Research progress in friction stir processing of magnesium alloys and their metal matrix surface composites: Evolution in the 21^(st )century

Rising concerns about climate change drive the demand for lightweight components.Magnesium(Mg)alloys are highly valued for their low weight,making them increasingly important in various industries.Researchers focusing on enhancing the characteristics of Mg alloys and developing their Metal Matrix Composites(MMCs)have gained significant attention worldwide over the past decade,driven by the global shift towards lightweight materials.Friction Stir Processing(FSP)has emerged as a promising technique to enhance the properties of Mg alloys and produce Mg-MMCs.Initially,FSP adapted to refine grain size from the micro to the nano level and accelerated the development of MMCs due to its solid-state nature and the synergistic effects of microstructure refinement and reinforcement,improving strength,hardness,ductility,wear resistance,corrosion resistance,and fatigue strength.However,producing defect-free and sound FSPed Mg and Mg-MMCs requires addressing several variables and their interdependencies,which opens up a broad range of practical applications.Despite existing reviews on individual FSP of Mg,its alloys,and MMCs,an attempt has been made to analyze the latest research on these three aspects collectively to enhance the understanding,application,and effectiveness of FSP for Mg and its derivatives.This review article discusses the literature,classifies the importance of Mg alloys,provides a historical background,and explores developments and potential applications of FSPed Mg alloys.It focuses on novel fabrication methods,reinforcement strategies,machine and tool design parameters,material characterization,and integration with other methods for enhanced properties.The influence of process parameters and the emergence of defects are examined,along with specific applications in mono and hybrid composites and their microstructure evolution.The study identifies promising reinforcement materials and highlights research gaps in FSP for Mg alloys and MMCs production.It concludes with significant recommendations for further exploration,reflecting ongoing advancements in this field.

Self-lubricating behavior of Fe_(22)Co_(26)Cr_(20)Ni_(22)Ta_(10)high-entropy alloy matrix composites

Eutectic high entropy alloys(EHEAs)have high temperature stability,good mechanical properties,and are promising for tribological applications at high temperatures.To study the high temperature lubrication behavior,Fe_(22)Co_(26)Cr_(20)Ni_(22)Ta_(10)−(BaF_(2)/CaF_(2))x(x=3−20,wt.%)composites were prepared by spark plasma sintering(SPS),with BaF_(2)/CaF_(2) eutectic powder used as solid lubricant.The lubrication behavior and mechanical properties were studied at both room and high temperatures.With the increase of the content of BaF_(2)/CaF_(2) eutectic powder,the friction coefficients and the wear rates of the composites at 600 and 800℃ decrease significantly.The composites with eutectic powder content of 15 and 20 wt.%have the best lubricating performance at 600℃,with low friction coefficient and wear rates,mainly due to the good mechanical properties of EHEA matrix,the lubrication effect of BaF_(2)/CaF_(2) phase and the oxides formed on the worn surface.

In situ prepared Al-Si alloy matrix composites reinforced by γ-Al_2O_3p

A γ-Al2O3 particles reinforced Al-Si alloy matrix composite was fabricated by adding NH4Al（SO4）2 to molten aluminum alloy. TEM observation shows that in-situ γ-Al2O3 particles are generally spherical and uniformly distributed in the matrix. The results of dry sliding wear tests show that the wear resistance of the composites increases with increasing mass fraction, and the volume loss is considerably lesser than that of the matrix and is lesser than that of the composites by adding γ-Al2O3 particles directly.

Wear behavior of Al-Si alloy matrix composites reinforced by γ-Al_2O_3 decomposed from AACH

The Al-Si alloy matrix composite reinforced by γ-Al2O3 particles was produced by adding NH4AlO(OH)HCO3(AACH) into molten Al-Si alloy at 850 ℃. During stirring γ-Al2O3 particles are formed by the decomposing reaction of AACH. It is found that the γ-Al2O3 particles distribute more uniformly in the matrix by adding AACH than by adding γ-Al2O3 directly. The wear tests show that the volume loss of the unreinforced Al-Si alloy matrix is about 3 times larger than that of the γ-Al2O3 reinforced composites and that of the composites fabricated by adding γ-Al2O3 is larger than that by adding AACH.

Mixed rare earth metal conversion coatings on 2024 alloy and Al6061/SiC_p metal matrix composites

The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning electron microscope. X ray diffraction analysis revealed that the coatings are amorphous structure. The results of X ray photoelectron spectroscopy indicated that the mixed REM conversion coatings consist predominantly of Ce and O, the contents of other rare earth elements (such as La, Pr) are relatively low, the coatings are about 2～4 μm thickness with excellent adhesion and wearability. The results of mass loss test showed that the mixed REM conversion coatings produce corrosion resistant surface of 2024 alloy and Al6061/SiC p. [

Fabrication and fracture analysis of MoSi_2 matrix composites by mechanical alloying

Four composites, MoSi 2+ZrO 2, MoSi 2+ZrO 2(Y 2O 3), MoSi 2+ZrO 2+SiC and MoSi 2+ZrO 2(Y 2O 3)+SiC are fabricated by mechanical alloying. It is clear that cracks produced on the MoSi 2 matrix composites during hardness testing belong to the Palmquist crack system. The value of highest fracture toughness of MoSi 2+ZrO 2+SiC composite is 7.58?MPa·m 1/2 , which is nearly three times that of monolithic MoSi 2. This can be attributed to well distributed ZrO 2 and SiC particles along the boundaries of very fine MoSi 2 grains.

Review of recent trends in friction stir welding process of aluminum alloys and aluminum metal matrix composites

Welding is a vital component of several industries such as automotive,aerospace,robotics,and construction.Without welding,these industries utilize aluminum alloys for the manufacturing of many components or systems.However,fusion welding of aluminum alloys is challenging due to several factors,including the presence of non-heat-treatable alloys,porosity,solidification,and liquation of cracks.Many manufacturers adopt conventional in-air friction stir welding(FSW)to weld metallic alloys and dissimilar materials.Many researchers reported the drawbacks of this traditional in-air FSW technique in welding metallic and polymeric materials in general and aluminum alloys and aluminum matrix composites in specific.A number of FSW techniques were developed recently,such as underwater friction stir welding(UFSW),vibrational friction-stir welding(VFSW),and others,for welding of aluminum alloy joints to overcome the issues of welding using conventional FSW.Therefore,the main objective of this review is to summarize the recent trends in FSW process of aluminum alloys and aluminum metal matrix composites(Al MMCs).Also,it discusses the effect of welding parameters of the traditional and state-of-the-art developed FSW techniques on the welding quality and strength of aluminum alloys and Al MMCs.Comparison among the techniques and advantages and limitations of each are considered.The review suggests that VFSW is a viable option for welding aluminum joints due to its energy efficiency,economic cost,and versatile modifications that can be employed based on the application.This review also illustrated that significantly less attention has been paid to FSW of Al-MMCs and considerable attention is demanded to produce qualified joint.

Rheological behavior of semi-solid Mg_2Si/AM60 magnesium matrix composites at steady state

The microstructure and rheological behavior of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state were investigated.The results show that the primary α-Mg phases are knapped by mechanical stirring and the Chinese script type reinforced Mg2Si phases exist in liquid phase and grain boundary.The analysis of apparent viscosity indicates that the apparent viscosity of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state increases with increasing the volume fraction of Mg2Si and solid fraction of primary α-Mg,but decreases with increasing the shearing rate and shearing time,and the apparent viscosity keeps stable when shearing time reaches 300 s.

Effect of hot extrusion on microstructure and tribological behavior of Al_(2)O_(3p) reinforced 7075 aluminum-matrix composites

The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).The experimental consequences reveal that the optimal addition of Al_(2)O_(3p) was 2 wt%.After hot extrusion,the Mg(Zn,Cu,Al)2 phases partially dissolve into the matrix and generate many uniformly distributed aging precipitation particles,the Al_(7)Cu_(2)Fe phases are squeezed and broken,and the Al_(2)O_(3p) become uniform distribution.The microhardness of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites reaches HV 170.34,increased by 41.5%than as-cast composites.The wear rate of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites is further lower than that of as-cast composites under the same condition.SEM-EDS analyses reveal that the reinforced wear resistance of composites can put down to the protective effect of the Al_(2)O_(3p) reinforced transition layer.After hot extrusion,the transition layer becomes stable,which determines the reinforced wear resistance of the as-extruded composites.

Hot Deformation Behavior of Squeeze Casting SiC_p/2 A50 Matrix Composites

The flow stress behaviors of squeeze casting SiCp/2A50 matrix composites were investigated by means of compression tests on a Gleeble 1500 therma1 mechanical simulator at isothermal constant strain rates ranging from of 0.001 to 1.0 with the testing temperature ranging from 350 to 500 ℃. The experiments showed that the relationship between stress and strain was obviously influenced by the strain rate and temperature. Dynamic recrystallization generally occurred at a higher temperature and a 1ower strain rate. A linear equation could be fitted between the Zener-Hollomon parameter Z and stress in the experiments. The mean value reciprocal of temperature at every true strain had a linear relation with natural logarithm of Z parameter, and the correlation coefficient, R=0.99, which was very significant by examination. The hot deformation activation energy of SiCp/2A50 matrix composites was 163.47 KJ/mol by calculation.

Self-propagating high temperature synthesis of MoSi_2 matrix composites

MoSi2 is presently regarded as the most important material for electrical heating and as one with huge potential for high temperature structural uses. MoSi2 and MoSi2 matrix composites were prepared by self-propagating high temperature synthesis （SHS）. Pure MoSi2 was obtained and a compound of MoSi2 and WSi2was synthesized in the form of predominant solid solution （Mo,W）Si2. By adding aluminum of 5.5 at.% to Mo-Si, the crystal structure of MoSi2 changed into a mixture of tetragonal Cllb MoSi2and hexagonal C40 Mo（Si,Al）2. The （Mo,W）Si2-Mo（Si,Al）2-W（Si,Al）2 composite materials were synthesized by adding aluminum of 5.5 at.% to Mo-W-Si. However, if the amount of the added aluminum was not larger than 2.5 at.%, it did not have any significant effect. SHS is an effective technology for synthesis of MoSi2 and MoSi2 matrix composites.

Microstructure and Tribological Behavior of Al2O3 Particle Reinforced Al Matrix Composites Fabricated by Spark Plasma Sintering

Nanoparticles and microparticles reinforced Al matrix composites were fabricated by spark plasma sintering, and the microstructure and tribological properties were investigated systemically. The nano-Al2O3 particle and micro-Al2O3 particle uniformly dispersed in Al matrix composites. The introduction of nanoparticles is beneficial to the decrease of friction coefficient and wear rate, while microparticles are responsible to the high friction coefficient, resulting in the abrasive wear. With the introduction of both nanoparticles and microparticles, their synergic effect will lead to the variation of tribological behavior.

The Role of Particles in Fatigue Crack Propagation of Aluminum Matrix Composites and Casting Aluminum Alloys

Fatigue crack propagation （FCP） behaviors were studied to understand the role of SiC particles in 10 wt pct SiCp/A2024 composites and Si particles in casting aluminum alloy A356. The results show that a few particles appeared on the fracture surfaces in SiCp/Al composites even at high △K region, which indicates that cracks propagated predominantly within the matrix avoiding SiC particles due to the high strength of the particles and the strong particle/matrix interface. In casting aluminum alloy, Si particle debonding was more prominent.Compared with SiCp/Al composite, the casting aluminum alloy exhibited lower FCP rates, but had a slight steeper slope in the Paris region. Crack deflection and branching were found to be more remarkable in the casting aluminum alloy than that in the SiCp/Al composites, which may be contributed to higher FCP resistance in casting aluminum alloy.

Aluminum matrix composites reinforced by in situ Al_2O_3 and Al_3Zr particles fabricated via magnetochemistry reaction

Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles are fabricated from A356-Zr(CO3)2 system via magnetochemistry reaction,and the morphologies,sizes and distributions of the in situ particles as well as the microstructures,mechanical mechanisms of the composites are investigated by XRD,SEM,TEM and in situ tensile tests.The results indicate that with the pulsed magnetic field assistance,the morphologies of the in situ particles are mainly with ball-shape,the sizes are in nanometer scale and the distributions in the matrix are uniform.The interfaces between the in situ particles and the aluminum matrix are net and no interfacial outgrowth is observed.These are due to the strong vibration induced by the applied magnetic field in the aluminum melt,which in turn,accelerates the melt reactions.The effects of the magnetic field on the above contributions are discussed in detail.

Microstructure and properties of mechanical alloying particles reinforced aluminum matrix composites prepared by semisolid stirring pouring method

Aluminum matrix composites reinforced with mechanical alloying particles(SiC_p) were fabricated by the semisolid stirring pouring method. The inf luence of mechanical alloying particles and Mg on the microstructure and mechanical properties of the composites was investigated by means of optical microscopy(OM), X-ray diffraction scanning(XRD), electron microscopy(SEM) and energy dispersive spectroscopy(EDS). Results show that the addition of Mg converts the agglomerate mechanical al oying particles in ZL101 matrix composites into dispersed distribution in ZL101-Mg matrix composites, large matrix grains into f ine equiaxed matrix grains, and eutectic phase into f ine particles. So the mechanical properties of ZL101-Mg matrix composites are better than those of ZL101 matrix composites. The mechanical properties of ZL101/ZL101-Mg matrix composites are gradually increased with the increase of the volume fraction of mechanical alloying particles. When the volume fraction of mechanical alloying particles is 3%, the Vickers hardness and ultimate tensile strength of the ZL101/ZL101-Mg matrix composites reach their maximum values.

Microstructure and Mechanical Properties of as Cast Aluminium Alloy 7075/Basalt Dispersed Metal Matrix Composites

This paper aims to study the effects of short basalt fiber reinforcement on the mechanical properties of cast aluminium alloy 7075 composites containing short basalt fiber of content ranging from 2.5 to 10 percent by weight in steps of 2.5 percent and fabricated using compo-casting technique. The objective is to investigate the process feasibility and resulting material properties such as young’s modulus, ductility, hardness & compression strength. The properties obtained are compared with those of as-cast that were manufactured under the same fabrication conditions. The results of this study revealed that, as the short basalt fiber content was increased, there were significant increases in the ultimate tensile strength, hardness, compressive strength and Young’s modulus, accompanied by a reduction in its ductility. Furthermore, the microstructure & facture studies were carried out using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) in order to establish relationships between the quality of the fiber/aluminium interface bond and hence to link with mechanical properties of the composites.

Microstructure Characteristics of Interaction Layer of Zn-Al Eutectic Alloy with Al_2O_3p/6061Al Composites

The interaction between Zn-AI eutectic alloy and Al203p/6061AI composites in the vacuum furnace was investigated. Great attention has been paid to the elements diffusion, the microstructure and formation of the interface between Zn-AI eutectic alloy and Al2O3p/6061AI composites. Experimental results show that Zn-AI eutectic alloy has a good wetting ability to Al2O3p/6061 Al composites and the wetting angle decreases with increasing the temperature in vacuum. After the interaction, an interaction layer forms between Zn-AI alloy and Al2O3p/6061 Al composites. The phases in the interaction layer mainly consist of α-AI(Zn), Al2O3 and CuZn5 resulted from the diffusion of elements from the Zn-AI alloy. Several porosities distribute in the region near the interface of the Zn-AI alloy/interaction layer. The amount of shrinkage voids in the interacting layer is relevant to the penetration of Zn element into Al2O3p/6061Al composites which is a function of temperature. So it is necessary to lower heating temperature in order to limit the Zn penetration.

Influence of Al addition on microstructures of Cu-B alloys and Cu-ZrB2 composites

The influence of Al addition on the microstructure of Cu-B alloys and Cu-ZrB2 composites was investigated using scanning electron microscopy, X-ray diffraction and first-principles calculation. The results show that the eutectic B in Cu-B alloys can be modified by Al from coarse needles to fine fibrous structure and primary B will form in hypoeutectic Cu-B alloys. As for Cu-ZrB2 composites, Al can significantly refine and modify the morphology of ZrB2 as well as improve its distribution, which should be due to its selective adsorption on ZrB2 surfaces. The first-principles calculation results indicate that Al is preferentially adsobed on ZrB2■, then on ZrB2■, and finally on ZrB2(0001). As a result, smaller sized ZrB2 with a polyhedron-like, even nearly sphere-like morphology, can form. Due to Al addition, the hardness of Cu-ZrB2 composites is greatly enhanced, but the electrical conductivity of the composites is seriously reduced.