Increasing Homogenization Temperature Research Articles

Regulating the microstructure and mechanical properties of Al-Cu-Li alloys via optimizing Cu/Li ratio and homogenization

The effect of homogenization process on the microstructure evolution and mechanical properties of Al-Cu-Li alloys with various Cu/Li ratios (ranging from 2.4 to 3.7) are studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and synchrotron radiation X-ray computed tomography (SR-CT) analysis. The results show that with the increase in the Cu/Li ratio, the volume fraction of the secondary phase (fv) in the as-cast alloys gradually increases, and the morphology of the secondary phases transforms from spherical-like to chain-like. For the single-step homogenization (SSH), the fv decreases with increasing homogenization temperature and time. The 510 ℃ /24 h is identified as the optimal SSH regime due to the alloys exhibiting a lower fv and a shorter SSH time than other SSH regimes. Interestingly, the alloys processed by double-step homogenization (DSH) exhibit a lower fv compared with the SSH process. The residual secondary phases consist of a small number of regular block-Al2Cu, dispersed Al20Cu2Mn3 phase and spherical-like Zr-rich phase after SSH and DSH. Furthermore, according to the results of diffusion kinetics analysis, the secondary phases can be dissolved completely into the matrix after homogenization treatment at 510 °C for 22.9 h. Therefore, the 450 ℃ / 12 h+510 ℃ / 24 h (DSH-24) is determined as the optimal homogenization regime. After DSH, a large number of spherical-like GP-Li and Al3Li nanoparticles are precipitated during natural aging. The critical resolved shear stress calculation model suggests that the Al-4.1Cu-1.3Li alloy with a Cu/Li ratio as 3.2 possess high yield strength. The Al-4.1Cu-1.3Li alloy processed by DSH-24 exhibits excellent mechanical properties, with yield strength of 299 MPa, ultimate tensile strength of 449 MPa, and elongation of 18.8 %. This study provides a foundation for the development of high-performance Al-Li alloys.

Effect of melt homogenization on the structure and properties of zirconium-rich basalt fibers

The slow dissolution process of zirconium oxide (ZrO2) limits the efficient and energy-saving production of zirconium-rich basalt fibers with excellent alkali resistance for fiber-reinforced concrete. Therefore, it is necessary to investigate the optimum homogenization conditions to produce high-performance zirconium-rich basalt fibers. In this study, quenched zirconium-rich glasses and zirconium-rich fibers with the addition of 7 wt% ZrO2 at different homogenization temperatures and time were prepared. The quenched melt structure was characterized by XRD and FTIR, and followed information about the melt structure obtained by Gaussian curve fitting of the FTIR spectra. The results indicated that obvious ZrO2 crystals appeared in the melts and fibers with homogenization temperature below 1500 °C and time below 4 h. The degree of polymerization of zirconium-rich basalt melt was found to increase with increasing homogenization temperature and time. Meanwhile, the tensile strength and production stability of zirconium-rich fibers increased with increasing the degree of polymerization. The optimum homogenization temperature and time for zirconium-rich basalt fibers were concluded to be 1580 °C and 10 h, and the corresponding tensile strength is 1799 MPa and 1761 MPa, respectively. By diffusion experiment of ZrO2 in basalt melt with altered major component content, it was found that the Ca, Mg, Na, and Fe significantly facilitated the melting of ZrO2 into basalt melt by XRD and EDS. It was mainly attributed to the charge-compensating effect of metal cations on the [ZrO6] octahedra, which promoted the homogenization of ZrO2 in basalt melt.

The formation of three phases containing Fe and Mn in 5182 aluminum alloy

The categories, crystal types, morphology, dimension, distribution and selectivity of precipitation positions of alloy phases containing Fe and Mn in the DC casting ingot of 5182 aluminum alloy under industrial production conditions after being treated with different homogenization processes were studied through TEM and EPMA with FIB sample preparation. The formation process of three phases containing Fe and Mn was clarified as well. The results showed that there was only one category of alloy phase containing Fe and Mn in the as-cast 5182 aluminum alloy, which was one category of skeletal nonequilibrium constituent Al19(Fe,Mn)4′ with orthorhombic structure formed by the eutectic reaction L → α(Al)′ + Al19(Fe,Mn)4′. After the ingot was homogenized at a high temperature above 460 °C, there were three categories of alloy phases containing Fe and Mn, which were skeletal equilibrium phase Al19(Fe,Mn)4 with orthorhombic structure, short rod-like intermetallic phase Al3(Fe,Mn) with monoclinic structure and acicular alloy phase Al6(Fe,Mn) with orthorhombic structure, respectively. The metastable constituent Al19(Fe,Mn)4′ transformed into the equilibrium phase Al19(Fe,Mn)4 with orthorhombic structure and the alloy phase Al3(Fe,Mn) with monoclinic structure by desolation transformation Al19(Fe,Mn)4′ → Al19(Fe,Mn)4 + Al3(Fe,Mn). In addition, acicular alloy phase particles Al6(Fe,Mn) with orthorhombic structure were precipitated from the alloy matrix with supersaturated solute Fe and Mn atoms through the desolation reaction α(Al)′ → α(Al) + Al6(Fe,Mn). With increasing homogenization temperature, the skeletal constituent Al19(Fe,Mn)4 particles with orthorhombic structure were almost the same, and the short rod-like alloy phase Al3(Fe,Mn) particles, with monoclinic structure changed unobviously in morphology and size, but its number increased significantly. At the same time, the number and the size of acicular Al6(Fe,Mn) alloy phase particles with orthorhombic structure precipitated from the alloy matrix increased.

Microstructure and mechanical properties of Al0.4Co0.5V0.6FeNi high-entropy alloys processed by homogenization treatment

Al0.4Co0.5V0.6FeNi high-entropy alloys (HEAs) are fabricated by the vacuum arc melting method and homogenization treatment (HT) at 1000, 1100 and 1200 °C for 5 h (samples denoted as HT-1000, HT-1100 and HT-1200, respectively), followed by water quenching. The microstructural characteristics and mechanical properties of the HEAs are investigated by a combination of optical, scanning and transmission electron microscopy, X-ray diffraction and tension tests. The solidification of the Al0.4Co0.5V0.6FeNi HEAs is calculated using Pandat software to show that the FCC phase forms in the liquid phase, which then undergoes a eutectic reaction to form the FCC and BCC/B2 phases. The Al0.4Co0.5V0.6FeNi HEAs exhibit a typical eutectic microstructure with an alternating lamellar structure. Compared with that in the as-cast state, the volume fraction of the FCC phase in the HT state increases from 53.16% to 60.75% and the yield strength of the HT-1200 alloy increases by ∼27.5% with increasing homogenization temperature. Fine small spherical and ellipsoidal nanoprecipitates are uniformly distributed within the FCC matrix. These FCC phase nanoprecipitates become the most important factor contributing to the yield strength.

Homogenization Process for Aluminum As-Cast from Waste of Beverage Cans

Development an ingot originated from the waste of aluminum product had many the advantages and could reduce the cost of aluminum metal production compared to primary process from ore. In this research used the waste of beverage aluminum cans One of the manufacturing methods conducted recycling aluminum waste is the casting process, Commonly, the problem with this casting process was that they are not homogeneous in the as-cast due to segregation. So that in this study a homogenization process on recycling aluminum castings would be carried out to obtain more homogeneous mechanical properties and microstructure. The variables that influence during the homogenization process was heating temperature and holding time. The heating temperature for this was in range from 450 C to 550 C, and the holding time was 2 to 4 hours. Further the effect of the parameter would observe. The observation included mechanical properties, such as tensile strength and hardness, and Microstructure of the ingot. The operation temperature and holding time influenced to grain size and hardness of Aluminum. In general, increasing homogenization temperature would reduce mechanical properties.

Effects of raw material homogenization on the structure of basalt melt and performance of fibers

In this study, basalt from a base in Hebei, China, was selected as the raw material. Water-quenched basalt glasses and basalt fibers were prepared at different homogenization times and temperatures. The water-quenched glass structure was characterized by XRD and a Raman spectrometer followed by fitting of their Raman spectra by Gaussian curves to obtain information about melt structure. The fiber performance was characterized by fiber strength meter and fiber fineness meter. The results demonstrate that homogenization time and temperature had significant effects on the structure of basalt melt. The degree of polymerization of the melt increased with increasing homogenization time and decreased with increasing homogenization temperature. The fiber strength increased with increasing the degree of polymerization. As the homogenization time and temperature increased, coefficients of variation of fiber strength and fiber diameter decreased, indicating enhanced fiber stability.

Influence of homogenization treatment on microstructure and mechanical properties of Al-Zn-Mg alloy extruded by porthole die

The effects of homogenization parameters on microstructure and mechanical properties of Al-Zn-Mg profile extruded by porthole die were investigated. During homogenization treatment, the eutectic phases in as-cast billet dissolved or transformed to S(Al2CuMg) phase, while the compositions of Fe-containing phase varied slightly and only partial of them dissolved. Moreover, the fine dispersoids precipitated during air cooling. The billet hardness was decreased by increasing homogenization temperature. If the water quenching was employed, the precipitation of fine dispersoids was prevented, resulting in strong solution strengthening and relatively high hardness. The extruded profile could be divided into welding zone with fine grained structure and matrix zone with elongated and coarse grains. The quantity of coarse phases in extruded profile continuously decreased with increasing the homogenization temperature, while the fine dispersoids showed the opposite tendency. The hardness in welding zone is always lower than that in matrix zone. The profile extruded from the as-cast billet exhibited the highest tensile strength but the lowest elongation. The coarse phases exhibited stronger strengthening effect than the fine dispersoids, while they are harmful on elongation. After homogenizing the billets or increasing the homogenizing temperature, the corrosion in welding zone was reduced, while the corrosion in matrix zone became more severe.

Study on constitutive model and dynamic recrystallization softening behavior of AZ80A magnesium alloy

The microstructures of as-cast AZ80A magnesium alloy before and after homogenization treatment were studied. The flow behaviors of the homogenized alloy under different deformation conditions were studied by isothermal compression tests. Based on the flow stress-strain curves of the homogenized alloy, the constitutive model was established by the strain compensation method. The strain rate sensitivity index maps with different strains were constructed to quantify the dynamic recrystallization softening behavior of the homogenized alloy. Based on this, the influence of deformation temperature and strain rate on strain rate sensitivity index and dynamic recrystallization microstructure evolution were studied. The results show that both increasing homogenization temperature and holding time are beneficial for the β-phases to dissolve and alloying elements to diffuse. It is concluded that the proper homogenizing parameter of as-cast AZ80A magnesium alloy is 683 K for 20 h. Both the increase of deformation temperature and the decrease of strain rate are beneficial to the increase of strain rate sensitivity index. The region with an index greater than 0.22 corresponds to dynamic recrystallization softening zone and has good deformation properties.

Hydride Precipitation Behavior with Hydrogen Concentration and Homogenization Temperature in Zr-2.5%Nb Pressure Tube Material

The precipitation characteristics of hydrides in Zr-2.5% Nb pressure tube material were investigated for various hydrogen concentrations and homogenization temperatures. A surface hydride was formed using the electrolytic method and homogenized at various temperatures up to at 550 °C. The homogenization treatment was carried out at 300-550 °C over 240 hours, and the hydrogen concentration in the Zr-2.5% Nb alloy varied from 28 to 144 ppm. Hydrides were observed by optical microscopy and the precipitation parameters of the hydrides were analyzed by MATLAB, quantitatively. This is the first achievement of quantitative analysis of hydrides in Zr-alloys. The length of hydrides increased linearly with hydrogen concentration when homogenized at or below 400 °C. The area fraction of hydrides increased linearly with the hydrogen concentration regardless of homogenization temperature. The length and the ratio (length/thickness) of the hydrides decreased with increasing homogenization temperature at 350-475 °C in 81-86 ppm hydrogen. The changes in the precipitation behavior of the hydrides with homogenization temperature are considered to be due to microstructure changes, both the decomposition of β-Zr and grain growth of α-Zr. Key words: Zr-2.5%Nb alloy, homogenization, hydrogen concentration, hydride, microstructure

Correlation between homogenization treatment and subsequent hot extrusion of Al–Mg–Si alloy

The homogenization treatment was conducted on an Al–Si–Mg alloy at various temperatures or holding times, and the subsequent hot extrusion experiments were carried out to clarify the correlation between homogenization conditions and the extruded microstructure. The results showed that the grain size of the as-cast billets was not affected by homogenization, while the coarse δ-Al(FeMnCr)Si particles dissolved and transformed into fine α-Al(FeMnCr)Si particles with a spherical shape. Moreover, during homogenization, the AlCuMgSi and Mg2Si phases completely dissolved into the Al matrix, and a large number of fine Mn-containing dispersoids precipitated. With increasing homogenization temperature or time, the extruded grains clearly became coarser, and the quantity of intermetallic particles continuously decreased. Notably, it was observed that the Mg2Si phase reprecipitated during the hot extrusion. Only the deformation textures existed in the alloy extruded from the billet homogenized at high temperature (570 °C) for long time (14 h), while both the deformation and recrystallization textures were found in other specimens. The homogenized billets exhibited a higher hardness and a better electrical conductivity than those of the as-cast billet, while the hardness was decreased and the electrical conductivity was improved after extrusion. Overall, both the tensile strength and elongation of the extruded alloys increased with increasing homogenization temperature or holding time. However, if the homogenization is performed at high temperature for long time, the strength of the extruded alloy is dramatically decreased.

TLP repaired IN738LC superalloy with uneven surface defect gap width after post heat treatment: Microstructure and mechanical properties

Cracks repairing of superalloy is very important to the aerospace industry. Most of the crack repairing studies have the same “crack width” which is quite different from the taper-shaped crack in reality. In this study tapered slots with maximum 200 μm width were artificially made by femtosecond laser in small plates of IN738LC superalloy to imitate service cracks. The “cracks” were repaired by diffusion brazing with a mixed filler alloy at 1100 °C for 24 h and followed by homogenization at temperatures of 1160 °C (HT-1), 1180 °C (HT-2) and 1190 °C (HT-3). With increasing homogenization temperature and time, the volume faction of borides in diffusion affected zone (DAZ) decreased. During the homogenization with HT-3, most of the borides in the DAZ of the joint dissolved, merely a small quantity of others coarsened by Ostwald ripening. In order of the processes as-bonded, HT-1, HT-2 and HT-3, the chemical composition of the isothermal solidification zones (ISZs) gradually came close to that of the base metal and the hardness of the ISZs increased, while the hardness of the DAZs decreased. A uniform bonded joint could be obtained with HT-3, and the shear strength of the joint reached up to approximately 95% of the base metal. The corresponding fracture path and fractography of the samples were observed to explain the mechanism of strength evolution.

Effect of Homogenization Temperature on the Microstructure and Property of 6061 Aluminum Alloy with Erbium

The microstructure and mechanical properties of as-homogenized 6061 aluminum alloy with 0.2wt.% Er were investigated. The microstructures of the as-casted and homogenized alloys were analyzed using optical microscopy (OM) and scanning electron microscopy (SEM). Energy dispersion X-ray spectroscopy (EDS) was used to analyze the phase chemical composition. The results showed that the homogenizing treatment had a significant influence on the precipitate morphology of the alloy. With increasing homogenization temperature, the long strip-like Fe-rich grain distributed on the boundary phase became discontinuous and sparseness, transforming to short rod and granular shape. In addition, the Fe-rich phase with a large fish-bone structure became smaller. During homogenizing treatment, a large number of dispersive Mg2Si phase appeared inside grains, and large number of the phases containing Er were dissolved into the matrix.

In-Situ Fracture Observation and Fracture Toughness Analysis of Ni-Mn-Ga-Fe Ferromagnetic Shape Memory Alloys

The fracture property improvement of Ni-Mn-Ga-Fe ferromagnetic shape memory alloys containing ductile γ particles was explained by direct observation of microfracture processes using an in-situ loading stage installed inside a scanning electron microscope (SEM) chamber. The Ni-Mn-Ga-Fe alloys contained a considerable amount of γ particles in β grains after the homogenization treatment at 1073 K to 1373 K (800 °C to 1100 °C). With increasing homogenization temperature, γ particles were coarsened and distributed homogeneously along β grain boundaries as well as inside β grains. According to the in-situ microfracture observation, γ particles effectively acted as blocking sites of crack propagation and provided the stable crack growth, which could be confirmed by the R-curve analysis. The increase in fracture resistance with increasing crack length improved overall fracture properties of the Ni-Mn-Ga-Fe alloys. This improvement could be explained by mechanisms of blocking of crack propagation and crack blunting and bridging.

Effect of homogenization treatment on microstructure and properties of Al-Mg-Mn-Sc-Zr alloy

The effect of homogenization on the hardness, tensile properties, electrical conductivity and microstructure of as-cast Al-6Mg-0.4Mn-0.25Sc-0.12Zr alloy was studied. The results show that during homogenization as-cast studied alloy has obviously hardening effect that is similar to aging hardening behavior in traditional Al alloys. The precipitates are mainly Al3(Sc,Zr) and Al6Mn. When homogenization temperature increases the hardness peak value is declined and the time corresponding to hardness peak value is shortened. The electrical conductivity of the alloy monotonously increases with increasing homogenization temperature and time. The decomposition of the supersaturated solid solution containing Sc and Zr which is formed during direct chilling casting and the precipitation of Al3(Sc, Zr) cause hardness increasing. The depletion of the matrix solid solubility decreases the ability of electron scattering in the alloy, resulting in the electrical conductivity increased. Tensile property result at hot rolling state shows that the optimal homogenization treatment processing is holding at 300–350 °C for 6–8 h.

Thermoelectric Properties of Arc-Melted Ba<sub>8</sub>Al<sub>16</sub>Si<sub>30</sub> Clathrate

Ba8Al16Si30 type I clathrate was produced by arc melting and thermoelectric properties were investigated. The phase transformation behavior of arc-melted type I Ba8Al16Si30 was examined by thermogravimetric analysis, differential scanning calorimetry, hardness test, density measurement, X-ray diffraction and scanning electron microscope analyses. Homogenization was carried out to induce the transformation to a thermoelectric phase at 773K to 973K for 5 hours and 24 hours in the vacuum furnace. Thermoelectric properties in the temperature range between 300K and 600K were measured and evaluated. Electrical conductivity was decreased and Seebeck coefficient was increased with increasing homogenization temperature and time. The arc-melted and the homogenized specimens represented n-type conduction at temperatures examined, and they showed reliable thermoelectric behaviors with increasing homogenization temperature and time.

Homogenization Conditions Affect the Oxidative Stability of Fish Oil Enriched Milk Emulsions: Lipid Oxidation

In this study fish oil was incorporated into commercial homogenized milk using different homogenization temperatures and pressures. The main aim was to understand the significance of homogenization temperature and pressure on the oxidative stability of the resulting milks. Increasing homogenization temperature from 50 to 72 degrees C decreased droplet size only slightly, whereas a pressure increase from 5 to 22.5 MPa decreased droplet size significantly. Surprisingly, emulsions having small droplets, and therefore large interfacial area, were less oxidized than emulsions having bigger droplets. Emulsions with similar droplet size distributions, but resulting from different homogenization conditions, had significantly different oxidative stabilities, indicating that properties of significance to oxidation other than droplet size itself were affected by the different treatments. In general, homogenization at 72 degrees C appeared to induce protective effects against oxidation as compared to homogenization at 50 degrees C. The results thus indicated that the actual composition of the oil-water interface is more important than total surface area itself.

Effect of different homogenization treatments on the hot workability of aluminium alloy AA2024

Hot-torsion tests have been carried out on samples of an aluminium alloy AA 2024 homogenized at 460 or 500 °C for 8 or 24 h followed by a water quench. The tests have been carried out with strain rates between 0.1 and 10 s −1 at 340, 370 and 400 °C. The peak stress, the softening during torsion and the apparent activation energy are higher but the ductility is lower for the samples homogenized at 500 °C than for those treated at 460 °C. The increases in peak stress and softening and the decrease in ductility with increasing homogenization temperature is more pronounced at low than at high test temperatures. An increase in the homogenization time from 8 to 24 h has almost no effect on the values of peak stress and softening but improves the ductility owing to particle solution. The effects are discussed in terms of solid solution hardening and dynamic precipitation.

The structure of the “influenced grain boundary region” of an Al‐12at.% Zn alloy in dependence on quenching conditions

AbstractIt is known that in the AlZn alloys the nucleation and growth of the G.P. zones during isothermal ageing in the RT‐range considerably depend on the applied quenching treatment and often certain “irregularities”, e.g. an inversion of the decomposition rate with increasing homogenization temperature (Tq), are observed. Various conceptions were developed in order to explain these inversions, but none of them can consistently interpret the observed main features. For more details see Siebert and Kroggel et al. It is of interest for the present work to mention that various models were developed to explain the structure of the precipitation free zone (PFZ). They are mainly based on suggesting that the profile of the vacancies or that of the solute atoms or both in the GB‐region determine the width and the structure of the PFZ (see e.g. Synecek et al.).It was the idea of the authors to gain more information on the effect of the GB on the structure changes proceeding in its vicinity on investigating not only the width and structure of the PFZ, but the details of the structure changes occurring from the regions very close to the GB up to the midgrain in dependence on various quenching conditions (Tq and quenching rate, vq).For this reason we selected an Al‐12at.%Zn alloy produced from materials of purity 4N and aged the samples of thickness 0.12 mm, after various quenching treatments, at 100 °C for 1 h in order to attain precipitates suitable to be determined in size sufficiently accurately. The samples were annealed at Tq = 300 °C or 490 °C for 0.5 h, quenched to RT into water, fluid W250, or oil, stored at RT for 10 s, and finally aged at 100 °C for 1 h. The foils investigated in the TEM of type TESLA BS 540 operating at 120 kV were electrolytically thinned by the well‐known window method.