silicon added. The Young's modulus followed the rule of mixtures.

Utilization of machining chips waste for production of functionally gradient magnesium matrix composites

In this study, lightweight functionally gradient materials (FGMs) with graded behavior were produced utilizing AZ91D magnesium chips reinforced with boron carbide particles through a centrifugal casting method. Innovatively, the influence of reuse magnesium chips generated during machining processes on the gradient formation and mechanical characteristics of graded composites was investigated. Also, the effect of strengthening mechanisms on graded composites was deeply explored. The results showed a considerable improvement in particle distribution inside the matrix, owing mostly to a pre-mixing technique for chips and particles before melting during the preparation steps. The study also found that due to the higher particle concentration, the mechanical characteristics of the graded composite were much better in the outer region than in the transition and inner regions. As a result of the microstructure gradient, the tensile strength of the graded composites increased from 164 MPa to 210 MPa (at the outer zone), the compressive strength increased from 312 MPa to 339 MPa (at the outer zone), and the hardness increased from 63.7 HV to 110.8 HV (at the outer zone). Additionally, the findings reveal that the theoretical values are in good agreement with the experimental values of the concentration of B4C particles within the AZ91D matrix alloy. The above research work can provide a new perspective on using magnesium chips as a matrix material reinforced with ceramic particles for fabricating gradient composites, hence promoting potential applications.

Wear characteristics of functionally graded composites synthesized from magnesium chips waste

In this study, an attempt was made to reuse magnesium chips for producing gradient composite reinforced with silicon carbide particles to evaluate wear behavior. The findings revealed a significant improvement in the distribution and gradient of particles within the matrix as a result of the use of magnesium chips, which led to an improvement in wear characteristics. The hardness and wear resistance of the graded composite with chips at the outer zone improved by 23 % and 20 %, respectively, compared to the composite without chips, and by 48 % and 57 %, respectively, compared to the AZ91D alloy. Additionally, wear results suggest that using chip waste to make gradient composites with outstanding surface wear resistance is a sustainable way of reusing magnesium chips.

From waste to high strength alloy – recycling of magnesium chips

Abstract Ultrafine grained magnesium alloy was synthesized via mechanical milling of AZ91 chips. Mechanical property measurement revealed enhanced yield strength of 470 MPa after mechanical milling. The increase in yield strength is associated with reduction in grain size which restricts twining and dislocation gliding. The present investigation demonstrates that magnesium alloys can be cost-effectively recycled through the process of mechanical milling.

Evaluating the morphology and distribution uniformity of AZ91D-SiC composite powder produced from magnesium chips by mechanical milling and alloying method

The AZ91D-SiC composite powder was produced from machining chips using the mechanical milling and alloying processes as an effective recycling method. The mechanical milling and alloying were conducted in a high-energy planetary ball mill. The effects of milling time and ball-to-powder weight ratio (BPR) on the morphology, distribution uniformity, and powder yield were evaluated. In the mechanical milling process, the four stages of chip milling were investigated. The optimum conditions of the milling were equal to milling for 10 h and a BPR of 25:1. The powder yield was at its maximum value and did not change much by changing the milling conditions. In the mechanical alloying, a higher BPR had a more significant effect on the uniform distribution of the particles compared to a higher milling time. The uniformity of the particle distribution is higher for 5 h alloying and a BPR of 20:1. A new peak in the XRD pattern of the composite powder obtained did not appear during the mechanical alloying process. It was observed that the amount of reinforcement phase has little effect on the particle size of the composite powder, while the particle distribution was improved by reducing it up to 40%.

Process Parameter Optimization to Synthesize Magnesium Silicide Magnesium Matrix in-situ Composite

In recent years, the synthesis of magnesium matrix composites via in-situ reaction has gained significant attention. Reinforcing magnesium matrix through in-situ production of magnesium compound has emerged as a promising method of developing magnesium matrix composites with desired properties. Silicon carbide (SiC) can be a potential reinforcement for in-situ reaction with magnesium. The main objective of this experiment was to produce an in-situ magnesium silicide (Mg 2 Si) reinforcement phase to achieve better microstructural and mechanical properties than pure magnesium. For better results, SiC was heat-treated to remove any contaminations on the SiC particles and activate the surface. SiC mixed with pure magnesium chips and magnesium alloy blocks were heated in the furnace in the presence of argon gas to prevent oxidation of the magnesium. The process was carried out at different temperatures and time durations to determine the optimum temperature and time for the successful production of the desired composite. Heating a mixture of SiC, pure Mg chips, and Mg alloys at 9000C for 1 hour produced a composite of Mg/ Mg 2 Si.

Improving the method and equipment of thermo-acidic pulsation treatment

Initially, the method of thermo-acid pulsation was intended for heavily drained wells. But, as practice has shown, it can also be successfully used in the processing of wells of other categories, and depending on the diameter of the production string and the diameter of the reactor (jacket), the acid flow can be changed. A reactor with a diameter of 114 mm is usually used, but for 114 or 127 mm of the production string, a reactor with a diameter of 48 or 88 mm, respectively elongated, can be used to maintain the required capacity in order to accommodate the right amount of magnesium chips. The efficiency of acid treatment operations by pulsing is greater than the efficiency of thermo-acid treatments according to the results of calculations of both the increase in oil production and the duration of the wells at increased production.

THERMO ACID IMPULSING METHOD FOR OIL RECOVERY INCREASING

The injection rate created by the units does not provide uniform heating of the acid solution of thermal acid samples. The first portion of the solution is overheated, and the subsequent ones turn out to be insufficiently heated. Therefore, the efficiency of acid and thermal acid treatments of highly drained wells with low reservoir pressure is rather low. To increase the efficiency, a method of acid and thermal acid impulses was proposed, a methodology for its application was developed, and simple structures for the necessary underground and ground equipment for wells were developed (tip reactors and a universal wellhead). The method of thermal acid pulsation is based on the use of a special tip reactor. The reactor, the main components of which are the valve and the reactor itself, filled with magnesium chips, is lowered into the well on tubing until it stops in the bottom with its perforated nozzle-tip. The volume of solution poured into the tubing during thermal acid treatment by pulsation depends on their length and internal diameter. Usually it is assumed 1.2-2.0 m3. If in a well planned for thermal acid treatment by pulsation, the filter or some part of it turned out to be blocked by a sand plug, then they were preliminarily cleaned with a bailer without opening the sump. Thermal acid (as well as acid) well treatment by impulsing is carried out without the use of a pumping unit, which can significantly reduce costs. Accelerating the movement of the acid solution, heating the entire volume to the desired temperature and creating pressure (due to the weight of the column of solution) increase the depth of penetration and the effectiveness of the effect of acid on the formation. Based on the experiments, the following conclusions were drawn. 1) The process of thermal acid pulsation to achieve uniform heating of the acid solution is controlled by: a) increase in pumping pressure (the pressure is regulated by a column of liquid filled into the pipes); b) reduce the download speed; the speed of passage of the solution from the column of pumping pipes through the reactor with magnesium chips is initially much higher than the speed created by the injection of the acid solution by the unit; then, as the level of acid in the pipes drops, its outflow rate decreases; as a result, uniform heating of the acid solution to the required temperature is achieved. 2) Inhibition of HC1 with formalin and Unicol inhibits the reaction. However, only Unicol is able to stretch the reaction of HCI with magnesium for the required time, during which the entire process of pumping acid through nozzles proceeds. Thus, the most suitable acidic solution for thermal acid pulsation is 15 % HCl, inhibited by Unicol.

Microstructure and tensile properties of magnesium nanocomposites fabricated using magnesium chips and carbon black

In this study, carbon black (0, 0.01, 0.03 and 0.08 wt%) and AZ31 (Mg–3Al–1Zn) magnesium chips were used to fabricate carbon black-reinforced magnesium matrix composites with extrusion or a combination of extrusion and high-ratio differential speed rolling. After hot pressing at 693 K and extrusion at 623 K with an extrusion ratio of 22, the magnesium chips coated with carbon black were soundly bonded into a bulk composite material. The grain sizes of the extruded materials were similar with a size of 48.2–51.5 µm despite the difference in the amount of carbon black. The yield strength and ultimate tensile strength increased from 177 to 191 MPa and from 240 to 265 MPa, respectively, as a result of the addition of 0.01% carbon black; however, a further increase in the strength was marginal with additional carbon black. The same trend was observed in the strain hardening behavior. The tensile elongation increased by to the addition of 0.01% carbon black (from 15.8% to 17.4%) due to the increased work hardening effect, but decreased with additional carbon black due to its agglomeration and poor dispersion at higher concentration. After high-ratio differential speed rolling (HRDSR) on the extruded materials and subsequent annealing, the AZ31 and AZ31 composites had a similar fine grain size of 16.3–17.9 µm. The annealed HRDSR composites showed the best mechanical properties at a higher content of carbon black (0.03%) compared to that (0.01%) for the extruded composites. This resulted from the enhanced dispersion effect of the carbon black due to the high shear flow induced during the HRDSR process. The extruded composites exhibited the three distinct hardening stages (stage II, stage III and stage IV), while the annealed HRDSR composites mainly displayed the stage III hardening. The addition of carbon black increased the strain hardening rate at all the strain hardening stages in both of the extruded and annealed HRDSR materials. At the initial hardening stage, the strain hardening rates of the extruded composites were higher than those of the annealed HRDSR composites, but this became reversed at the later stage of hardening. Possible explanations for this observation were discussed. The strength analysis suggests that dislocation-carbon black interaction by Orowan strengthening and dislocation generation due to a difference in thermal expansion between matrix and carbon black are the major strengthening mechanisms.

Structure and properties of magnesium chip blanks

This article describes the practical application of hot extrusion for compaction of magnesium shavings in semi-finished products and the study of the influence of process parameters on the mechanical properties of the obtained MA5 (AZ80) magnesium alloy bars. Production of bars was carried out at different heating temperatures and plastic deformation degree to find technology provide the best combination of tensile and compressive properties. The resulting bars are somewhat higher in strength characteristics than the strength of deformed cast bars made from MA5 alloy, however, they are significantly lower in ductility.

Magnesium alloy-silicon carbide composite fabrication using chips waste

Interest in Mg-based composites has grown with their potential use as engineering materials due to having a high strength-to-weight ratio, wear resistance, and creep behavior. While magnesium chips are typically considered as waste on production shop floors, there can be a promising way to fabricate Mg-based composites with carefully distributed reinforcements. This research is concerned with the reuse of AZ91 magnesium-alloy chips to fabricate Mg-based composites. The fabrication process requires to collect and clean magnesium chips and then mix them with SiC particles as reinforcements. Finally, this composition is melted and stirred by a stir casting method to fabricate the AZ91/SiC composites. The results clearly show that not only magnesium chips waste can be reused in a sustainable way, but also that they improve the reinforcement distribution substantially, leading to enhanced mechanical properties so that the composite yield strength increases by 62.7% when adding 5% SiC particles, volume percentage. Moreover, the composites with 5% reinforcements, demonstrate a hardness increase of about 46%.

Predicting microstructure evolution for friction stir extrusion using a cellular automaton method

Friction stir extrusion (FSE) offers a solid-phase synthesis method consolidating discrete metal chips or powders into bulk material form. In this study, an FSE machine tool with a central hole is driven at high rotational speed into the metal chips contained in a chamber, mechanically stirs and consolidates the work material. The softened consolidated material is extruded through the center hole of the tool, during which material microstructure undergoes significant transformation due to the intensive thermomechanical loadings. Discontinuous dynamic recrystallization is found to have played as the primary mechanism for microstructure evolution of pure magnesium chips during the FSE process. The complex thermomechanical loading during the process drives the microstructure evolution. A three-dimensional finite element process model is developed using commercial software DEFORM 11.0 to predict the thermal field, mechanical deformation and material flow during the FSE process. Using the simulated thermomechanical loadings as input, a cellular automaton model is developed to simulate the dynamic evolution of the material grain microstructure. The predicted grain size is in good agreement with the experimentally measured grain size. This numerical study provides a powerful analysis tool to simulate the microstructure transformation for friction stir-based processes.

JUSITFICATION OF DRY CHEMICAL POWDERS TESTING PROCEDURE

The analysis of the problem of extinguishing fires of magnesium and its alloys is carried out. The urgency of studying the problem is confirmed by the fact that during the extinguishing of class D fires there are factors that can complicate the quenching process. Often, these metals actively react with water, which leads to an even greater spread of the fire and even an explosion. Therefore, special fire extinguishers, which have passed the proper test, are more effective in locating the fire and prevent the burning of the powder to form the "tongues" of the flame. In Ukraine, there is no method for testing the effectiveness of fire extinguishants of special purpose for the extinguishing of class D fires. The normative documents have been analyzed, which specify the procedures for testing extinguishing fire-extinguishing special-purpose fire extinguishing class D. Specifically: the methods are described in the international standard ISO 7165: 2017 «Fire fighting – Portable fire extinguishers – Performance and construction» and GOST 53280.5-2009 Fire fighting systems automatic. Extinguishing agents.
 Both methods have a number of shortcomings that need to be addressed when creating a Ukrainian fire test method for extinguishing fire extinguishing class D, namely: the dimensions of the metal frame made of sheet steel with a side (500 ± 10) mm, height (150 ± 5) mm for testing with magnesium chips are small; Not specified quantity of gasoline necessary for the rise of magnesium; The gas or oxygen torch used to dissolve magnesium does not provide full-value combustion throughout the area, but only creates separate cells of ignition.
 A draft methodology has been developed that determines the fire-extinguishing efficiency of powdered powders used in Ukraine. The required amount of fuel for burning magnesium and its alloys is determined. It was ascertained that for the firing of magnesium chips it is necessary to use at least 127 grams of gasoline of the mark A 92.
 Key words: test method, fire extinguishers of special purpose, extinguishing of fires of magnesium alloys

E(μ-NBbp)]2 (E = P, As) - group 15 biradicals synthesized from acyclic precursors.

The synthesis of Bbp stabilized biradicals of the type [E(μ-NBbp)]2 (E = P, As) (Bbp = 2,6-bis[bis(trimethylsilyl)methyl]phenyl) was investigated. Contrary to the established synthetic protocol for terphenyl substituted biradicals [E(μ-NTer)]2 by reduction of [ClE(μ-NTer)]2, the analogous Bbp substituted precursor [ClE(μ-NBbp)]2 could only be obtained in low yields. For this reason, a new synthesis had to be found to generate [E(μ-NBbp)]2. Instead of using cyclic [ClE(μ-NBbp)]2 we prepared the acyclic Bbp-N(ECl2)2 species starting from Bbp-NH2 and ECl3 and studied the reduction with magnesium chips, which led to the formation of the desired biradicals [E(μ-NBbp)]2. All species along the reaction path were fully characterized.

Semi-solid state mixing of Mg-Zn-RE alloys—microstructure and mechanical properties

Mixing two kinds of alloys in semi-solid temperature range allows obtaining new one with superior properties. Critical challenges facing the process are determination of mutual interaction of slurries, selection of appropriate temperature process, and designing optimal heat treatment conditions. Two kinds of magnesium chips E21 and WE43B containing different compositions of rare earth elements and similar solidus-liquidus temperature ranges were mixed in equal weight/volume ratio using thixoforming technology. Granules were hot compressed at 400 °C/5 min/200 MPa and thixoformed at 625 °C, which corresponded to about 25% of the liquid phase. Structure of E21WE43B thixo-cast consisted of globular grains of average size 59 μm. They were surrounded by the eutectic mixture coming from both alloys. X-ray analysis confirmed the presence of magnesium solid solution as well as intermetallics Mg3Nd and Mg24Y5 phases located in interglobular areas. T6 heat treatment consisted of solutioning at 525 °C for 8 h and aging at 190 °C for 120 h leading to increase of hardness from 57 to 85 HV. High resolution transmission electron microscopy studies allowed identifying β’ planar precipitates, approximately 8 x 2 nm in size and coherent with matrix, homogeneously distributed in the α(Mg) in the T6 treated sample. They were responsible for strengthening of E21WE43B thixo-cast leading in consequence to yield strength 190 MPa at compression strength 475 MPa at plasticity 13.1%.

Semi-Solid Remelting of Magnesium Chips

Compact and loose magnesium chips were processed by means of remelting. The remelting was successfully performed using the new method of semi-solid melting, without the addition of flux, at temperatures between 580°C and 600°C. In this temperature range, the exothermic reaction between magnesium and the oxygen present in the surrounding atmosphere is avoided; in addition, the oxygen layer of the chips is stripped off by the particles of the semi-solid melt. Results show that more than 95% of the magnesium chips can be recovered as metal. Experiments were performed on different scales to obtain production parameters for the recycling process. Larger particle sizes of magnesium chips can be remelted faster than smaller ones. The ability to remelt at temperatures in the semi-solid region of alloys demonstrates the possibility of recovering virtually all of the metal from the chips.