Magnesium Matrix Research Articles

Interface design of Ti3C2TX/ZK61 composites by thermal reduction

Ti3C2TX (Mxene) is a new attractive reinforcement in composites due to its two-dimensional structure, excellent mechanical properties and active surface, but in metal matrix composites Ti3C2TX has been neglected for its poor performance. To improve the strengthening ability of Ti3C2TX in magnesium (Mg) matrix composites, the surface functional groups of Ti3C2TX are modified by thermal reduction. After thermal reduction, it is found that the oxygen-containing functional groups combined with the inner C atoms in the Ti3C2TX increase significantly, which reduces the structural stability of Ti3C2TX and promotes the interface reaction between the Ti3C2TX and Mg matrix. The violent interface reaction leads to the partial oxidation of Ti3C2TX sheets and increase of the in-situ synthesized MgO particles, which strengthens the interface bonding. In comparison to the original Ti3C2TX, the thermally reduced Ti3C2TX shows a better performance in improving the mechanical properties. This study provides new insights into the interface design and oxides formation mechanism of advanced Ti3C2TX/Mg matrix composites with enhanced mechanical properties.

Tribological behavior of ZK60 magnesium matrix composite reinforced by hybrid MWCNTs/B4C prepared by stir casting method

In this study, ZK60 alloy matrix composites reinforced by 10 wt% boron carbide (B4C) and various 0–1 wt% multi-walled carbon nanotubes (MWCNTs), and 0.5 wt% MWCNTs and different 5–20 wt% B4C contents were prepared via stir casting method. The wear behavior of the samples was assessed using the pin-on-disk configuration at room temperature under loads of 40 and 80 N, and the sliding speed of 0.5 m/s. The worn surface and tribo-layer generated were investigated using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses. The results demonstrated that at low loading the friction coefficients of samples containing MWCNTs were lower compared to those of the samples with different B4C contents. The wear rates were decreased by increasing the MWCNTs content up to 0.5 wt%, while they were increased by increasing the B4C content to higher levels. The worn surfaces of the samples showed that at 40 N, the abrasion and plastic deformation mechanisms were dominant, while delamination and oxidation wear were dominant at 80 N. All in all, the sample containing 10% B4C and 0.5% MWCNTs showed the highest wear resistance.

Types of Component Interfaces in Metal Matrix Composites on the Example of Magnesium Matrix Composites.

In this paper, a summary of investigations of the microstructure of cast magnesium matrix composites is presented. Analyses of the interfaces between the reinforcing particles and the magnesium alloy matrices were performed. Technically pure magnesium and four various alloys with aluminum and rare earth elements (RE) were chosen as the matrix. The composites were reinforced with SiC and Ti particles, as well as hollow aluminosilicate cenospheres. Microstructure analyses were carried out by light, scanning, and transmission electron microscopy. The composites with the matrix of magnesium and magnesium–aluminum alloys with SiC and Ti particles exhibited coherent interfaces between the components. In the composites based on ternary magnesium alloy with Al and RE with Ti particles, a high-melting Al2RE phase nucleated on the titanium. Different types of interfaces between the components were observed in the composites based on the magnesium–rare earth elements alloy with SiC particles, in which a chemical reaction between the components caused formation of the Re3Si2 phase. Intensive chemical reactions between the components were also observed in the composites with aluminosilicate cenospheres. Additionally, the influence of coatings created on the aluminosilicate cenospheres on the bond with the magnesium matrix was presented. A scheme of the types of interfaces between the components is proposed.

Augmented mechanical properties of magnesium AZ91 reinforced with graphene

Graphene has been impressing us in recent years by boasting some very spectacular things. Its outstanding mechanical properties made the material to be used in composites for amplifying the strength. Mechanical properties usually take precedence for magnesium alloy when it would be used as a structure material. The main focus of this project is to manufacture magnesium reinforced metal matrix composites using graphene nano powder through stir casting to enhance the mechanical properties. The uniform distribution of graphene nano powder and its large specific surface area per volume is embedded in magnesium matrix leads to increase in micro hardness, tensile solidity, fracture exertion of the composite. Compared with standard single crystal magnesium, the Mg AZ91 with 0.3 and 0.7 wt % graphene nano powder composite indicates improvement in mechanical properties. In addition to standard procedures for the tests and dissection of mechanical properties of synthesized composite, de-wintor invertor trinocular metallurgical microscopy, is used to investigate the phase segmentation, grain size and phase contrast. Additionally, Mechanical properties of synthesized composites of two different composition of graphene were compared.

Investigations on compressive strength of titanium diboride and graphite reinforced Magnesium Matrix Composites

Magnesium matrix composites are widely used materials because of its excellent properties and low weight. In this work, the magnesium-based composites have been fabricated using powder metallurgy (PM) route. The compressive strength (CP) of the Mg-1wt.% Gr- 6 wt.% T1B2 composites were studied and reported. The effect of the compaction pressure (P), sintering temperature (T) and sintering time (h) on the compressive strength was analyzed. The increase in compaction pressure increases the mechanical properties of the composites. The optimum level of parameters for the high CS is that, A3B3C3 that is higher Pressure, temperature and time produced the high strength composite. ANOVA showed the compaction pressure is the highly influenced parameter with the F value of 180.85. Sintering time is the least contributing factor for the response for the present study.

Microstructure, Mechanical, and Corrosion Behavior of Al2O3 Reinforced Mg2Zn Matrix Magnesium Composites.

Powder metallurgy (PM) method is one of the most effective methods for the production of composite materials. However, there are obstacles that limit the production of magnesium matrix composites (MgMCs), which are in the category of biodegradable materials, by this method. During the weighing and mixing stages, risky situations can arise, such as the exposure of Mg powders to oxidation. Once this risk is eliminated, new MgMCs can be produced. In this study, a paraffin coating technique was applied to Mg powders and new MgMCs with superior mechanical and corrosion properties were produced using the hot pressing technique. The content of the composites consist of an Mg2Zn matrix alloy and Al2O3 particle reinforcements. After the debinding stage at 300 °C, the sintering process was carried out at 625 °C under 50 MPa pressure for 60 min. Before and after the immersion process in Hank’s solution, the surface morphology of the composite specimens was examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. With the hot pressing technique, composite specimens with a very dense and homogeneous microstructure were obtained. While Al2O3 reinforcement improved the mechanical properties, it was effective in changing the corrosion properties up to a certain extent (2 wt.% Al2O3). The highest tensile strength value of approximately 191 MPa from the specimen with 8 wt.% Al2O3. The lowest weight loss and corrosion rate were obtained from the specimen containing 2 wt.% Al2O3 at approximately 9% and 2.5 mm/year, respectively. While the Mg(OH)2 structure in the microstructure formed a temporary film layer, the apatite structures containing Ca, P, and O exhibited a permanent behavior on the surface, and significantly improved the corrosion resistance.

Influence of high pressure torsion on microstructure evolution and mechanical properties of AZ80/SiC magnesium matrix composites

The effect of applying 1, 5 and 10 turns of high pressure torsion (HPT) as a severe plastic deformation technique on the microstructural evolution, hardness, tensile and shear strength of an as-cast AZ80-SiC magnesium matrix composite is investigated in the present study. The results show that HPT at room temperature refines the microstructure of the as-cast material having an average grain size of 176 ± 58.9 μm to a fine grain structure with average grain sizes of 4.2 ± 4.1 μm and 2.5 ± 2.1 μm in 5 and 10 turns HPT samples, respectively. In addition, ultra-fine grained regions (grain size <1 μm) with volume fractions of about 12, 27 and 31 vol% are obtained in the samples processed by 1, 5 and 10 turns of HPT, respectively. Based on microstructural observations, it is concluded that 5 and 10 turns HPT samples are almost similar in terms of grain size, recrystallized fraction, low-angle grain boundary fraction, and recovered parts. The ultimate tensile and shear (achieved from shear punch tests) strengths of the as-cast sample are improved by applying HPT due to grain size and texture hardening mechanisms. The highest strength values are obtained after performing the first HPT turn due to the more significant effect of texture hardening in comparison to the 5 and 10 turns HPT-processed samples. Similar to the strength results, the hardness of the as-cast material is also enhanced from 66 ± 6 HV to about 123 ± 3 HV through HPT processing.

Study on improving interface bonding performance of magnesium potassium phosphate cement mortar

To enhance the interfacial bonding performance between magnesium potassium phosphate cement (MKPC) repair mortar and matrix concrete, in this study, MKPC modified mortar was used as the repair material to splice long prismatic test pieces. The four-point bending test was used to determine the flexural bearing capacity of the long prism, and the influence of changing the interface conditions and the modifying the MKPC repair mortar on the improvement of the basic performance of the splicing component is investigated.The research results show that, when the matrix concrete section is in a natural state, applying silica-fume modified MKPC interface agents on the interface with a repair thickness of 3 cm can improve the interface bonding performance. Furthermore, the working performance and mechanical properties of the MKPC repair mortar modified using nickel-iron slag and steel fibers have been significantly improved.

Effects of hot pressing temperature and annealing temperature on microstructure and compressive properties of a bulk nanocrystalline AZ61 magnesium alloy contain Ti

Involving rare-earth-free Mg alloys, developing microstructure of nanocrystalline matrix and dispersing stable nano-scale precipitates, being a great challenge, is the key to achieve ultra-high strength. In this work, bulk nanocrystalline magnesium alloy was prepared by mechanical milling and subsequent vacuum hot pressing. The effect of hot pressing temperature on microstructure, densification and mechanical properties was analyzed. After hot pressing at 723 K for 60 min, the powders got densified and the average grain size of magnesium matrix was ~76 nm. Nano-scale Ti3Al precipitates with a particle size of ~10 nm were detected by X-ray diffractometer and high-resolution electron microscope. After that, annealing treatment was carried out at 573 K for various times. Both strength and ductility got improved evidently. After annealing at 573 K for 80 h, the yield strength, compressive strength, fracture strain and hardness were 498 MPa, 553 MPa, 4.9% and 1.44 GPa, respectively. Based on analysis on strengthening mechanisms, the contribution rates owing to grain boundary strengthening effect, Orowan effect and load transfer effect were calculated to be 64%, 33% and 3%. It was certified that nanocrystalline magnesium phase together with nano-scale Ti3Al precipitates play a crucial role in realizing ultra-high strength.

Interfacial microstructure and strengthening mechanisms of Cf/Mg composite with double-layer interface

In order to overcome the interfacial incompatibility of carbon fiber reinforced magnesium matrix (Cf/Mg) composites, a double-layer interface (ZrO2–MgO) is designed in this work. Carbon fiber was modified with ZrO2 coating by sol-gel process. Microstructural examination reveals that MgO layer forms on the surface of ZrO2 coating by ZrO2 reacting with Mg during the composite fabrication. Such double-layer interface could inhibit Al4C3 and hence prevent fiber damage. Meanwhile, the wettability was improved for the reaction between ZrO2 and Mg. Thus the tensile strength of ZrO2-Cf/AZ91D composite was 68.0% higher than that of the unmodified one. Due to the fiber bundle pull-out, debonding and crack deflection, the toughness of Cf/Mg composite with double-layer interface is increased simultaneously.

Microstructure evolution and corrosion resistance improvement of Mg–Gd–Y–Zn–Zr alloys via surface hydrogen treatment

A surface hydrogen treatment is proposed to improve the corrosion resistance of a long-period stacking ordered (LPSO) phase-enhanced Mg–Gd–Y–Zn–Zr alloy. After hydrogen treatment, the block-like LPSO phases are replaced by novel strip-shaped Gd0.5Y0.5H1.96 aggregates in the surface hydrogenated layer with 260 ± 42 μm thickness. The results of immersion tests in a 3.5 % NaCl solution show that hydrogen treatment improves the corrosion resistance of the alloy. As the LPSO phase decomposes, the Zn enriched in the LPSO phase dissolves into a magnesium matrix, which increases the Volta potential of the surface hydrogenated layer.

Influence of micro- and nanoparticles on mechanical properties of magnesium and magnesium alloys

Magnesium and magnesium alloys were reinforced with various micro- and nanoparticles (SiC, Inconel718, AI2O3, ZrC2, BN, graphite) Composites were prepared by squeeze casting and using powder metallurgy followed by hot extrusion. Tensile and compression tests were performed at elevated temperatures up to 300 °C. The influence of micro- and nanoparticles on mechanical characteristics is discussed on the base of physical models. Bonding at the interface between particles and magnesium matrix plays an important role for the resulting composite properties.

Microstructural evolution and interfacial characterization of Al18B4O33w/ GWZ1031K magnesium matrix composite during heat treatment

In this work, we have studied the microstructural and interfacial characteristics of Al18B4O33w reinforced Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy matrix composite under as-cast and heat-treated conditions. Results show that compared with the as-cast state, the interplanar spacing of (0002) and (101¯0) lattice planes of Mg matrix in the composite increases after heat treatment at 500 °C for 6 h, and then decreases with the further extension of heating time to 12 h. In the as-cast composite, two adjacent interface layers are formed between the Mg matrix and whiskers, which results from the interfacial reaction and atomic diffusion. The outer layer near the matrix is serrated with a thickness of about 49 nm, and the inner layer near the whiskers is cotton-like with a thickness of about 45 nm. After heat treatment at 500 °C for 6 h, the initial serrated interface layer gradually dissolves into the matrix due to atomic diffusion and a portion of it migrates to the interface to participate in the interfacial reaction. As a result, only the interface layer close to the whiskers remains, with a slight increase in thickness. When the heating time is increased to 12 h, the interfacial reaction continues and two adjacent interface layers are formed again on the whisker surface, resulting in severe degradation of the whisker eventually. This work offers an insight into the microstructure and interface of Mg-RE alloy matrix composite during heat treatment, and helps to screen suitable heat treatment conditions for the composite.

Preparation process and new progress in carbon fiber reinforced magnesium matrix composites

The carbon fiber reinforced magnesium matrix (Cf/Mg) composites are considered as the most promising structural materials with great potential in both aerospace and automotive applications, which have high specific strength, high specific stiffness, excellent thermal conductivity, great electrical conductivity and good damping properties, as well as close to zero thermal expansion coefficient and good dimensional stability. In the present review, the craft principles and characteristics, as well as the current development status and the key technical problems of powder metallurgy, diffusion bonding, squeeze casting, etc that can be used to prepare Cf/Mg composites are discussed deeply. Then the new progresses made in the preparation of Cf/Mg composites in recent years are hackled. Furthermore, engineering application cases of Cf/Mg composite that have a significant promotion effect and potential application prospects in the fields of national defense and national economy are introduced. Additionally, the facing challenges of Cf/Mg composite are analyzed, and the future development directions are prospected.

Effect of Vanadium Reinforcement on the Microstructure and Mechanical Properties of Magnesium Matrix Composites

In this work, vanadium particles (VP) were utilized as a novel reinforcement of AZ31 magnesium (Mg) alloy. The nanocrystalline (NC) AZ31–VP composites were prepared via mechanical milling (MM) and vacuum hot-press sintering. During the milling process, the presence of VP contributed to the cold welding and fracture mechanism, resulting in the acceleration of the milling process. Additionally, increasing the VP content accelerated the grain refinement of the matrix during the milling process. After milling for 90 h, the average grain size of AZ31-X wt % Vp (X = 5, 7.5, 10) was refined to only about 23 nm, 19 nm and 16 nm, respectively. In the meantime, VP was refined to sub-micron scale and distributed uniformly in the matrix, exhibiting excellent interfacial bonding with the matrix. After the sintering process, the average grain size of AZ31-X wt % VP (X = 5, 7.5, 10) composites still remained at the NC scale, which was mainly caused by the pinning effect of VP. Besides that, the porosity of the sintered composites was no more than 7.8%, indicating a good densification effect. As a result, there was little difference between the theoretical and real density. Compared to as-cast AZ31 Mg alloy, the microhardness of sintered AZ31-X wt % VP (X = 5, 7.5, 10) composites increased by 65%, 87% and 96%, respectively, owing to the strengthening mechanisms of grain refinement strengthening, Orowan strengthening and load-bearing effects.

Influence of GNPs and B4C reinforcements on mechanical, thermal and wear properties of magnesium matrix composite produced by powder metallurgy

In this study, graphene nanoplatelets (GNPs) and boron carbide (B4C) nano reinforcements were incorporated to the pure magnesium (Mg). Powder metallurgy route was used to fabricate composite samples. Microstructures of specimens were examined and tensile, hardness, wear tests were performed to determine the mechanical and tribological performance of produced samples. The results indicate that the hardness was increased especially with the addition of 2% B4C and 0.5% GNPs reinforcements. A general trend was observed for the enhancements of yield and tensile strengths when nano reinforcements were added to the pure magnesium. The composite samples showed better wear resistance than the unreinforced sample. However, thermal conductivity began to decrease with the addition of B4C reinforcements. It is also observed that the porosity level was also higher for the composite samples.

Redox reaction in a Mg/Nb2O5 nanocomposite processed by high-pressure torsion

Severe plastic deformation by high-pressure torsion can induce solid-state reactions, including redox reactions, which can affect the mechanical properties of metal matrix composites and hybrids. The present paper shows evidence of a redox reaction between magnesium and nanostructured niobium pentoxide. These chemical reactions release metallic niobium and magnesium oxide. Accordingly, aglomerations of nanocrystalline magnesium oxide is found in the magnesium matrix and a supersaturated solid solution is formed with niobium. Hardness and indentation creep tests show a minor increase in strength and decrease in strain rate sensitivity in the processed material, compared to data for pure magnesium in the literature.

Development and Parametric Optimisation of Pure Magnesium Matrix Surface Composite by Friction Stir Processing

Friction stir processing (FSP) is an emerging method for improving surface properties of materials by composite fabrication. This study aims at optimizing the major FSP parameters and analysis of their real-time influence on the mechanical performance of a surface composite fabricated with Magnesium (Mg) matrix and Titanium Carbide (TiC) as reinforcement. Effects of different process parameters, tool rotational speed, plunge depth, the linear speed of the tool, cooling condition, and number of FSP passes have been examined. Using L27 array, a total of 27 combinations of these process parameters were analyzed by taking microhardness as an output response to find influential parameters by Taguchi's technique. Maximum micro-hardness was achieved when tool rpm of 600, cooling temperature of -10o C, tool feed of 15 mm/min, plunge depth of 0.35 mm, and 3 passes of FSP tool were chosen with the help of Taguchi's method. Analysis of variance indicated that cooling temperature, the tool feed, and the number of passes of the FSP tool were the most significant parameters.

The effect of addition of hardystonite on the strength, ductility and corrosion resistance of WE43 magnesium alloy

A composite material based on the WE43 magnesium alloy and containing nano-sized hardystonite ceramic particles was processed by means of friction stir processing (FSP). Compressive strength and strain-at-failure of the WE43 alloy increased as a combined result of FSP and nanoparticle reinforcement. The results of potentiondynamic polarization and electrochemical impedance spectroscopy tests indicated that the corrosion mechanism of the nanocomposite is combination of uniform corrosion and localized pitting corrosion which is not different from the base metal. However, the corrosion rate is significantly decreased as a result of reduced localized corrosion of the base metal after FSP and the effect of hardystonite to reduce pitting corrosion. The polarization resistance is increased from 192.48 to 339.61 and 1318.12 Ω/cm2 by applying FSP on WE43 and addition of nano-sized hardystonite particles, respectively. Indeed, the fabricated nanocomposite shows significantly increased corrosion resistance. Enhanced strength, ductility and corrosion resistance were attributed to grain refinement in addition to the fragmentation and redistribution of second-phase particles in the magnesium matrix, occurring during FSP.

Preparation and Thermal Properties of BN and LPSO Hybrid Reinforced Magnesium Matrix Composite

Hexagonal boron nitride (h-BN) is a ceramic material with high thermal conductivity (TC) and low coefficient of thermal expansion (CTE), which can improve multiple thermal properties of metal-matrix composites as a reinforcing particle, but its wettability with metal melt is very poor. In order to enhance the wettability between the h-BN and magnesium alloy melt, the electroless plating was used to coat a thin layer of pure nickel on h-BN particles, which was proved to be effective and efficient in this study. The results showed that by adding Y element to magnesium alloy melt to consume Ni element melted from the nickel-plating layer, the long period stacking ordered (LPSO) structure composed of Mg-Ni-Y was successfully formed, and the magnesium matrix composite reinforced by hybrid h-BN and LPSO structure was obtained. After ultrasonic treatment (UT), the TC of the magnesium composite containing 3 vol% h-BN and 14.16 vol% LPSO is 99.92 W/(m·K), which is a 8.3% enhancement compare to the composite without UT. The average CTE (293-373 K) of the composite is 18.36×10-6 K-1, which is reduced by 29.4% compared with pure magnesium.