Min Of Annealing Research Articles

Effect of Annealing Time on Grain Structure Evolution and Superplastic Response of Al-Mg 5xxx Alloys

The impact of annealing on the recrystallized grain structure and superplastic behavior of two Al-Mg 5xxx alloys used for high-speed blow forming (HSBF) was studied. The results revealed that both alloys demonstrated rapid static recrystallization after only a few minutes of annealing at 520 °C, forming fine and equiaxed grain structures. After four min of annealing, Alloy 2 (Al-4.0Mg-1.18Mn) exhibited a higher fraction of small grains (<10 µm) compared to Alloy 1 (Al-4.5Mg-0.74Mn). Moreover, Alloy 2 displayed enhanced resistance to grain coarsening with increasing annealing times, which was attributed to its higher amount of Al6(Mn,Fe) intermetallic particles and a higher number density of Mn dispersoids. Optimizing the annealing time can effectively develop a fine and stable grain structure in Al-Mg 5xxx alloys. During tensile deformation, Alloy 2 consistently showed higher ductility compared to Alloy 1 at low strain rates (170% vs. 138% at 0.001 s−1 and 163% vs. 134% at 0.01 s−1), whereas at a high strain rate of 1 s−1, both alloys displayed comparable tensile elongation. The high superplastic response of Alloy 2 at low strain rates renders it a superior superplastic alloy for HSBF applications.

Tuning the giant magnetoimpedance response of a glass-coated microwire reinforced polymer by in-situ laser annealing

The ability to modify the giant magnetoimpedance (GMI) effect in amorphous glass-coated ferromagnetic Co-based microwire reinforced polymer via laser irradiation is presented. Through in-situ laser annealing of microwires embedded into a polymer matrix, a 25 % improvement in the GMI response is demonstrated after only 4.9 min of annealing. This improvement is compared to a conventional oven anneal technique, requiring an hour of oven annealing, subsequent sample cooling and polymer casting. This unique in-situ technique offers a novel and expedient path toward tailorable multi-functional composites in the areas of tunable electromagnetic shielding, structurally integrated antennas and magnetic sensors.

Phase formation in the Ni-enriched zone below the surface oxide on NiTi

Upon exposure to oxygen, NiTi forms a Ti-rich surface oxide layer, and mass balance requires that a Ni-enriched zone forms below the oxide. Both the surface oxide layer and the Ni-enriched zone are discussed to affect key properties of NiTi as material for minimally invasive medical application or for actuators, e.g., the release of Ni and the resistance to initiation and propagation of cracks when exploiting the shape memory effect/pseudoelasticity. However, owing to the small extension of the Ni-enriched zone of a few nanometers, little is known about its crystallinity, phase and evolution of composition.We study the formation of the surface layers during annealing at ∼500 °C for up to 10 min, as routinely applied for shape-setting. With an approach employing nano beam electron diffraction in a transmission electron microscope and an in-house software package for phase analysis it is shown for the first time that phase transformations in the Ni-enriched zone, specifically from NiTi to Ni4Ti3, occur already after 2 min of annealing, much earlier than documented in the literature. Furthermore, the phase transformation to the thermodynamically stable Ni3Ti in the Ni-enriched zone is shown to be mediated by metastable Ni4Ti3. In contrast to Ni4Ti3 precipitates in NiTi bulk, the morphology of the crystalline phases is granular. Considering the swift formation of Ni-rich phases below the surface oxide and the observation of a band-like diffraction contrast in the TEM images originating from crystal interfaces, a phase transformation mechanism in the Ni-enriched zone is suggested consisting of short range order rearrangements of atoms.

Comparative study on the annealing of cold-sprayed boron nitride nanosheet/copper coating using spark plasma sintering and atmosphere furnace

Cold spray is an emerging additive manufacturing technique, as it provides an avenue for oxide-free and non-phase-transformation deposition. Pores within the cold-sprayed coatings generally adversely affect the mechanical performances of the coatings. In this work, a comparative study on the annealing of cold-sprayed boron nitride nanosheets (BNNSs)/copper (Cu) composite coating using spark plasma sintering (SPS) and the atmosphere furnace (AF) was performed at various temperatures. SPS exhibited a much higher efficiency in reducing the coating porosity: the porosity reduced from 1.31 % to 0.65 % after merely 5 min of annealing by SPS, while the value was 1.1 % after one-hour annealing at 600 °C in the AF. The bending test showed that the SPS-treated coatings had higher ductility than AF-treated ones due to their better interfacial bonding. The possible mechanisms are proposed as follows: the higher interfacial healing efficiency may arise from multiple physical fields of SPS, which promotes the destruction of the oxide layer, the cleaning of the particle surface, and the atomic diffusion. Thus, BNNSs prevent crack propagation during fracture, thereby improving the coating ductility.

The annealing microstructural evolution of Al-10Zn alloy prepared by continuous extrusion of mixed heterogeneous elemental powders

Al and Zn powders in the ratio of 9:1 (wt%) were alloyed into rods with a dense structure by using the continuous extrusion technique. To promote metallurgical bonding of heterogeneous elements, the microstructures of these rods with different holding times (1, 3, and 5 min) at the same annealing temperature were investigated. With the increase of annealing time, the microstructure consisted mainly of (α-Al) and (α + η) phases and an (α +η)-rich phase. The solid solubility of Zn into Al also gradually increased. The calculated x-ray diffraction (XRD) data showed that the lattice parameter of Al decreased to 4.04793 Å after 5 min of annealing, which was decreased by 0.062% compared to the lattice parameter of Al in the powder state. The microscopic stress and dislocation density of Al were increased by 0.27% and 12.52 × 1014 m−2 respectively after extrusion, and the microscopic deformation and dislocation density were decreased to 0.2% and 8.71 × 1014 m−2 respectively after being annealed for 5 min. The dislocation density and lattice distortion after annealing gradually decreased with increasing annealing time, and the scanning electron microscopy (SEM) results indicated that the mass percentage of Zn increased with increasing annealing time.

Bifacial Cu2ZnSn(S,Se)4 Thin Film Solar Cell Based on Molecular Ink and Rapid Thermal Processing

AbstractThe use of transparent conducting oxides (TCO) as a back contact for Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cell enables light absorption from both front and rear sides and allows for the fabrication of semi‐transparent photovoltaic devices. However, the CZTSSe solar cell based on TCO substrate suffers from high parasitic losses owing to the long post‐annealing time at elevated temperature required for high‐quality absorber. This work aims to overcome this issue by carefully tailoring the annealing conditions to obtain high‐performance solar cell. Rapid thermal processing is used to instantaneously generate high Se vapor pressure at target temperature and shorten the annealing time. The crystalline quality, morphology, and particularly the photovoltaic performance of the resulting CZTSSe thin film are systematically investigated. It is found that the increase of annealing temperature and time improves the crystalline quality but unfortunately deteriorates the device performance owing to increasing parasitic losses. Increasing the amount of Se allows to get highly crystalline absorber within 7 min of annealing, yielding a total area 5.56% efficient CZTSSe solar cell with front illumination resulting from reducing parasitic losses. This work provides a simple approach to preserve the back contact without using a complex interfacial layer.

Characterization of structural transformation of graphene oxide to reduced graphene oxide during thermal annealing

Abstract

Optoelectronic properties of infrared rapid-thermal-annealed SnOx thin films

We investigated rf-sputtered SnOx thin films after thermal oxidation in ambient air at 245°C (below the temperature for the disproportionation reaction 2SnO→Sn+SnO2) using an infrared rapid heating furnace. The most significant changes occur during the initial 2.5min of thermal annealing. The amorphous as-deposited film rapidly crystallized with metallic Sn and SnO phases as identified by XRD after thermal annealing. Both EPMA and XPS indicate decreasing [Sn]/[O] ratios after the initial 2.5min of annealing, suggesting the occurrence of an oxidation process that is hindered for longer annealing durations. The lower [Sn]/[O] ratio identified by XPS than by EPMA suggests more severe oxidation at the surface. Thermal oxidation improves the transmittance and increases the band gap from 1.80 to 2.79eV. The annealed films exhibit resistivity of ~16Ωcm, hall mobility of ~0.6cm2V−1s−1, and carrier concentration of ~7×1017cm−3. Both Hall and Seebeck coefficient measurements confirm p-type conductivity for all annealed films.

Microstructure and Texture Evolution During Annealing of Caliber Rolled Mg–3Al–1Zn Alloy

Mg–3Al–1Zn (AZ31) alloy was caliber rolled isothermally at the temperature of 300 °C to develop fine grains of 3 µm size. The microstructure and texture evolution of caliber rolled bar during annealing at 300 °C was investigated for 5 to 6000 min. The grain growth from 6 to 17 µm was observed. The grain growth was noted to be faster initially but it became sluggish after ~60 min of annealing. The changes in pole figure intensity, mis-orientation angle, kernel average mis-orientation and grain orientation spread were observed after caliber rolling and after annealing. The microstructure and presence of twins after caliber rolling play a vital role in formation of texture after annealing. The changes in microstructure and texture were analysed and the mechanisms involved are discussed.

Effect of pre-annealing strains on annealing texture developments in commercially pure (CP) titanium

Hexagonal commercially pure titanium (cp-titanium) plates were subjected to unidirectional-rolling (rolling), accumulative roll-bonding (ARB) and cross-rolling in a laboratory rolling mill. Rolling and cross-rolling were carried out to impart 90% reduction in thickness and ARB processing was performed for six passes. The deformed plates were then subjected to annealing at 600 °C for a large range of soaking time starting from 0.17 min (10 s) to 30 min. It was observed that the samples were fully recrystallized after 5 min of annealing, irrespective of the rolling processes employed in this study. Also, the samples were seen to develop almost similar texture when annealing was carried out beyond 5 min of annealing time. However, before annealing, the texture development was seen to be different in the respective samples subjected to different rolling processes. The initial texture present in the deformed structure got strengthened during annealing of the samples under investigation. It was also observed that the texture development was insignificant in ARB-processed samples after annealing.

In situ confocal micro‐Raman spectroscopic investigation of rearrangement kinetics and phase evolution of UHMWPE during annealing

Ultrahigh molecular weight polyethylene was investigated using in situ confocal micro‐Raman spectroscopy during annealing at 110.0 °C. Based on the Raman spectra, crystalline, amorphous, and all‐trans noncrystalline fractions were recognized to evaluate rearrangement kinetics during isothermal annealing at 110.0 °C and phase evolution during cooling from 110.0 to 30.0 °C. For the crystalline fraction, a substantial increase from 0.600 ± 0.001 to 0.639 ± 0.008 was observed during the first 24.2 min of annealing; a very gradual increase from 0.639 ± 0.001 to 0.679 ± 0.001 occurred during the following 114.6 min. For the amorphous phase fraction, conversely, a sharp decrease from 0.240 ± 0.000 to 0.213 ± 0.004 was exhibited during the first 24.2 min of annealing, and then, a flat decrease happened from 0.213 ± 0.004 to 0.192 ± 0.001 as time expanded to 138.8 min. For the all‐tans noncrystalline fraction, a gradual decrease was shown from 0.160 ± 0.000 at 0.0 min to 0.128 ± 0.001 at 138.8 min. The rearrangement rate constant K was obtained to be 0.632 by an Avrami equation. During cooling from 110.0 to 30.0 °C, there were two phase evolution regions: region 1 from 110.0 to 90.0 °C and region 2 from 90.0 to 30.0 °C. The crystal lamella thickened faster in region 1 than in region 2. The amorphous layer continually decreased in content in the combined region of 1 and 2. The all‐trans noncrystalline phase obviously decreased in region 1 and then almost maintained a constant level in region 2. Copyright © 2014 John Wiley & Sons, Ltd.

Improvement of the blasting induced effects on medical 316 LVM stainless steel by short-term thermal treatments

Blasting of 316 LVM steel was performed by using alumina and zirconia particles that yield rough (up to Ra ~8μm) and nearly smooth (up to Ra ~1μm) surfaces, respectively. Besides roughening, the severe plastic deformation imposed during blasting yields subtle sub-surface microstructural changes such as grain size refinement, α′-martensite formation, and work hardening. In this work we investigate the thermal treatment at 700°C of the blasted steel, aimed to reverse the strain induced α′-martensite to austenite, with special emphasis in the correlation of the microstructural changes with the fatigue resistance. Blasting with rounded zirconia particles increases the fatigue resistance whereas the opposite effect is observed using alumina ones, which are more abrasive and cause a huge amount of embedded particles acting as stress raisers. It is shown that thermal treatment at 700°C is very effective in the reversion of martensite, even after 2min of annealing. Interestingly, the short thermal treatment of the alumina blasted steel increases the fatigue strength to values close to non-blasted material (400MPa). Prolonged exposures, however, contribute to a full relaxation of the beneficial compressive residual stresses, being the net effect a decrease in the fatigue limit (340MPa).

Magnetic and structural investigations on as-grown and oxygen annealed PLD SnO2 : Co thin films

Detailed structural and magnetic characterization has been performed on dilute magnetic oxide SnO2 : Co thin films deposited on R-cut sapphire substrates via pulsed laser deposition from a doped target of 5 at.% nominal Co concentration. These studies demonstrate that the films are highly crystalline, composed of single phase SnO2 : Co grains, with no formation of Co nanoclusters in the oxide matrix, and are ferromagnetic at room temperature. It was found that ferromagnetism and electrical conduction are strongly dependent on the growth rate, film thickness and post deposition annealing protocols and suggest that the magnetic properties are related to the number of defects, and thus the crystallinity of the films. For thicknesses above 70 nm, films are electrically conducting and ferromagnetic, with a relatively constant MS of about 20 emu cm−3 at room temperature. Moreover, the moment per unit area varies linearly with the film thickness, showing that the ferromagnetism of the studied materials is a volume property. Samples annealed in conditions similar to their growth display a dramatic increase of MS in the first 5 min of annealing. Temperature dependent magnetization measurements reveal that approximately one third of the cobalt couples ferromagnetically with the remaining two thirds existing in the form of paramagnetic isolated cobalt spins. Experimental evidence supports the conclusion that films are formed of single crystal grains of SnO2 doped with Co, held together by defect-rich grain boundaries.

The Role of Surface Area of ZnO Nanoparticles as an Agent for some Chemical Reactions

Synthesising zinc oxide nanoparticles (ZnO-NPs) to get certain characteristics to be applied in Enhanced Oil Recovery (EOR) is still challenging to date. In this work, the importance of high surface area of ZnO nanoparticles as EOR agent was highlighted. A simulation on density of state (DOS), band structure and adsorption energy of hydrogen and nitrogen gases on the surface of ZnO was carried out; it is observed that from the band structure of the band gap value for ZnO is 0.808ev. For the ZnO, Zn 4s states contribute to conduction band and O 2p states contribute to valence band. ZnO-NPs were synthesised using the sol-gel method by dissolving zinc nitrate hexahydrate in nitric acid and varying the stirring time (1 and 24h) and sintering time (30 and 40 min). A microwave oven was used for annealing ZnO without insulating the samples in any casket. The results show that 30 and 40 min of annealing and stirring for 1 & 24 h influenced the morphology and size of ZnO-NPs. These parameters could be tailored to generate a range of nanoparticle morphology (flask and/with agglomerated nanoparticles in a corn shape) obtained by Field Emission Scanning Electron Microscope (FESEM) and hexagonal crystal, determined by X-ray diffractometer (XRD), with the mean size of 70.5 & 74.9 nm and a main growth at the peak (101). The prepared sample via stirring for 24h and sintering for 40 min was chosen to prepare ZnO nanofluid because it has the highest surface area (BET) among the rest of samples, 0.23 m2/g. 10% of Original Oil In Place (OOIP) was recovered successfully to prove that ZnO is a good candidate to be applied in some chemical reactions. Moreover, it was found that ZnO is a promising catalyst for ammonia synthesis based on the adsorption energy of hydrogen and nitrogen gases (-1.05 and-1.60 kcal/mol respectively).

Formation and characterization of nanoporous structures on surface of LPD-derived GeO2 ceramic film

This work represents an idea of forming nanoporous structures on surface of a LPD (liquid phase deposition)-derived GeO2 ceramic film by thermal reduction of GeO2 under hydrogen atmosphere. SEM, XRD and Raman analyses show that well-defined nanopores with size in range of 10–100 nm have been formed on surface of GeO2 film by annealing at 600 °C for 5–10 min. The pore formation process is furthered by structural defects which serve as active sites for the thermal reduction reaction. Fast phase transformation from hexagonal GeO2 to tetragonal GeO2 has occurred within the first 5 min of annealing. Green-yellow (2.32 eV) and violet (2.9 eV) photoluminescences originating from $$ {\text{O}} {-} \mathop {\text{Ge}}\limits^{ \bullet \bullet } {-} {\text{O}} $$ and ≡Ge–Ge≡ defects are observed in the film samples. The photoluminescence peak intensity decreases with increase of annealing time due to diminution of O/Ge ratio. The film annealed for 5 min exhibits a maximum green-yellow to violet PL peak ratio, which is related to generation of some new $$ {\text{O}} {-} \mathop {\text{Ge}}\limits^{ \bullet \bullet } {-} {\text{O}} $$ defects at the phase interface.

Evolution of strength and microstructure during annealing of heavily cold-drawn 6.3 GPa hypereutectoid pearlitic steel wire

Hypereutectoid steel wires with 6.35GPa tensile strength after a cold-drawing true strain of 6.02 were annealed between 300 and 723K. The ultrahigh strength remained upon annealing for 30min up to a temperature of 423K but dramatically decreased with further increasing temperature. The reduction of tensile strength mainly occurred within the first 2–3min of annealing. Atom probe tomography and transmission electron microscopy reveal that the lamellar structure remains up to 523K. After annealing at 673K for 30min, coarse hexagonal ferrite (sub)grains with spheroidized cementite, preferentially located at triple junctions, were observed in transverse cross-sections. C and Si segregated at the (sub)grain boundaries, while Mn and Cr enriched at the ferrite/cementite phase boundaries due to their low mobility in cementite. No evidence of recrystallization was found even after annealing at 723K for 30min. The stability of the tensile strength for low-temperature annealing (<473K) and its dramatic drop upon high-temperature annealing (>473K) are discussed based on the nanostructural observations.

Annealing effects on the photoluminescence yield of Gd2O3:Eu nanoparticles produced by solution combustion synthesis

Abstract Post-synthesis annealing is commonly required to achieve intense luminescence from nanoparticles synthesized by means of the solution combustion synthesis (SCS) method. We carried out investigation to gain insight on the underpinning mechanisms related to this enhancement. Gd2O3:Eu nanoparticles were prepared by SCS and characterized in their structure, crystallinity, crystallite size, photoluminescence (PL) and PL lifetime. After synthesis, samples were calcined at 500 °C for 4 h to eliminate organic residues, and annealed in air at 1000 °C for up to 180 min. The fast increase of PL intensity in the first ∼15 min of annealing is understood by the decrease of the probability of non-radiative recombination through the elimination of quenching defects. This is in agreement with increasing crystallinity, as determined by the absolute intensity of the (222) and (440) diffraction peaks as a function of annealing time. The systematic measurements of crystallinity, crystallite size, PL intensity and lifetime as a function of annealing time carried out in this work supports the assignment of a major role to crystallization and the elimination of structural disorder on PL yield of SCS-prepared materials.

Electron backscatter diffraction analysis applied to [0 0 1] magnetite thin films grown on MgO substrates

Electron backscatter diffraction (EBSD) analysis is applied to [0 0 1] oriented magnetite thin films grown on MgO substrates. A high image quality of the Kikuchi patterns was achieved enabling multi-phase scans. Several types of magnetite thin films were analyzed; one as-grown and the others after different annealing steps in oxygen atmosphere. From the EBSD mappings, we learn that the optimum orientation in [0 0 1]-direction is not yet achieved for the as-grown sample, but develops upon oxygen treatment. Furthermore, the distribution of misorientation angles within the investigated area (=1 grain) is found to change during the annealing steps. After 3 min of annealing, most of the misorientations around 30°–40° have vanished, and some islands with high misorientation angles remain, which may play a role as antiferromagnetic pinning centers.

Phase Transition and Thermoelectric Property of Ultra-Fine Structured β-FeSi&lt;sub&gt;2&lt;/sub&gt; Compounds

FeSi2 compounds were fabricated by rapid solidification and hot pressing, which is considered to be a mass production technique for this alloy. Structural behavior of melt-spun ribbon during heat-treatment and Seebeck coefficient of the hot pressed bulk were systemically investigated and compared with conventionally fabricated alloys. The melt-spun ribbon consists of α-Fe2Si5 and ε-FeSi phase. With increasing annealing time, the phase transition to β-FeSi2 phase occurred more rapidly. 20 min of annealing is sufficient for a homogeneous formation of β-FeSi2 phase in melt-spun ribbon, while it is 100 h in as-cast alloy. In this research, the formation mechanism of β-FeSi2 phase during annealing is a transition of α+ε→β. The microstructure of sintered bulk generally consist of a randomly distributed β-FeSi2 phase with an average grain size of 0.9 μm. The increase of Seebeck coefficient in melt-spun and sintered specimen is due to fine grain size formed by rapid solidification.

PAX2 Activates WNT4 Expression during Mammalian Kidney Development

The transcription factor PAX2 is expressed during normal kidney development and is thought to influence outgrowth and branching of the ureteric bud. Mice with homozygous null Pax2 mutations have developmental defects of the midbrain-hindbrain region, optic nerve, and ear and are anephric. During nephrogenesis, PAX2 is also expressed by mesenchymal cells as they cluster and reorganize to form proximal elements of each nephron, but the function of PAX2 in these cells is unknown. In this study we hypothesized that PAX2 activates expression of WNT4, a secreted glycoprotein known to be critical for successful nephrogenesis. PAX2 protein was identified in distal portions of the "S-shaped" body, and the protein persists in the emerging proximal tubules of murine fetal kidney. PAX2 activated WNT4 promoter activity 5-fold in co-transfection assays with JTC12 cells derived from the proximal tubule. Inspection of the 5'-flanking sequence of the human WNT4 gene identified three novel PAX2 recognition motifs; each exhibited specific PAX2 protein binding in electromobility shift assays. Two motifs were contained within a completely duplicated 0.66-kb cassette. Transfection of JTC12 cells with a PAX2 expression vector was associated with a 7-fold increase in endogenous WNT4 mRNA. In contrast, Wnt4 mRNA was decreased by 60% in mesenchymal cell condensates of fetal kidney from mice with a heterozygous Pax2 mutation. We speculated that a key function of PAX2 is to activate WNT4 gene expression in metanephric mesenchymal cells as they differentiate to form elements of the renal tubules.