Morphology Of Second Phase Research Articles

Microstructures and Mechanical Properties of Extruded Mg-Gd-Al Alloys: Influence of Initial Second-Phase Morphology Before Extrusion

Microstructures and Mechanical Properties of Extruded Mg-Gd-Al Alloys: Influence of Initial Second-Phase Morphology Before Extrusion

High-Pressure Die Casting of Al–Ce–La–Ni–Fe Alloys

The effects on phase equilibria of La and Fe additions to the Al–Ce–Ni-based alloy system are explored under high-pressure die casting conditions. The addition of La to Al–Ce–Ni-based alloy system only reacts with Ce synergistically to promote the formation of the Al11(Ce,La)3 intermetallic phase as predicted by CALculation of PHAse Diagrams (CALPHAD) and verified experimentally. High Fe additions react with Ni to form the Al9FeNi intermetallic phase, which is an additional eutectic former. The targeted co-precipitation type eutectic morphology is achieved in the alloys studied. Additional coarse particles of Al11(Ce,La)3, present in the alloys studied and not predicted by CALPHAD, are attributed to possible inclusions of Ce and La oxide, present in the mischmetal feedstock used. Both alloys exhibit exceptional mechanical stability after 10 hours at 400 °C due to the stability of the phases formed during solidification. The alloy with high Fe additions possessed better mechanical properties after heat treatment based on the higher eutectic content and more substantial improvement to the morphology of secondary phases after treatment.

Effect of Sm Addition on the Electrochemical Behavior and Discharge Performance of Mg-1Sn-1Ca-0.3Mn Alloy as Mg-Air Battery Anodes

Sm element is a relatively inexpensive rare Earth element. The effect of Sm content on the microstructure, electrochemical behavior and discharge performance of Mg-1Sn-1Ca-0.3Mn (TX11) alloy was investigated through scanning electron microscopy (SEM), electrochemistry workstation and Mg-air battery tests. Results reveal the addition of Sm does not change second-phase morphology of TX11 alloy, CaMgSn and Mg2Ca phases solidly dissolves Sm elements. The electrochemistry results depict that Sm addition deteriorates the corrosion resistance and electrochemical activity of TX11 alloy, which is attributed to Sm solid solution changing the original second phase properties. In addition, Mg-1Sn-1Ca-0.5Sm-0.3Mn anode presents the highest anodic efficiency and specific capacity among Mg-1Sn-1Ca-xSm-0.3Mn (x = 0. 0.5, 1, 2 wt%) alloys, those value is 60.2% and 1306.801 mA h g−1, respectively, which attribute to the highest dissolution activity and the smoother discharge surface morphology. Micro-Sm alloyed is beneficial for improving the anodic efficiency of TX11 anode.

High strength, ductility and sheet formability by normalizing and quenching of low carbon microalloyed dual-phase steel

This work investigates the possibility of developing high strength, ductility, and normal-anisotropy in cold rolled (CR, ∼84%) 0.05 wt% carbon microalloyed dual-phase (DP) steel sheets by normalizing (N, 920°C, 30 min) followed by intercritical annealing and quenching (IA&Q, 80 0°C, 3 min). CR + N produces ferrite with ∼6.9μm grain size and ∼0.23 bainite fraction with ∼5.3μm packet size. A high engg. (true) strength of ∼605(∼798)MPa; uniform engg. (true) strain eU≈0.32 (εU≈0.28); engg. fracture strain, ef≈0.48; with high normal average anisotropy (r‾) of ∼1.84 and low planar anisotropy, Δr of ∼0.30 could be obtained. Further, IA&Q produced ferrite with ∼6.3μm average grain size, ∼0.25 martensite fraction (Ceq≈0.16) with ∼3.2μm island size. A high engg. (true) strength of 690(864)MPa; engg. (true) uniform strain of ∼0.25 (∼0.22); engg. fracture strain ∼0.39; and high r‾ of ∼1.51, low Δr of ∼0.31, suitable for sheet metal formability, were obtained. The high strength could be attributed to (a) fine ferrite grain size, (b) secondary phase fraction (∼0.23B/∼0.25M), packet size and island morphology, and (c) geometrically necessary boundaries (GNB). High ductility could be due to (a) fine ferrite grains with secondary phase morphology, (b) GNB, coincident site lattice boundaries (CSLB), and random high angle grain boundary (RHAGB) networking. Better anisotropic properties could be associated with strong γ-fiber, and suppression of α-fiber and θ-fiber texture. Loci in the stress and strain space indicate that the hydraulic bulge and plane-strain biaxial strength-ductility improves to 950MPa-0.41 and 1030MPa-0.67 after CR + N, and to 968MPa-0.30 and 1070MPa-0.58 after CR + N + IA&Q.

Morphology prediction of elastically interacting Zr hydride precipitates and cracks in [formula omitted]-Zr using atomistically informed Eshelby’s ellipsoidal inclusion

We propose an atomistically informed Eshelby’s inclusion analysis to investigate the morphology of secondary phases, which elastically interacted with each other through their respective local strain fields. Using the proposed method, we predict the morphology of δ-hydride precipitates and cracks, which interacted in the α–Zr matrix. Planar cracks nucleate along the basal-normal δ-hydride disk. And at the crack tip, the prismatic-normal δ-hydride disk also nucleates depending on the stress condition around the crack, constructing the hydride-crack network. The findings contribute to the understanding of the fracture mechanism of Zr alloys, such as delayed hydride cracking, which is caused by Zr hydride.

Thermal Conductivity of Aluminum Alloys-A Review.

Aluminum alloys have been extensively used as heatproof and heat-dissipation components in automotive and communication industries, and the demand for aluminum alloys with higher thermal conductivity is increasing. Therefore, this review focuses on the thermal conductivity of aluminum alloys. First, we formulate the theory of thermal conduction of metals and effective medium theory, and then analyze the effect of alloying elements, secondary phases, and temperature on the thermal conductivity of aluminum alloys. Alloying elements are the most crucial factor, whose species, existing states, and mutual interactions significantly affect the thermal conductivity of aluminum. Alloying elements in a solid solution weaken the thermal conductivity of aluminum more dramatically than those in the precipitated state. The characteristics and morphology of secondary phases also affect thermal conductivity. Temperature also affects thermal conductivity by influencing the thermal conduction of electrons and phonons in aluminum alloys. Furthermore, recent studies on the effects of casting, heat treatment, and AM processes on the thermal conductivity of aluminum alloys are summarized, in which processes mainly affect thermal conductivity by varying existing states of alloying elements and the morphology of secondary phases. These analyses and summaries will further promote the industrial design and development of aluminum alloys with high thermal conductivity.

Corrosion behavior of severely plastically deformed Mg and Mg alloys

Magnesium (Mg) alloys have several advantages, such as low density, high specific strength and biocompatibility. However, they also suffer weak points, such as high corrosion, low formability and easy ignition, which makes their applications limited. Many studies have been conducted to overcome these disadvantages and further improve the advantages of Mg alloys. Severe plastic deformation (SPD) is one of the most important techniques and has great effects on the microstructure refinement of Mg alloys and improvements in their strength and formability. Several researchers have studied the corrosion behavior of SPD-processed Mg alloys in recent decades. However, these studies have reported some controversial effects of SPD on the corrosion of Mg alloys, which makes the research roadmap ambiguous. Therefore, it is important to review the literature related to the corrosion properties of Mg alloys prepared by SPD and understand the mechanisms controlling their corrosion behavior. Effective grain refinement by SPD improves the corrosion properties of pure Mg and Mg alloys, but control of the processing conditions is a key factor for achieving this goal because texture, dislocation density, size and morphology of secondary phase also importantly affects the corrosion properties of Mg alloys. Reduced grain size in the fine grain-size range can decrease the corrosion rate due to the increased barrier effect of grain boundaries against corrosion and the formation of a stable passivation layer on the surface of fine grains. Basal texture reduces the corrosion rate because basal planes with the highest atomic planar density are more corrosion resistant than other planes. Increased dislocation density after SPD deteriorates the corrosion resistance of the interior grains and thus proper annealing after SPD is important. The fine and uniform distribution of secondary phase particles during SPD is important to minimize the micro-galvanic corrosion effect and retain small grains during annealing treatment for removing dislocations.

Influence of thermo-mechanical conditions on the microstructure and mechanical property of spray-formed 7055 aluminum alloy

A series of isothermal compression experiments under a deformation temperature ranging from 380 ℃ to 440 ℃ and strain rates ranging from 0.1 s−1 to 15 s−1 were carried out to investigate the flow behavior of a spray-formed 7055 aluminum alloy. The microstructural morphology, chemical composition and orientation characteristics were examined by optical microscopy (OM) and scanning electron microscope (SEM) combined with energy dispersive spectroscopy (EDS) detection and electron back scattered diffraction (EBSD) technology. The results show that the dynamic softening mechanisms were profoundly affected by different thermo-mechanical conditions and the deformation stage, which caused a complicated material flow behavior with the related microstructure development and texture evolution. A partially dynamic recrystallized behavior was observed, which occupied a relatively small volume fraction of the total deformed microstructure under current deformation conditions. The relationship between the different mechanisms for dynamic recrystallization (DRX) and the hot deformation conditions was discussed and confirmed through crystal orientation research. The changes in chemical composition and morphology of second phases were studied and their existing forms, with corresponding impacts on microstructure under different hot deformation conditions, were analyzed. The microhardness tests of the deformed matrix were implemented to reveal the material strengthening mechanism. This work contributes to the comprehensive understanding of the high temperature flow behavior, microstructural characteristic and mechanical properties of spray-formed 7055 aluminum alloy, which provides theoretical support for related research and potential industrial applications.

Effect of the nanostructuring by high-pressure torsion process on the secondary phase precipitation in UNS S32750 Superduplex stainless steel

In this work, the precipitation and the morphology of secondary phases after severe plastic deformation (SPD) processing followed by an isothermal treatment was investigated. High-pressure torsion (HPT) was the SPD process carried out on superduplex 2507 (UNS S32750) stainless steel material under P = 6 GPa at room temperature. At this high strain levels (ε up to 170) samples have shown grain size decrease and strained microstructure with high dislocation density and nanostructure features. After a short isothermal treatment at 830 °C, the sigma phase and chromium nitrides were revealed as the main secondary phases identified by scanning and transmission electron microscopy and element analysis by energy dispersive spectroscopy. Scanning precession electron diffraction and automated crystal orientation mapping have been carried out in order to confirm the precipitation of the secondary phases. In fact, the results provide evidence that the precipitation of chromium nitrides seems to be the preferred nucleation site for sigma phase at higher deformation strain, in addition to the intergranular precipitation of sigma. Both the sigma phases nucleated integranularly and besides chromium nitrides are randomly orientated.

Effects of Ca addition on microstructure, electrochemical behavior and magnesium-air battery performance of Mg-2Zn-xCa alloys

• Effect of Ca on the properties of second phases in Mg-Zn-Ca alloys was studied. • The optimal alloy exhibits beneficial corrosion resistance and discharge properties. • Discharge sequence of precipitated second phases was investigated. In this research, the micro-morphologies, electrochemical behaviors and battery discharge performances of the Mg-2Zn- x Ca alloys as potential anode materials were investigated. The micro-morphology results showed that for the alloy with low Ca content ( x = 0.1 and 0.2), only the Ca 2 Mg 6 Zn 3 phase was observed to precipitate in a punctate form within the crystal. As the Ca content rose, the amount of the punctate Ca 2 Mg 6 Zn 3 increased while the strip-shaped Ca 2 Mg 6 Zn 3 phase precipitated at the grain boundary was also observed. When the Ca content reached 0.5 wt% and higher, the second phases were observed to be both Mg 2 Ca and Ca 2 Mg 6 Zn 3 phase which precipitated at the grain boundary and the morphology of second phases gradually changes into a continuous network. Among the four tested alloys, the Mg-2Zn-0.2Ca sample delivered the best electrochemical activity with more negative corrosion potential and larger corrosion resistance in electrochemical experiments. Battery performance tests showed that the Mg-2Zn-0.2Ca anode exhibited an improved specific capacity of 1344.1 mAh g −1 and high anodic efficiency of 61.0% at 10 mA cm −2 . The discharge order of the precipitated phase has been derived as follows: Mg 2 Ca > Mg > Ca 2 Mg 6 Zn 3 .

Particle surface effects on the spall strength of particle-reinforced polymer matrix composites

Prior research has observed that the presence of secondary phases in metal alloys influence the failure behaviour of the bulk material, a response which varies based on secondary phase morphology and adhesion to the matrix material. Particle-reinforced polymer composites offer a material system in which variations in adhesion between the sub-phase and polymer matrix can be manipulated with relative ease. In the present study, we investigate the influence of both the particle morphology and matrix-particle interface adhesion on the spall strength of particle-reinforced polymer composites. Adhesion control was achieved using a adhesion-impeding silane treatment of the surface of micron-sized alumina particles. The composites were characterized based on their dynamic tensile (spall) failure strengths. The results showed that while particle morphology effects were minimal, the loss of surface adhesion resulted in a drastic reduction in spall strength. Fractography performed on the fracture surface of the recovered samples showed evidence of poor wetting in the silane-treated composites, confirming the role of particle adhesion in moderating this failure mode.

Effect of nonmetallic inclusions morphology on destruction of a perspective high strength corrosion-resistant steel 04Х20Н6Г11М2АФБ

Alloying by nitrogen imparts to a steel high strength, viscosity, corrosion resistance and enables to save expensive alloying elements. As a result of theoretical and experimental studies carried out last decades, the problems of composition optimization, plastic deformation and thermomechanical treatment were solved as a whole. The solutions were used at elaboration of new perspective high strength corrosion-resistant steels, in particular, of steel 04 Х 20 Н 6 Г 11 М 2 АФБ . The items of comprehensive hardening of nitrogen-bearing steel of the mentioned composition for plates production were studied quite well. Effect of grain and subgrain metal structure, recrystallization, morphology of secondary phases, their composition and other factors on mechanical and corrosion properties of the steel were studied earlier. However, there are practically no studies dealing with morphology, chemical composition, sulphide and oxide nonmetallic inclusions distribution, evaluation of their influence on deformability and properties of high strength nitrogen-bearing steels, including properties in Z-direction. The aim of this study was revelation of dependence of the steel destruction character at rupture on the type and morphology of nonmetallic inclusions. Study of morphology, chemical composition, sulphide and oxide nonmetallic inclusions distribution density was carried out, as well as evaluation of their influence on properties of hot-rolled sheet, made of experiment high strength steel 04 Х 20 Н 6 Г 11 М 2 АФБ . It was determined, that nonmetallic inclusions of oxides, sulphides and nitrides can locate in a plane, parallel to Z-direction in both ways: evenly and forming stitches, at that one stitch can contain particles of various types. Comparatively low level of plasticity in Z-direction is stipulated both by general contamination of the metal by oxide inclusions and by stitch morphology of accumulation of nonmetallic inclusions of various types. It was shown, that at comparatively low density of nonmetallic inclusions stitches, their length plays the main role in the plasticity decrease in Z direction. In case of many stitch accumulations, the distance between them begins to play the leading role.

Effect of Solidification Time on Microstructure, Wettability, and Corrosion Properties of A205-T7 Aluminum Alloys

In the present study, the grain size, second-phase morphology, hardness, water wetting behavior, and corrosion resistance of A205, as a function of solidification time, were investigated. A205 is aluminum–copper alloy that is described in the AA Pink Sheets as “Primarily used for making metal matrix composites” (AA Registration Record Pink Sheets, ISSN: 2377-6722, Footnote 13, Aluminum Association, 2018) and as defined by AMS as a “dilute aluminum/TiB2 metal matrix composite” (AMS D Nonferrous Alloys Committee in Cast aluminum alloy composite 4.6Cu–3.4Ti–1.4B–0.75Ag–0.27Mg (205.0/TiB2/3p-T7P) investment cast, solution, and precipitation heat treated, SAE International, 2014). To study the effect of solidification time, a step sand casting, with varying section thickness, was made and subjected to a modified T7 heat treatment. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis were utilized to study microstructure, morphology, elemental composition, and phases in the A205 samples, respectively. Potentiodynamic polarization experiment was used to measure the corrosion resistance of the A205 samples. The casting process was also simulated by use of a commercial software. Conclusions drawn from the simulation process show that larger thickness allows for higher solidification time and greater microporosity. It was observed that solidification time has a direct impact on grain size. The phase identification result shows that the two main phases of the alloys are Al and TiB2, while a modified heat treatment cycle makes a complete solution of copper in the grains. Wetting study shows that surface chemistry is not a controlling factor on contact angles, while corrosion result shows a relationship between solidification time and corrosion resistance of the A205 samples. It was observed that there is almost 70% decrease in corrosion rate from the sample with the least section thickness to the sample with the largest section thickness.

Microstructure of the novel biomedical Mg–4Y–3Nd alloy prepared by spark plasma sintering

One of the prominent applications of magnesium alloys, thoroughly investigated in recent years, is medicine. The commercial WE43 (Mg-4wt.%Y-3wt.%mischmetal) alloy was reported to exhibit superior in vitro and in vivo performance, however, the presence and possible harmful effect of rare earth (RE) elements mischmetal in this alloy have been vastly debated. For this reason, the RE mischmetal was substituted in this study by pure neodymium, which exhibits rather low toxicity. In this way, a novel WN43 (Mg-4wt.%Y-3wt.%Nd) alloy was prepared, with well-defined composition. In order to attain a good control over the grain size and phase distribution, a modern spark plasma sintering (SPS) method was employed. The main objective of this study was to examine the effect of sintering parameters on the resulting microstructure (type and morphology of secondary phases, grain structure, and residual strain) and microhardness (Hv). The application of relatively high pressure (100 MPa) during consolidation leads to the production of practically fully compact final material. Increasing sintering temperature (from 400 up to 500 °C) stimulated homogenization and stabilization of the microstructure and reduction of the internal strain. On the other hand, the effect of sintering time (3 or 10 min) was rather negligible. Furthermore, the microhardness experiments revealed that the softening effect due to homogenization and decrease in the dislocation density at higher sintering temperatures was well-compensated by precipitation hardening as the hardness values were comparable in all the samples. The understanding of microstructure evolution as a function of sintering parameters can be of particular importance for subsequent mechanical, corrosion and in vivo degradation testing of this novel biomedical magnesium alloy.

Boosting the superconducting properties of Fe(Se, Te) through hexagonal phase manipulation

Halogen doped Fe(Se, Te) superconducting materials were successfully synthesized through the eutectic transformation method. Both the distribution and morphology of the secondary hexagonal phase were tuned accordingly by substituting halogen elements. The morphology of the hexagonal phase was transformed from plate-like lamellar to agglomerated dots or bulk precipitates as the doping elements changed from F to Cl and Br. Moreover, the flux pinning mechanism, which represents the ability of materials to trap the penetrating magnetic field, was observed to change from Δκ to point pinning when doped by elements with heavier atomic mass. As a result, tremendous optimization of the critical current, upper critical field, and thermally activated flux flow activation energy were achieved in the as-prepared samples, with a specific value of 7 times, 2 times, and 3 times, respectively, in FeSe0.45Te0.5F0.05 compared with the values for the undoped sample. Our results reveal that the light-halogen element doping is a promising way to optimize the superconductivities in the Fe(Se, Te) systems and inspire us to manipulate the morphology of secondary phase to boost the superconductivities in iron-based superconductors.

Novel insight into mechanism of secondary phase's morphology evolution in hypomonotectic Cu-Pb-Sn alloy during solidification

In the present study, hypomonotectic Cu-Pb-Sn alloys with Pb-rich secondary phase particles (SPPs) in different morphology were prepared at specific casting temperature (Tq) corresponding to different molar fraction (fS0) of the existing primary α-Cu (S0) before pouring. The results show that the SPPs transform from continuously network to independently rod-like morphology and then become abnormally coarsening with increasing Tq. Phase-field calculation was carried out to discuss the morphology evolution mechanism of the secondary phase droplets (L2), which can effectively overcome the experimental difficulty of the investigation about the monotectic reaction with an extremely high reaction rate. It is found that fS0 can strongly affect such morphology evolution. A relatively high fS0 corresponding to a lower Tq is proven to promote the formation of network L2. In contrast, a lower fS0 corresponding to a higher Tq can promote the formation of rod-like L2, which is mainly benefitted from the immiscibility of the Cu-rich residual liquid (L1) and L2. However, if Tq continuously increases, abnormally coarsening of L2 will occur mainly through collision and coagulation driven by the Marangoni force and the solidification front's pushing. The coarsening process of L2 during heating was observed through synchrotron radiation. This work reveals the morphology evolution mechanism of the SPPs in hypomonotectic Cu-Pb-Sn alloy during the monotectic reaction.

Influence on the Quality of Secondary Aluminum Alloy Casts by Mn Addition

Abstract The quality of aluminum casts is necessary in order to reach sufficient properties required for application. The decreasing in the properties of aluminum cast mainly related with microstructure, especially with size and morphology of second phases. One of such second phases in aluminum alloys are the β-phases. These phases are unwonted mainly because of the decreasing of mechanical properties. The contribution is deal with influence of addition of Mn to affecting the formation of β-phases in the AlSi7Mg0.3 and AlSi7Mg0.6 cast alloys. These materials are used for application especially automotive industry. The results shows, that addition of Mn is not sufficient for affecting of formation of the Fe-rich phases in AlSi7Mg0.6 cat alloys, but in the AlSi7Mg0.3 this addition lead to changes in formation of Fe-rich intermetallic phases.

The influence of Sc addition on microstructure and tensile mechanical properties of Mg–4.5Sn–5Zn alloys

Abstract The microstructure and tensile properties of the as-cast and as-rolled Mg–4.5Sn–5Zn alloys by adding various Sc content were investigated. Improvement of the tensile properties in as-cast Sc-containing alloys is attributed to the grain refinement and modification of secondary phase morphology. Three types of precipitates, namely spherical Mg2Sn, rod-like MgZn and Sc-rich phases were dispersed in the matrix of the Sc added Mg–4.5Sn–5Zn alloys after hot rolling deformation. In addition, weakening and deflecting of the basal texture in as-rolled alloys were found and were attributed to Sc addition. Further increasing the Sc addition rate to 0.4 wt.%, however, resulted in the clustering of the Sc-rich phases and was found to reduce the tensile properties of the alloy, especially the elongation. The as-rolled Mg–4.5Sn–5Zn–0.3Sc alloy exhibits an optimum combination of tensile properties. The ultimate tensile strength, yield strength and elongation are 293.0 MPa, 164.2Mpa and 21.5%, respectively, and the elongation is about 68% higher than that of Sc-free alloy.

Influence of small amount and different morphology of secondary phases on impact toughness of UNS S32205 Duplex Stainless Steel

Duplex Stainless Steels (DSSs) are biphasic austenite-ferrite stainless steels, with higher mechanical properties and corrosion resistance than the other stainless steels grades. Impact toughness is a very important mechanical property and even though DSSs have a lower impact toughness as compared to the austenitic grades, the transition to ductile to brittle behavior is more gradual and it occurs at lower temperature than ferritic grades. On the other hand, DSSs suffer from embrittlement due to secondary phase precipitation, which affects all mechanical and corrosion properties, in particular impact toughness, even in low amount.In this research paper, the influence of a small amount (< 2%) and different morphologies of secondary phases (coarse and finely dispersed) on the ductile to brittle transition of standard Duplex Stainless Steel UNS S32205 was studied. Two isothermal heat treatments were conducted on the solubilized DSS in order to precipitate the same amount but different morphologies of secondary phases. Charpy tests were conducted on a temperature range between 20 °C and − 196 °C.The wrought material retained a very good impact toughness even at − 90 °C (100 J), but a small volume fraction of secondary phases affected the impact toughness even at room temperature. Coarser secondary phases affect the impact toughness largely as compared to small and finely dispersed particles.

Secondary-Phase Stochastics in Lithium-Ion Battery Electrodes.

Lithium-ion battery electrodes exhibit complex interplay among multiple electrochemically coupled transport processes, which rely on the underlying functionality and relative arrangement of different constituent phases. The electrochemically inactive solid phases (e.g., conductive additive and binder, referred to as the secondary phase), while beneficial for improved electronic conductivity and mechanical integrity, may partially block the electrochemically active sites and introduce additional transport resistances in the pore (electrolyte) phase. In this work, the role of mesoscale interactions and inherent stochasticity in porous electrodes is elucidated in the context of short-range (interface) and long-range (transport) characteristics. The electrode microstructure significantly affects kinetically and transport-limiting scenarios and thereby the cell performance. The secondary-phase morphology is also found to strongly influence the microstructure-transport-kinetics interactions. Apropos, strategies have been proposed for performance improvement via electrode microstructural modifications.