Double Annealing Research Articles

Impact of Heat Treatment on the Mechanical Properties and Fracture Morphology of Ti555211 Alloy.

Heat treatment is important for optimizing the strength performance and improving the toughness of titanium alloys. In this study, we investigated the impact of three heat treatment methods (β-annealing, double annealing, and solid-solution and aging treatment) on the mechanical properties and fracture morphology of Ti555211 titanium alloy. The results show that after β-annealing treatment, the alloy retains a high strength, while showing almost no ductility, and no yield strength. The alloy after double annealing has a high elongation rate (~54%) and lower strength. After solid-solution and aging heat treatment, the alloy was able to retain both high strength and a certain degree of ductility. The optimal heat-treatment process is solid-solution treatment at 820 °C/2 h and aging at 560 °C/12 h, which results in a maximum tensile strength of 1404 MPa and an elongation rate of 11%.

The effect of double intercritical annealing on micromechanical behavior of a medium Mn transformation induced plasticity steel investigated by in situ high energy X-ray diffraction

The micromechanical behavior of a medium Mn transformation induced plasticity (TRIP) steel processed by intercritical annealing (IA) and double intercritical annealing (DIA) has been investigated by using in situ high energy X-ray diffraction during uniaxial tensile deformation. The results show that the ultimate tensile strength (UTS) and total elongation are 777.1 MPa and 39.6 % for IA and 953.6 MPa and 59.1 % for DIA, and that the product of UTS and total elongation is 30.8 GPa·% for IA and 56.4 GPa·% for DIA, respectively. Discontinuous phase transformation from austenite to martensite leads to Portevin-Le Châtelier (PLC) band propagation for both IA and DIA. The pronounced TRIP effect takes place in DIA step by step during deformation and contributes to higher strain hardening, which results in almost doubling the product of UTS and total elongation. The stepwise phase transformation highly corresponds to the lattice strain evolution of ferrite and austenite, indicating that load partitioning occurs during the deformation. The change of grain structure generated by different heat-treatments correlate with the load partitioning, thereby inducing large discrepancy in micromechanical behavior. The present investigation provides a deeper fundamental understanding of the effect of double inter-critical annealing on micromechanical behavior and effective engineering strategies for improving the product of UTS and total elongation for the medium Mn TRIP steels.

Towards High Strength-Ductility Balance Using Double Annealing Cycles

Impact of first annealing on the formation and evolution of the microstructure during second annealing and on the final mechanical properties was investigated. Simple Fe-C-Mn-Si steel was used in this study. Dilatometry tests coupled with metallographic examinations were carried out to monitor the evolution of phase transformations and associated microstructure. Difference in the austenite evolution between simple and double annealing was highlighted. Based on the obtained results, conditions were selected for the annealing trials on bigger sample. Mechanical properties of heat-treated steels were assessed through the standard tensile tests. Double annealing treatment resulted in a better strength-ductility balance and in a good stability against soaking and quenching temperature variation. Complex ultra-fine multiphase microstructure containing at least 5 different microstructural constituents was revealed and observed using Scanning Electron Microscopy. As well, retained austenite fraction was estimated through magnetization saturation method.

Synergistic and competitive mechanisms of plastic anisotropy in high-efficiency laser melting deposited TC11 alloy

The layer-by-layer processing features of laser melting deposited (LMD) TC11 titanium alloy inevitably lead to microstructural inhomogeneity, and the grain morphology associated with micro-orientations induces plastic anisotropy, which causes uneven deformation and further performance deterioration. Understanding the main causes of these characteristics and how to distinguish their relative roles in inducing plastic anisotropy is critical. In this work, a high-efficiency LMD process is developed. Then, the individual factors causing the formation of elongated grains, microstructural inhomogeneity and micro-orientations are isolated to investigate the synergistic and competitive mechanisms of plastic anisotropy for high-efficiency LMD TC11 titanium alloy before and after various heat treatments. Initially, the TC11 titanium alloy is prepared by the LMD technique under high laser power and then heat-treated via three methods of double annealing in the α+β phase zone. Subsequently, the macro- and microscopic morphology, microstructure, and micro-orientations are characterized by optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The individual effects of grain shape, α grain boundary (αGB) and micro-orientations on tensile plastic anisotropy are systematically and thoroughly investigated via a hybrid method consisting of experimental and crystal plasticity finite element simulation methods. By introducing a redefined evaluation indicator of dislocation plugging coefficients, elongated grains are found to be the main source affecting the tensile strength in different loading directions. In addition, with increasing primary annealing temperature, the breakage degree of αGB parallel to the building direction (BD) is significantly higher than that perpendicular to the BD, which leads to an increase in tensile strength and elongation. Moreover, the preferred <0 0 0 1> orientation leads to different tensile strengths perpendicular and parallel to the BD, which is caused by the transformation between easy-to-slip and hard-to-slip orientations. The micro-orientations mainly affect the yield strength and elongation, while the tensile strength and elongation are simultaneously controlled by the grain morphology and αGB.

Effect of Capped Cu Layer on Protrusion Behaviors of Through Silicon via Copper (TSV-Cu) Under Double Annealing Conditions: Comparative Study

Annealing process is generally adopted to reduce the residual stress and stabilize the microstructure of TSV-Cu in IC manufacturing. In this paper, the effects of capped Cu layer on the protrusion behaviors of TSV-Cu are investigated considering various double annealing processes. Higher protrusions of TSV-Cu with capped Cu layer are observed compared with that of TSV-Cu without capped Cu layer. The reason is that capped Cu layer impedes the elimination of grain boundaries and local misorientation during the first annealing, resulting in the remaining of larger amounts of atoms and higher energy in the grain boundaries. Thus, it is easier to induce protrusion by grain boundary migration during the second annealing. In addition, the capped Cu layer effects on mechanical properties of TSV-Cu under various double annealing conditions are investigated by nanoindentation test. The values of elastic modulus and hardness are generally higher in the presence of capped Cu layer. The reason is also discussed and clarified.

Texture characteristics and fracture mechanism of linear friction welded joints of dissimilar titanium alloys after annealing

In the paper, we discussed the effect of annealing on the microstructure, crystal texture, and toughness of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si (TC11) and Ti–4Mo–4Cr–5Al–2Sn–2Zr (TC17) linear friction welding (LFW) joint. The results reveal that the microstructure difference on both welded zone (WZ) decreases. The TC11 WZ consists of supersaturated solid solution α′ phase and β phase, the coarse α grains disappear and the orthorhombic martensite α″ phases transform into lamellar α+α′ phases on the TC17 WZ after the double furnace annealing. Two β textures (shear and annealing textures) and two α textures (D and E textures) exist at the original joint, and both of them transform into new β textures (brass and copper textures) and α textures (F and G textures) after the double furnace annealing. The dislocation density of the TC17 WZ is significantly higher than that of the TC11 WZ at the original joint. After the double furnace annealing, dislocation density, grain type, and Schmid factor (SF) distribute uniformly throughout the entire WZ. The average dislocation density decreases slightly and the low SF (μ<0.25) almost disappears. The microhardness value of the entire joint is more uniform and stable, and the fracture toughness is 137% higher than that of the original joint, approximately reaching 91% of the TC11 fracture toughness. The research provides a theoretical basis for preparing high-toughness joints of dissimilar titanium alloys.

Achieving superior mechanical properties in electron beam welded joints of Ti-5Al-5Mo-5V-1Cr-1Fe alloy thick plate using novel annealing treatments

The strength reduction of Ti-5Al-5Mo-5V-1Cr-1Fe alloy (Ti-55511) thick plate joints after electron beam welding (EBW) largely limited their engineering application. In this study, three annealing treatments, including single, double and triple annealing, after EBW were designed to regulate the morphology and distribution of α phase in the Ti-55511 alloy weld 30 mm in thickness, which largely enhanced the joint strength. Among three annealing treatments, double annealing enhanced the joint strength most, with the increase in the yield and tensile strengths from 873 MPa and 919 MPa for the as-welded joint to 1025 MPa and 1095 MPa for the annealed joint, respectively, which were even superior to those of the base material. The great increase of the joint strength after double annealing was mainly attributed to the alternate distribution of the newly formed lamellar α and acicular secondary α phase, which was achieved via the transformation and growth of punctated martensite (FCC) phase during the first annealing and the precipitation of acicular secondary α phase from the metastable β grains during the second annealing. The microstructural evolution during welding and subsequent annealing was discussed. This study provides a novel annealing treatment to improve the strength of titanium alloy EBW joints.

Влияние замещения ионами Bi-=SUP=-3+-=/SUP=- на структурно-фазовое состояние и особенности магнитной структуры твердого раствора BaFe-=SUB=-12-x-=/SUB=-Bi-=SUB=-x-=/SUB=-O-=SUB=-19-=/SUB=-

The results of studies of the features of the phase composition, crystal and magnetic structure of Bi-substituted barium hexaferrite BaFe12-xBixO19 (0.1≤ x≤ 1.2) by methods of Mossbauer spectroscopy, X-ray phase analysis, as well as image analysis by scanning electron microscopy are presented. Samples of Bi-substituted hexaferrites - BaFe12-xBixO19 (where x=0.1; 0.3; 0.6; 0.9 and 1.2) were synthesized by the method of solid-phase reactions with double annealing (at T=1100oC for 6 h) and intermediate grinding (for 0.5 h). The X-ray phase analysis allowed us to establish the limit of substitution of Fe3+ ions by Bi3+ ions. It has been shown that at a low level of substitution (x≤0.3) there are no impurity phases detected and the samples are characterized by a single-phase state with the spatial group P63/mmc. When the degree of substitution increases (x&gt;0.3) the formation of impurity phases is noted, which can be explained by the difficulties of ion diffusion in the process of solid-phase synthesis, as well as the formation of defects in the structure of magentoplumbite due to the large ionic radius of Bi3+. As impurity phases in the studied compositions (x&gt;0.3) Marked: BiFeO3 (Pr. Gr. Pnma); BiO2 (Pr. Gr. Fm-3m); BaBi2O6 (Pr. Gr. R-3) and BaO0,5Bi1,5O2,16 (Pr. Gr. Im-3m). The content of the main phase (Pr. Gr. P63mmc) at the same time decreases from 95.11 to 88.27 vol.% when increasing x from 0.6 to 1.2, respectively. The analysis performed by the method of Messbaurov spectroscopy showed that all Fe ions have a charge of 3+. And all parameters lie within the values characteristic of Fe3+ ions corresponding to the coordination of polyhedra: 12k. 4f2, 2a - octahedra, 4f1 - tetrahedron, and 2b - bipyramide. It is possible to single out a small monotonous decrease only for the 12k position. The analysis of SEM images showed an increase in the average particle size up to 10 mkm, depending on the concentration of bismuth oxide during the synthesis of hexaferrite.

The effects of double intercritical annealing on microstructure and mechanical properties of 0.107C-2.39Mn-0.453Si dual phase steel

In this study, double intercritical annealing was applied to modify the mechanical properties of 0.107%C-2.39%Mn-0.453%Si dual phase steel. The effects of the double intercritical annealing (DIA) method were investigated via microstructure observation and tensile test, and then compared with the single intercritical annealing (SIA) method. By increasing the intercritical annealing temperature, yield and tensile strengths increase while ductility decreases primarily due to the increase of martensite fraction. DIA leads to a slight reduction of the ferrite size and the martensite fraction regardless of the intercritical annealing temperature. Tensile results showed that DIA increases ductility without losing significant amount of strength. The outcome implies that the DIA method can be used to modify the mechanical properties of DP steels without adding excessive complexity to the process.

Effect of double annealing on microstructure and mechanical properties of Mn-TRIP steel

A novel double annealing process was applied to a Mn-TRIP steel. As a result, a great combination of yield strength of 829MPa, tensile strength of 1132MPa and total elongation of 42.1% was obtained. The improvement of mechanical property was contributed to microstructure evolution. By double annealing process, ferrite grains were refined and VC could effectively precipitate instead of cementite, which contributed to the enhancement of yield strength. Austenite fraction was increased and two types of austenite morphology (block and lath) were obtained. In addition, Mn partitioning was promoted, leading to high Mn enrichment in austenite grains. Consequently, the austenite grains with high stability provided continuous and active TRIP effect, contributing to a great work-hardening behavior and increasing strength and ductility.

Kinetics of Gamma-Alpha-Transformation of Retained Austenite in Maraging Steel after Double Annealing at Sub-Zero Temperatures and Loads

Kinetics of Gamma-Alpha-Transformation of Retained Austenite in Maraging Steel after Double Annealing at Sub-Zero Temperatures and Loads

Comparison of Sb2O3 and Sb2O3/SiO2 Double Stacked pH Sensing Membrane Applied in Electrolyte-Insulator-Semiconductor Structure.

In this study, electrolyte-insulator-semiconductor (EIS) capacitors with Sb2O3/SiO2 double stacked sensing membranes were fabricated with pH sensing capability. The results indicate that Sb2O3/SiO2 double stacked membranes with appropriate annealing had better material quality and sensing performance than Sb2O3 membranes did. To investigate the influence of double stack and annealing, multiple material characterizations and sensing measurements on membranes including of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were conducted. These analyses indicate that double stack could enhance crystallization and grainization, which reinforced the surface sites on the membrane. Therefore, the sensing capability could be enhanced, Sb2O3/SiO2-based with appropriate annealing show promises for future industrial ion sensing devices.

Kinetics of γ → α Transformation of Retained Austenite in Maraging Steel after Double Annealing at Subzero Temperatures and Loads

Kinetics of γ → α Transformation of Retained Austenite in Maraging Steel after Double Annealing at Subzero Temperatures and Loads

Effect of Polyimide-Phosphating Double Coating and Annealing on the Magnetic Properties of Fe-Si-Cr SMCs.

Fe-Si-Cr soft magnetic powder cores (SMCs), with high electrical resistivity, magnetic permeability, saturation magnetic induction, and good corrosion resistance, are widely applied to inductors, filters, choke coils, etc. However, with the development of electronic technology with high frequency and high power density, the relative decline in the magnetic properties limits the high-frequency application of SMCs. In this paper, the phosphating process and polyimide (PI) insulation coating is applied to Fe-Si-Cr SMCs to reduce the core loss, including hysteresis loss and eddy current loss. The microstructure and composition of Fe-Si-Cr powders were analyzed by SEM, XRD, and Fourier-transform infrared spectra, respectively. The structural characteristics of the Fe-Si-Cr @ phosphate layer @ PI layer core–shell double coating were studied, and the best process parameters were determined through experiments. For SMCs with 0.4 wt% content of PI, the relative permeability is greater than 68%, and the core loss is the lowest, 7086 mW/cm3; annealed at 500 °C, the relative permeability is greater than 57%, and the core loss is the lowest, 6222 mW/cm3. A 0.4 wt% content of PI, annealed at 500 °C, exhibits the ideal magnetic properties: μe = 47 H/m, P = 6222 mW/cm3.

Protrusion of Through-Silicon-Via (TSV) Copper with Double Annealing Processes

Protrusion of Through-Silicon-Via (TSV) Copper with Double Annealing Processes

Research on the microstructure and mechanical properties of doubled annealed laser melting deposition TC11 titanium alloy

TC11 titanium alloy has the advantages of light weight and high strength, and it has great potential to replace high-strength steel as the material of aerospace main bearing to achieve lightweight application. In this study, TC11 titanium alloy was prepared by laser melting deposition, and the deposited TC11 titanium alloy was subjected to double annealing heat treatment, so as to study the effects of different annealing temperatures and time on the microstructure and mechanical properties. The results indicated that the microstructure of TC11 titanium alloy grew alternately by the turns of columnar crystal / equiaxed crystal along the deposition direction. The deposited microstructure was mainly composed of the Widmanstatten structure and mesh basketweave structure. After double annealing, the α phase was coarsened and the aspect ratio decreased, and the continuous grain boundary α phase appeared discontinuous; however, when the annealing temperature was 1025 °C, the intragranular microstructure changed into a fine basketweave structure, and the continuous α phase was reformed at the grain boundary. With the extension of high time, the coarsening phenomenon of the αs phase was obvious. The microhardness increased firstly and then decreased with the annealing temperature, and reached the maximum at 995 °C. After double annealing, the impact toughness of TC11 titanium alloy was significantly improved, which was better than the forging standard. The strength and plasticity of TC11 titanium alloy were also significantly improved, meeting the forging standard, but when the annealing time was extended to 2 h, the strength was significantly reduced. The strength anisotropy of TC11 titanium alloy was less than 3% during the annealing in the two-phase region; the anisotropic plasticity increased firstly and then decreased with the increase of annealing temperature; with the extension of annealing time, both the anisotropy of strength and plasticity showed an increasing trend.

Performance enhancement of WS2 transistors via double annealing

Herein, we report the double annealing strategy to improve the device performance of WS2 transistors fabricated using multilayer WS2 flakes on SiO2/p++-Si substrates. In the double annealing approach, the annealing is performed twice, both before and after electrode formation. The statistical analysis of 50 WS2 transistors indicated that, compared to the conventional single annealing, the double annealing increased the average field-effect mobility and reduced the average contact resistance. The enhanced device performance could be attributed to the improved interface quality between WS2 and the electrodes, owing to the removal of organic residues and desorption of surface adsorbents during the first annealing before the electrode formation. These results demonstrate the effectiveness of double annealing in enhancing the device performance of WS2 transistors, suggesting the important role of process optimization in fabricating WS2 transistors and other transition metal dichalcogenide devices.

Effect of annealing treatment on mechanical and fatigue properties of Inconel 718 alloy melted by selective laser melting

Inconel 718 alloy which was prepared using selective laser melting (SLM) forming technology underwent various annealing treatments. Optical microscope, scanning electron microscope, electron backscattered diffraction and MTS testing machine were used to study the microstructure, mechanical and fatigue properties of Inconel 718 alloy melted by selective laser melting under different annealing treatments. The results show that the microstructure of Inconel 718 alloy after homogenization and doubleaging annealing is the most obvious, and the microstructure of the alloy is mainly recrystallized. The microstructure contains a large number of annealing twins and the grain boundaries are flat. The yield strength, tensile strength and microhardness of Inconel 718 alloy formed by selective laser melting after different annealing treatments are greatly increased, while the elongation after fracture is significantly decreased. The fatigue properties of Inconel 718 alloy after double aging annealing and solution dual aging annealing are improved slightly, while the fatigue properties after uniform double aging annealing are decreased slightly.

A new processing route to develop nano-grained structure of a TRIP-aided austenitic stainless-steel using double reversion fast-heating annealing

Abstract A novel processing route comprising double reversion annealing (DRA) was designed for developing bulk nano-grained (NG) structure of an austenitic stainless steel (Type 301LN). The new processing concept of DRA comprised two subsequent intrinsic type processes i.e., two times cold reductions (~53% and 63%) followed by fast induction heating (~200 °C/s) and short duration annealing at different temperatures (first at 690 °C/60s and second at 750–900 °C/0.1–1s). The NG structure revealed a remarkable improvement of the mechanical properties compared to the counterparts processed by single reversion annealing. Furthermore, outstanding combination of strength and formability is achieved for the DRA structures, significantly higher than those of high-Mn TWIP steels, low-alloy TRIP steels and 304 stainless steel. For instance, a superior combination of yield strength (~950–1030 MPa) and formability index (11.8–12.5 mm) obtained after DRA at 750 °C/0.1s and 800 °C/1 s, respectively. However, the corresponding values are 300 MPa and 12 mm for TWIP steels, 500 MPa and 10 mm for TRIP steels, and 270 MPa and 12 mm for 304 stainless steel. In order to reveal the effect of DRA on the stretch formability, Erichsen cup testing was conducted of both the initial and DRA steel specimens. Moreover, Erichsen cup testing also simulated by the finite element method (FEM) to survey further details of their deformation.

Оцінка метрологічних характеристик методу спектрального аналізу для визначення морфології еритроцитів

Spectral photometry is currently widely used for quantitative and qualitative analysis of biological molecules in medical biology. The method is based on the ability of molecules to absorb electromagnetic radiation. Modern clinical laboratory diagnostics extensively uses optical methods of analysis that rely on these physical properties of semitransparent objects, such as blood components. Knowing the absorption spectra of blood and its components, it is possible to quantify the concentration of all the components by solving the mathematical system of equations corresponding to these spectra. However, the existing methods of optical analysis of erythrocytes do not allow quantifying their geometric parameters, which may also indicate certain diagnostic signs and be used to analyze the clinical condition of the patient's body. The aim of this work is to evaluate the metrological characteristics of the newly developed method of determining the geometric parameters of erythrocytes, which combines spectral analysis and double annealing. The input data for the 3D imaging of erythrocytes were taken from the images of the sample both made in natural light and illuminated by a coherent light source with different wavelengths. The latter, after some additional image correlation, increases the reliability of the result. The calculation results on the errors and the measuring channel resolution of the digital interference microscope indicate an acceptable accuracy of the method. The accuracy of the three-dimensional image obtained by the proposed method is more than 20% higher than that of other known methods. This allows determining the informative geometric parameters of the structure of erythrocytes more accurately and using them to obtain additional clinical diagnostic characteristics of the patient's body.