Effect Of Second Phase Particles Research Articles

Finite element modeling of ultrasonic attenuation and dispersion in graded multilayer polymer composites

In this paper, finite element models of ultrasonic wave propagation in Cu–PMMA composites are established. The effects of second-phase particles, ultrasonic properties, and graded interfaces on the ultrasonic propagation behavior are investigated, and the contributions of particle-independent scattering, particle interactions, and matrix viscoelasticity to the ultrasonic attenuation are quantitatively evaluated. The results show that there is no obvious coupling between particle scattering and matrix viscoelasticity in Cu–PMMA composites, and the longitudinal wave speed has little effect with the variation of particle size, ultrasonic frequency, and graded interface, while the variation of the acoustic attenuation coefficient is related to the disorder of ultrasonic energy propagation direction. In the intra-layer uniform model, with the increase in Cu particle size and ultrasonic frequency, the scattering effect of Cu particles on the ultrasonic waves is enhanced, resulting in a significant increase in the acoustic attenuation coefficient. In the inter-layer graded multilayer model, there is a strong reverse energy propagation between the layers, causing the acoustic attenuation coefficient to increase significantly.

Phase Field Simulation of the Effect of Second Phase Particles with Different Orientations on the Microstructure of Magnesium Alloys.

In this study, the phase field method has been used to study the effect of second phase particles with different shapes and different orientations on the grain growth of AZ31 magnesium alloy, after annealing at 350 °C for 100 min. The results show that the shape of the second phase particles would have an effect on the grain growth; the refinement effect of elliptical particles and rod-shaped particles was similar, and better than the spherical particles; the spatial arrangement direction of the second phase particles had no significant effect on the grain growth. On the other hand, when the microstructure of AZ31 magnesium alloy contained second phase particles with different shapes, the effect of mixing different shapes of second phase particles on the grain refinement was enhanced gradually with the decrease im the volume fraction of spherical particles.

A Computationally Efficient Multiscale, Multi-Phase Modeling Approach Based on CPFEM to Assess the Effect of Second Phase Particles on Mechanical Properties

Crystal plasticity finite element (CPFEM) modeling of metals that can be age hardened consisting of second phase particles is extensively performed based on representative volume element (RVE) models. The RVE model is generated for ferritic low-carbon steel using the data obtained from microstructural observation through optical microscopy (OM) and electron backscatter diffraction (EBSD). The generated RVE is required to statistically represent the original material in terms of grain topology and texture in microscale, as well as the configuration of second phase particles in submicron scale. The multiscale, multi-phase nature of the generated RVE leads to a computationally expensive modeling procedure. To overcome this issue, an alternative multiscale modeling approach based on a homogenization scheme is proposed, in which the effect of second phase particles on deformation behavior is accounted for with no need for the explicit presence of particles in RVE. Lastly, a thorough parametric analysis is performed to investigate the sensitivity of the mechanical properties to the second phase particles in terms of size, volume fraction, geometrical distribution, and deformable or non-deformable properties of precipitates in the investigated material. The results show that the proposed multiscale modeling approach successfully accounts for the effect of second phase particles on deformation behavior, while the computational cost is reduced by more than 99%. In addition, the simulations show that the configuration of second phase particles at a microscale plays an important role in defining the mechanical behavior of the material.

Phase-Field Simulation on the Effect of Second-Phase Particles on Abnormal Growth of Goss Grains in Fe-3%Si Steels.

A phase-field model was revised to study the abnormal growth of Goss grains during the annealing process in Fe-3%Si steels, in which the interaction between the second-phase particles and Goss grain boundaries (GBs) was considered. The results indicate that the abnormal growth of Goss grains occurs due to the different dissolvability of the particles at Goss GBs compared with the other GBs. Moreover, the degree of abnormal growth increases first and then decreases with an increasing particle content. Meanwhile, the size advantage of Goss grain can further promote the degree of abnormal growth. Two types of island grains were found according to the simulated results, which is consistent with the experimental observations. A proper GB dissolvability of particles is the key factor for the formation of isolated island grains, and a higher local particle density at GBs is the main reason for the appearance of serial island grains. These findings can provide guidance for the desired texture control in silicon steels.

The Effect of Second Phase Particles on the Corrosion Resistance of A286 Alloys

A286 alloy (AISI 660) is an austenitic precipitation hardness stainless steel that is widely used in the gas turbine industry, due to its high-temperature strength and oxidation resistance [1]. A286 alloy contains higher Ni (24.23 wt.%) and lower Cr (14.5 wt.%) than AISI 316 and AISI 304. The main precipitation strengthening phase of this alloy is gamma phase γ' [Ni3(Al, Ti)], and second phase particles, which form during solution treatment and aging, include eta phase η (Ni3Ti) and metal carbides and nitrides (TiC, TiN).Unlike the relation between precipitates (γ', η) and pitting corrosion [2], the influence of TiC and TiN on the pitting corrosion is rarely studied. To investigate the influence of the various second phase particles on the corrosion behavior of A286 alloys, three samples were employed, including the hot-rolled (HR), HR + solution treatment at 980 °C for 1 h, and HR + solution treatment + aging at 720 °C for 16 h.The corrosion resistance of the various A286 alloy samples were examined by potentiodynamic tests in 3.5 wt.% NaCl solution. The microstructure was investigated via scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS).The second phase particles of HR A286 were mainly TiC and a few TiN, which were several micrometers in size and distributed intragranularly in the austenite matrix (Fig. 1a, 1d, and 1e). After the solution treatment, many TiC particles with sizes of a couple of micrometers precipitated along the austenite grain boundaries (Fig. 1b). Further aging resulted in the formation of γ' and η particles (Fig.1c). The potentiodynamic curves (Fig.1f) showed that the HR A286 had the lowest pitting potential (Epit) and smallest passivation range, suggesting the formation of TiC particles did not deteriorate the corrosion resistance. Meanwhile, the γ' and η particles resulted in a slight decrease in the Epit and passivation range.Reference:[1] H. De Cicco, M.I. Luppo, L.M. Gribaudo, J. Ovejero-García, Microstructural development and creep behavior in A286 superalloy, Materials Characterization 52 (2004) 85-92.[2] P. De Tiedra, O. Martín, M. San-Juan, Potentiodynamic study of the influence of gamma prime and eta phases on pitting corrosion of A286 superalloy, Journal of Alloys and Compounds 673 (2016) 231-236. Figure 1

Effects of residual stress and intragranular particles on mechanical properties of hot-pressed Al2O3/SiC ceramic composites

Al2O3/SiC ceramic composites with different SiC contents have been prepared by powder metallurgy at 1600 °C for 120 min at 30 MPa pressure. The effect of second phase particles on the microstructure and mechanical properties of composites have been studied. The results show that SiC particle has a significant impact on the matrix subjected to residual stress, and on the microstructure of the composites as well. The average grain size of alumina matrix decreases as the SiC particle content increases. Simultaneously, it has been found that the mechanical properties of the material are significantly enhanced in comparison with monolithic Al2O3. The highest strength and toughness are obtained when the SiC content is 15 vol%, and the values are 1237 MPa and 5.68 MPa m1/2, respectively. The mechanisms of strengthening and toughening have been discussed.

Effect of second phase particles on the microstructure and texture of rare earth elements containing magnesium matrix surface-composite produced by friction stir processing

The present research clarifies the texture and microstructure evolution of a rare earth (RE) containing magnesium composite reinforced by SiC particles (Mg-RE/SiC) during friction stir processing. Rotating tool induced mechanical stirring and frictional heat lead to occurrence of dynamic recrystallization (DRX) and development of the strong basal texture component. The presence of second phase particles in the matrix could stimulate the occurrence of continuous dynamic recrystallization (CDRX) and particle stimulated nucleation (PSN) and postpone discontinuous dynamic recrystallization (DDRX). The presentation of crystallographic orientations in an appropriate reference frame indicated formation of a new rare earth texture (RE-texture) component, near the <11-24>//shear plane normal (SPN) and <20-21>-<11-21>//shear direction (SD) orientations. This texture component was developed through simultaneous activity of basal and non-basal slip systems during dynamic recrystallization.

The influence of pearlite fraction on the shock properties of ferrite–pearlite steel microstructures: Insight into the effect of second-phase particles

The goal of this work is to investigate the effect of varying phase fractions on the overall spall strength and damage behavior of a material. Specifically, two plain carbon, ferrite–pearlite steels (1045 and A283) were subjected to spall recovery experiments to investigate the effect of pearlite fraction on spall strength and total damage. The A283 (20% pearlite) alloy exhibited a higher Hugoniot elastic limit and spall strength compared with 1045 (60% pearlite). Discontinuous and continuous yielding behaviors were observed at quasi-static and dynamic rates for A283 and 1045, respectively. The yielding behavior was connected to pearlite fraction and the prevalence of dislocation-emitting, ferrite/cementite interfaces. Postmortem characterization revealed cementite lamellae cracking within pearlite of 1045, suggesting that pearlite reduces spall strength by providing low-energy damage nucleation sites. The rate of damage growth and coalescence was similar between the two alloys; however, 1045 exhibited more continuous cracks than A283, which exhibited a greater prevalence of discrete voids.

Modeling discontinuous dynamic recrystallization containing second phase particles in magnesium alloys utilizing phase field method

Pre-existing second phase particles can induce particle stimulated nucleation (PSN) and pinning effect on grain boundaries during DRX process of magnesium alloys. The interaction among pinning effect, PSN mechanism and strain-induced grain boundary migration (SIBM) nucleation mechanism imposes challenge in quantitative study of microstructure evolution. A phase field model that describes discontinuous dynamic recrystallization process considering second phase particles (PF-DDRX-SP) which mainly distribute along grain boundaries is developed. The second phase order parameter with diffusion interface is introduced to the free energy function. With considering the pinning effect of second phase particles on grain boundaries, the grain boundary energy couples the interaction between second phase and grains. The effect of second phase on dislocation density evolution is considered in the model, and the PSN and SIBM mechanism are both executed by limiting the nucleation position to the grain boundary and the second phase interface. For the validation, the initial topology consistent with initial microstructure is applied to the simulation of DRX kinetics and flow behavior of AZ80 magnesium alloy, and great reliability and accuracy of developed model is indicated. Furthermore, through the model, the microstructure evolution with different particle size and with different volume fraction of round particle during DRX process were simulated. The results show that particles with higher dispersion reduce the number of DRX nuclei, which indicate that second phase particles suppress the nucleation at grain boundaries because of the pinning effect. More importantly, the proposed model could also quantitatively predict the relationships between the parameters of second phase particles and DRX behaviors, and enable to optimize the initial second phase structure in a uniform grain structure during thermomechanical process.

Investigations on microstructure and mechanical properties of HfC particle-reinforced W[sbnd]Mo composites

The W-Mo-HfC composites were prepared by using the conventional powder metallurgy with the two different sintering temperature and the same forging technology. The phase component, microstructure and mechanical properties of composites were investigated, and the effects of second phase particles were focused on particularly. The two types of W-Mo-HfC composites are composed of the WMo matrix, HfC and HfO2 second phase particles. As a result, the W-Mo-HfC composite sintered at 2100 °C can yield a higher tensile strength of 993 MPa and a larger elastic modulus of 336.3 GPa. Firstly, a relatively lower sintering temperature gives rise to a smaller average grain size of the WMo matrix and the size of second phase particles, which effectively utilizes the fine grain strengthening mechanism. Secondly, HfC second phase particles at the grain boundary have the ability to capture oxygen impurity and increase the bonding strength of interface. In addition, the enhancement mechanisms of HfC particles were proposed.

Effect of Second Phase Particles on Solid Particles Erosion of Air Plasma Sprayed Yttria Stabilized Zirconia

Yttria stabilized zirconia (YSZ) based composite topcoats were prepared with three advanced ceramic materials as second phase component; CaZrO3, (La0.75Nd0.25)2Zr2O7 and Nd2Ce2O7. The solid particles erosion (SPE) testing of the air plasma sprayed composite topcoats was carried out at room temperature and 900 °C to study the effects of second phase on erosion behavior. The erodent was angular fused alumina of 40-45 mm size. The erosion mechanism was followed in all topcoats with cracking and fracturing of the plasma sprayed splats due to erodent particles impact and impingement, whereas micro-ploughing was observed after 900 °C SPE testing as an additional feature. The hardness and intrinsic properties of second phase component in the composite topcoats played a crucial role in improving the erosion rate (ER) at ambient as well as 900 °C. The Nd2Ce2O7/YSZ topcoat show lower ER due to combatively higher hardness of Nd2Ce2O7 and good interfacial bonding with YSZ. The overall lowering of ER at 900 °C as compared to that of at ambient conditions was ascribed to the anelastic mechanical response of the ceramic topcoats due to thermal cycling involved in the SPE testing at high temperature.

Effect of second-phase particles on the oxidation behaviour of a high-manganese austenitic heat-resistant steel

In this work, the presence of second-phase particles was found can significantly improve the oxidation and spallation resistances of a high-manganese austenitic heat-resistant steel. We show this unexpected improvement is originated from three correlated phenomena caused by the second-phase particles. First, the stratified growth of scale is avoided due to the chemical inhomogeneity of the novel steel. Further, the selective oxidation of second-phase particles provides a pinning effect for the scale. Last but not least, the accelerated outward diffusion of Mn reduces the critical Cr concentration for the formation of a stable protective Cr2O3 layer.

Effect of second phase particles on the dynamic recrystallization in Ni-W alloys during thermal compression

The existence of second phase particles may raise the deformation heterogeneity in the alloys, providing favorable sites of recrystallization nucleation in thermal deformation. The influence of large W second phase p articles (>1 µm) on the dynamic recrystallization in Ni-42W alloys (with 42 wt% W) is studied in this paper by electron backscattered diffraction (EBSD). The Ni-42W alloys are composed by NiW matrix and W particles. The W particles are of two kinds of shapes including ellipsoidal shape with a diameter of 3–10 µm and rod-like shape with 3 µm in width and 5–15 µm in length. The phenomenon of particles stimulated nucleation is observed in the Ni-42W alloys during thermal deformation. The recrystallized grains are located not only at the areas with high-angle grain boundaries but also at the deformation heterogeneities around W particles. A divergent distribution of deformation heterogeneities is formed around the ellipsoidal W particles and the distortion degree near the adjacent ellipsoidal particles can be accumulated. Large distortion exists at the tips of the rod-like particles. The deformation is weak at the middle region between rod-like particles with parallel alignment, which is not conducive to recrystallization nucleation. Based on the EBSD results, the dynamic recrystallization evolution diagram is established for Ni-42W alloys with large second phase particles.

In Situ Observation of Deformation-Induced Spherical Grains in Semi-Solid State of C5191 Copper Alloy.

The formation mechanism of spherical grains during the strain-induced melt activation is investigated by in situ observation of the cold rotary swaged materials during heat treatment. The microstructure of the cold rotary swaged material changed from original dendritic structure to spherical grains after heating semi-solid state, whereas the as-received alloy without deformation exhibited non-spherical grains. These results show that static recrystallization, preferential melting of grain boundaries, and small grains cause the deformed grains to form the initial spherical grain structure during the temperature rising to semi-solid state; besides, the Zener pinning effect of second-phase particle and the heterogeneous nucleation of solidification also play negative roles in spherical grain growth up freely during the cooling process.

Recrystallized fine grains induced by nanoparticles in Al–Si–Mg–Cu-based alloy sheets

The effects of second-phase particles on recrystallization behavior were investigated for Al–Si–Mg–Cu based alloy sheets containing a small amount of Cr and Mn elements. Microscale (>1 μm) and nanoscale (<500 nm) particles were distributed in cold-rolled sheets. Particle-stimulated nucleation by microscale particles, such as Mg2Si and β-AlFeSi, was not effective, while the α-Al(FeCrMn)Si nanoparticles (~5 nm) actively induced the formation of fine recrystallized grains. When the α-Al(FeCrMn)Si nanoparticles had a round-shaped and partially coherent interface with the Al matrix, they could act as heterogeneous nucleation sites for recrystallization grains. However, after homogenization heat treatment, the α-Al(FeCrMn)Si nanoparticles grew, decreased in number, and lost their coherency, which increased the recrystallized grain size. The sheet with a small grain size of 15 μm exhibited higher yield strength, ultimate tensile strength, and elongation than those of other sheets due to grain boundary and particle strengthening. In addition, the smallest-grain-sized sample was obtained when Mn or Cr content was 0.08 wt%, which is considered as a state in which nanoparticles can effectively participate in recrystallization nucleation.

Effects of Second-Phase Particles on Microstructure Evolution in Mg-2Zn Based Magnesium Alloys during Annealing Treatment

As an important fabrication process, annealing treatment is conducted to eliminate distortion in magnesium alloy sheets. Second-phase particles can provide nucleation sites for recrystallization grains, and the basal texture is related to the recrystallization behavior. Three experimental Mg-2Zn-based magnesium alloy sheets were investigated by the salt bath annealing process. Combined with variations in hardness softening, evolution of microstructure and basal texture, the effect of second-phase particles on microstructure evolution was analyzed. The results showed that the significant influence of size and distribution of second-phase particles on static recrystallization in magnesium alloy sheets was exhibited, which lead to the formation of two stages in the annealing process, combined with static recovery behavior. Second phase particles with coarse size were beneficial to recrystallization grains’ nucleation and increased recrystallization behavior in the initial stage of annealing. Second-phase particles with fine size inhibited recrystallization behavior and weakened the softening of hardness. The basal texture was weakened by second phase particles at the stage of recrystallization nucleation. The change in basal texture at the stage of grain growth was related to the size of second-phase particles. The regulation of basal texture enhancement can be envisioned by modifying second-phase particles.

Effect of the Deformation and Heat Treatment on the Microstructural Evolution and Mechanical Properties of Mg-4%Y Alloy

This study aimed to evaluate the effects of extrusion process and subsequentheat-treatment on microstructural evolution and mechanical properties of Mg-4%Y alloy. Theresults showed that the dynamic recrystallization occurred during extrusion, the microstructure istiny equiaxial grains, the shearing stripes and parallel streamlines which distribute along theextrusion direction are especially obvious. The tensile curve has obvious yield phenomenon. Afterannealing, parallel streamlines disappear, the yield phenomenon of tensile curve eliminates, theyield strength(σ0.2) and the tensile strength(σb) decrease, the plasticity increases. The underneathmechanism for mechanical properties can be ascribed to the weak pining effect of second-phaseparticles on the movement of dislocation and release of the pile-up dislocations.

The effect of second phase particles on light transmission of ZnS/diamond nanocomposite

The effect of second phase size (200, 400, 600 and 800 nm) and volume fraction (10, 20 and 30%) on light transmission behavior of ZnS/diamond composite was simulated using Mie theory and FDTD method. It is expected that the results of FDTD method to be close to experimental results. To validate this approach, simulation results of Mie theory and FDTD method were compared with experimental light transmission (T) of 88.7–11.3 vol% ZnS/diamond composite, reported previously by Xue and et al, and it is shown that results of FDTD method matched well with these experimental results. Because of considering particles interaction and the higher accuracy of the FDTD method in calculating the scattering cross section than the Mie theory, the difference between simulation curves of ZnS/diamond nanocomposite based on Mie theory and FDTD method became more significant with increasing second phase size particularly at greater volume fractions and at short wavelengths. Simulated light transmission curves obtained by FDTD method showed that the optimized second phase size should be smaller than 800 nm for volume fraction of 10% and smaller than 200 nm for volume fractions of 20 and 30%. On the other words, within these sizes, the reduction of light transmission of ZnS/diamond composite compared to monolithic ZnS is lower than 10%.

Effect of second phase particles on mechanical properties and grain growth in a CoCrFeMnNi high entropy alloy

Effect of annealing of a cold-worked CoCrFeMnNi alloy at temperatures of 500–900 °C for 1–50 h on the structure and mechanical properties was studied in the present work. Annealing for an hour resulted in: i) recrystallization of the face-centered cubic (fcc) matrix at 600–900 °C; ii) precipitation of a Cr-rich body-centered cubic (bcc) phase at 500–700 °C or a sigma phase particles at 600–800 °C. Moreover, an increase in the annealing time to 50 h at 600 °C resulted in a continuous growth of both the fcc grans and bcc/sigma particles and in an increase in the fraction of the sigma phase at the expense of the bcc phase particles. The fcc grains growth was found to be controlled by the pinning effect of the second phase particles. Soaking for an hour at 500–600 °C resulted in a substantial increase in strength of the alloy due to the second phases precipitation. Meanwhile annealing at the higher temperatures as well as an increase in the annealing time at 600 °C resulted in softening; however, even after 50 h annealing, the alloy demonstrated reasonably high strength. In the latter case fine fcc grains, preserved due to the pinning effect by the second phases particles, contributed to strength mainly.

Hot Deformation Mechanisms of Ti22Al25Nb Orthorhombic Alloy

In this paper, the hot deformation behavior of Ti22Al25Nb was investigated by hot compression over a range of temperatures (950-1050 °C) and strain rates (0.001-1 s−1). Considering the adiabatic heating and friction, the original curves were corrected. The friction-corrected data were lower than the measured flow stress data. The flow stress data increased after the temperature correction owing to the elimination of the softening effect. In addition, the work hardening effects on the hot deformation of the normal and multi-peak flow stress curves were compared. A critical dislocation density was proposed to analyze the multi-peak phenomenon. When the dislocation density decreased to a critical value, the work hardening and dynamic recrystallization mechanisms reached a balance. Then, a new work hardening mechanism became dominant, and the flow stress increased. The effect of second-phase particles on the hot deformation mechanisms was investigated. The result showed that second-phase particles led to a high nucleation rate and a low growth rate of new recrystallization grains during the rapid hot deformation.