Magnesium Alloy Chips Research Articles

The production of $B_{4}C$ reinforced metal matrix composite from waste $AZ91$ magnesium alloy using the ball milling method

In this study, the Mg/$B_4$C composite reinforced with boron carbide particles was produced by mechanical milling method using waste AZ91 magnesium alloy chips. The mechanical and tribological properties of the produced composites were investigated through hardness and wear tests. A mixture of AZ91 magnesium alloy chips, aluminum, and $B_4$C powders was milled at a rotation speed of 300 rpm with a ball-to-powder ratio of 20:1 for 3 hours. The milled powders were first cold pressed and then sintered at 550 °C for 3 hours. In density measurement, it was observed that the sample reinforced with B4C exhibited an increase in density. In X-ray diffraction analysis, peaks corresponding to Mg, $Mg_{17}Al_{12}$, and MgO were detected, while the $B_4$C phase could not be identified. On the other hand, $B_4$C particles in the microstructure were revealed in the energy dispersive X-ray spectroscopy analysis. Scanning electron microscope images revealed that the Mg/$B_4$C composite had lower porosity, consistent with density measurements. It was found that the hardness and wear resistance of the Mg/B4C composite were higher than those of the Mg alloy, which can be attributed to the presence of homogenously distributed hard B4C particles within the microstructure.

Solid-State Synthesis of SiC Particle-Reinforced AZ91D Composites: Microstructure and Reinforcement Mechanisms

Safe and efficient recycling of industrially generated machined chips is a high-priority technological issue. In this study, the effect of SiC particles (SiCp) on the microstructure and mechanical properties of SiCp/AZ91D composites is systematically analyzed, and the reinforcement mechanism of SiCp on composites is investigated. Different contents of SiCp/AZ91D composites are fabricated by solid-state synthesis. The results show that the incorporation of SiCp refined the grains of SiCp/AZ91D composites, which is related to the uniform distribution of SiCp at the grain boundaries. The strong bonding of SiCp with the AZ91D matrix inhibited the generation and extension of cracks, which led to the simultaneous increase in the yield strength (YS) and elongation (EL) of the SiCp/AZ91D composites. The mechanical properties of the 3 wt.% SiCp/AZ91D composites are the most superior, with an average grain size, Vickers hardness, ultimate tensile strength (UTS), YS, and EL of 6.69 ± 4.48 μm, 89.5 ± 2.5 HV, 341 ± 11 MPa, 172 ± 8 MPa, and 4.43 ± 0.18%, respectively. The reinforcement mechanisms of SiCp/AZ91D composites are mainly grain refinement and dislocation strengthening. Solid-state synthesis is an effective method for recycling magnesium alloy chips.

Production of hydrogen using magnesium alloy chips generated by machining

Production of hydrogen using magnesium alloy chips generated by machining

Assessment of tribocorrosion properties of friction extruded wires fabricated from recycled magnesium alloy chips

This work examines the tribological characteristics and microstructural alterations of an alloy of recycled wire exposed to friction extrusion (FE). According to microstructural examination, the FE method causes dynamic recrystallization, which produces fine grains and fractured precipitates. Initial contact with the tool triggers the friction extrusion mechanism, which causes homogenous deformation and strain-induced recrystallization. In contrast to the base metal's 100 µm grain size, the recycled wire's grain size lowered to 18 µm. The FE recycled wire has a higher hardness than the base alloy, according to the Hall-Petch relationship. Wet sliding tribological tests show reduced friction coefficients as a result of lubrication; the FE recycled wire shows more resilience to wear and tribocorrosion. In contrast, FE-recycled wire exhibits plastic deformation and increased tribocorrosion resistance. Dry and wet average friction coefficients varied between 0.2 and 0.14, less than those of the base metal, 0.3 and 0.25. Surface inspection of worn samples reveals considerable deformation, delamination, and severe material loss in the base alloy. The recycled wire reflects 20 µm, as opposed to the base metal, 80 µm, indicating that this tendency continues to the wear track depths.

Influences of Carbon Addition on Mechanical Properties and Hydrogen Evolution of Thixomolded AM60B and AZ91D Magnesium Alloys

In this study, the effects of carbon nanoparticles fixed to the surfaces of AM60B and AZ91D magnesium alloy chips on the mechanical properties were examined. The manufacture of magnesium–carbon alloy is not easy because carbon does not possess the property of wettability for magnesium. However, magnesium alloy chips fixed to carbon nanoparticles enable magnesium–carbon alloys to be produced by the thixomolding process. Mechanical properties such as the tensile and fatigue strengths were improved by only 0.1 mass% of the carbon addition because of the decrease in the void and the refinement of crystal grains. In addition, the AZ91D magnesium alloy was proven to be more effective than the AM60B magnesium alloy for the decrease in the void and the refinement of crystal grains by the carbon addition. The aluminum content of the AZ91D magnesium alloy is higher than that of the AM60B alloy. It seems that the void formation is based on the hydrogen by the reaction between aluminum in the magnesium alloy and water. Therefore, the effect of carbon addition on the mechanical properties was dependent on the aluminum content in the magnesium alloys.

Thermotechnical properties of the fire-extinguishing powder for extinguishing materials based on magnesium alloy chips

The article addresses the relevant issue of determining the thermotechnical characteristics of the fire-extinguishing powder for thermal insulation of the fire center of materials based on magnesium alloy chips to prevent fire development and propagation and its effective extinguishing. To solve this problem, laboratory and field experimental studies of the heat-insulating ability of the fire-extinguishing powder of combined effect were conducted. As a result, we obtained the data on the temperature in the center of the fire of materials based on magnesium alloy chips and outside during their suppressing by the fire-extinguishing powder with a combined effect. In this case, the temperature of the non-heated side of the fire-extinguishing powder layer does not exceed 170 °C at the average temperature of the fire center of 740 °C, which indicates high insulation capacity of the powder and, consequently, its high fire-fighting efficiency in extinguishing the fires of materials based on magnesium alloy chips. The obtained temperature data were used to determine the thermophysical parameters of the layer of the fire-fighting powder using the created mathematical model of the heat transfer process in the powder layer at the heat insulation of the fire center. To create a mathematical model of the heat transfer process, the main provisions during consecutive consideration of several experimental situations were stated. The first experimental situation meets the conditions of the stationary thermal process, and other experimental situations meet the conditions of the non-stationary thermal process. These experimental situations were created with the help of changing the thickness of the fire-fighting powder layer at different parameters of its feeding to the fire center. The mathematical model of the process is based on the use of the differential equation of heat transfer at its approximation by the method of finite differences. At the same time, it is believed that the heat transfer conditions at the boundary between the non-heated side of the insulating layer of the fire-extinguishing powder and the environment in each experimental situation are the same. Using the created model, the coefficient of heat transfer between the non-heated side of the insulating layer of the fire-extinguishing powder and the environment was determined. It amounted to 395.7 W(m 2 ×°С). The dependence of the effective thermal conductivity coefficient on the thickness of the insulating layer was explored. It was shown that this dependence can be approximated by linear dependence l(d)=–0.016+93.907×d (d is the thickness of the layer of the fire-extinguishing powder in meters). After conducting the necessary calculations, we obtained the value of the required thickness of the layer of fire-extinguishing powder d=45.2 mm

COMBINED EXTINGUISHING OF CLASS D, CLASS A AND CLASS B FIRES

The scope of magnesium and aluminium and their alloys in industry, construction and life are expanding over time. As a rule, there are no clean fires of class D, which include combustion of magnesium, aluminium and their alloys. The problem is that the temperature of combustion of magnesium and its alloys can rise above 2800 Celsius degree. Magnesium burns even in the atmosphere of nitrogen and carbon dioxide and such fire is very difficult to extinguish. When water contacts the magnesium or other light metals, the area of fire expands.
 The main purpose of this work is to study the combined extinguishing of light metals fires, Class A fires and class B fires with a special dry chemical powder and high resistance foaming agent.
 The problem of extinguishing fires at objects with the using of light metals (magnesium, aluminium) and their alloys has been explored. Class D fires usually lead to class A and class B fires. They occur at high temperatures, and may cause explosions. Scenarios for the development of fires can be as follows: burning of light metals or solid combustible materials ad initium and light metal fire that requires combined extinguishing methods afterwards. Dry chemical powder formulation for extinguishing class A, B, D and and electrical installations under voltage, which includes: sodium chloride, blast furnace slag, ammophos, aerosol has been developed. Testing of this powder has been carried out in the laboratory using chips of magnesium and aluminium alloys. The combustion area in all experiments has been equal to 2.85 × 10-2 sq. m. The quality of the powder has been evaluated by the intensity of the D class fire and the extinguishing time of the B class fier. Dry chemical powder KM-2 has been tested for extinguishing fires 21B, 1A. and for magnesium alloy chips fires. Combined extinguishing tests were conducted on class D, class A and class B fires in field conditions. Method of combined extinguishing with the dry chemical powder followed by covering the entire burning area with high-expansion foam has been proposed (the fire with total area of 2.5 square meters has been extinguished for 45 s). Extinguishing methods have been tested on model fires. Safety measures for light metal extinguishing have been developed.
 Conclusions: formulation for universal KM 2 dry chemical powder for extinguishing class D, A, B fires, which consists of sodium chloride, ammophos, slag, aerosil, has been developed. Successful extinguishing of class D and B fires has been carried out succesfully; technology of combined fire fighting D and A has been substantiated.

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%.

Fabrication of AZ91D/SiCp composites by mechanical milling of magnesium alloy chips and spark plasma sintering in a semi-solid regime

ABSTRACTIn the present study, the capability of spark plasma sintering (SPS) in a semi-solid regime to produce AZ91D/SiCp composites, prepared by mechanical milling (MM), was investigated. An SPS process was used to densify AZ91D/SiCp composite powders by heating them to a semi-solid temperature of 497°C or 516°C, at a heating rate, holding time and pressure of 50 °C/min, 1 min and 40 MPa, respectively. In preparing the requisite powders, MM was used as an effective recycling method to prevent excessive consumption of energy and raw materials while converting magnesium alloy chips into powder in a planetary ball mill. The simultaneous effects of milling parameters (time and ball-to-powder weight ratio (BPRs)) on the MM powder were investigated by FESEM and PSA. Mechanical alloying (MA) of the milled powder with 40 wt% −2 µm SiC and characterization of the obtained powder by OM and PSA were also carried out. The phase compositions of the powder and sintered samples were analyzed by XRD. The microstructure, density, hardness and compressive strength of the sintered samples were also studied. The results show that composites with few porosities and good mechanical properties were prepared by SPS in a semi-solid regime.

Study on hydrolysis property of Mg-8Li alloy for hydrogen production

Vacuum induction melting technology was used to prepare Mg-8Li alloy. Magnesium and lithium alloy chips were reacted with aqueous solution. The hydrogen production rate and hydrogen production rate of the alloy were tested and characterized by drainage method. The effect of NH4Cl solution with different concentration and temperature on hydrogen production rate and reaction degree of Mg-8Li based alloy was investigated. The results showed that with the increase of NH4Cl concentration and hydrogen production, NH4+, Cl−, and H+ could promote the hydrolysis reaction. Hydrogen production volume at 25 °C and 45 °C range increases with temperature decrease, high hydrogen content increases with the temperature when it is higher than 65 °C.

The Status of Magnesium Injection Molding in China

Thixomolding, or magnesium injection molding as it is more generally known, is an established semi-solid casting process for producing thin-walled near net shape components from magnesium alloys. Magnesium injection molding produces components using a machine similar to a plastic injection molder, where magnesium-alloy chips are feed into the back end, and a rotating screw feeds the chips forward as they are heated to the semi-solid temperature range. The semi-solid alloy collects in a nozzle at the front of the screw, where it is then injected into a re-usable steel die. This paper will initially describe the commercial status of magnesium injection molding in China, and will review several types of components being produced commercially. Comparisons to conventional hot chamber magnesium die casting will be made, and a new magnesium injection molding machine design that incorporates an intensifier will be introduced. In addition, new technology trends utilizing the magnesium injection molding process will be described. One such application involves the magnesium injection molding of Mg-Li alloys. Lithium has the lowest density of all metals, and so the addition of lithium further reduces the density of the magnesium.

Effect of Chip Size on Semi-Solid Microstructure of AZ91D Magnesium Alloy Prepared by CRP Process

In this paper, chip recycled pressing process (CRP for short), a new method for recycling magnesium alloy chips, was put forward to prepare semi-solid billet. AZ91D magnesium alloy chips of different sizes were respectively recycled to prepare semi-solid billet by CRP process. Effect of chip size on compactness, microstructure and oxidation of CRP billet were investigated. And then CRP billet were heated to semi-solid state and its semi-solid microstructures were studied. The results showed that with the increase of chip thickness, grain refinement effect weakened, deformation uniformity aggravated and oxygen content of CRP billet decreased. Under the same CRP process conditions, the relative densities of four kind of CRP billet were 98.27%, 98.13%, 98.05% and 97.92%, respectively. Meanwhile, there was no significant difference in compactness and microstructure between them. Normally, oxygen content was not more than 1.8% and uniformly dispersed in CRP billet. Hence, the influence of size and deformation inhomogeneity of chip on compactness and microstructure of CRP billet were eliminated via CRP process. In CRP billet, microstructure and strain were uniform and this inherited during semi-solid isothermal treatment.

Investigation of ignition temperature, time to ignition and chip morphology after the high-speed dry milling of magnesium alloys

Purpose The purpose of this paper is to determine time-to-ignition of magnesium alloy chips and the ignition-preceding stages as well as to examine chip morphology. The tests were conducted according to the following pattern: directly after a milling operation, after ignition using a special test stand located outside the machine tool and after intensive oxidation which prevented ignition. Design/methodology/approach Milling is a machining process widely used in the manufacturing of various parts that are applied, e.g. in the aircraft industry. Milling is used for both roughing and finishing machining. In the dry machining of magnesium alloys, spontaneous ignition can occur; therefore, the analysis of chip temperature in the cutting area is of great significance. Additionally, time-to-ignition and chip morphology are crucial when considering the safety of magnesium alloy machining processes. Findings The experimental results demonstrate the effect of parameters of the milling process on time-to-ignition of chips made of magnesium alloys AZ31 and AZ91HP. The experiments also involved examining the morphology of a selection of chips produced at the maximum cutting velocity vc and feed per tooth fz. In addition, we analysed the morphology of both ignition products and chips subjected to high temperature where ignition did not occur. Practical Implications Based on the time-to-ignition and chip morphology results, it is possible to indicate both safety levels in machining and the efficient range of parameters in the milling of aircraft parts made of magnesium alloys. Originality/value The paper presents a new approach to assessing safety in milling operations. The results of the tests of chip flammability (time-to-ignition) which were run at a special test stand placed outside the machine tool enabled determination of both safety and efficiency range of the milling process.

11105 AZ31マグネシウム合金切削屑を用いた摩擦固化成形体の機械的性質に及ぼす予熱過程の影響

11105 AZ31マグネシウム合金切削屑を用いた摩擦固化成形体の機械的性質に及ぼす予熱過程の影響

Morphology of oxide and interface structure in AZ31B magnesium alloy prepared by solid state recycling

Ultrathin AZ31B magnesium alloy chips were recycled by solid state recycling process at different extrusion ratios. The morphology and distribution of the oxide in recycled magnesium alloy were characterised, and the interface structure between the oxide and magnesium alloy matrix was investigated by means of high resolution transmission electron microscopy. The results indicate that the oxide film introduced from the surface of the chip was broken up in the process of extrusion. MgO shows a nanoscale spherical particle and homogeneously distributes in some tiny areas in the magnesium alloy matrix. In the investigated extrusion ratio range, the diameter of the MgO particle differs little. However, the oxide film was not broken up completely in the recycled alloy with low extrusion ratio. The oxide particle exhibits good bonding with the magnesium matrix. The dispersion strengthening of MgO particle will contribute to the higher strength of recycled magnesium alloy, whereas the good bonding of MgO and magnesium matrix is the prerequisite.

Influence of Heat Treatment on Microstrudture and Mechanical Properties of AZ31B Magnesium Alloy Prepared by Solid-State Recycling

This work is to study the influence of heat treatment on microstrudture and mechanical properties of AZ31B magnesium alloy prepared by solid -state recycling. AZ31B magnesium alloy chips were recycled by hot extruding. Three different heat treatments were conducted for recycled alloy. Mechanical properties and microstructure of the recycled specimen and heat treated specimen were investigated. 300°C×2h annealing specimen exhibits finer grain due to static recrystallization, and microstructure of 400°C×2h annealing specimen becomes more coarse. 300°C×2h annealing treatment improves obviously strength and ductility of recycled alloy. Ultimate tensile strength of alloy decreases and elongation to failure increases after 400°C×2h annealing. Grain size, dislocation density and bonding of chips have an effect on the elongation of recycled materials. 190°C×8h ageing has no influence on microstructure and mechanical properties of recycled alloy.

Microstructure evolution of hot pressed AZ91D alloy chips reheated to semi-solid state

AZ91D magnesium alloy chips, which were directly collected on the spot of machining process, were recycled to prepare billet via hot pressing for semi-solid processing. The semi-solid microstructure evolution of the billet during reheating was investigated. The results indicate that there are three stages during reheating to semi-solid state: the dissolution of Mg17Al12 and diffusion of Al into α-Mg matrix, the melting of the region with high content of solute and formation of isolated solid particles, and spheroidization and growth of solid particles. Meanwhile, a number of entrapped liquid droplets form within solid particles. In addition, the number and size of entrapped liquid droplets rely on the holding time in the semi-solid temperature range. With increasing isothermal holding time, the solid fraction remains unchanged when the solid-liquid system reaches the dynamic equilibrium at last, while the solid particles become more globular and the average size of solid particles increases owing to the decreasing of interfacial energy and the effect of interfacial tension.

Solid-state recycling of AZ91D magnesium alloy chips

A method for recycling AZ91D magnesium alloy chips by solid-state recycling was studied. The experiments were carried out adopting the cold-press pressure and hot extrusion. The results indicate that recycled specimens of AZ91D magnesium alloy present better mechanical properties and consist of fine grains due to dynamic recrystallization. The mechanisms of dynamic recrystallization depend on plastic deformation process and change with the deformation temperature. At 300-350 °C, the deformation mechanisms are associated with the operation of basal slip and twinning, and the “necklace” structures are formed. At 350-400 °C, the cross slip results in the formation of new grains and grain refinement. At above 400 °C, the dynamic recrystallization mechanisms are controlled by dislocation climb, and recrystallized grains are homogeneous. The tensile strength of recycled specimens increases with the increase of the strain rate. When the strain rate is overhigh, the cracks and fractures in the surface appear and affect the tensile strength of recycled specimens.

Effect of Cutting Parameters on Ignition of AM50A Mg Alloy during Face Milling

The ignition of magnesium alloy chips is an important problem during dry machining. In this paper, the influence of cutting speed, feed rate, and depth of cut on ignition of AM50A magnesium alloy during high-speed face milling was investigated. It was found that ignition could easily be caused under some cutting speed and feed rate when the depth of cut was fixed and ignition was rarely observed when the depth of cut was 80 µm. Moreover, the relationship between morphology of chip and frequency of ignition was explored. We found that intertwined chips easily produced ring of fire.

Microstructure of AZ91D magnesium alloy semi-solid billets prepared by SIMA method from chips

AZ91D magnesium alloy chips were adopted to prepare semi-solid billets. The chips were subjected to a series of isothermal treatments for various holding times at 783-843 K after being compressed into billet at 523 K. The semi-solid microstructure of AZ91D magnesium alloy containing spherical solid particles was studied. The effects of reheating temperature and holding time on microstructures were investigated. And the semi-solid forming mechanism was discussed. The result shows that semi-solid billets with highly spheroidal and homogeneous grains can be prepared from chips by strain induced melt activation(SIMA) method. Meanwhile, it is found that increasing the heating temperature can accelerate the spheroidizing process and reduce the solid volume fraction. With the increase of the holding time, the solid particles become more globular, the grains grow slowly and the solid volume fraction slightly changes. At the same time, owing to the decrease of interfacial energy, the intragranular liquid phases form by the diffusion of solute atoms, the grain boundaries melt and grains separate from each other during the isothermal treatment. The grains gradually spheroidize and begin to merge with a further increase of the holding time. It is considered that the semi-solid forming process includes three stages: the recrystallization and the growth of grain stage, the semi-solid microstructure forming stage controlled by the diffusion of solute, and the spheroidization of solid particle stage controlled by the liquid-solid interface tension.