Increasing Heat Treatment Temperature Research Articles

Microstructure and properties of SLM-Hastelloy X alloy after different hot isostatic pressing + heat treatment

In this paper, the microstructure and mechanical properties of SLM-Hastelloy X alloy treated by hot isostatic pressing and heat treatment (HIP + HT) were studied. The microscopic characteristics show that the grains are transformed into equiaxed grains after different HIP + HT. The precipitates of M23C6 carbide are distributed in grains and grains boundaries. The number of precipitates in grains decreased during the increase of the temperature of the heat treatment. The results of nano-indentation experiments show that the average elastic modulus first increases and decreases with the growth of heat treatment temperature, and the average hardness fluctuates significantly in increasing the temperature of post-treatment. When the heat treatment temperature reaches the maximum value, the minimum value of average hardness is obtained of 2.46 GPa. The Vickers hardness decreases from 204HV0.5 to 188HV0.5 with the increase of heat treatment temperature. According to tensile tests, a good combination of strength and plastic properties of SLM-Hastelloy X alloy after HIP + HT treatment is obtained except for HIP+1150 °C/h.

Identification on Chemical Constituent of Alpinia purpurata Hydrosol Extracted by Hydro Distillation Method

Alpinia purpurata (Halia Bara) is a perennial herbaceous plant with virtually identical qualities to common ginger, but with smaller and more pungent rhizomes. It is widely known for ornamental purposes and is also applied in the medicinal field. Extraction of essential oil and hydrosol of Alpinia purpurata can be done through the hydro distillation method. The essential oil contains α-pinene, β-caryophyllene, geranial, neral and β-pinene that contribute to medicinal values while hydrosol's chemical components are yet to be identified. Hence, the primary objective of this study is to use the hydro distillation method to identify the chemical constituents and functional groups of active chemical compounds present in Alpinia purpurata's rhizomes hydrosol. Hydro distillation is also done at different heating temperatures and distillation times to see what influence temperature and distillation time have on the components and active compounds in the hydrosol. The powdered sample is used for extraction at 60°C, 80°C, and 100°C, with distillation periods of 1, 1.5, 2, and 2.5 hours. Burette is used to extract essential oil from the hydrosol. To further investigate the hydrosol, gas chromatography-mass spectrometry (GC-MS) and Fourier-transform Infrared Spectroscopy (FTIR) are utilised extensively. The major chemical constituents detected in Alpinia purpurata's hydrosol at 100°C for 2.5 hours of distillation time include 1-Dodecanamine (40.08 %) and functional groups present are O-H, N-H, C-H, and C=H stretching, according to GC-MS and FTIR data. The increased heating temperature and distillation time caused the denaturation of substances in the extracted hydrosol. The chemical constituents present in hydrosol are greatly different from the chemical constituents that are present in essential oil qualitatively and quantitatively.

Growth Kinetics and Mechanical Properties of Rare-Earth Vanadiumizing Layer on GCr15 Steel Surface

In this paper, rare-earth vanadiumizing layers were prepared on the surface of GCr15 steel by powder pack cementation. The tissue thicknesses of the vanadiumizing layers were characterized by metallographic microscopy, scanning electron microscopy, X-ray diffraction, electron microprobe analysis and microhardness testing at 1173, 1193, 1213 and 1223 K for 1, 3, 5 and 7 h, respectively, and the growth kinetics of the rare-earth vanadiumizing layers were investigated first. The experimental results showed that: a dense and uniform vanadiumizing layer was obtained on the surface of the substrate, and the layer mainly consisted of VCx and α-Fe; the thickness of the vanadiumizing layer increased with the increase in heating temperature and holding time, and the variation range was 4.65–12.65 µm; the microhardness of the vanadiumizing layer increased with the increase in heating temperature and holding time, and the variation range was 1892.3–2698.6 HV, compared with the substrate. The electron probe microanalysis showed that the rare earth entered the diffusion layer and affected its tissue hardness. The experimental diffusion activation energy of the GCr15 steel powder-embedded rare-earth vanadiumizing layer was 164.85 KJ/mol.

A microstructural study on the alkali-treated titanium subjected to induction heating

Alkali-treated titanium and its alloys (with or without heat treatment) have been paid more attention in the biomaterial field for the formation of a nanoporous layer that can induce apatite deposition and improve bone-implant integration. In this work, a hierarchical micro-nano structure was fabricated by alkali treatment and subsequent induction heating at different temperatures. The surface morphology, phase composition, microstructure, and elemental binding state were investigated using scanning electron microscopy (SEM), X-ray diffractometer (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. As the induction heating temperature increases, the porous structure of the outmost sodium titanate layer is maintained with increased anatase TiO2 and decreased wetting angle from 21.8° to 11.8°. At a relatively high temperature (700 °C), the composite layer is composed of a porous sodium titanate layer with a thickness of around 1 μm and a titanium oxide layer of about 2 μm thickness with nanopores. Importantly, the amorphous structure with the oxygen vacancy that exists on the sample surface is conducive to apatite deposition. The assessment of the in-vitro bioactivity performed in 1.5 simulated body fluid shows that the ability to induce apatite deposition increases with the increasing induction heating temperature from 500 to 700 °C. These results are helpful to understand the microstructure of the alkali and induction heating treated titanium that may be responsible for its bioactivity.

Study on Corrosion Behavior of Simulated Welding Microstructure of Austenitic Stainless Steel

In this paper, the simulated welding structure of austenitic stainless steel is prepared by external heating, and the corrosion resistance of austenitic stainless steel in different areas of heat affected zone (HAZ) is evaluated by means of metallographic structure analysis, electrochemical impedance spectroscopy (EIS) test and equivalent circuit numerical fitting analysis. The result shows that the simulated welding structure of austenitic stainless steel had a growth trend with the increase of heating temperature, but the growth trend is not very obvious. The short thermal process has insufficient driving force for the growth of single-phase austenitic structure. The resulting of product resistance and charge transfer resistance of simulated welding microstructure of austenitic stainless steel is not completely consistent. The simulated welding microstructure of stainless steel shows the tendency of corrosion resistance degradation with the heating temperature increasing, and it has slightly lower when the maximum heating temperature locating at 1000-1100 °C.

Study on Grain Boundary Sensitization in Heat Affected Zone of Austenitic Stainless Steel and its Evaluation Method

In this paper, the simulated welding structure at different areas of heat affected zone (HAZ) of austenitic stainless steel are prepared by heating furnace, and the deference of intergranular corrosion resistance of all samples were determined by comparative methods of oxalic acid etching, hot-acid test and electrochemical potentiodynamic reactivation tests (EPR), and the effectiveness of all those methods were analysis and determination at the same time. The result shows that the susceptibility degree at different areas of HAZ increased with the heating temperature increase, but all structures can pass hot-acid test and EPR test, indicating that it could maintain good performance of intergranular corrosion resistance. The hot-acid test results have good consistency with EPR test , but inconsistent with oxalic acid etching test. The results show that the evaluation of oxalic acid etching is too much strict to be used as a judgment method, so that not suitable of use for inspection.

Aqueous sol-gel synthesis, structural, thermoanalytical studies, and conductivity properties of lithium lanthanum titanate

Newly developed aqueous sol-gel preparation technique was applied for the synthesis of lithium lanthanum titanate with the initial composition of Li0.35La0.55TiO3. The influence of hydrochloric acid, which plays a crucial role in the formation of Li–La–Ti–O tartrate gel precursor, was also investigated. The dissolution mechanism of titanium in the concentrated hydrochloric acid and its relation with the corresponding lithium and lanthanum salts was proposed. Besides, the effect of the tartaric acid as a ligand to the formation of transparent sol and homogeneous gel precursor was discussed. X-ray diffraction revealed that below the temperature of 800 °C starts the crystallization of the final tetragonal crystal phase for Li0.3La0.567TiO3 ceramic. Rietveld refinement of the crystalline samples showed the tendency of crystallites growing with the increase of heat-treatment temperature. Besides, the single crystalline ceramic compounds heat-treated at 1000 °C and 1250 °C of temperatures were obtained only for the initial composition of Li0.35La0.55TiO3. The calculated values of the tolerance factor and structural distortion parameters in octahedral coordination of TiO6 octahedral network for tetragonal and orthorhombic crystal structures confirmed the phase transition tendency by the increase of heat treatment temperature. The scanning electron microscopy proved the formation of the dense structure of the sample for Li0.35La55TiO3 ceramic after the additional heat treatment at the temperature of 1,250 °C. In addition, the quality of synthesized ceramic was confirmed by the impedance spectroscopical measurements, which revealed that the conductivity value for bulk at the temperature of 27 °C (300 K) is equal to 0.123 S m–1.

Investigating the relationship between heating temperature and thermal runaway of prismatic lithium-ion battery with LiFePO4 as cathode

As a core of safety issue on lithium-ion batteries (LIBs), thermal runaway (TR) can be easily induced when LIBs are exposed to high temperature environment. Clarifying the relationship between heating temperature and TR is crucial for improving the safety of LIBs. In this work, the impact of heating temperature on TR of the individual battery is revealed through experiments. Only safety venting is captured at 175 °C heating temperature owing to inadequate internal energy change of the LIB, whereas TR is observed to occur once the heating temperature is higher than 200 °C. With the increase in heating temperature, the time interval between safety venting and TR becomes shorter, and the temperature difference within the LIB exhibits a downtrend. In addition, contributions of the self-generated heat to trigger TR at different heating temperatures are identified. The heating temperature of 200 °C results in the highest self-generated heat before TR, which is found responsible for inducing more exothermic reactions within the LIB to generate sufficient heat to trigger TR. Furthermore, the critical input energy for triggering TR is analyzed and obtained. The findings provide new insights into the impact of temperature on TR and can benefit the safety monitoring of LIBs.

Temperature effect on mechanical performance of recycled glulam towards to sustainable production

In order to utilize recycled glulam as basic elements in novel composite structural components towards to sustainable production, the physical and mechanical properties of recycled glulam after exposed to elevated temperatures were experimentally studied, by considering the effect of heating duration (2, 4 and 6 h) and heating temperature (60, 100, 120, 160 and 200 °C). The failure modes and strength of the recycled glulam under compression and shear were analyzed respectively in detail. The results show that the influence of heating temperature on the color change of the specimens is greater than that of heating duration, among which 160 °C is the critical temperature for the obvious color change of glulam. According to the test results, the prediction formulas of weight loss ratio and dimensional change ratio under the influence of heating duration and temperature are established. The compressive strength parallel to the grain of glulam first increases and then decreases, and the shear strength decreases with the increase of heating duration and temperature. The prediction model of mechanical properties of recycled glulam under the influence of heating duration and temperature is established. The decreasing speed of the descending section in the compressive stress-strain curve of glulam increases with the increase of heating duration and temperature. The descending section of the shear stress-strain curve shows two-stage sharp drops due to the obvious brittleness during shear failure. The compression constitutive model and shear constitutive model affected by heating duration and temperature are proposed.

Performance of high-temperature lightweight multilayer insulations

Multilayer insulation (MLI) is a kind of high-temperature insulation which employs multiple high-reflective screens to retard the radiation heat, but analyzing and optimizing its heat transfer characteristics by experimental and theoretical models remains low-efficiency and non-visualization. In this work, finite element analysis (FEA) models verified by comparing the simulation and experiment results are established to systematically reveal the numerous and complex effect factors, including the number of layers, thermal boundary, fibrous insulation density and emissivity of reflective screens. The results show that the top temperature of MLIs can be reduced by increasing the number and the emissivity of reflective screens, and the density of fibrous insulation, but there is a reasonable number of layers to achieve the best comprehensive performance of MLI. In addition, the proportion of radiative heat transfer in the total heat transfer increases with increasing heating temperature. The feasibility of optimizing thermal insulation performance based on the FEA models is confirmed by designing the MLIs with stainless steel and aluminum as reflective screens. And the results indicate that the FEA methods can significantly reduce the number of trials and realize the optimal design of MLI.

Microstructure identification of powder in tube Nb3Al wires during rapid heating process and properties of the transformed superconductors

This paper systematically studied the microstructure and phase formation sequence in the powder in tube (PIT) Nb3Al processed by rapid heating and quenching (RHQ), which is a crucial issue to fabricate reliable high performance practical Nb3Al superconductors. Due to significantly inhomogeneous of the Nb/Al diffusion couple distance, an eutectic phase with liquid characteristic happened during the RHQ process, where the phase formation sequence is: Nb + Al → eutectic phase + NbAl3 → Nb3Al + Nb2Al → grid morphology bcc → band feature bcc with the increase of rapid heating temperature. The phase and microstructure during RHQ are mainly determined by the RHQ condition and local Nb/Al distribution that similar feature was shown in the quenched wires with initial Al content of 22–28 at.% in the raw powders. Grid and band microstructure of the bcc phase was related to the Al content of ~32 at.% and ~ 22 at.%, respectively. After transformation process at 800 °C, quenched wires with coexist of gird and band micro-structure show the best superconducting properties, including Tc, ΔTc, Birr, and Jc. The microstructure identification confirms that uniform and thin Al layer in the precursor wire plays an essential role in obtaining a homogeneous bcc solid phase.

Modeling the diffusion of flammable hydrogen cloud under different liquid hydrogen leakage conditions in a hydrogen refueling station

Constructing hydrogen refueling stations will be popular for hydrogen energy use in the future, and investigating the diffusion characteristics of hydrogen in a leakage incident is quite significant. The instantaneous evolution of flammable hydrogen clouds arising from liquid hydrogen leakage in a hydrogen refueling station is predicted using Ansys Fluent, and parametric analyses are conducted to reveal the effects of storage pressure, source height, and leakage direction on the distributions of the flammable regions. In addition, the feasibilities of heating the ceiling or the ground of the station after the leakage of liquid hydrogen to accelerate the hydrogen dilution are examined. The results show that the flammable region is stabilized at 90 s, the corresponding flammable hydrogen cloud volume is about 333 m3, and the extensions of downwind and vertical directions reach 10 m and 9.3 m. Storage pressure has a finite effect on the downwind diffusion distance of the flammable cloud. A lower source height tends to format the high-concentration hydrogen cloud near the ground while a higher source height helps separate the flammable clouds from the ground. The upward leakage direction leads to the maximum downwind diffusion distance of about 10.2 m while the downward leakage direction makes the high hydrogen concentration region confined below the ceiling. Just maintaining the ceiling at the initial temperature of 300 K is effective for accelerating the hydrogen dilution in the upward leakage. The maximum hydrogen concentration and the flammable volume can be reduced at rates of 0.35 vol % and 8% for every 50 K increase in heating temperature. For the downward leakage, keeping the ground at the initial temperature just works for the first 40 s in reducing the maximum hydrogen concentration, while increasing the heating temperature receives a gradually declined effect on reducing the flammable volume.

Effect of High Temperature Treatment on the Photoluminescence of InGaN Multiple Quantum Wells

In this work, the photoluminescence (PL) properties of three as-grown InGaN/GaN multiple quantum well (MQW) structures which are heat-treated under different temperatures with nitrogen (N2) atmosphere are investigated. Temperature-dependent photoluminescence (PL) analysis was used to characterize the depth of localized states and defect density formed in MQWs. By fitting the positions of luminescence peaks with an LSE model, we find that deeper localized states are formed in the MQWs after high-temperature treatment. The experimental results show that the luminescence intensity of the sample heat-treated at 880 °C is significantly improved, which may be due to the shielding effect of In clusters on defects. While the luminescence efficiency decreases because of the higher defect density caused by the decomposition of the InGaN QW layer when the sample is heat-treated at 1020 °C. Moreover, the atomic force microscope results show that the increase in heat-treatment temperature leads to an increase in the width of surface steps due to the rearrangement of surface atoms in a high-temperature environment.

Heat Treatment‐Induced Wear Transition in Electroplated Ni–Co Coating on Copper

Herein, the effect of heat treatment on the high-temperature wear resistance of Ni–Co electroplating coating on copper surface is systematically investigated. Results show that the oxide layer formed on the surface of coating during heat treatment induces the wear mechanism transition of coating. Under the condition without oxide layer formation (heat treatment at 400 °C), the coating suffers severe adhesive wear due to the low hardness caused by grain growth. After heat treatment at 600 °C, the formation of CoO and Co3O4 oxide layers on the surface of coating improves wear resistance, and the wear mechanism changes to oxidative wear and adhesive wear. The density of the oxide layer determines the degree of adhesive wear. As the heat treatment temperature increases (900 °C), the formation of a denser NiCo2O4 oxide layer with higher hardness further inhibits the adhesive wear mechanism of the coating. Until more than 6 h, the formation of scale-shaped NiCo2O4 and 3CoO·NiO oxide layers significantly improves the wear resistance of the coating and completely eliminates adhesive wear. The wear mechanism is transformed into oxidative wear.

Synthesis, photoluminescence, and up-conversion luminescence properties of YTiTaO6:Er3+/Yb3+

The relationship between the factors (i.e. the concentrations of Yb3+ and Er3+ and heating temperature in air) and the properties of photoluminescence (PL) and up-conversion luminescence of YTiTaO6:Er3+/Yb3+ whose crystalline phase depended on heating temperature in air was examined using samples synthesized hydrothermally. The intense green emission (: 2H11/2,4S3/2→4I15/2 transitions of Er3+) was obtained by the excitation at 288 ​nm using the indirect energy transfer from the YTiTaO6 host crystal, which was about 1.8 times stronger than that obtained by the direct excitation at 380 ​nm via the f-f transition (: 4I15/2→4G11/2) of Er3+. Aeschynite phase exhibited intermediate luminescence property. The up-conversion emission intensity increased with increasing heating temperature and became the maximum at x ​= ​0.10 and y ​= ​0.20 with euxenite phase, although the co-presence of Yb3+ gave negative effect on the PL intensity of ErxYbyY1-x-yTiTaO6. As heating temperature rose to 1300–1400 ​°C the intensity of the red up-conversion emission (: 4F9/2→4I15/2 transition) became greater than that of the green emission (: 4S3/2→4I15/2 transition), accordingly the position of the color chromaticity coordinates shifted slightly from green to yellow.

Bonding Performance of CFRP-Steel Interface after Continuous High Temperature

The bonded shear performance of CFRP-reinforced steel structures following continuous high-temperature natural cooling was investigated experimentally, and 30 CFRP-steel specimens were subjected to single-shear tensile testing. In analyzing the shear stress-displacement relationship in each working condition, the equation for the coupling effect of the heating temperature and duration on the ultimate shear stress was proposed. The results show that the ultimate shear stress at the CFRP-steel interface tends to decrease with the increase of heating temperature, and the ultimate shear stress at the heating temperature of 300°C is 32.37% of that at 25°C. The high-temperature duration has an obvious influence on the bonding performance of the CFRP-steel interface, and the CFRP-steel specimens fail when the heating temperature is 300°C and lasts for 120 min.

High efficient removal of lead(II) and cadmium(II) ions from multi-component aqueous solutions using polyacrylic acid acrylonitrile talc nanocomposite

This study is interested in the removal of Pb(II), Cd(II), Co(II), Zn(II), and Sr(II) onto polyacrylic acid acrylonitrile talc P(AA-AN)-talc nanocomposite. P(AA-AN)-talc was fabricated using γ-irradiation-initiated polymerization at 50 kGy. Different analytical tools were used to investigate the functional groups, morphology, particle size, and structure of this composite. The ability of P(AA-AN)-talc to capture (Pb2+, Cd2+, Co2+, Zn2+, and Sr2+) as multi-component aqueous solutions was performed by a batch method. Saturation capacity and the effect of (agitating time, pH, initial metal concentrations, and temperature) were investigated. The distribution coefficients at different pHs have order: Pb2+ > Cd2+ > Co2+ > Zn2+ > Sr2+. The saturation capacity decreases by increasing heating temperatures. Reaction kinetic obeys the pseudo-second-order model. Sorption isotherms are more relevant to a Langmuir isotherm, and the monolayer sorption capacity is closed to saturation capacity. Thermodynamic parameters (∆G˚, ∆H˚, and ∆S˚) were endothermic and spontaneous. P(AA-AN)-talc is used for loading and recovery of studied cations in the column system. The study confirms that P(AA-AN)-talc is a promised composite for the sorption of the studied ions from aqueous solutions and should be considered as potential material for decontaminating these ions.Graphical abstract

Change in electronic state of nitrogen in oxidized titanium nitride

The changes in the electronic state and local structure of nitrogen in TiN powders heated in air were investigated by X-ray diffraction, diffuse reflectance, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge-structure (XANES) measurements. The oxidation of TiN powder accompanied by desorption of nitrogen started from the surface of the powder particle, resulting in a transformation from TiN to TiO2 with increasing heating temperature. The diffuse reflectance spectra showed the formation of nitrogen-doped TiO2 with an absorption band at 2.9 eV by heating TiN powder above 600 °C. XPS measurement revealed the presence of nitrogen with a negative charge in TiN powders and with a neutral or positive charge in highly-oxidized powders containing a small amount of nitrogen. XANES measurement for nitrogen clarified the presence of nitrogen bound to oxygen which form some complex species such as NO molecule in the powders oxidized above 400 °C.

Effect of Heat Treatment on the Formability of Zn‐Coated Hot Stamping Steel

Herein, the effect of heat treatment with die quenching on Zn‐coated hot stamping steel is analyzed. Heating temperatures are 850, 880, 900, and 930 °C, and soaking times are 4 and 8 min. Then, microstructure, hardness, coating layer morphology, element diffusion and distribution, formation of microcrack and microvoid, and oxidation are analyzed. Results reveal that as heating temperature increases, the Vickers hardness of Zn‐coated hot stamping steel increases when soaking time is 4 min, while it decreases when soaking time is 8 min. The least average hardness value is still larger than 460, resulting from the formation of the martensitic phase. The diffusion tends to be significant as heating temperature and soaking time increase. Both the diffusion and the evaporation affect the thickness of the coating layer remarkably. The average layer thickness is at least 18.2 μm. Microcrack generates in the coating layer due to different thermal expansions between substrate and coating layer and the melting of Zn or Zn–Fe binary phase with high content of Zn. Microvoid forms in the coating layer, resulting from the Kirkendall effect and oxidation of the Zn element. Moreover, with the increase in heating temperature and soaking time, Fe2O3 is also generated on the coating surface along with ZnO.

Role of aluminum on liquid metal embrittlement susceptibility for Zn–Al–Mg/Sn coated hot-formed steels

In order to reduce the susceptibility of liquid metal embrittlement (LME) on advanced high strength steels, this paper proposes a strategy to increase the thickness of the inhibition layer and retard the interdiffusion of Fe and Zn by adjusting the Al content in the coating, so as to improve this key problem in industrial application. On the basis of it, phase transformation of Zn–Al–Mg/Sn coated hot-forming steel during austenitization is studied via CALPHAD method and results show that Fe–Al intermetallic layer may break down gradually with the increase of heating temperature, leading to the penetration of liquid zinc into steel substrate. Hence it is necessary to analyze the Fe–Zn interdiffusion behavior during heat treatment. And then, the formation of LME crack is investigated by austenitization treatment. It is shown that, when the aluminum content in Zn–xAl–1.8Mg coating increases from 0.2 wt.% to 3.5 wt.%, not only the thickness of inhibition layer increases, but the temperature for the inhibition layer breaking down increases from 420 °C to 750 °C as well. Moreover, after the addition of Sn element, the inhibition layer of Zn-3.5Al–1.8Mg–0.8Sn coating has better stability compared with that of Zn–3.5Al–1.8Mg coating at the same high temperature. Additionally, it is found that the Zn–3.5Al–1.8Mg coating/steel interface zone shows a better ductility property than that with that of lower Al content on the same deformation conditions during high temperature tensile process. It is illustrative that the presence of Sn can weaken the liquid Zn penetration into the steel, so as to control the LME phenomenon.