Additive manufacturing of magnesium matrix composites: Comprehensive review of recent progress and research perspectives

The magnesium matrix composites(MMCs) formed by introducing reinforcements to magnesium alloys overcome the limitations of the mechanical properties to a certain extent, presenting unique and excellent properties that any component does not have, such as high specific stiffness and specific strength, good dimensional stability, outstanding shock absorption performance, excellent electromagnetic shielding and hydrogen storage characteristics, etc. As an emerging manufacturing technology, additive manufacturing(AM) is based on the design of threedimensional(3D) data model to obtain 3D objects through layer-by-layer processing, which possesses the advantages of short manufacturing cycle, high material utilization rate, high degree of design freedom, excellent mechanical properties and the ability to fabricate complex structural components. Combining the high stiffness and high strength properties of MMCs and the technical advantages of AM forming complex structural parts with high performance, the prepared AM MMCs have huge potential advantages and broad application prospects in new high-tech industries such as automobile, aerospace, consumer electronics and biomedicine, etc. This paper reviews the research progress in the field of AM MMCs, mainly introduces the main AM technologies, including selective laser melting(SLM), electron beam selective melting(EBSM), laser engineered net shaping(LENS) and wire and arc additive manufacturing(WAAM). The formation mechanism and control methods of the typical defects including balling effect, porosity, poor fusion, loss of alloy elements and cracks produced during AM are discussed. The main challenges of AM MMCs are proposed from the aspects of composition design and the preparation of powder raw material. The relationship between the microstructure and mechanical properties, corrosion performance and biocompatibility of AM MMCs are elaborated in detail. The application potential of AM MMCs in various fields at present and in the future is introduced. Finally, the development direction and urgent problems to be solved in the AM MMCs are prospected.

Microstructures and mechanical properties of titanium-reinforced magnesium matrix composites: Review and perspective

Currently, many gratifying signs of progress have been made in magnesium(Mg) matrix composites(MMCs) by virtue of their high mechanical properties both at room and elevated temperatures. Although the commonly used reinforcements in MMCs are ceramic particles,they often provide improved yield and ultimate stresses by a significant loss in ductility. Therefore, hard metallic phases were introduced as alternative candidates for the manufacturing of MMCs, especially titanium(Ti). It has a high melting point, high Young’s modulus, high plasticity, low level of mutual solubility with Mg matrix, and closer thermal expansion coefficient to that of Mg metal than that of ceramic particles. It is highly preferable to provide both high ultimate stress and ductility in Mg matrix. However, many critical challenges for the fabrication of Ti-reinforced MMCs remain, such as Ti’s homogeneity, low recovery rate, and the optimization of interfacial bonding strength between Mg and Ti, etc. Meanwhile, different fabrication methods have various effects on the microstructures, mechanical properties, and the interfacial strength of Ti-reinforced MMCs. Hence, this review placed emphasis on the microstructural characteristics and mechanical properties of Ti-reinforced MMCs fabricated by different techniques. The influencing factors that govern the strengthening mechanisms were systematically compared and discussed. Future research trends, key issues, and prospects were also proposed to develop Ti-reinforced MMCs.

Microstructure and Mechanical Behavior of Squeeze Cast SiC_w/AZ91 Magnesium Matrix Composites

The interfacial microstructure and tensile properties of the squeeze cast SiCw/AZ91 Mg composites were characterized. There exist uniform, line and discrete MgO particles at the interface between SiC whisker and magnesium in the composites using acid aluminum phosphate binder. The interfacial reaction products MgO are beneficial to interfacial bonding between SiCw and the Mg matrix. resulting in an improvement of the mechanical properties of the composite.

Microstructure,mechanical properties and wear resistance of Ti particles reinforced AZ31 magnesium matrix composites

The compromise between strength and plasticity has greatly limited the potential application of particles reinforced magnesium matrix composites(MMCs).In this work,the Ti particles reinforced AZ31 magnesium(Mg)matrix composites achieved simultaneous improvement in strength,elongation and wear resistance.The Ti particles reinforced AZ31 composites were fabricated by ultrasonic-assisted stir casting with hot extrusion.The results showed that a strong interfacial bonding was obtained at Ti/Mg interface because of the formation of semicoherent orientation relationship of Ti Al/Mg,Ti Al/Al_(2)Ti and Al_(2)Ti/Mg interfaces.The as-extruded 6 wt.%Ti/AZ31 composite presented the best compressive mechanical properties and wear resistance with ultimate tensile strength,elongation and wear rate of 327 MPa,20.4%and 9.026×10^(-3)mm^(3)/m,obviously higher than those of AZ31 alloys.The enhanced mechanical properties were attributed to the grain refinement and strong interfacial bonding.The improved wear resistance was closely related to the increased hardness of composites and the formation of protective oxidation films.

Processing,microstructure and mechanical properties of bimodal size SiCp reinforced AZ31B magnesium matrix composites

The bimodal size SiC particulates(SiCp)reinforced magnesium matrix composites with different ratios of micron SiCp and nano SiCp(M-SiCp:N-SiCp=14.5:0.5,14:1,and 13.5:1.5)were prepared by semisolid stirring assisted ultrasonic vibration method.The AZ31B alloy and all as-cast SiCp/AZ31B composites were extruded at 350℃ with the ratio of 12:1.Microstructural characterization of the extruded M14+N1(M-SiCp:N-SiCp=14:1)composite revealed the uniform distribution of bimodal size SiCp and significant grain refinement.Optical Microscopy(OM)observation showed that,compared with the M14.5+N0.5(M-SiCp:N-SiCp=14.5:0.5)composite,there are more recrystallized grains in M14+N1(M-SiCp:N-SiCp=14:1)and M13.5+N1.5(M-SiCp:N-SiCp=13.5:1.5)composites,but in comparison to the M13.5+N1.5 composite,the average grain size of the M14+N1 composite is slightly decreased.The evaluation of mechanical properties indicated that the yield strength and ultimate tensile strength of the M14+N1 composite were obviously increased compared with other composites.

Influence of processing route on microstructure and wear resistance of fly ash reinforced AZ31 magnesium matrix composites

Utilizing fly ash(FA)as reinforcement for magnesium matrix composites(MMCs)brings down the production cost and the land pollution.Magnesium alloy AZ31 was reinforced with FA particles(10 vol.%)successfully by two different processing methods namely conventional stir casting and friction stir processing(FSP).The microstructural features were observed using optical microscope,scanning electron microscope and electron backscatter diffraction.The sliding wear behavior was tested using a pin-on-disc wear apparatus.The stir cast composite showed inhomogeneous particle dispersion and coarse grain structure.Some of the FA particles decomposed and reacted with the matrix alloy to produce undesirable compounds.Conversely,FSP composite showed superior particle dispersion and fine,equiaxed grains by dynamic recrystallization.FA particles encountered disintegration but there was no interfacial reaction.FSP composite demonstrated higher strengthening and wear resistance to that of stir cast composite.The morphology of the worn surface and the wear debris were studied in detail.

Effect of Ti Particles on the Microstructure and Mechanical Properties of AZ91 Magnesium Matrix Composites

Spherical micro-Ti particle(TiP)-reinforced AZ91 magnesium alloy composites were fabricated by semi-solid stirring assisted ultrasonic vibration,which were then subjected to hot extrusion.The microstructure results showed that the addition of Ti particles refined the grain size and decreased the texture intensity of the as-extruded AZ91 alloy.An Al3Ti phase with a thickness of 100 nm formed at the Ti/Mg interface,which had a non-coherent relationship with the magnesium matrix.The as-extruded 1 vol.%TiP/AZ91 composite exhibited the best comprehensive mechanical properties,with yield strength,ultimate tensile strength,and elongation at break of 366 MPa,456 MPa,and 14.6%,respectively,which were significantly higher than those of the AZ91 alloy.Therefore,the addition of Ti particles can improve the strength and ductility of the AZ91 alloy,demonstrating the value of magnesium matrix composites for commercial applications.

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

Graphene reinforced magnesium matrix composites have wide applications in automotive,electronics,aerospace and military fields due to the fascinating mechanical properties.However,it is difficult to realize the high strength and ductility simultaneously.In this work,the in situ liquid-state method was utilized to prepare GNPs/Mg6Zn composites via CO_(2)/Mg chemical reaction.Tensile strength of the GNPs/Mg6Zn composites was improved with increasing content of the GNPs.Meantime,the composites also exhibit a notable plastic deformation stage,and especially the ductility of 0.12 GNPs/Mg6Zn composites reaches 27.6%.Therefore,this novel preparation method has great potential application for fabricating Mg matrix composites with high strength and high ductility.

Machine Learning-Based Research on Tensile Strength of SiC-Reinforced Magnesium Matrix Composites via Stir Casting

SiC is the most common reinforcement in magnesium matrix composites,and the tensile strength of SiC-reinforced magnesium matrix composites is closely related to the distribution of SiC.Achieving a uniform distribution of SiC requires fine control over the parameters of SiC and the processing and preparation process.However,due to the numerous adjustable parameters,using traditional experimental methods requires a considerable amount of experimentation to obtain a uniformly distributed composite material.Therefore,this study adopts a machine learning approach to explore the tensile strength of SiC-reinforced magnesium matrix composites in the mechanical stirring casting process.By analyzing the influence of SiC parameters and processing parameters on composite material performance,we have established an effective predictive model.Furthermore,six different machine learning regression models have been developed to predict the tensile strength of SiC-reinforced magnesium matrix composites.Through validation and comparison,our models demonstrate good accuracy and reliability in predicting the tensile strength of the composite material.The research findings indicate that hot extrusion treatment,SiC content,and stirring time have a significant impact on the tensile strength.

Corrosion Behavior of Graphene Nanosheets Reinforced Magnesium Matrix Composites in Simulated Body Fluids

Magnesium(Mg)alloy is considered as a promising biodegradable implant material but restricted to rapid degradation.Here,the new strategies based on thixomolding process had been explored to utilize the outstanding anti-permeability of graphene nanosheets(GNPs)while inhibit its galvanic corrosion with the matrix,so as to improve the corrosion resistance of composites.The agglomerate of GNPs with 0.9 wt%content is the main reason for the deterioration of corrosion performance due to the formation of micro-galvanic corrosion.The grain refinement of composites with 0.6 wt%content had positive effects on the better corrosion resistance.After process adjusting,the unique distributions of GNPs along grain boundaries play a vital role in improving the corrosion resistance.It can be ascribed to the following mechanisms:(I)The barriers can be established between the Mg matrix and corrosive medium,hence blocking the charge transfer at the interface;(II)The GNPs can effectively promote apatite deposition on the Mg matrix,leading to form dense apatite layers and prevent the further invasion of SBF;(III)The GNPs acting as reinforcements exists in the corrosion layer and apatite layer,impede the apatite layer falling off from the Mg matrix.These findings broaden the horizon for biomedical applications in Mg matrix composites to realize desired performances.

Processing,Microstructures,and Mechanical Properties of Magnesium Matrix Composites:A Review

In the last two decades, light-weight magnesium matrix composites have been the hot issue of material field due to their excellent mechanical and physical properties, e.g., high-specific strength and modulus, good wear resistance, and damping capacity. As compared with aluminum matrix composites, magnesium matrix composites have merit in their specific weight and have wide applications in aerospace and aeronautical fields. Generally, the processing techniques for magnesium matrix composites can be categorized as conventional and special processing routes. In recent years, as a special processing route, metal melt infiltration into porous ceramic preform featured by its low cost and availability of high-volume fraction of reinforced ceramics have been receiving much attention. Thus, in this review, one emphasis was put on the description of this processing technique in association with the means to obtain good wettability, the prerequisite for this kind of processing method. Based on the recognized fact that there exist clean interface and bonding ability between ceramics and matrix metal, in-situ reaction synthesis is usually utilized to fabricate magnesium matrix composites. Therefore, the interfacial feature was also reviewed for the in-situ reaction synthesis. Characterizations of microstructures and various mechanical-physical properties were finally summarized for magnesium matrix composites including tensile response, wear resistance, creep behavior, and damping capacity.

Preparation and theoretic study of semi-solid Al_2Y/AZ91 magnesium matrix composites slurry by ultrasonic vibration

Abstract： Semi-solid A12Y/AZ91 magnesium matrix composites slurry was prepared by ultrasonic vibration, effect of ultrasonic vi bration temperature and time on microstructure of semi-solid slurry was investigated. The results showed that with the ultrasonic vibration temperature decreasing the solid volume fraction of semi-solid slurry increased. The best ultrasonic vibration temperature was 600 ℃. With the increase of ultrasonic vibration time, the average grain diameter of primary a-Mg particles decreased firstly, then increased, the average shape factor increased gradually and decreased slightly after 90 s, and a few rosette dendrites were observed after 120 s. The best semi-solid slurry with average grain diameter of 75 μm and shape factor of 0.7 were gained after the melt was treated by ultrasonic vibration for about 60 s at near liquidus temperature （600 ℃）. At last, the microstructure evolution mechanism of semi-solid magnesium matrix composites slurry was analyzed by the theories of thermodynamics and kinetics.

Effect of Graphene Nanoplate and Silicon Carbide Nanoparticle Reinforcement on Mechanical and Tribological Properties of Spark Plasma Sintered Magnesium Matrix Composites

Processing of magnesium （Mg） matrix composites reinforced with low reinforcement content （up to 4-5 vol.%） of graphene nanoplates （GNPs） and silicon carbide （SIC） nanoparticles using bait milling and spark plasma sintering （SPS） is reported. Near full densification was observed for all the composite compositions at the sintering temperature of 450 ~C （soaking time of 5 min and applied pressure of 50 MPa）. Detailed analysis of the microstructure and mechanical and tribological （under dry sliding contact with alumina counter-face） properties with reinforcement content in Mg-GNP and Mg-SiC is presented. Mg-GNP and Mg-SiC composites reinforced with about 2 vol.% of reinforcement content exhibited significant improvement in microhardness and wear resistance as compared with Mg compacts.

Tailoring the texture and mechanical properties of 3%Y_(2)O_(3)p/ZGK200 composites fabricated by unidirectional and cross rolling followed by annealing

3%Y_(2)O_(3)p/ZGK200 composites were subjected to unidirectional rolling(UR)and cross rolling(CR)at 400℃and 350℃followed by annealing at 300℃for 1 h.The microstructure,texture and mechanical properties of rolled and annealed composites were systematically studied.The rolled composites exhibited a heterogeneous microstructure,consisting of deformed grains elongated along rolling direction(RD)and Y_(2)O_(3)particles bands distributed along RD.After annealing,static recrystallization(SRX)occurred and most deformed grains transformed into equiaxed grains.A non-basal texture with two strong T-texture components was obtained after UR while a non-basal elliptical/circle texture with circle multi-peaks was obtained after CR,indicating that rolling path had great influences on texture of the composites.After annealing process,R-texture component disappeared or weakened,as results,a non-basal texture with double peaks tilting from normal direction(ND)to transverse direction(TD)and a more random non-basal texture with circle multi-peaks were obtained for UR and CR composites,respectively.The yield strength of rolled composites after UR showed obvious anisotropy along RD and TD while a low anisotropic yield strength was obtained after CR.Some Y_(2)O_(3)particles broke during rolling.The fracture of the composites was attributed to the existence of Y_(2)O_(3)clusters and interfacial debonding between particles and matrix during tension,as a result,the ductility was not as superior as matrix alloy.

Microstructure and microwave absorption properties of MWCNTs reinforced magnesium matrix composites fabriccated by FSP

Multiwall carbon nanotubes(MWCNTs) reinforced magnesium matrix(MWCNTs/Mg) composites were successfully fabricated by friction stir processing(FSP). Microstructure and microwave-absorption properties of WCNTs/Mg composites are studied. The results show that with increasing the MWCNTs content to 7.1% in volume fraction,the agglomeration of MWCNTs is found in the WCNTs/Mg composites. The addition of MWCNTs has little effect on microwave-absorption properties. With increasing the frequency from 2 GHz to 18 GHz,the microwave absorption of the composites decreases. Compared with the absorption loss of the MWCNTs,the reflection loss of base material takes the most part of the loss of the microwave,and the increase of the reflection loss can promote electromagnetic shielding properties of the composites. Moreover,the electromagnetic shielding properties of the composites are less than-85 d B in the lower frequency range from 0.1 MHz to 3 GHz. With increasing the content of MWCNTs,the electrical conductivity of the composites is decreased,and the electromagnetic shielding properties is slightly enhanced.

Fabrication,microstructure and mechanical properties of Mg matrix composites reinforced by high volume fraction of sphere TC4 particles

A novel liquid settling method was investigated and applied to fabricate TC4 spherical particle reinforced AZ91 alloy matrix composites.This method was called liquid state settling technique in which TC4 particles would settle down under the force of gravity.High volume fraction(50%)particle reinforced AZ91 composites could be easily obtained via this novel method.This is difficult to achieve for other traditional liquid fabrication methods.In addition,there was a good dispersion of TC4 particles in the AZ91 matrix and no clusters were found,which indicate that this method was feasible.Interfacial reaction occurred and the reaction product was confirmed to be Al2Ti.Three kinds of pre-dispersion technologies were used before the settling process and different interfacial microstructures were found.Theoretical calculation and experimental results both indicated that the interfacial product which was embedded in the matrix strengthened the composites and improved the tensile strength.

Fabrication and performance of 3D co-continuous magnesium composites reinforced with Ti_(2)AlN_(x) MAX phase

Magnesium composites reinforced by N-deficient Ti_(2)AlN MAX phase were first fabricated by non-pressure infiltration of Mg into three-dimensional(3D)co-continuous porous Ti_(2)AlN_(x)(x=0.9,1.0)preforms.The relationship between their mechanical properties and micro-structure is discussed with the assessment of 2D and 3D characterization.X-ray diffraction(XRD)and scanning electron microscopy detected no impurities.The 3D reconstruction shows that the uniformly distributed pores in Ti_(2)AlN_(x) preforms are interconnected,which act as infiltra-tion tunnels for the melt Mg.The compressive yield strength and microhardness of Ti_(2)AlN_(0.9)/Mg are 353 MPa and 1.12 GPa,respectively,which are 8.55%and 6.67%lower than those of Ti_(2)AlN/Mg,respectively.The typical delamination and kink band occurred in Ti_(2)AlN_(x) under compressive and Vickers hardness(V_(H))tests.Owing to the continuous skeleton structure and strong interfacial bonding strength,the crack ini-tiated in Ti_(2)AlN_(x) was blocked by the plastic Mg matrix.This suggests the possibility of regulating the mechanical performance of Ti_(2)AlN/Mg composites by controlling the N vacancy and the hierarchical structure of Ti_(2)AlN skeleton.

Assessment of Ti-6Al-4V particles as a reinforcement for AZ31 magnesium alloy-based composites to boost ductility incorporated through friction stir processing

Poor ductility is the primary concern of magnesium matrix composites(MMCs)inflicted by non-deformable ceramic particle reinforcements.Metal particles which melt at elevated temperature can be used as reinforcement to improve the deformation characteristics.Ti-6Al-4V particles reinforced AZ31 MMCs were produced through friction stir processing(FSP)which was carried out in a traditional vertical milling machine.The microstructural features as well as the response to external tensile load were explored.A homogenous distribution of Ti-6Al-4V was achieved at every part of the stir zone.There was no chemical decomposition of Ti-6Al-4V.Further,Ti-6Al-4V did not react with Al and Zn present in AZ31 alloy to form new compounds.A continuous strong interface was obtained around Ti-6Al-4V particle with the matrix.Ti-6Al-4V particles underwent breakage during processing due to severe plastic strain.There was a remarkable refinement of grains in the composite caused by dynamic recrystallization in addition to the pinning of smaller size broken particles.Dense dislocations were observed in the matrix because of plastic deformation and the associated strain misfit.Ti-6Al-4V particles improved the tensile behavior and assisted to obtain appreciable deformation before fracture.Brittle mode of failure was avoided.

Modeling of transverse welds formation during liquid-solid extrusion directly following vacuum infiltration of magnesium matrix composite

Liquid-solid extrusion directly following vacuum infiltration(LSEVI)is an infiltration-extrusion integrated forming technique,and transverse weld between upper residual magnesium alloy and magnesium matrix composites is a common internal defect,which can severely reduce the yield of composite products.To improve current understanding on the mechanism of transverse welding phenomenon,a thermo-mechanical numerical model of LSEVI for magnesium matrix composites was developed.The formation of transverse weld during extrusion was visualized using finite element simulation method,and the formation mechanism was discussed from the aspect of velocity field using a point tracking technique.The simulation results were verified by the experimental results in term of weld shape.

Transient liquid phase bonding of TiC particulate reinforced magnesium metal matrix composite (TiC_p/AZ91D)

Microstructures and mechanical properties of transient liquid phase （TLP） bonded magnesium metal matrix composite （ MMC） joints using copper interlayer have been investigated. With an increase of bonding times from 5 min to 50 min at bonding temperature of 510 ℃ , the average concentration of copper in the bonded zone decreased, the microstructure in the zone changed from Cu, α-Mg and CuMg2 to α-Mg, CuMg2 and TiC, and mechanical properties of the joint increased. The shear strength of the joint bonded at 510 ℃ for 50 min reached 64 MPa due to the metallurgical bonding of the joint and improving its homogeneity of composition and microstructure. It is favorable to increase the bonding time for improving mechanical properties of TLP bonded magnesium MMC joint.