Particle Dispersion Strengthening Research Articles

Achieving high mechanical and wear properties in the AZ31/(CeO2+ZrO2)p surface composite using friction stir processing: Application of vibration

In this study, the friction stir vibration processing (FSVP) have been devoted to the study the impact of the vibration frequency on the metallurgical and mechanical behavior of the AZ31/CeO2–ZrO2 surface composite. The structure, local shear punching test (SPT), hardness, and wear performance of the produced surface composite were studied. The results showed that with the use of vibration during FSP, the stir zone area broadened and resulted in eradication of the flow voids and enhanced the materials flow and the (ZrO2+CeO2)p powders dispersion in the matrix. It was also found that vibrating motion acted as an auxiliary energy and resulted in the enhancement of the shear punching strength and wear resistance by about 29% and 48% in comparison to that of the FSPed sample. This is attributed to the absence of stress concentration sites and better particle dispersion-strengthening.

Physical constitutive modelling of hot deformation of titanium matrix composites

Second-phase particles have complex effects on the micro- and macro-deformation behaviours of titanium matrix composites (TMCs). Therefore, it is difficult to accurately predict the microstructure evolution and flow stress during their hot working. To address this issue, this paper presents a physical unified constitutive model for TMCs. In the model, the dislocation evolution is modelled by considering the geometrically necessary dislocations introduced by the mismatches of the elastic modulus and thermal expansion coefficient between the second-phase particles and matrix material, and the dynamic recrystallization (DRX) is modelled by considering the role of second-phase particles in promoting DRX grain nucleation and inhibiting DRX grain growth. Subsequently, the constitutive equation is developed considering the contributions of thermal activation stress, hardening by dislocation multiplication, DRX softening, second-phase particles dispersion strengthening, and Hall–Petch strengthening. The developed unified constitutive model is used to quantitatively investigate the effects of second-phase particles on the flow behaviour and microstructure evolution during the hot working of the (TiC+TiB)/Ti–6Al–4V alloy. This study is of great significance for optimising the hot-working parameters of TMCs.

Significant strength enhancement of FeCrNiMox medium-entropy alloys via hard intermetallic particles dispersion strengthening

Significant strength enhancement of FeCrNiMox medium-entropy alloys via hard intermetallic particles dispersion strengthening

Effect of Si on Microstructure and Mechanical Properties of FeCrNi Medium Entropy Alloys.

FeCrNi medium entropy alloy (MEA) has been widely regarded for its excellent mechanical properties and corrosion resistance. However, insufficient strength limits its industrial application. Intermetallic particle dispersion strengthening is considered to be an effective method to improve strength, which is expected to solve this problem. In this work, microstructural evolution and mechanical behavior of FeCrNi MEA with different Si content were investigated. We found that the precipitation of fine σ particles can be formed in situ by thermomechanical treatment of Si doping FeCrNi MEAs. The FeCrNiSi0.15 MEA exhibits a good combination of strength and ductility, with yield strength and tensile elongation of 1050 MPa and 7.84%, respectively. The yield strength is almost five times that of the as-cast FeCrNi MEA. The strength enhancement is mainly attributed to the grain-boundary strengthening and precipitation strengthening caused by fine σ particles.

Synergetic Enhancements on the Mechanical and Tribological Performance of Al10Cr17Fe20NiV4 Medium‐Entropy Alloys Induced by Nano‐Al2O3 Particles

Due to the lack of mature mechanisms to support the wear performance of medium‐entropy alloys (MEAs) with nonequiatomic ratios, the practical application of medium alloy in wear‐resistant structural materials is severely restricted. Herein, a nonequiatomic Al10Cr17Fe20NiV4 medium entropy reinforced by nano‐Al2O3 particles is designed and fabricated through high‐energy ball milling and hot pressing. During the high‐energy ball‐milling process, a supersaturated solid solution with a single face‐centered cubic structure is formed in the Al10Cr17Fe20NiV4. The hardness of Al10Cr17Fe20NiV4‐reinforced Al2O3 nanoparticles is 13.9 ± 0.4 GPa measured using nanoindentation, which is about twice high as that of MEAs. Both Al10Cr17Fe20NiV4 and Al10Cr17Fe20NiV4–Al2O3 are implemented to ball‐on disc sliding wear at ambient temperature against an alumina ball and Si3N4 ball. The wear test indicates that the wear rate of Al10Cr17Fe20NiV4‐Al2O3 against Al2O3 and Si3N4 is 13.87 × 10−5 and 9.47 × 10−5 mm3 N−1 m−1, which is lower than those of the Al10Cr17Fe20NiV4, respectively. The significant enhancements in the mechanical and wear performance can be mainly due to the coupled effects of grain refinement and particle dispersion strengthening induced by nano‐Al2O3 particles. The enhanced mechanical and wear properties of Al10Cr17Fe20NiV4 make it a competitive candidate to be applied in advanced mechanical manufacturing.

Development of oxide dispersion strengthened ferritic steel with enhanced strength–ductility combination through dispersion strengthening and back stress hardening

Oxide dispersion strengthened (ODS) ferritic steel is a potential structural material for fast neutron reactor and fusion reactor application. In this study, a new Fe–13Cr–2W-0.4Ti-0.6Zr/0.35Y2O3 ODS ferritic steel was designed and fabricated through hot isostatic pressing. Results show that the ODS ferritic steel consists of highly dispersive nano-oxide particles, identified as Y2(Ti0.4Zr0.6)2O7 and Y4Zr3O12, with average particle size of 5.34 nm and particle distribution density of 4.2 × 1023 m−3. In addition, heterogeneous coarse/ultrafine grains (CGs/UFGs) structure is also achieved in the matrix. The Fe–13Cr–2W-0.4Ti-0.6Zr/0.35Y2O3 ODS ferritic steel exhibits superior mechanical properties at both room temperature (σb = 1208 MPa, δ = 14%) and high temperature (σb, 700°C = 382 MPa, δ700°C = 32%). The high strength is mainly due to the synergistic effect of particle dispersion strengthening and back stress strengthening, while the good ductility can be attributed to the excellent deformation ability of the coarse grains and the back stress hardening effect induced by the heterogeneous CGs/UFGs structure.

Excellent high-temperature strength and ductility of the ZrC nanoparticles dispersed molybdenum

The interface control is critical in the development of high-performance molybdenum (Mo) alloys for high-temperature applications like space reactors. In this work, nanostructured Mo-ZrC alloy with excellent mechanical properties at both room temperature and high temperatures was fabricated by nanoscale ZrC dispersion and interface control. The average grain size of Mo-ZrC alloy is only 0.67 μm owing to the homogeneous dispersion of nanoscale ZrC particles. At room temperature, the ultimate tensile strength (UTS) and total elongation (TE) of the Mo-ZrC alloy are 928 MPa and 34.4%, respectively. At 1000 °C, the UTS is still as high as 562 MPa, which is significantly higher than those reported in oxide dispersion-strengthened Mo alloys, while the TE remains a high value of 23.5%. Additionally, the recrystallization start temperature of Mo-ZrC alloy is about 1400 °C, indicating remarkable thermal stability. First-principles calculations revealed that the interstitial oxygen reduces grain boundary cohesion, while C and ZrC could increase the fracture strength of the boundaries owing to the strong Mo-C bonds. The excellent mechanical properties and thermal stability of the Mo-ZrC alloy can be attributed to a synergistic effect of nanoscale ZrC particles dispersion strengthening, fine-grain strengthening, and grain boundary purification. The strategy could be applied to design other refractory alloys with both high strength and ductility for high-temperature applications.

Comparison of Particle Dispersion Strengthening Estimated by Orowan Model and Ashby-Orowan Model

In the steels with different particle dispersion, particle dispersion strengthening Δσ was theoretically estimated by Orowan model and Ashby-Orowan model. The comparison of experimental data with theoretical values proved the reasonability of Orowan model rather than Ashby-Orowan model. In Ashby-Orowan model, the line tension coefficient of dislocation is evaluated much smaller and this leads to the under-estimation of Δσ. It was also confirmed that there is no effect of grain size on 0.2% proof stress of the steels used. As a result, it is concluded that the yield stress of steels with finely dispersed particle can be explained by the addition of friction stress and particle dispersion strengthening, in the case the grain size is sufficiently larger than the particle dispersion spacing.

Effects of Zirconium and Yttrium Oxide on Mechanical and Oxidation Properties of Mo–3Si–1B–1Zr–1Y2O3 (wt.%) Alloy

Mo–3Si–1B alloys with zirconium (1 wt.%) and yttrium oxide (1 wt.%) additives were fabricated by vibrating sintering techniques. The doped Mo–3Si–1B alloys consisted mainly of α-Mo, Mo3Si, and Mo5SiB2 (T2) phases. It was found that the grains were reduced, and the intermetallics particles were dispersed more homogeneously after the addition of Zr and Y2O3. The optimization in microstructure induced corresponding improvements in both fracture toughness and oxidation resistance. The predominant strengthening mechanisms were fine-grain strengthening and particle dispersion strengthening. In addition, fracture toughness test showed that the additions could improve the toughness of Mo–3Si–1B alloys, for which the toughening mechanism involved a crack trapping by α-Mo phases and extensive small second phase particles in the alloys. What should be paid attention to is the satisfactory oxidation resistance, both at medium-low temperature (800 °C) and high temperature (1200 °C) with doped additives.

The effect of carbon fiber strengthening on the mechanical properties and wear resistance of 24CrNiMo alloy steel fabricated by laser deposition

Carbon fiber (CF) strengthened 24CrNiMo alloy steel was fabricated by laser deposition, and the microstructure, mechanical properties and wear resistance were thoroughly examined. As a microstructural feature of a macroscopic property, 24CrNiMo alloy steels with 0vol%, 4vol%, 8vol% and 12vol% CFs were characterized by differentiated interface bonding and fiber distributions. As indicated by mechanical tests and wear process assessments, the best interface bonding and fiber distribution were found in the 24CrNiMo steel matrix with 8vol% CF, showing high average microhardness and a tensile strength of 752 HV0.3 and 667MPa, which increased by 61.5% and 23.7% respectively compared with those of the 3D-printed no CF variant. Additionally, the wear process of the steel with the addition of 8vol% CF exhibited reduction of wear weight loss by approximately 70%. The excellent performances in these analyses can be mainly attributed to the particle dispersion strengthening, good interfacial bonding between CFs and matrix, the inhibitory effect of CFs on the nucleation and the propagation of microcracks as well as the lubrication effect. The results from this study allow for fabrication of a complex-shaped CF-reinforced alloy steel matrix material with the desired properties suitable for a wide range of practical applications.

Effect of vacuum annealing treatment on dry sliding wear behavior of TiC/Ti-1100-0.5Nb composite under different operating temperatures

Dry sliding wear tests at 25 °C and 500 °C were performed for TiC/Ti-1100-0.5Nb composites on the quenched and tempered GCr15 steel counter-face disks in this work. Meanwhile, the TiC/Ti-1100-0.5Nb composites were treated at the annealing temperature of 1050 °C, 1100 °C, 1150 °C, respectively. Results demonstrate that the TiC quantity and α-laths spacing increase with the increase of annealing temperature. The composites have better high temperature wear properties. The composites under 1100 °C vacuum annealing treatment possess the best wear performance, which benefited from the coordination of granular TiC particles dispersion strengthening and the solid solution strengthening of carbon atoms. The wear mechanism of the composite changes from the adhesive and abrasive wears at room temperature to oxidative mild wear at 500 °C. The formation of nano Fe2O3 and TiO2 oxide particles on worn surface plays a protective role during the wear process, which improved the high temperature wear properties.

Synergetic strengthening effects on copper matrix induced by Al2O3 particle revealed from micro-scale mechanical deformation and microstructure evolutions

Abstract The micro-scale effect of Al 2 O 3 particle on the deformation behaviors of the copper matrix was investigated using nanoindentation. Moderate strengthening effects were produced by the Al 2 O 3 as indicated from the mechanical deformation evolutions. Specifically, the displacement recovery ratio and elastic work ratio is 6% and 9% higher for the Cu-5 wt% Al 2 O 3 (C5A) composite material compared with that of the pure copper (PC) material, respectively. While for the indentation hardness and indentation modulus, the increment is 36% and 75%, respectively. Notably, the moderate strengthening effects were quantitatively illuminated from the power law index m for the C5A indent (1.2) and PC indent (1.1–1.3). In addition, synergetic strengthening effects were proposed from the microstructure evolutions in the C5A composite material. Specifically, the increment in yield strength deduced from the grain refinement is 120 MPa, which is 67% higher than that of the Al 2 O 3 particle dispersion strengthening. The synergetic strengthening effects revealed from the microstructure evolutions are expected to provide new strengthening approaches for the ceramic particle reinforced metal matrix composite materials.

Mechanical properties and biodegradation of porous Zn-1Al alloy scaffolds

Biodegradable porous Zn-1Al alloy scaffolds were fabricated by air pressure infiltration method (APIM) for biomedical applications. The grains of porous Zn-1Al alloy scaffold are significantly refined due to the addition of Al. Tiny (Al) solid solution particles uniformly disperse in the grains of Zn matrix. Under the combined effect of grain size reduction and (Al) solid solution particles dispersion strengthening, the compressive yield strength of the porous alloy scaffolds is improved remarkably. During immersion tests in simulated body fluid (SBF), the porous Zn-1Al alloy scaffold can effectively induce Ca-P precipitation. In addition, the porous alloy scaffold has a lower degradation rate than the porous pure Zn scaffold in SBF.

Plastic deformation and dissolution of ε-Cu particles by cold rolling in an over-aged particle dispersion strengthening Fe-2mass%Cu alloy

Deformation and dissolution behaviors are important characteristics of soft dispersion particles in steel to improve the deformability of high strength steel sheets by controlling the work hardening/softening and fracture processes associated with particle dispersion strengthening. In this study, the deformation and dissolution behaviors of ε-Cu precipitate particles in a ferrite matrix were investigated to understand how relatively soft dispersion particles influence mechanical responses of the steel compared to hard dispersion particles such as alloy carbides. 35 nm diameter nearly spherical ε-Cu particles were initially elongated along the rolling direction by cold rolling, and then these were partly dissolved into the ferrite matrix as the equivalent strain increased. The dissolution of the Cu particles was suggested to be caused by a dynamic partitioning of Cu atoms from the precipitates into the matrix by dislocation shearing at the particle tip sharpened by severe cold working. Simultaneously, the contribution of the ε-Cu particles to the dispersion strengthening appeared to be decreased with increasing dislocation density in the matrix during cold rolling. The dislocation density and other defects in the ε-Cu particles also increased and the particle/matrix interfaces were serrated or became indistinct as deformation progressed. The morphology, internal defects, and interface structure changes of fine dispersion particles and their correlation with mechanical responses of the alloy are discussed in reference to an identically processed, hard particles dispersed Fe-V binary alloy.

Effect of Dy Addition on the Magnetic and Mechanical Properties of Sintered Nd–Fe–B Magnets Prepared by Double-Alloy Powder Mixed Method

Many new approaches have been successfully developed to reduce the Dy content, such as double alloy method, grain refinement and grain boundary diffusion processes [1, 2]. However, as for the mass production of sintered Nd-Fe-B magnets, these methods have some disadvantages in the cost of production. Sintered Nd-Fe-B magnets are very brittle, and easily crack during assembly and machine work and operation, which limit their applications. Many methods including grain boundary toughening and particle dispersion strengthening have been used to enhancing the mechanical properties of sintered Nd-Fe-B magnets to extend their applications. Double-alloy powder mixed method can modify the compositions and realize the microstructure regulation, and be used for mass production of sintered Nd-Fe-B magnets. In the present work, the effect of Dy addition on the magnetic and mechanical properties of sintered Nd-Fe-B magnets prepared by double-alloy powder mixed method was studied.

Photocatalytic TiO2 nanoparticles enhanced polymer antimicrobial coating

Copper (Cu) containing coatings can provide sustainable protection against microbial contamination. However, metallic Cu coatings have not been widely used due to the relatively high cost, poor corrosion resistance, and low compatibility with non-metal substrates. Titanium dioxide (TiO2) possesses antibacterial functions by its photocatalytic properties which can destroy bacteria or suppress their reproduction. TiO2 also has the function of improving the mechanical properties through particle dispersion strengthening. We have recently developed an innovative polymer based coating system containing fine particles of Cu and TiO2 nanoparticles. These polymer based coatings simultaneously display excellent antimicrobial and good mechanical properties. The results showed that the addition of TiO2 has improved the antimicrobial property under sunlight, which provides extended applications in outdoor environment. The elimination of 106 bacterial by contacting the coatings without TiO2 needs 5h, while contacting with the Cu/TiO2– 1wt.% TiO2 took only 2h to kill the same amount of bacteria. The coatings also presented enhanced hardness and wear resistance after adding TiO2. The width of wear track decreased from 270μm of the Cu-polymer coating to 206μm of Cu/TiO2-polymer coatings with 10wt.% TiO2. Synchrotron Infrared Microscopy was used to in-situ and in-vivo study the bacteria killing process at the molecular level. The real-time chemical images of bacterial activities showed that the bacterial cell membranes were damaged by the Cu and TiO2 containing coatings

Effects of lanthanum oxide content on mechanical properties of mechanical alloying Mo–12Si–8.5B (at.%) alloys

Mo–12Si–8.5B alloys with different mass fraction (0wt.%, 0.3wt.%, 0.9wt.%, 1.5wt.%, 2.5wt.%) lanthanum oxide (La2O3) additive were fabricate by using mechanical alloying and hot pressing sintering techniques. XRD results indicate that the doped Mo–12Si–8.5B alloys are consisted mainly of α-Mo, Mo3Si and Mo5SiB2 (T2) phases. It is found that addition of La2O3 has little effect on both the grains and intermetallic sizes. The intermetallic particles are more homogeneously dispersed within α-Mo matrix by increasing the La2O3 content. Compression test and three-point bending test showed that both compression and flexure strength of alloys were obviously improved by the addition of La2O3. The predominant strengthening mechanisms are fine-grain strengthening and particles dispersion strengthening. In addition, fracture toughness tests showed that the fracture toughness values of all alloys were on the order of 9MPa·m1/2 that revealed the addition of La2O3 had little effect on improving the alloys toughness.

Effect of Operating Temperature on Direct Recycling Aluminium Chips (AA6061) in Hot Press Forging Process

A method of solid-state recycling aluminum alloy using hot press forging process was studied as well as the possibility of the recycled chip to be used as secondary resources. This paper presents the results of recycled AA6061 aluminium alloy chip using different operating temperature for hot press forging process. Mechanical properties and microstructure of the recycled specimens and as-received (reference) specimen were investigated. The recycled specimens exhibit a good potential in the strength properties. The result for yield strength (YS) and ultimate tensile strength (UTS) at the minimum temperature 430°C is 25.8 MPa and 27.13 MPa. For the maximum operating temperature 520°C YS and UTS are 107.0MPa and 117.53 MPa. Analysis for different operating temperatures shows that the higher temperatures giving better result on mechanical properties and finer microstructure. The strength of recycled specimen increases due to the grain refinement strengthening whereas particle dispersion strengthening has minor effects. In this study, the recycled AA6061 chip shows the good potential in strengthening as the comparison of using only 17.5% of suggested pressure (70.0/400.0) MPa, the UTS exhibit 35.8% (117.58/327.69) MPa. This shows a remarkable potential of direct recycling by using hot press forging process.

Microstructure and mechanical properties of lanthanum oxide-doped Mo–12Si–8.5B(at%) alloys

Abstract Mo–12Si–8.5B alloys with different mass fraction (0, 0.6 wt%, 12 wt%) lanthanum oxide(La2O3) additive were fabricated by using arc-melting and spark plasma sintering (SPS) techniques. The doped Mo–12Si–8.5B alloys are consisted mainly of α-Mo, Mo3Si and Mo5SiB2(T2) phases. It is found that the grains are reduced and the intermetallics particles are dispersed more homogeneously after the addition of La2O3. The optimization in microstructure induces corresponding improvements in both compression strength and breaking strain of the alloys. The predominant strengthening mechanisms are fine-grain strengthening and particles dispersion strengthening. In addition, fracture toughness test shows that the addition of La2O3 can improve the toughness of Mo–12Si–8.5B alloys, for which the toughening mechanism involves crack trapping by α-Mo phases and extensive small second phase particles in the alloys.

Mechanical Properties of Ultra Fine Particle Dispersion Strengthened Ferritic Steel

The influence of carbides diameter on the mechanical properties of the ferritic steel that was strengthened by the interface precipitated carbides in rows was investigated. Low carbon steel containing titanium as much as carbon in atomic concentration was induction-melt and hot-rolled, followed by the soaking at some temperatures to obtain completely transformed ferrite in which fine carbides precipitated. Lowering holding temperature resulted in fine carbide generation and reduction of the row spacing. Yield strength significantly increased with the decrease in the carbide diameter. The amount of the particle dispersion strengthening was close to the calculation result according to Ashby-Orowan Mechanism. On the other hand, elongation slowly decreased. The decrease in elongation is caused by the reduction of the uniform-elongation. Local elongation did not change by the change of the diameter of the fine carbides in the matrix since voids in the specimen were generated not besides fine carbides but beside large TiN during tensile test.