Amount Of Second Phase Particles Research Articles

Influence of Spray Angle on Particle Deposition and Thermal Shock Lifetime of Embedded Micro-Agglomerated Particle Coatings

The development of gas turbine technology has led to an increase in the complexity of the geometric shape of the sprayed workpiece. Consequently, it has become more difficult to maintain the perpendicularity of the spraying angle during the spraying process, thereby impacting the structure and performance of the coating. This study uses the atmospheric plasma spraying method to simultaneously spray two types of powder for the preparation of embedded micro-agglomerated particle (EMAP) coatings. The spraying process is conducted at four different angles, ranging from 90° to 30°, in order to analyze the influence of the spray angle on the particle deposition and coating performance. The experimental results demonstrate that the relative deposition efficiency, hardness, and elastic modulus of the EMAP coatings decreased as the spray angle decreased. The porosity exhibited a reduction when the spraying angle dropped from 90° to 50°, followed by a significant rise at 30°. The greatest relative amount of second phase particles embedded in the coating appeared at a spraying angle of 90°, amounting to 10.8%. The smallest amount was found at a spraying angle of 30°, with a relative quantity of 2.2%. Furthermore, the molten droplets of the first phase matrix powder underwent extension and fragmentation along the angular direction at low angles. At an angle of 90°, the maximum average thermal shock life was 40.6 cycles, with the best stability of thermal shock life. The decrease in the spraying angle resulted in a deterioration in both the thermal shock life and its stability.

Structure, defect substructure and fracture surface of low-carbon alloy steel welds

By the methods of scanning and transmission electron microscopy a structural phase state, defect substructure and fracture surface of low carbon alloy steel welds produced with use of carbon-containing addition and without it are investigated. The study of etched metallographic section structure of welds revealed a presence of a large amount of second phase particles (carbides, sulfides, oxides, etc.). It is shown that in weld with a carbon-containing addition the particles locate chaotically, and in weld without addition they decorate boundaries of ferrite grains. Dimensions of second phase particles vary in the limits from 0.8 μm to 5 μm and are identical for both types of welds. Analysis of fracture surface structure of welds is carried out. A presence of nonmetallic inclusions is detected. They are typical of mainly weld produced without a carbon-containing addition which may indicate its increased brittleness. Amount of micropores in fracture of weld with carbon-containing addition is many times greater than that in weld without addition, which is indicative of gas removal in use of carbon-containing addition. The quantitative analysis of structure and dislocation substructure parameters of weld metal is carried out, the estimates of contributions of scalar and excess dislocation density to strength of welds are performed. It is shown that higher values of scalar and excess dislocation density in the weld formed without carbon-containing addition in flux may be responsible for material embrittlement. A large quantity of stress concentrators in the weld without carbon-containing addition may result in material embrittlement.

A significant toughness enhancement, and microstructural evolution of an electric resistance welded (ERW) microalloyed steel

In this investigation, microstructural evolution and mechanical properties of an X52 microalloyed steel processed by a full scale industrial electric resistance welding (ERW) equipment was studied. The need for adequate level of mechanical properties, in particular toughness, in the welded pipes is discussed due to its industrial prominence. Optical microscopy (OM) and scanning electron microscopy (SEM) were used for microstructural evolution and fractography analysis. Results showed that employing a special annealing treatment of the welded pipe could enhance the mechanical properties and alleviate low toughness problem. Results also showed a significant variation in the microstructure of the pipe as a result of welding and its subsequent heat treatment processes. Electron backscatter diffraction (EBSD) results for the initial plate and the ERW processed cases showed a significant grain size refinement for the case of as weld and after the two-stage heat treatment. A fully random texture component was observed in {111} pole figure of the initial plate. A textured structure, with the components of Copper, Brass, S and Cube, was seen in the as weld condition. These texture characteristics remained in the system, though with lower intensity, after the normalizing stage heat treatment. Hence for its unpredictable toughness behavior. A completely weakened undesirable texture components was detected after the second stage of heat treatment together with smaller amount of second phase particles and smaller grain sizes. Finally, it was concluded that a proper mechanical properties combinations, particularly toughness value, could be attained as a result of this microstructural evolution.

Annealing Effect on the Microstructure and Mechanical Properties of AA 5182 Aluminum Alloy

Abstract The properties of aluminum alloys can be improved by the processing conditions that cause changes in the microstructure and by the addition of alloy elements. In order to understand the physical behavior and mechanical properties of aluminum alloys, it is important to be aware of some of the microstructural characteristics. Some of these characteristics are the morphology, alloy elements, volume and size, and second phase. In this study, we analyzed the effect of annealing on the mechanical and microstructural properties of the laminated AA 5182 aluminum alloy, when subjected to different annealing conditions. The alloy was heated to temperatures of 50o C, 100o C, 150o C, 200o C, 250o C and 300o C for 10 minutes and left to cool naturally. The evolution of the microstructure was characterized by optical and electronic microscopy with EDS, and, to obtain the mechanical properties, a tensile test was performed and the fractures were subsequently analyzed. The results showed that the heat treatment used reduced the amount of second phase particles and this influenced the mechanical properties.

Microstructure, texture, mechanical properties and biodegradability of extruded Mg–4Zn‒xMn alloys

The influence of 0.5 and 1.0 wt% Mn addition on the microstructure, texture, mechanical properties and biodegradability of the extruded Mg–4Zn alloy was investigated. The addition of Mn resulted in significant grain refinement as well as the formation of a strong fiber texture. The results of grain boundary misorientation analysis indicated that extension twinning plays an important role in dynamic recrystallization at elevated temperatures. Tensile test results showed substantial improvement in the yield stress (YS) from 198.4 MPa for the base Mg–4Zn alloy to 233.4 and 246.7 MPa for the Mg–4Zn–0.5Mn and Mg–4Zn–1Mn alloys, respectively. The same trend was observed in the ultimate tensile strength (UTS), while the high elongation to fracture of 33% was almost independent of the Mn content. The contributions of various strengthening mechanisms were measured to elucidate the main strengthening mechanisms. The obtained results indicated that the grain boundary, texture, and solid solution hardening have the most important contributions to the obtained overall YS, the effect of particles and dislocation strengthening being minute. The in-vitro degradation was evaluated by performing electrochemical and hydrogen evolution analyses. It was observed that the Mg–4Zn–0.5Mn alloy exhibits the lowest degradation rate, due to the optimum amounts of second phase particles, twins, and lower grain orientation spread (GOS) value.

Effect of molybdenum on properties of zirconium components of nuclear reactor core

The paper presents results of studies of the effect of Mo on properties of Zr and its alloys. In a structure of binary Zr-Mo alloys and Zr-Nb-Mo alloys a strong and corrosion-resistant phase ZrMo2 additionally appears. In Zr-Sn-Nb-Fe alloys Mo alloying leads to an increase in amount of second phase particles, reduces their dimensions and dissolves in Laves phase particles Zr(Nb, Fe)2. These structural changes led to increased strength of all studied Zr alloys. Alloying by Mo also improves corrosion properties of experimental Zr alloys containing Nb and Sn, the best being alloys with a content of 0.1–0.15% mass of Mo. Adding of 0.1% Mo in standard claddings from the E635 alloy (Zr-Sn-Nb-Fe) notably reduced their hydrogenation and propensity for nodular corrosion. The testing results and their comparison with a literature data made possible to determine the prospects and directions for further work on using of Mo for alloying Zr alloys.

Development of New Fast Algorithms for Calculation of Texture Evolution during Hot Continuous Rolling of Al-Fe Alloys

A new model for fast calculation of texture evolution during the hot rolling of low-alloyed aluminum sheets with iron addition in continuous mill is developed. Experiments are carried out for developing a relationship between accumulated strain and deformation texture components. A special fast analytic algorithm is used for the calculation of strip temperature and accumulated strain. For the recrystallization texture components calculation, Vatne's approach is used. For its successful realization, some additional experiments and model improvement are also carried out. These experiments help to establish the rate of grain border movements and the amount of second-phase particles with size critical for recrystallization nucleation. The developed model is used for calculation of the texture evolution during 8011 alloy hot rolling in an industrial continuous mill. The results enable us to choose the correct temperature and deformation parameters that allow us to obtain the necessary texture composition. In addition, the approach can be also adjusted for other aluminum alloys after some additional improvements. Generally, the method can be applied to steels, but in this case some empirical formulations for deformation and recrystallization textures formation used in calculations should be revised.

A study on microstructure and mechanical properties of AA 3003 aluminum alloy joints by underwater friction stir welding

The friction stir welding of AA 3003 aluminum alloy with different initial microstructures was carried out under different welding conditions. The microstructural evolution and mechanical properties of weld joints were investigated. The results showed that the size of recrystallized grains and the amount of second-phase particles in the weld nugget zone (WNZ) decreased with decreasing welding ambient temperature. At the same welding condition, the size of recrystallized grains in the hot bands was smaller than that in the annealed hot bands, while the volume fraction of (Fe,Mn)Al6 particles in the hot bands was lower than that in the annealed hot bands. The relationship between the yield strength and grain size was characterized by the Hall-Petch equation. The values of σ0 and k in WNZ for the hot bands were higher than those for the annealed hot bands.

Effects of Si Content on the Tensile Strength and Machinability of Al-Mg-Si-Cu-Mn-Cr Alloys

This study investigated the effects of the Si content on the tensile properties and machinability of 6xxx−series aluminum alloys for application in hydrogen container valve housing. Four types of extruded Al−Mg−Si−Cu−Mn−Cr alloy specimens with different Si contents of 0.6−3.0 mass% were prepared. The effects of the Si content on characteristics such as microstructural features, tensile strength, and drill machinability were examined and compared with those of a commercial A6061 alloy. These specimens were found to exhibit different microstructures, tensile strengths, and chip segmentation behaviors after T6 heat treatment. These results were attributed to the interaction of the amount of second phase particles and solid-solute Mn and Cr with changes in the Si content.

Electrochemical behavior of anodized AA7075-T73 alloys as affected by the matrix structure

A set of standard 7075-T73 alloy samples was prepared for comparison with samples that had been cold-rolled before the T73 treatment. One set of samples was subjected to cold rolling at room temperature and another deep-cooled in liquid nitrogen prior to rolling. Both sets of samples were then subjected to a T73 treatment. The microstructure of the different samples was observed and their micro-hardness was tested and recorded. The samples that had first been subjected to the deep-cooling treatment prior to rolling and T73 treatment (CRST73) showed few subgrains and smaller amounts of second phase particles in the matrix than was the case with the other two sets of samples. The experimental results also indicated that the matrix of the CRST73 samples mostly displayed disk-like precipitates of Mg2Zn and Al2Cu. After anodization, this batch of samples demonstrated superior corrosion resistance and the lowest passive current density during potentiodynamic polarization testing.

EFFECT OF Bi ADDITION ON THE CORROSION RESISTANCE OF Zr-lNb ALLOY IN DEIONIZED WATER AT 360 °C AND 18.6 MPa

The effect of Bi contents on the corrosion resistance of Zr-1Nb-xBi (x=0.05—0.3, mass fraction, %) was investigated in deionized water at 360 and 18.6 MPa by autoclave tests. The results show that the corrosion resistance of Zr-1Nb alloy can be improved by adding Bi, and the more the Bi content is, the better the corrosion resistance is. TEM and EDS analyses on the microstructures of the alloys show that there are two types of second phase particles (SPPs), including ZrNbFe and β- Nb. The Bi contents have little effect on the type, size and amount of SPPs, 0.3%Bi can be completely dissolved in α-Zr matrix and has no influence on the solution content of Nb in α-Zr matrix. From the fracture and inner surface morphology of oxide films observed by SEM, it can be seen that the Bi dissolved in the α-Zr could noticeably slow down the microstructural evolution of oxide film, including the propagation of micro-cracks and the transformation from columnar grains to equiaxed grains in the oxide film.

Study on the Effect of Doping With Poly Zinc Acrylate Complex (PZA) on the Superconducting Properties of Bulk ${\rm MgB}_{2}$

In this work, the effect of doping with 5% to 20% Poly Zinc Acrylate complexes (PZA) on the MgB2 phase formation was studied. The changes of the lattice parameter and the amount of substituted Carbon, of the microstructure as well as the critical current temperature (Tc) and the critical current density (Jc) of bulk MgB2 have been studied systematically. The DTA-TG and IR results show that the PZA was decomposed between 400°C and 600°C and the main decomposition products were carbonized polymers and ZnO. The lattice parameters ? in all PZA doped MgB2 samples were decreased by different degrees, which indicates a gradual substitution of Carbon for the Boron sites in the MgB2 lattice structure. Comparing with the undoped sample, the Jc values of all the doped samples were enhanced for about an order of magnitude under high magnetic fields. The Jc value of MgB2 sample with 20% PZA doping and sintered at 800°C for 1 h reached 0.8 × 104 A/cm2 at 5 k and 8 T. TEM images reveled a considerable amount of second phase particles of ~5 nm size and high density dislocations were observed in MgB2 grains.

Effect of equal-channel angular pressing routes on high-strain-rate deformation behavior of ultra-fine-grained aluminum alloy

The effect of equal-channel angular pressing (ECAP) route on the high-strain-rate deformation behavior of ultra-fine-grained aluminum alloy was investigated. The 8-pass ECAPed specimens deformed via three different routes consisted of ultra-fine grains 0.5 μm in size, and contained a considerable amount of second-phase particles, which were fragmented and distributed in the matrix. In the torsion tests, the maximum shear stress significantly increased with increasing number of ECAP passes, while the maximum shear stress and fracture shear strain were lowest in the specimen deformed via route A among the three 8-pass ECAPed specimens. Observation of the deformed area beneath the fractured surface revealed the adiabatic shear bands of 100 μm in width in the specimen deformed via route A, which minimized the maximum shear stress and fracture shear strain, whereas they were hardly formed in the specimens deformed via route B or C. The formation of adiabatic shear bands was explained in terms of critical shear strain, deformation energy required for void initiation, and microstructural homogeneity related to ECAP routes.

Influence of spark plasma sintering temperature on sintering behavior and microstructures of dense bulk MoSi 2

Spark plasma sintering was employed to synthesize high-density bulk MoSi 2 in one step, using Mo and Si element powders as starting materials. Influence of sintering temperature on sintering behavior and microstructures of MoSi 2 were investigated. The sintering behavior at whatever temperature (1473, 1673 and 1873 K) is characterized by four stages, i.e., initial expansion, slight shrinkage, abrupt shrinkage and slight expansion. The maximum shrinkage displacement increased with increasing sintering temperature. When the sintering temperature reaches 1673 K or 1873 K, the second phases, i.e., SiO 2 and Mo 5Si 3/Mo 4.8Si 3C 0.6, were uniformly distributed in the synthesized MoSi 2 matrix accompanied with a small amount of porosity. Most of SiO 2 and Mo 5Si 3/Mo 4.8Si 3C 0.6 particles were concentrated at grain boundaries. The relative density of the products (atomic ratio: Mo/2.00Si) was improved tremendously from 89% to 98.2% over the range 1473–1673 K, and much smaller enhancement up to 99.0% was achieved from 1673 to 1873 K. At the same time, the grain size and amount of second phase particles (mainly Mo 5Si 3/Mo 4.8Si 3C 0.6) consistently increased with increasing temperature over 1473–1873 K. However, the use of a slight excess of Si (e.g., atomic ratio: Mo/2.06Si) at 1673 K resulted in dense products of MoSi 2 nearly free of Mo 5Si 3/Mo 4.8Si 3C 0.6, with the relative density of 99.2% and the average grain size of 5–10 μm. Thereby, in order to pursue an equilibrium among densification, microstructural refinement and formation of second phases, the most suitable sintering temperature and stoichiometry for fabrication of MoSi 2 by SPS are recommended to be 1673 K and a hyperstoichiometry of Mo/2.06Si in the present work.

Plane strain fracture toughness of scandium doped Al–6Mg alloy

The effect of microstructural parameters on the plane strain fracture toughness of scandium doped Al–6Mg alloys has been studied. Al–6Mg alloys with trace addition of scandium are subjected to annealing at different temperatures. Plane strain fracture toughness property ( K IC) of the alloys under different thermal conditions is measured. It is found that fracture of coarse insolubles adversely affect the fracture toughness of binary Al–6Mg alloy. Scandium treated alloys have shown improvement in fracture toughness due to the reduction in size and amount of second phase particles. The isochronal age hardening behaviour of low scandium alloy is found similar to the variation of fracture toughness with ageing temperature. However, high scandium alloy records a minimum in fracture toughness value at the peak age hardening temperature due to extensive formation of planar slip bands.

Numerical simulation of thermal residual stress in Mo- and FeAl-toughened Al 2O 3

Microstructure-level residual stresses occur in composite ceramics during processing, mainly as a result of thermal expansion anisotropy. The magnitude of these stresses can be sufficiently high to cause spontaneous microcracking when cooled from the processing temperature. They are also likely to affect where cracks initiate and propagate under macroscopic loading. Alumina-based composites containing different amount of second phase particles with lower (Mo) and higher thermal expansion coefficient (FeAl) were prepared. Fluorescence spectroscopy was used to measure the residual stress distribution due to thermal expansion anisotropy in these composites. A finite element model was also established for two-phase ceramics. The residual stress distribution in the model was analyzed, and the variation regularity of internal stress along with the second phase particle's volumetric proportion was given.

Dynamic deformation and fracture behavior of ultrafine-grained aluminum alloy fabricates by equal-channel angular pressing

In the present study, ultrafine-grained microstructures of a conventional 5083 aluminum alloy were fabricated by equal-channel angular pressing, and their dynamic deformation and fracture behavior were investigated. Dynamic torsional tests were conducted on four aluminum alloy specimens using a torsional Kolsky bar, and then the test data were analyzed in relation to microstructures, tensile properties, and adiabatic shear-banding behavior. The equal-channel angular-pressed (ECAP) specimens consisted of ultrafine grains and contained a considerable amount of second-phase particles, which were refined and distributed homogeneously in the matrix as the equal-channel angular pressing pass number increased. The dynamic torsional test results indicated that the maximum shear stress increased, while the fracture shear strain remained constant, with increasing equal-channel angular pressing pass number. Observation of the deformed area beneath the dynamically fractured surface showed that a number of voids initiated mainly at second-phase particle/matrix interfaces and that the number of voids increased with increasing pass number. Adiabatic shear bands of 200 to <300 µm in width were formed in the as-extruded and 1-pass ECAP specimens having coarser particles, whereas they were hardly formed in the four-pass and eight-pass ECAP specimens having finer particles. The possibility of adiabatic shear-band formation was explained by concepts of absorbed deformation energy and void initiation.

Investigation of Nucleation Mechanisms of Recrystallization in Warm Rolled Fe&lt;sub&gt;3&lt;/sub&gt;Al Base Alloys

It has been shown in literature that the mechanical properties of Fe3Al base alloys are strongly dependent on the heat treatment subsequent to warm rolling. Therefore, the recrystallization behavior of 3 different hot and warm rolled and annealed Fe3Al-based alloys has been investigated. Two of these alloys contain different forms and amounts of second phase particles, while a pure binary alloy was taken as reference. All alloys develop a-(&lt;110&gt;||RD) and g-(&lt;111&gt;||ND) fiber bcc-type rolling and annealing textures, however, the amount of a- and g-fibers vary in dependence of the alloy composition. The current work presents the investigations on the nucleation process during annealing that has been studied by means of high resolution backscatter electron diffraction (EBSD) in the SEM. In particular the occurrence of orientation gradients in the deformed structure and their crystallographic relationship to the formation of new grains was investigated. It was shown, that small particles favor the a-fiber component by hindrance of the growth of new grains. In contrast, large particles lead to particle stimulated nucleation. This weakens the overall texture but does not randomize it since the orientation gradients around particles keep a relationship with the matrix orientation.

An improved equation for crystal size distribution in second-phase influenced aggregates

A model is presented to calculate crystal size distributions (CSDs) for coarsened mineral aggregates. The equations consider the second-phase particles inside coarsening aggregates. This approach is different from other published kinetic growth equations. The proposed model includes grain size limits due to the presence of second-phase particles. These limits control the behavior of growing grains. The physical basis for this model is taken from a neighborhood-coarsening model. The model is able to compute coarsening of a given set of crystal sizes, to simulate the evolution of the CSD, and to describe the influence of the amount and size of the second-phase particles. The model is limited to rocks that can be described as matrix with second phases. For very low second-phase concentrations (volume fraction 0.5), the model would not allow coarsening or the system can be no longer described as matrix and second-phase particles. Depending on the size and amount of second phases, the CSD develops similar to LSW at high growth rates, but intermediate growth rates produce CSDs that are unknown in other closed-system coarsening models. To test the model, natural data from a contact-metamorphic calcite marble with different mica contents have been compared with simulated CSDs. The measured and simulated CSDs can be well described by the proposed model for variable amounts of second-phase particles. The two-phase model is applicable to impure carbonates, mica-bearing quartzites, or impure dunites. The proposed model has interesting applications to experimental data, where porosity may influence grain coarsening.

Ａｌ−Ｍｇ−Ｓｉ系合金板材の機械的性質に及ぼす鉄量の影響

The influence of iron content on mechanical properties of Al–1.0mass%Si–0.5mass%Mg–0.1mass%Mn alloy T4 sheets was investigated. The amount of Al–Fe–Si second phase particles increased with iron content, thus silicon atoms were consumed by formation of Al–Fe–Si particles. Furthermore, tensile strength of the samples in T4 condition was not influenced by iron content, but the paint bake response decreased over 0.5 mass%. This was the result of lowering age hardening rate at the early stage of artificial aging because of the loss of silicon atoms. Also, bendability of the samples became worse with iron content. But, it was the worst at 0.5 mass% of iron content, while it at over 0.5 mass% became better or the same. The reason was considered as below. Cracking by bending occurred along the second phase particles and the shear bands. And the amount of second phase particles increased with iron content, whereas the formation of shear bands decreased with iron content over 0.5 mass% because of the loss of silicon. In addition, formability became worse slightly with iron content.