Magnesium Matrix Research Articles

LCF and HCF of Short Carbon Fibers Reinforced AE42 Mg Alloy.

Lightweight magnesium alloys and magnesium matrix composites have recently become more widespread for high-efficiency applications, including automobile, aerospace, defense, and electronic industries. Cast magnesium and magnesium matrix composites are applied in many highly moving and rotating parts, these parts can suffer from fatigue loading and are consequently subjected to fatigue failure. Reversed tensile-compression low-cycle fatigue (LCF) and high-cycle fatigue (HCF) of short fibers reinforced and unreinforced AE42 have been studied at temperatures of 20 °C, 150 °C, and 250 °C. To select suitable fatigue testing conditions, tensile tests have been carried out on AE42 and the composite material AE42-C at temperatures of up to 300 °C. The Wohler curves σa (NF) have shown that the fatigue strength of the reinforced AE42-C in the HCF range was double that of unreinforced AE42. In the LCF range at certain strain amplitudes, the fatigue life of the composite materials is much less than that of the matrix alloys, this is due to the low ductility of this composite material. Furthermore, a slight temperature influence up to 150 °C has been established on the fatigue behavior of the AE42-C. The fatigue life curves Δεtotal (NF) were described using the Basquin and Manson-Coffin approaches. Fracture surface investigations showed a mixed mode of serration fatigue pattern on the matrix and carbon fibers fracturing and debonding from the matrix alloy.

Microstructure and mechanical properties of AZ91D/Si3N4 composites using squeeze casting method

The material utilized in the aerospace and automotive industries must be capable of withstanding significant loads while maintaining a minimal structural weight. In pursuit of novel lightweight materials for industrial applications, magnesium is quickly displacing aluminum-based alloys. In this study, a magnesium (AZ91D) matrix composite reinforced with nano ceramic silicon nitride (Si3N4) of varying weight proportion (2 wt%,4 wt% and 6 wt%) was synthesized using vacuum stir casting method. The microstructural study of uniform distribution of nano Si3N4 particles are revealed by an optical microscope. Micro hardness (26.8%) and tensile strength (32.12%) increased with increasing weight percentages of Si3N4 particles in a magnesium alloy matrix, whereas percentage of elongation decreased (6.52%). With an increase in weight% of Si3N4 particles in the magnesium matrix, the porosity of composites decreased (1.02%) and density of composites increased to minimum (0.06%). The corrosion characteristics were examined using B117 salt spray test. The test illustrated that an increase in percentage of reinforcement accelerates corrosion resistance (17.52%) due to induced segregation, dislocation, and micro crevice formation. Based on the results, it can be concluded that the manufactured composite can be employed in a variety of industrial applications where lighter structural materials are required.

Damping performance of SiC nanoparticles reinforced magnesium matrix composites processed by cyclic extrusion and compression

This work dealt with the damping performance and its underlying mechanism in SiC nanoparticles reinforced AZ91D composite (SiCnp/AZ91D) processed by cyclic extrusion and compression (CEC). It was found that the CEC process significantly affects the damping performance of the composite due to alterations in the density of dislocations and grain boundaries in the matrix alloy. Although there would be dynamic precipitation of the Mg17Al12 phase during processing which increases the phase interface and limits the mobility of dislocations and grain boundaries. The results also showed that the damping capacity of 1%SiCnp/AZ91D composite continuously decreases with adding CEC pass number and it consistently increases with rising the applied temperature. Considering the first derivative of the tanδ–T curve, the dominant damping mechanism based on test temperature can be divided into three regions. These three regions are as follows (i) dislocation vibration of the weak pinning points (≤Tcr), (ii) dislocation vibration of the strong pinning points (Tcr∼TV), and (iii) grain boundary/interface sliding (≥TV).

Influence of titanium diboride reinforced magnesium composites using squeeze casting method

In the current investigation, squeeze casting was used to create titanium diboride-reinforced magnesium composites in a varying weight proportion (2 wt%,4 wt% and 6 wt%). SEM was used for the morphological analysis, and ASTM standards were followed in creating the performance metrics. The distribution of the ceramic reinforcing particles inside the magnesium matrix was observed to be uniform. Due to a powerful interfacial response between the intermixtures, the hardness (24.52%), tensile strength (18.52%), and wear resistance (28.52%) of synthetic magnesium composites dramatically enhanced. The corrosion resistance of magnesium composites was assessed using a salt spray test, and it was found that by reducing the size of the -phase Mg17Al12, the corrosion resistance greatly increased (36.52%) when compared to that of the cast alloy.

Microstructure evolution, mechanical properties and corrosion resistance of biological particles reinforced AZ31 magnesium matrix composites fabricated by high rotating speed friction stir processing

Friction stir processing (FSP) with high rotating speed were successfully employed to fabricate a novel AZ31 magnesium matrix composites (MMCs) reinforced by biological particles of nano-hydroxyapatite (nHA) and nano-magnesium oxide (nMgO). The influences of tool rotating speed on the microstructure evolution, mechanical properties and corrosion resistance of MMCs were investigated. In results, high rotating speed not only significantly refined the grains of the stirred zone (SZ) in MMCs due to sufficient dynamic recrystallization (DRX), but also reduced the size of β-Al12Mg17 precipitates and caused them homogeneously distributed. With the increase of rotating speed, the bio-reinforced particles exhibited a larger range with uniform distribution in SZ of MMCs, and the microhardness, tensile strength and corrosion resistance of MMCs were also improved. At high rotating speed of 6000 rpm, MMCs had a maximum tensile strength of 235.5 MPa with cleavage fracture of ductile-brittle mixed mode. Meanwhile, the self-corrosion potential of MMCs (−1.408 V) was 10.4% higher than the matrix (−1.571 V), while the self-corrosion current density (9.328 × 10−5 A/cm2) was 96.4% much lower than the matrix (2.607 × 10−3 A/cm2), indicating that the corrosion resistance of MMCs was significantly enhanced than matrix. And the corrosion morphologies of MMCs presented mud cracking due to relatively uniform corrosion.

Atomic Ordering and Interfacial Interaction at Liquid-Mg/SiC{0 0 0 1} Interfaces: An Ab Initio Molecular Dynamics Study

We present the results of ab initio molecular dynamics investigations on the atomic ordering and chemical interactions at the interfaces between liquid Mg and SiC{0 0 0 1} interfaces. The simulations reveal distinct borders between the SiC substrates and liquid Mg. The liquid Mg atoms adjacent to the substrates are bonded to the outmost C/Si atoms and are positively charged. The terminating Mg layers contain a variety of atomic vacancies, being topologically rough. The liquid Mg atoms adjacent to the substrates display unusual prenucleation phenomenon with strong layering but weak in-plane ordering. The obtained information here is helpful to get insight into the formation and interfacial interactions in the SiC joined nano-sized magnesium matrix composites and the role of SiC particles as potential nucleation sites during solidification, and further helps understand interfacial interactions at the grain boundaries in ceramic/metal composites and welded parts, etc. in general.

Fabrication of biocompatible Mg-based nano composites by using friction stir alloying

In the present research, friction stir processing technique was performed to ameliorate the MB3 magnesium alloy surface through grain reduction and integration of bio-ceramic Nano particles. The friction stir processing was carried out at 1140 rpm and 100 mm/min by using a tapered tool pin profile. The incorporated bio-ceramic Nano particles are hydroxyapatite, tri-calcium phosphate and aluminum oxide. The results revealed that all processed samples have finer grain structure than that of the magnesium matrix, which caused an increase in the average microhardness values in the stirred zone. Furthermore, the tensile properties revealed an enhancement in elongation of all processed samples with deterioration in both ultimate tensile and yield strength values. On the other hand, the electrochemical impedance spectroscopy results exposed larger capacitive radius of all samples compared with the base material which reflects the improvement in the corrosion resistance. Accordingly, the potentiodynamic polarization results of all manufactured samples showed better bio-corrosion resistance in simulated body fluid than that of the base material, where the best corrosion resistance was achieved by magnesium-hydroxyapatite composite. The results obtained from the immersion test results manifested lower corrosion rates of all processed samples; where the friction stir processed and magnesium-hydroxyapatite samples corrosion rates were about 66% and 31% respectively of the base material. The corroded surfaces of all samples contained filiform and pitting corrosions after 72 h of immersion in simulated body fluid.

Improving the ductility and toughness of nano-TiC/AZ61 composite by optimizing bimodal grain microstructure via extrusion speed

In this study, the nano-TiC/AZ61 composites with different heterogeneous bimodal grain (HBG) structures and uniform structure are obtained by regulating the extrusion speed. The effect of HBG structure on the mechanical properties of the composites is investigated. The increasing ductility and toughening mechanism of HBG magnesium matrix composites are carefully discussed. When the extrusion speed increases from 0.75 mm/s to 2.5 mm/s or 3.5 mm/s, the microstructure transforms from uniform to HBG structure. Compared with Uniform-0.75 mm/s composite, Heterogeneous-3.5 mm/s composite achieves a 116.7% increase in ductility in the plastic deformation stage and almost no reduction in ultimate tensile strength. This is mainly because the lower plastic deformation inhomogeneity and higher strain hardening due to hetero-deformation induced (HDI) hardening. Moreover, Heterogeneous-3.5 mm/s composite achieves a 108.3% increase in toughness compared with the Uniform-0.75 mm/s composite. It is mainly because coarse grain (CG) bands can capture and blunt cracks, thereby increasing the energy dissipation for crack propagation and improving toughness. In addition, the CG band of the Heterogeneous-3.5 mm/s composite with larger grain size and lower dislocation density is more conducive to obtaining higher strain hardening and superior blunting crack capability. Thus, the increased ductility and toughness of the Heterogeneous-3.5 mm/s composite is more significant than that Heterogeneous-2.5 mm/s composite.

Fabrication, Microstructure and Mechanical Properties of in situ GNPs Reinforced Magnesium Matrix Composites

Fabrication, Microstructure and Mechanical Properties of in situ GNPs Reinforced Magnesium Matrix Composites

Effect of SiCp on the microstructure and tensile properties of the Mg–3Y magnesium alloy

Magnesium matrix composite is another competitive light metal matrix composite following aluminum matrix composite, with excellent application prospects in the aerospace and automotive fields. In this paper, the Mg - 3Y – xSiCp (x = 0, 1, 3, 5 wt%) composites are fabricated by stir casting with ultrasonic vibration followed by extrusion. The microstructure of the alloys is investigated by means of scanning electron microscopy (SEM) imaging and electron backscatter diffraction (EBSD) techniques. The results reveal that the composites have a finer grain size due to the particle promoted nucleation (PSN) mechanism. When the SiCp content is 3 wt%, the grain size is the smallest (0.76 μm), and the refinement rate is about 16.7%. Moreover, the addition of SiCp can inhibit the transformation from low-angle grain boundaries (LABGs) to high-angle grain boundaries (HABGs), thus hindering the dynamic recrystallization (DRX) of the alloy, which decreases from 55.7% to 15.4%. The reduction in the proportion of recrystallized grains in the composite leads to increasing the maximum intensity of the texture. In addition, the tensile properties and the strengthening mechanism of the alloys are investigated. The results show that the composites have higher ultimate tensile strength (UTS) and yield strength (YS) due to the combination of grain refinement and dislocation strengthening. When the SiCp content is 5 wt%, the UTS (291 MPa) and YS (283 MPa) increase by ∼12.7% and ∼17.1%, respectively, over the matrix alloy. However, the addition of SiCp causes more oxides and holes in the alloys, which leads to a fracture strain (δ) decrease in the composites.

Investigating the influence of NaCl concentration on the electrochemical corrosion behavior of metal oxide reinforced magnesium matrix composites

Investigating the influence of NaCl concentration on the electrochemical corrosion behavior of metal oxide reinforced magnesium matrix composites

Synthesis and characterisation of magnesium-based nano-composite – A review

In the recent decades, the need for light weight and high specific strength has been the hot issue in many engineering field and also biomedical sectors. Magnesium and its alloys are considered as a light weight material due to its low density that can replaced aluminium, steel and titanium. However, at room temperature, magnesium alloys have closely packed hexagonal crystalline structure with restricted number of freely actuated independent slip system that suffers from poor ductility by 5%–8% approximately. Therefore, Magnesium alloy creates some challenges for the application of many industrial sectors. One technique that can improve strength properties without significant reduction of ductility is to add reinforcing nanoparticles within the magnesium matrix and making them an attractive choice for light weight structural application. The performance of magnesium matrix-based composites to a current stage depends upon the proper selection of composition and combination of reinforcement particles within the matrix materials. In light of the writing overview, the inclusion of reinforcing particles, for example, TiC, SiC, B4C, Al2O3, hybrid reinforcement and so forth is the way to betterment of the tribological behaviour and the mechanical properties of magnesium matrix composites. This paper presents a brief overview based on the available literature survey that the effect of different geometries and percentage contribution of reinforcement particles in various processing techniques on the mechanical properties, microstructure and wear behaviour of magnesium-based metal composites.

Effect of tool profile on wear and mechanical behaviors of CeO2 and ZrO2-reinforced hybrid magnesium matrix composite developed via FSP technique

A dual/double eccentric-pin tool was used for the reinforcement of the CeO2 and ZrO2 particles into a 5 mm thick AZ31B magnesium alloy through the application of the friction stir processing route to develop a composite with improved properties. A comparison of the developed composite's properties with that of the single pin-processed counterpart was carried out to ascertain the improvement recorded. The structure, hardness, shear punching strength, tensile, corrosion, and wear properties of the hybrid AZ31B/(ZrO2 + CeO2)p composite were investigated. The findings show that the dual/double eccentric pin tool widened the stir zone at the shoulder area, eliminated flow-related voids, and improved the flow of material and the particle distributions within the composite. The extra pin-induced plastic shearing/straining and dynamic recrystallization of the tool meaningfully refined the grain structure (5.6–3.35 μm) and the particle size (6.4–4.8 μm) of the composite while aiding even dislocation spread across the stir zone. In relation to the singular probe tool, the dual/double eccentric-pin tool also enhanced the hardness (102–141 HV), the shear punching strength (148–219 MPa), the tensile strength (175–225 MPa), the wear properties (coefficient of friction, rate, and loss), and the corrosion behavior of the hybrid AZ31B/(ZrO2 + CeO2)p composite due to the uniform and fine particle dispersion-strengthening and the elimination of stress raiser. The dual/double eccentric pin tool is thus recommended as a better tool for improving the performances of Mg-based composites.

Direct conversion of CO2 to graphene via vapor–liquid reaction for magnesium matrix composites with structural and functional properties

Converting CO 2 to valuable materials is attractive in environmental protection and resource utilization. In this study, a vapor–liquid interface reaction system for mass production of high-quality graphene is reported. The graphene obtained has high crystallinity and few defects during the reaction of CO 2 and Mg melt. The growth mechanism of graphene is demonstrated in vapor–liquid interface area by combining the CO 2 bubbles as a soft template to guide growth with the confinement effect of dense MgO nanoparticles. The quality of the graphene is verified by epoxy composites with high electromagnetic shielding effectiveness. Additionally, the V–L reaction method ingeniously solves the dispersion of graphene in metal, providing a preparation strategy of Mg matrix composites with structure and function integration.

FRICTION STIR PROCESSING AND CLADDING: AN INNOVATIVE SURFACE ENGINEERING TECHNIQUE TO TAILOR MAGNESIUM-BASED ALLOYS FOR BIOMEDICAL IMPLANTS

Regarding biocompatibility, toxicity, degradation, and interaction with body cells, the materials as well as fabrication process used for biomedical implants are crucial aspects. Implant materials are chosen in accordance with these criteria. The most recent medical implants are made of materials, i.e. stainless steel, Co–Cr and titanium alloys. Although these conventional implant materials generate hazardous ions and have a stress shield effect in many medical implant situations, the implants must be removed from the body within a certain period of time. In order to avoid the need for implant removal, researchers advise using magnesium metal matrix composite (Mg-MMC) as an implant material. Magnesium composites are subjected to a variety of engineering processes to enhance their mechanical and biocompatibility properties, including the addition of reinforcement, treating the surface, and changing the synthesis processes. The solid-state “friction stir process” is discussed for the fabrication of magnesium metal matrix composites. The influence of various reinforcing materials’, process parameters and reinforcing strategies are summarized in this review study with respect to the microstructure, mechanical characteristics, and corrosion behavior of biodegradable magnesium matrix composites. This study provides an importance of magnesium-based composites for biomedical implants and the degradation behavior reduces the secondary activities to remove implants.

Development of ceramic/Mg lamellar composites with superior high-temperature mechanical properties

The probe into development of lightweight magnesium matrix composites (MMCs) able to operate at high temperatures exceeding 300 °C is of vital importance in producing structural components in aerospace and automotive industries. In this work, a range of new lamellar ceramic/Mg composites were prepared via infiltrating molten Mg alloy into porous ceramic scaffolds. Due to the introduction of the specific microture, the composites showed excellent mechanical properties at temperatures above 300 °C. The high temperature mechanical properties of the new MMC are proportional to the ceramic content, enhancing the flexural strength from 197 MPa to 287 MPa at 300 °C, demonstrating a 45.69% increase. Additionally, as the test temperature increased, the flexural strength of the optimal composites rose firstly and then decreased, in which showed its maximum (407 MPa) at 200 °C. It delivered the flexural strength of 287 MPa at 300 °C, which was basically identical to that at 25 °C. It is worth mentioning that it has almost never been achieved in previous studies. The results of this research provide new design ideas and lay foundation for further investigation of the magnesium matrix composites capable of working at temperatures above 300 °C.

Examination of fuel elements irradiated in the reactor of the World’s First NPP after long-term storage

Examinations of fuel elements with two different fuel compositions, U-Mo+Mg and UO2+Mg, irradiated in the AM reactor after their long-term storage do not reveal any visible defects on the surface of their outer claddings. However, in the fuel elements with U-Mo fuel, an increase in the diameter of the outer cladding is observed. This is most noticeable in the upper part of the fuel element. Storage of the fuel elements with UO2 fuel for 15–22 years does not lead to a change in their diameter within the measurement accuracy. At the same time, metallographic studies have shown that on the external surface of the outer cladding and the internal surface of the inner cladding of the fuel elements with U-Mo+Mg and UO2+Mg fuel compositions, after long-term storage, defects are observed in the form of intergranular and irregular frontal corrosion, pits and pittings up to 20 µm deep. No interaction is found at the points of contact between the fuel claddings and the fuel composition of the layers. There is no noticeable decrease in the thickness of the outer and inner claddings of the fuel elements after long-term storage, nor does the thickness of the claddings at the locations of defects go beyond its minimum initial value, taking into account the technological tolerance for variations in thickness. It is noteworthy, however, that cracks are found in both types of fuel elements both in the fuel grains and in the magnesium matrix. As a result of long-term storage of the fuel elements with U-Mo fuel for 45–55 years, the mechanical properties of their outer claddings gradually degrade, due to which the plasticity of the cladding is significantly reduced.

Effect of Nano-Ti Particles on Microstructure and Mechanical Properties of Mg-3Al-1Zn Matrix Composites

In this paper, a new nanoscale metal Ti particle-reinforced Mg-3Al-1Zn matrix composite was successfully designed and prepared, which is mainly characterized by the fact that in addition to the "light" advantages of magnesium matrix composite, it also realizes bidirectional improvement of strength and ductility of the composite, and can be used as an alternative material for military light vehicle armor and individual armor. The SEM test shows that the nano-Ti particles are uniformly distributed at the grain boundary under the extruded state, which nails the grain boundary, inhibits the grain growth, and significantly refines the grain. XRD tests show that the addition of nano-Ti particles increases the crystallinity of the composite, which is consistent with the SEM test results. In addition, the EBSD test shows that the weakening of the texture of Ti/Mg-3Al-1Zn matrix composites and the increase in the starting probability of slip system are the main reasons for the improvement in ductility. Mechanical tests show that the yield strength, tensile strength, and elongation of the 0.5 wt% Ti/Mg-3Al-1Zn matrix composites exceed the peak values of ASTM B107/B107M-13 by 38.6%, 26.7%, and 20%, respectively.

Utilization of Silicon Enriched Natural Halloysite Nano Tube: Mechanical, Tribological, and Corrosion Behaviour in Magnesium Matrix Composites

Utilization of Silicon Enriched Natural Halloysite Nano Tube: Mechanical, Tribological, and Corrosion Behaviour in Magnesium Matrix Composites

Microstructure and Mechanical Properties of Magnesium Matrix Composites Reinforced by In Situ Reduced Graphene Oxide.

Due to their excellent mechanical properties and large specific surface area, graphene and its derivatives are widely used in metal matrix composites as reinforcements. In this study, the thermal reduction behavior of large-size graphene oxide are investigated systematically, and reduced graphene oxide (RGO) with few residual oxygen groups and good structural integrity is obtained. ZK61 matrix composites with varying content of in situ RGO are fabricated using the semi-powder metallurgy method. The results reveal that the addition of RGO can cause the refinement of the grains and the second phase, which is attributed to the uniform distribution of the RGO throughout the matrix. The formation of nano-MgO particles is beneficial in increasing the interfacial bonding strength between the RGO and the matrix, resulting in simultaneous increments in yield strength and elongation in the RGO/ZK61 composites. The composite containing 0.6 wt.% RGO shows a superior mechanical property, including microhardness of 79.9 HV, yield strength of 203 MPa and excellent elongation of 17.5%, with increases of 20.9%, 8.6% and 7.4%, respectively, when compared with the ZK61 alloy. Quantitative analysis indicates that the main strengthening mechanisms of RGO-reinforced magnesium matrix composites are load transfer strengthening and grain refinement strengthening.