Influence Of Aging Temperature Research Articles

Influence of Aging Temperature on Precipitation Kinetics, Morphology and Hardening Behavior of Al-7475 Alloy

In this research, the precipitation hardening behavior of Al-7475 alloy is investigated by a comprehensive experimental study on the relationship between thermal aging and evaluation of the kinetics and hardening properties of the alloy. The investigation was carried out using X-ray diffraction analysis (XRD), differential scanning calorimetry, scanning and transmission electron microscopy investigations and Vickers hardness (HV) test. The XRD results show that increasing the aging temperature, from 273 to 620 K, enhances the coarsening and evolution of precipitates which leads to an increase in the particle size. The thermal analysis shows the precipitation kinetics of the observed phases such as $$\upeta '$$ , $${T}'$$ , and $$\upeta $$ , based on the correlation between migration and diffusion of spread atoms in the Al matrix. In addition, the TEM micrographs indicate that needle-shaped precipitates distinguish the development of $$\upeta '$$ and/or $${T}'$$ - precipitates which at most contribute to the material strengthening. Moreover, the reaction order values of $$\upeta '$$ and $$\upeta $$ -precipitate nucleation indicate that the developed phases are radially grown.

The influence of ageing temperature on carbide phases precipitation at grain boundaries of P/M Ni-base superalloys

The way to set ageing regimes of P/M Ni-base superalloy for disk application was demonstrated. The optimal ageing temperatures were identified by microstructure investigations. Mechanical tests of the material with different volume ratio of carbide phases were carried out. The obtained results confirm the correctness of the detected patterns.

Microstructure and property of laser additive manufactured alloy Ti–6Al–2V–1.5Mo–0.5Zr–0.3Si after aged at different temperatures

The solid solution and aging treatment for conventional manufacturing processes might not be suitable for laser additive manufactured titanium alloys due to the different lamellar microstructures. In this study, the influence of aging temperatures (600, 700 and 800 °C) on microstructure and mechanical properties of titanium alloy Ti–6Al–2V–1.5Mo–0.5Zr–0.3Si was investigated. The results indicate that after solid solution treatment at 970 °C followed by water quenching, the alloy mainly consists of coarsening lamellar α phase in martensite α′ matrix. Aging at 600 °C will not change the size of primary lamellar α phase but lead to huge amount of secondary α phases (αs) generating with very fine microstructure. By increasing the aging temperature, the number of αs decreases but with coarsened microstructures. When aged at 800 °C, the width of the αs phase reaches 350 nm, almost 7 times wider than that aged at 600 °C. The changing size of αs obviously influences the property of the alloy. The fine αs leads to high strength and microhardness but low plasticity, and specimen aged at 700 °C with suitable αs size has the best comprehensive properties.

Influence of aging temperature and Mg/Zr molar ratio on transformation of C2H6 to C2H4 over VOx catalyst supported on Mg–Zr nanocomposite

To identify active and selective catalysts for oxidative dehydrogenation of ethane in presence of CO2, MgO–ZrO2 supports with varying amounts (0–100 wt%) of ZrO2 were synthesized via a coprecipitation method then impregnated with NH4VO3. In addition, the impact of the aging temperature on the structural properties and catalytic activity was examined. To characterize the prepared catalysts, X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) spectroscopy, Brunauer–Emmett–Teller (BET) measurements, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy (DRS), and Fourier-transform infrared (FTIR) analysis were applied. The results of XRD and EDX analyses confirmed successful synthesis of MgO–ZrO2 nanocomposite. In presence of zirconia, the dispersion of V-species was improved, decreasing the particle size of vanadium oxide and thus promoting the catalytic activity. However, for higher concentration of ZrO2 on the support, agglomeration of particles was observed and the ratio of the tetragonal to monoclinic phase of zirconia decreased. On the other hand, the presence of MgO stabilized the tetragonal phase of zirconia. According to the applied characterization methods and catalytic activity tests, VOx/ZrO2(25)–MgO(75)-A was selected as the most active catalyst, showing C2H4 yield of 60.13 % as well as ethane conversion of 67.14 % at 700 °C. This catalyst remained stable during 10 h on stream at 700 °C, indicating that the presence of a proper amount of zirconia not only increased the activity of the catalyst but also prevented its deactivation.

Optimal Synthesis of Hierarchical Porous Composite ZSM-5/SBA-16 for Ultradeep Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene. Part 2: The Influence of Aging Temperature on the Properties of NiMo Catalysts

ZSM-5/SBA-16 (ZS) supports were prepared using the two-step hydrothermal crystallization method. The effect of the aging temperature on the structural properties of the series ZS supports was studied. The prepared samples were analyzed by X-ray diffraction, scanning electron microscopy, N2 physisorption, 27Al magic angle spinning nuclear magnetic resonance, H2 temperature-programmed reduction, Raman, X-ray photoelectron spectroscopy, pyridine–Fourier transform infrared spectroscopy, and high-resolution transmission electron microscopy. The hydrodesulfurization performances of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were examined at T = 340 °C and PH2 = 4 MPa. The NiMo/ZS-45 catalyst synthesized at the aging temperature of 45 °C exhibited the best catalytic activities of DBT and 4,6-DMDBT, which were attributed to its regular shape, well-organized pore structure, high sulfidation degree, and a compromise between the acidity and metal–support interaction (MSI, Mo–O–Si). Moreover, the possible DBT and 4,6-DMDBT HDS reaction networks over NiMo/ZS-45 were proposed.

Microstructural Evolution and Mechanical Properties during Homogenization and Ageing Treatment of Al-Mg-Si Alloy Wire Cold Drawn

The objective of the present investigation is to study the changes in microstructures and mechanical properties during ageing and homogenization treatment of Al-Mg-Si alloy wire cold drawn at the different deformation in ENICAB (Biskra), destined for the transport of electric energy. And also to understand the phase formation during the cold drawing of Al-Mg-Si alloy wires, as well as the combined influence of the plastic deformation level and the influence of aging temperature. Wire section reduction shows a change in microstructure and texture. Characterization methods used in this work is: Optical Microscopy (OM), Scanning Electron Microscope (SEM) and X-ray diffraction.

Modeling of natural fiber reinforced composites under hygrothermal ageing

In this paper, we focus on the mechanical performance of fibers naturally derived from plants as reinforcement of a composite structure. A nonlinear constitutive model for the whole hygrothermal ageing process of natural fiber reinforced composites is established. This theoretical model accounts for large elastic and inelastic deformation, diffusion of water molecules and hydrolysis reaction. Based on the non-equilibrium thermodynamic framework, the Helmholtz free energy functions and the corresponding dissipation laws are established. The effects of matrix cracking, fiber-matrix interfacial debonding and change in the microstructure of natural fibers are all considered in this theoretical model. And the competition between the loss and the recovery of mechanical properties of natural fibers is investigated. Moreover, this theoretical model is applied to analyze the elastic response of natural fiber reinforced composites and the influence of ageing temperature is discussed. The obtained theoretical results are compared with corresponding experimental data and it is shown that the present theoretical model is capable of describing the evolution of elastic moduli of composite samples and their temperature dependence during the whole hygrothermal ageing process.

Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution

The general corrosion behavior of sintered 17-4 PH stainless steel processed under different processing conditions in dilute sulfuric acid solution at 25 °C was studied by open-circuit potential measurement and potentiodynamic polarization technique. The corrosion resistance was evaluated based on electrochemical parameters, such as polarization resistance, corrosion potential, corrosion current density as well as corrosion rate. The results showed that the precipitation-hardening treatment could significantly improve the corrosion resistance of the sintered 17-4 PH stainless steel in studied environment. As far as the influence of aging temperature on corrosion behavior of the sintered 17-4 PH stainless steel is concerned, polarization resistance and corrosion rate are reduced with increasing aging temperature from 480 up to 500 °C regardless of the temperature of solution treatment. It can be concluded that the highest corrosion resistance in 0.5 M H2SO4 solution exhibits 17-4 PH after solution treatment at 1040 °C followed by aging at 480 °C.

Modeling the precipitation kinetics and tensile properties in Al-7Si-Mg cast aluminum alloys

The extensive application of Al-7Si-Mg cast aluminum alloys in the automotive and aerospace industries raises the need to better understand the relationship between microstructures and properties. In present work, an integrated precipitation/strengthening/strain-hardening numerical model is developed in order to model the precipitation kinetics and tensile properties in Al-7Si-Mg alloys. The influence of solidification and solution treatment conditions on yield strength is reflected by a term ∆σ0. The strain hardening model takes into account the effect of Orowan loops on the dislocation storage and recovery as well as kinematic contributions. Application of this integrated model to various aging treatments of Al-7Si-Mg alloys is conducted and the predictions both for precipitate microstructure and yield strength are compared well with experimental results. The influence of aging temperature, solution treatment temperature as well as Mg concentration on yield strength is investigated. Using the strain hardening model, the stress-strain curves are predicted and the influence of aging treatment on k1 and k20 parameters as well as the strain hardening behavior is analyzed. Through combining with the empirical expression (σUTS−σYS)=m·σYS+n+f(Tss), the ultimate tensile strength and elongation for the samples in Al-7Si-Mg alloys aged at 160°C and 180°C are predicted. Finally, the limitations of present model and the factors influencing the prediction precision of tensile properties are discussed.

Grain Boundary Segregation and Mechanical Properties of an Aged Ni-20Cr-18W-1Mo Superalloy at Different Temperatures

The influence of aging temperature (200 to 800 °C) on grain boundary segregations in a Ni-20Cr-18W-1Mo superalloy was investigated by scanning electronic microscope (SEM), transmission electron microscopy (TEM), electron microprobe analyzer (EMPA) and a mechanical testing machine. Results indicate that the grain boundary segregation critical time of sulfur and phosphorus decreases with increasing of the aging temperature. Increasing of the aging temperature has a conspicuous effect on the concentration distribution in the grain boundary and the grain core. Grain boundary concentrations of sulfur and phosphorus increase with raising the testing temperature until a peak value is obtained at 650 and 400 °C, respectively, which is the essential reason to the declined mechanical properties from 200 to 600 °C

Influence of aging temperature on mechanical properties and thermal expansion of aluminium hybrid composite

Influence of aging temperature on mechanical properties and thermal expansion of aluminium hybrid composite

Strengthening mechanisms in ultrafine grained Al-Mg-Si alloy processed by hydrostatic extrusion – Influence of ageing temperature

Microstructure of hydrostatically extruded Al-Mg-Si alloy was studied by the combination of electron backscattered diffraction and transmission electron microscopy. Three different grain types which feature various defects arrangements were detected. Post deformation ageing at two temperatures caused different precipitation phenomena which were strongly dependent on type of grain boundaries in the considered grain types. Thus, a combination of plastic deformation and ageing resulted in a material with complex microstructure. Based on transmission electron microscopy observations, contributions of different strengthening mechanisms were estimated and compared to experimental results. A good agreement between obtained data points confirmed that depending on grain type, different strengthening mechanisms are operative and the overall strength is a sum of hardening given by each of them. Ageing of ultrafine grain structure results in efficient precipitation strengthening. On the other hand ageing causes annihilation of low and high angle grains boundaries in which leads to softening of investigated material. This effect cannot be compensated by precipitation hardening.

Influence of aging temperature on strength and toughness of laser-welded T-250 maraging steel joint

This paper presents an investigation on the strength and toughness of laser-welded T-250 maraging steel joint, aimed at elucidating the influence mechanism of aging temperature on microstructures and mechanical properties of the joints. The results showed that as the aging temperature increased, the ultimate tensile strength of welded joints increased, reaching a maximum of 1640.5MPa at 520°C, and then decreased. The static toughness of welded joints decreased at first and increased later with the aging temperature increasing. The minimum of 38.8MJm−3 for the static toughness was obtained at 560°C. There were two types of reverted austenite respectively distributing in grain boundaries and in the matrix of martensite, due to the change of aging temperatures. This study underscores that the Ni3(Ti, Mo) precipitate and reverted austenite are the critical factors influencing the strength and toughness of welded joints. The Ni3(Ti, Mo) precipitate in the weld metal improves the strength of welded joints remarkably as its volume fraction increases. The reverted austenite in grain boundaries is harmful to the toughness of welded joints, while the reverted austenite in the matrix is beneficial to the toughness of welded joints because of its finely dispersive distribution and its ability to prevent crack propagation. Increasing the amount of reverted austenite in the matrix is an effective way to improve mechanical properties of laser-welded maraging steel joints.

Phase Transformation and Its Effect on Mechanical Properties of C300 Weld Metal after Aging Treatment at Different Temperatures

The influence of aging temperature on phase transformation and mechanical properties of weld metal of maraging steel (grade C300) was studied. Microstructure was analyzed by means of optical microscopy, transmission electron microscopy, scanning electron microscopy and energy dispersive spectrum analysis. Gibbs free energy of Ni3Ti and Fe2Mo at different temperature was calculated by Thermal-calc software. The microstructure of weld metal in as-welded state is martensite. The yield strength of weld metal after 430 °C aging process may increase to 1561 MPa from 890 MPa in as-welded state, which is ascribed to the formation of spinodal constitute and GP zones. After 480 °C aging process, there are great deal of Ni3Ti precipitates in the martensite matrix and 10% reverted austenite phase in the cellular grain boundary, and the yield strength increases to 1801 MPa. After aging process at 580 °C, there are many Fe2Mo precipitates in the martensite matrix and 30% reverted austenite phase in the cellular grain boundary, and the yield strength is 1329 MPa, which is the lowest among the three cases. The phase transformation may also influence the toughness. It is found that precipitates make the toughness decrease and reverted austenite increases it. The mechanism of phase transformation on strength and toughness is discussed.

Effect of aging treatment on microstructure and creep behaviour of Sn–Ag and Sn–Ag–Bi solder alloys

The present study was undertaken to investigate the influence of aging temperature on the creep behaviour of Sn–Ag and Sn–Ag–Bi solder alloys at testing temperatures ranging from 333 to 363 K under constant stress of 7·80 MPa. The steady state creep rate was found to increase continuously with increasing aging temperature at all testing temperatures. Results show that addition of Bi to the binary Sn–Ag solder alloy led to a significant increase in the strength and improvement in the creep resistance. The activation energy for the creep process of Sn–Ag and Sn–Ag–Bi solder alloys was found to have an average value of 36 and 45 kJ mol−1 respectively. This might be characterised by diffusion of Ag in Sn. The microstructure of the aged samples for both alloys examined by X-ray diffraction measurements supported the improvement in the creep resistance for Sn–Ag alloy by adding a small trace of Bi.

Influence of aging temperature on corrosion behavior of Al–Zn–Mg–Sc–Zr alloy

Al–Zn–Mg–Sc–Zr alloy sheets were prepared using water chilling copper mould ingot metallurgy processing which was protected by active flux. The effect of aging temperature on the corrosion characteristics of Al–Zn–Mg–Sc–Zr alloy was investigated by means of exfoliation corrosion testing, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) combined with transmission electron microscopy, scanning electron microscopy and optical microscopy observation. It is found that with increasing the aging temperature the susceptibility to exfoliation corrosion decreases. Electrochemical measurements reveal that at early stage of immersion in testing solution, EIS plots of the samples are composed of a capacitive arc and an inductive loop. Inductive loop disappears with the increasing of immersion time and two time constants in impedance diagrams appear. Moreover, the trends of corrosion resistance are further confirmed by polarization curve and EIS test. In addition, transmission electron microscopy observations show that the improved corrosion resistance from increasing aging temperature is duo to the coarsening of matrix and separated precipitates at the grain boundary, and the increased spacing of grain boundary precipitates.

Influence of Ageing, Silver Loading and Type of Reducing Agent on the Lean NO x Reduction Over Ag–Al2O3 Catalysts

The influence of ageing temperature, silver loading and type of reducing agent on the lean NOx reduction over silver–alumina catalysts was investigated with n-octane and bio-diesel (NExBTL) as reducing agent. The catalysts (2 and 6 wt% Ag–Al2O3) were prepared with a sol–gel method including freeze drying and the evaluation of NOx reduction and aging were performed using a synthetic gas-flow reactor. The results indicate a relatively high NOx reduction for both reducing agents. The hydrothermally treated 6 wt% Ag–Al2O3 sample displays a maximum NOx reduction of 78 % at 350 °C for n-octane as reductant and the corresponding value for NExBTL is 60 %. Furthermore, the catalysts show high durability and an increase in activity for NOx reduction after ageing at temperatures up to 650 °C, with n-octane as reducing agent.

Influences of aging temperature and time on microstructure and mechanical properties of 6005A aluminum alloy extrusions

The influences of aging time and aging temperature on the microstructure and mechanical properties were investigated on the 6005A aluminum alloy extrusions. Artificial aging was performed on the alloy extrusions. The aging times were 4, 8 and 12 h, and the aging temperatures were 150, 175 and 200 °C. The results show that the morphologies of the coarse Al(Fe,Cr)Si particles formed in the extrusion process are evolved from granular to rod-like particles with the increase of the aging temperature or the aging time. The volume fraction of the submicron precipitates reaches the maximum value at the aging temperature of 175 °C. AlFeSi particles in size of 1-3 μm are precipitated at the grain boundaries at the aging temperature of 200 °C. The room temperature mechanical properties of the extrusions are more sensitive to the aging temperature than to the aging time. The optimum and stable mechanical properties are achieved when the aging procedure 175 °C, 4-8 h has been performed on the extrusions. The tensile strength and the yield strength in the longitudinal direction of the aged extrusions are more than 300 MPa and 270 MPa, respectively.

Influence of Aging Temperature on Microstructure and Creep Properties of Hot Continuous Rolled Ti-6Al-4V Alloy

Hot continuous rolling technique is a new processing method for preparing Titanium alloy, which may decrease the production cost and realize continuous industrial manufacture. Ti-6Al-4V alloy was prepared by hot continuous rolling (HCR) and solution and aging treated at different temperature. Creep curves of the alloys were measured, microstructure evolution feature of the alloys during creep was observed by SEM and TEM. The influence of aging temperature on the microstructure and creep property of the alloy is briefly discussed. Results show that, the microstructure of HCR alloy after solution treatment at temperature higher than β phase transus point consists of the fully "basket weave" structure. The alloy aged at 750 °C has higher strain rate and shorter creep lifetime, strain rate of the alloy during steady-state creep is measured to be 0.69 × 10-7/s, creep lifetime is measured to be 180h, and strain rate of the alloy aged at 480 °C is measured to be 0.33 × 10-7/s. The alloy aged at lower temperature has longer creep lifetime than the alloy aged at high temperature.

Effect of Aging Temperature on the Microstructure and Mechanical Properties of 1000MPa Grade Low Carbon Bainitic Steel

A kind of 1000MPa low carbon bainitic steel belonged to the Fe-Cu-Nb series was hot rolled and aged, the influence of aging temperatures on the microstructure and mechanical properties of the steel were investigated by using Scanning electron microscopy (SEM) and transmission electron microscopy(TEM). The results show that the microstructure of the low carbon bainitic steel consisted of lath-shaped bainite(LB), granular bainite(GB) and quasi-polygonal ferrite(QF), and the proportion of each kind of microstructure changed with the aging temperatures. The strength of steel with the increase of aging temperature first increased, then decreased, Aging temperatures had distinct effect on yield strength of the tested steel, and less effect on the ultimate tensile strength, we can get the best comprehensive properties yield strength 1011.87 MPa and elongation rate 16.38% of good tough match aged at 450°C. Through analysis it is concluded that the strength of the tested steels aged at 450°C reaches the maximum value, which is attributed to the precipitation of a large amount of fine ε-Cu particles(5~10nm) and a small number of(Nb,Ti)(C,N) precipitates.