Two-stage Homogenization Research Articles

Effect of Two-Stage Homogenization Heat Treatment on Microstructure and Mechanical Properties of AA2060 Alloy

The microstructure evolution of AA2060 Al alloy containing Li during two-stage homogenization treatment was investigated by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), differential scanning calorimeter (DSC), transmission electron microscopy (TEM), mechanical properties and Vickers micro-hardness test methods. The results demonstrate that severe precipitation of θ(Al2Cu) and S(Al2CuMg) phase existed in the as-cast alloy, especially in the center position. Cu elements were concentrated at grain boundary and gradually decreased from the boundary to the interior. Numerous eutectic phases of θ(Al2Cu) and S (Al2CuMg) containing Zn and Ag elements were segregated at grain boundaries. The overheating temperature of the as-cast alloy is 497 °C. After two-stage homogenization treatment, the θ(Al2Cu) and S (Al2CuMg) in the surface, middle and center positions were completely dissolved into the matrix, thus achieved uniform homogenization effect. Moreover, water cooling could prevent the precipitation after homogenization, which provided good performance of the studied alloy. The optimum two-stage homogenization treatment of AA2060 alloy was 460 °C/4 h + 490 °C/2 4 h. The homogenization kinetic analysis was discussed as well.

The Effects of a Trace Amount of Manganese and the Homogenization on the Recrystallization of Al-7Mg-0.15Ti Alloys.

The aim of this study is to explore the effects of Manganese addition and homogenization treatment on the microstructures and mechanical properties of the Al–7Mg–0.15Ti (B535.0) alloy. The optical microscopy, electrical conductivity measurements, transmission electron microscopy, scanning electron microscopy (SEM + EBSD), as well as Rockwell hardness and tensile tests, were exploited for this purpose. The main objectives are to refine the grain size, inhibit grain growth in the annealed state, and enhance the mechanical strength of the alloy. The results show that the addition of manganese to the Al–7Mg–0.15Ti alloys refined the as-cast and recrystallized grains of the alloys. During the homogenization process, Al4Mn high-temperature stable dispersoids were precipitated in the aluminum matrix. After annealing, the Al4Mn particles blocked the movement of grain boundaries during the growth of the recrystallized grains and inhibited grain growth. Consequently, the annealed alloys showed grain refinement and dispersion strengthening. The Al4Mn dispersoids of the alloys with manganese added were smaller and denser after a two-stage homogenization process compared to those that underwent a one-stage homogenization process. By contrast, for the alloys without the addition of manganese, the recrystallized grains showed normal growth after annealing, and different homogenization processes had no significantly different effects.

Optimized Birch Bark Extract-Loaded Colloidal Dispersion Using Hydrogenated Phospholipids as Stabilizer.

This study investigated the formulation and processing of aqueous colloidal dispersions containing a birch bark dry extract (TE) as the active substance and hydrogenated phospholipids (Phospholipon 90H) as stabilizer, which can be used in the preparation of electrospun wound dressings. Colloidal dispersions manufactured using a two-stage homogenization process had a bimodal particle size distribution, which was most significantly (p < 0.0001) affected by the phospholipid content. The size of the single particles decreased from an average particle size of about 4 µm to a particle size of approximately 400 nm. Dynamic interfacial tension studies performed using a profile analysis tensiometer (PAT) showed that the phospholipids strongly declined the interfacial tension, whereas a further decrease was observed when phospholipids were combined with birch bark extract. Interfacial viscoelasticity properties analyzed using the oscillating drop technique resulted in an increase of both interfacial elasticity and viscosity values. These results indicated that the phospholipids are preferentially located at the lipophilic/water interface and a stable film is formed. Furthermore, the results point to a synergistic interaction between phospholipids and TE. Confocal Raman microscopy (CRM) suggested that the TE is predominantly located in the oil phase and the phospholipids at the interface.

Microstructural evolution of Al-Cu-Li alloys with different Li contents by coupling of near-rapid solidification and two-stage homogenization treatment

Microstructural improvement of Al-Cu-Li alloys with high Li content plays a critical role for the acquisition of excellent mechanical properties and ultra-low density. In this regard, the Al-Cu-Li alloy castings with high Li content from 1.5wt.% to 4.5wt.% were prepared by near-rapid solidification, followed by two-stage homogenization treatment (490 °C/16 h and 530 °C/16 h). The microstructural evolution and solidification behavior of the as-cast and homogenized alloys with different Li contents were systematically studied by combining experiments with calculations by Pandat software. The results indicate that with the increase of Li content, the grain sizes decrease, the solution ability of Cu in the matrix α-Al phase increases, while the content of secondary dendrites increases and the precipitated phases change from low melting point phases to high melting point phases under the near-rapid solidification. Additionally, by the coupling of near-rapid solidification and two-stage homogenization, the metastable precipitated phases (Al7Cu4Li and AlCu3) can be dissolved effectively in the alloys with Li content of 1.5wt.%–2.5wt.%; moreover, the stable precipitated phases (Al6CuLi3 and Al2CuLi) uniformly distribute at the grain boundaries in the alloys with Li content of 3.5wt.%–4.5wt.%. As a result, the refined and homogenized microstructure can be obtained.

A two-stage homogenization for modelling of elastic-plastic functionally graded composites

PurposeThe purpose of this study is to develop a homogenization approach that ensures both high accuracy and time-efficient solution for elastic-plastic functionally graded composites.Design/methodology/approachThe paper presents a novel two-stage hybrid homogenization approach that combines advantages of the mean field homogenization and homogenization based on the finite element method (FEM). The groundbreaking nature of the developed approach is associated with division of the hybrid homogenization procedure into two stages, which allows to very efficiently determine the solution for arbitrary volume fraction of the reinforcement. This paper concerns also on modelling of composites with randomly distributed prolate and oblate particles. For this purpose, the hybrid homogenization was implemented in the framework of the discrete orientation averaging procedure involving pseudo-grain discretization method.FindingsAgreement between the results obtained using the proposed approach and the standard FEM-based homogenization is very good (up to the volume fraction of 0.3).Originality/valueThe proposed two-stage homogenization approach allows to obtain the solution for materials with arbitrary volume fraction of the reinforcement very efficiently; therefore, it is highly beneficial for the two-scale modeling of nonlinear functionally graded materials and structures.

Predicting effective thermal and elastic properties of cementitious composites containing polydispersed hollow and core-shell micro-particles

Micro- and nano-sized hollow and core-shell particles (CSPs) have attracted tremendous interests in developing functional cementitious composites and concretes. In this paper, a general method is developed to predict the thermal and elastic properties of cementitious composites containing core-shell and hollow micro-particles. The model follows a two-stage homogenization process – CSP inclusions together with their surrounding interfacial transition zone (ITZ) are first treated as equivalent solid particles, and then the homogenized properties of the composite system are obtained using numerical (i.e., finite element) or analytical (Mori-Tanaka) approaches. Compared with other homogenization methods, the proposed model is easy-to-use and versatile. The numerical model, validated by experimental results, is then used to guide the design of functional cementitious composites. The results show that CSP particle size (or relative shell thickness), volume fraction, shell property, and the size of the ITZ have significant impacts on the effective thermal and elastic properties of cementitious composites; whereas the particle size distribution pattern has relatively minor influence. In addition, the effective property of the composite is more sensitive to the particle property change when CSP inclusions are much stiffer or more thermally conductive than the matrix. Lastly, a scoping study is conducted to elucidate the relationship between the effective thermal conductivity and effective elastic moduli for cementitious composites containing CSP additives with different shell materials, particle sizes, and volume concentrations etc.

Yield and quality characteristics of paneer made from milk blend containing homogenized milk

The research was carried out to ascertain the feasibility of preparing paneer from milk blend containing low pressure homogenized milk to avail the benefits rendered by homogenization. Standardized milk was subjected to two-stage homogenization (4.90 and 0.98 MPa respectively) and then blended with unhomogenized standardized milk in three proportions (i.e. 3:7, 4:6 and 1:1, w/w). It was necessary to add calcium chloride to the milk blend to improve the firmness of resultant paneer. The experimental paneer samples obtained from ‘milk blend’ containing homogenized milk, as well as control sample (only from unhomogenized milk) were studied for their proximate composition, physico-chemical characteristics, textural properties and sensory quality. Paneer obtained from milk blend (homogenized:unhomogenized; 4:6 w/w) resulted in greater fat recovery and moisture content culminating in significantly higher yield compared to control paneer (CP). The hardness of paneer obtained from blended milks was lower, but the springiness of BMP3:7 sample was greater than that of CP. The total sensory score of experimental paneer BMP4:6 was similar to the score associated with CP, but greater than the scores associated with paneer samples BMP3:7 and BMP1:1. Blending of homogenized (low pressure) milk with unhomogenized milk in 4:6 proportion helped in obtaining paneer with superior fat recovery and yield compared to use of unhomogenized milk, without any adverse effect on sensory properties and with concomitant cost savings.

Microstructure Evolution of High-Alloyed Al–Zn–Mg–Cu–Zr Alloy Containing Trace Amount of Sc During Homogenization

Microstructure evolution of a new high-alloyed Al–Zn–Mg–Cu–Zr–Sc aluminium alloy during two-stage homogenization process was investigated by use of scanning electron microscope, transition electron microscope and high resolution transition electron microscope. The results indicate that the morphology and chemical composition of Al3(Sc, Zr) particles formed in the first stage were greatly affected by heating temperature. With the increase of heating temperature, the morphology of Al3(Sc, Zr) particles transform from cuboidal with evident faceting to spheroidal due to improved Zr diffusivity. More Zr atoms enrich in the interface of precipitate/matrix forming a thin layer. Moreover, the mean diameter of precipitates increases a little bit with the increase of heating temperature, showing very restricted coarsening rate and high thermal stability of Al3(Sc, Zr) particles. After an appropriate second stage heat treatment (474 °C × 48 h), the intermetallic formed in the solidification process could dissolve sufficiently and Al3(Sc, Zr) particles still keep very good coherency with Al matrix without abnormal growth.

Effect of extrusion speeds on the microstructure, texture and mechanical properties of high-speed extrudable Mg[sbnd]Zn[sbnd]Sn[sbnd]Mn[sbnd]Ca alloy

A new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt.%) (named as ZTMX3100) alloy ingot with good extrudability was prepared by semi-continuous casting. Two-stage homogenization treatment and hot extrusion were performed on the ingot. The effects of extrusion speeds (0.2–10 mm/s) on the extrudability, microstructure and mechanical properties of the alloy were investigated. The excellent extrudability of the alloy is attributed to the high incipient melting temperature of 572 °C resulting from the formation of thermally stable phase CaMgSn. CaMgSn phases distribute along the extrusion direction at each extrusion speed. The average grain size increases gradually and distribution uniformity of grain size firstly increases and then decreases. The as-extruded alloys exhibit textures with (0001) basal planes parallel to extrusion direction. Besides, the alloy exhibits a <101¯0> or <101¯0> − <112¯0> fiber texture depending on extrusion speed. The alloy extruded at 0.2 mm/s presents the highest mechanical property, which is attributed to the fine grain structure, strengthening effect from second phase particles, and weak basal texture. The alloy extruded at high speed of 10 mm/s (die-exit speed 18 m/min) still maintains a relatively high strength and elongation, which is mainly due to the combined effect of moderate alloying content and thermally stable phase CaMgSn.

Microstructural evolution of new type Al–Zn–Mg–Cu alloy with Er and Zr additions during homogenization

A comprehensive study on the microstructural evolution of a new type Al–Zn–Mg–Cu–Er–Zr alloy during homogenization was conducted by optical microscope, scanning electron microscope, transmission electron microscopy and X-ray diffraction analysis. The results show that serious segregation exists in as-cast alloy, and the primary phases are T(AlZnMgCu), S(Al2CuMg) and Al8Cu4Er, which preferentially locate in the grain boundary regions. The soluble T(AlZnMgCu) and S(Al2CuMg) phases dissolve into the matrix gradually during single-stage homogenized at 465 °C with prolonging holding time, but the residual Al8Cu4Er phase cannot dissolve completely. Compared with the single-stage homogenization, both a finer particle size and a higher volume fraction of L12-structured Al3(Er, Zr) dispersoids can be obtained in the two-stage homogenization process. A suitable homogenization scheme for the present alloy is (400 °C, 10 h)+(465 °C, 24 h), which is consistent with the results of homogenization kinetic analysis.

Investigation on As-Cast Microstructure in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and Its Evolution during Two-stage Homogenization

In this study, the as-cast microstructure of a high Zn-containing Al-Zn-Mg-Cu- Zr alloy and its evolution during two-stage homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The analysis shows the eutectic structures in as-cast the alloy were identified as α(Al) / Mg(Zn,Cu,Al)2, and also some Al2CuMg, Al2Cu and Fe-rich phases formed in the eutectic structures during solidification. With the prolonging of the second stage homogenization time, S(Al2CuMg), θ(Al2Cu) and Mg(Zn,Cu,Al)2 phases orderly dissolved into the matrix, and the insoluble Fe-rich phases exist in all five as-homogenized schemes in this study, but Zn and Mg elements changes detected in the these particles during the two stage homogenization.

Microstructure of As-Cast 7085 Aluminum Alloy by Homogenization

7085 aluminum alloy has been widely used in aviation and aerospace because of high fracture toughness, high strength, slow quench sensitivity and low density. In the as-cast microstructure, it is not avoidable for massive un-dissolved secondary phases and dendritic segregation. The microstructure of as-cast high strength 7085 aluminum alloy after two-stage homogenization was studied by optical microscopy (OM), X-ray diffractometer (XRD), scanning election microscopy (SEM), energy dispersive spectrometer (EDS) and differential scanning calorimeter (DSC). It was found that the severe dendritic segregation exists in as-cast 7085 aluminum alloy and a small amount of Al7Cu2Fe exists in the as-cast 7085 alloy. The evolution of primary eutectic structure of 7085 alloy consists of three processes: the dissolution of non-equilibrium eutectic phase α (Al) + Mg (Zn)2, the transformation from Mg (Zn)2 to Al2CuMg and the dissolution of new phase Mg (Zn)2. A suitable two-stage homogenization scheme for as-cast 7085 aluminum alloy is 300°C/8 h + 465°C/24 h.

Microstructure, Mechanical and Corrosion Properties of 5E61 Alloy

The microstructure of Al-6Mg-0.9Mn-0.07Zr-0.2Er (wt.%), registered as 5E61 alloy, were investigated using optical microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that the addition of 0.2 wt.% Er can refine the dendritic structure and form fine and coherent L12 structured Al3(ErxZr1-x) precipitates in the alloy. After a two-stage homogenization (280°C/10h, 460°C/36h), the recrystallization temperature of the alloy with 0.2 wt.% Er is about 15°C higher than that of the alloy without Er. The better recrystallization resistance may be related to the Al3(ErxZr1-x) precipitates, which can pin on dislocations and sub-grain boundaries. The hardness of the cold-rolled alloy with 0.2 wt.% Er is 143HV, which is 5% higher than the alloy without Er. The exfoliation corrosion and nitric acid mass loss test were also performed. The exfoliation corrosion of the alloy is N grade, and the mass loss is only 9.84mg/cm2.

Effect of three-stage homogenization on mechanical properties and stress corrosion cracking of Al-Zn-Mg-Zr alloys

The effect of three-stage homogenization on mechanical properties and stress corrosion cracking of Al-Zn-Mg-Zr alloys has been investigated. The results reveal that the interface of η phases provide the favorable sites for Al3Zr dispersoids under the first-stage homogenization at 350°C, and therefore three-stage homogenization can reduce size and improve density and homogeneity of Al3Zr dispersoids. Uniform, fine and dense Al3Zr dispersoids inhibit recrystallization effectively and improve the uniformity of the grains. Under the same T74 aging temper, the main strengthening mechanisms of the material are η' phases and dispersion strengthening, and as a result the strength of the material increases by 11.02MPa and 3.11MPa when compared with one-stage and two-stage homogenization, respectively. Al3Zr dispersoids can pin dislocations and reduce the accumulation of dislocations at grain boundaries significantly, besides, uniform grains contribute a lot to the elongation, leading to a higher elongation and impact toughness of the material. The improved corrosion resistance is due to a decrease in large-angle grain boundaries which are favorable channels for corrosion, and SCC susceptibility (ISSRT) of the material is only 2.6%.

Adaptive Hierarchical-Concurrent Multiscale Modeling of Ductile Failure in Heterogeneous Metallic Materials

This article addresses two topics on multiscale modeling of heterogeneous metals and alloys. The first topic focuses on developing an adaptive hierarchical-concurrent multilevel modeling framework for ductile fracture. The microstructure of aluminum alloys, for example, is characterized by a dispersion of heterogeneities such as silicon and intermetallics in a ductile aluminum matrix. The multilevel model invokes two-way coupling, viz. hierarchical models for homogenized constitutive modeling and concurrent models with scale transition in regions of localization and damage. Adaptivity is necessary for evolving microstructural deformation and damage. A macroscopic analysis in regions homogeneity incorporates homogenization-based continuum plasticity-damage models. A microscopic analysis using locally enhanced-Voronoi cell finite-element method is required for regions of high macroscopic gradients caused by underlying localized plasticity and damage. Coupled macroscopic and microscopic analysis is conducted concurrently. Physics-based level change criteria are developed to improve accuracy and efficiency. The second topic discusses a nested dual-stage homogenization method for microstructure-based homogenized continuum plasticity models for cast aluminum alloys with large secondary dendrite arm spacing. Two distinct statistically equivalent representative volume elements are identified and used in the asymptotic expansion-based homogenization and self-consistent homogenization processes, respectively. The two-stage homogenization enables an evaluation of the overall homogenized model of a cast alloy from limited experimental data, as well as material properties of constituents like interdendritic phase and pure aluminum matrix.

The Microstructure Evolution of AA7050 in the Process of Homogenization

This paper used the metallographic analysis, X-ray diffraction analysis (XRD), differential scanning thermal analysis (DSC), scanning electron microscope (SEM) and electron probe analysis (EPMA) system to research the evolution law of the microstructure and properties of AA7050 under different homogenization system. And analyzes the cause of this evolution combined with the test results put forward. The research shows that high melting point eutectic phase S (Al2CuMg) can be fully re-dissolution through two-stage homogenization, at the same time avoid the overburning of low melting eutectic phase. We optimized the AA7050 homogenization heat treatment system and the optimal homogenization scheme is 430°C/18h+467°C/12h.

Rheological properties and physical stability of o/w emulsions stabilized by OSA starch with trehalose

This study investigated the effect of oil content (10, 16 and 22% of rapeseed oil) and OSA starch content (4, 8 and 12%) as well as homogenization pressure (60/15, 36/12 and 12/4 MPa) on rheological properties, droplet size distributions and stability of o/w emulsions with the addition of trehalose. The composition of emulsions corresponded to that of the systems subjected to spray-drying during production of microencapsulated lipid powders. The majority of the prepared emulsions were shear-thinning non-Newtonian fluids. The factors that determined their rheological properties to the greatest extent were the content of oil phase and concentration of OSA starch which contributed to increased viscosity of emulsions and shear thinning effect. Pressure variants: 60/20 MPa and 36/12 MPa applied in two-stage homogenization enabled achieving satisfactorily small sizes of fat globules (<10 μm) that ensured physical stability of emulsions, especially at the highest applied concentration of OSA starch (12%), regardless of the oil content. Destabilizing processes of creaming occurred in the systems produced upon pressure homogenization at 12/4 MPa. Homogeneity of all emulsions in terms of droplet size distribution did not change significantly during 6 days of storage, and thus there was no coalescence of oil droplets. There were also no changes in the rheological properties of the emulsions during storage.

Thermal and X-Ray Microanalysis of Alloys B-1461 Ingots Based on the System Al – Cu – Li

Results are provided for thermal analysis and x-ray microanalysis of specimens from industrial ingots of aluminum alloy B-1461 based on the system Al – Cu – Li. A two-stage regime homogenization is proposed for industrial aluminum alloy B-1461 ingots, providing formation of uniformly distributed dispersed phases of compact shape within the microstructure, an increase in relative elongation, and a reduction in alloy yield strength in the temperature range 440 – 460°C.

Study on Processing Technique in Engineering Tests of Mg-7.1Gd-4.6Y-1.3Nd-0.5Zr Alloy

Combined with the pre-test results, homogenization, plastic deformation, aging and other processes of Mg-7.1Gd-4.6Y-1.3Nd-0.5Zr (EW75) magnesium alloy was studied in engineering tests. The results show that in engineering test the large ingots (Φ500×800~900mm) of the EW75 alloy using two-stage homogenization treatment had perfect homogenization effect and no burnt structure. After multi-directional forging and extruded deformation, the homogenized residual second phase particles were fully broken, and the structure was refined and uniform. The peak aged craft was 230°C×6h, with the aging time increasing, the tensile strength and elongation remained unchanged, showing a strong anti-aging ability. The two-stage homogenization treatment + multi-directional forging + direct extrusion deformation + peak aging treatment was used to prepare a high performance EW75 alloy and at longitudinal direction its ultimate tensile strength, yield strength and elongation were 450MPa, 385MPa, 12.0% respectively.

Impact of homogenization on particles in the Al–Mg–Mn alloy AA 5454 – Experiment and simulation

The purpose of the present work is to understand the evolution of microstructure and microchemistry during homogenization of the Al–Mg–Mn alloy AA 5454 (Al Mg3 Mn). It has previously been shown that a two-stage homogenization practice may alter the particles state and, in turn, facilitate recrystallization of the coiled hot strip of alloy AA 5454. In this paper we aim at reproducing and elaborating earlier results by means of a combined experimental and simulation-based approach. The evolution of the particle state during homogenization annealing is tracked with a variety of experimental characterization methods and simulated with microchemistry simulation tools to analyze the changes in solute level and precipitation.