Influence Of Aging Temperature Research Articles

Influence of Aging Temperatures and Times on Mechanical Properties of Vacuum High Pressure Die Cast Aluminum Alloy A356

In this study a number of thermal treatment schemes over a wide range of temperatures between 120˚ to 350˚ C and times (30 120 minutes) have been experimented in an effort to understand the effect of thermal treatment on tensile properties of vacuum die cast modified aluminum alloy A356. The results show that, the morphology of eutectic silicon has a sound effect on the tensile properties of the tested alloy. The content of magnesium-based intermetallic phases, their morphology and distribution throughout the matrix affect the mechanical properties of the aged alloy as well. The reduction in the strengths of the alloy treated at 350°C for two hours should be at least attributed partly to the absence of the magnesium-based intermetallic phase. However the presence of sufficient amount of magnesium intermetallic phase had played important role in strengthening the alloy thermally treated at 200°C for 90 minutes.

Influence of Aging Temperatures and Times on Mechanical Properties of Vacuum High Pressure Die Cast Aluminum Alloy A356

In this study a number of thermal treatment schemes over a wide range of temperatures between 120˚ to 350˚ C and times (30 120 minutes) have been experimented in an effort to understand the effect of thermal treatment on tensile properties of vacuum die cast modified aluminum alloy A356. The results show that, the morphology of eutectic silicon has a sound effect on the tensile properties of the tested alloy. The content of magnesium-based intermetallic phases, their morphology and distribution throughout the matrix affect the mechanical properties of the aged alloy as well. The reduction in the strengths of the alloy treated at 350°C for two hours should be at least attributed partly to the absence of the magnesium-based intermetallic phase. However the presence of sufficient amount of magnesium intermetallic phase had played important role in strengthening the alloy thermally treated at 200°C for 90 minutes.

Influence of ageing temperature and heating rate on the properties and microstructure of β Ti alloy, Ti–6Cr–5Mo–5V–4Al

► Effects of heat treatment on the ageing response of a Ti–6Cr–5Mo–5V–4Al alloy. ► Temperatures of 440–500 °C result in the greatest strengthening. ► Ageing response declines at higher temperatures as α precipitates coarsen. ► Fast heating rates result in coarser, more uneven distributions of precipitates. ► Fast heating rates exhibit rapid loss of hardness due to coarsening. A study of the effects of temperature and heating rate upon the ageing response of a Ti–6Cr–5Mo–5V–4Al alloy was undertaken. The degree of strengthening declined with increasing ageing temperature as the precipitate morphologies became coarser, while the extent and thickness of grain boundary α increased with temperature. Ageing at temperatures between 440 °C and 500 °C result in the greatest age hardening response in times of around 4 h due precipitation of the α phase. At 440 °C the hardness increases from the initial solution treated value of 275 H V to more than 450 H V . The rate of heating to reach the isothermal ageing temperature has a substantial impact on the ageing response. Greater scatter was observed in hardness results for the samples aged using a faster heating rate at 500 °C. For ageing at 560 °C a faster rate of heating to the ageing temperature led to rapid declines in the hardness after the peak, equivalent to around 20% of the peak value. Slower heating rates (5 °C min −1 ) appear to increase the number of nucleation sites for precipitation of the α phase, forming finer, more even distributions of precipitates. Faster heating rates (∼100 °C min −1 ) produce coarser, less evenly distributed precipitates which coarsen more rapidly.

Neutron diffraction study of aging process effect on phase structure of single crystal superalloy

The neutron diffraction results obtained by oscillating and fixing during data collection show that the high ageing temperature is effective to eliminate dendrite crystals and the microstrain exists mainly in the ' phase. Based on the microstructure obtained by neutron diffraction and scanning electron microscope, the influence of ageing temperature and time on ' phase are evaluated. The unique misorientations among ' phase grains are observed from superlattice measurements. According to the neutron diffractions of different crystal planes, the crystal symmetry is slightly changed from cubic to quartet (a c) due mainly to the matrix phase and the experimental results also prove the strain deviation in difference orientations, thus providing the basis for the existence of driving force for the raft model. The calculation based on the superlattice diffraction shows that in the interfaces between the and ' phases exists a complex distortion: the mismatch varies from -0.1% to -0.3% and the mismatch value can be reduced by high temperature during the first ageing and long time during the second ageing.

Microstructure and intergranular corrosion resistance of UNS S17400 (17-4PH) stainless steel

UNS S17400 or 17-4PH is a precipitation hardening martensitic stainless steel with many industrial applications. Quite different mechanical properties can be produced in this material by varying the aging temperature. In this work, the influence of aging temperature on the intergranular corrosion susceptibility was evaluated by electrochemical and metallographic tests. The microstructural features were investigated by X-ray diffraction, optical and scanning electron microscopy. Intergranular chromium carbide precipitation occurs in specimens aged at high temperatures, although NbC carbides were also observed. The results obtained by double loop electrochemical potentiodynamic reactivation tests (DL-EPR) show that the susceptibility to intergranular corrosion resistance increases with the increase of aging temperature. Healing due to Cr diffusion in the 600–650 °C range was not observed by DL-EPR tests.

Effect of Aging Temperature on Formation of Sol–Gel Derived Fluor-Hydroxyapatite Nanoparticles

Synthetic hydroxyapatite (HA) has been recognized as one of the most important bone substitute materials in orthopaedics and dentistry over past few decades because of its chemical and biological similarity to the mineral phase of human bone. One solution for reduction the solubility of HA in biological environments is replacing F- by OH in HA structure and forming fluor-hydroxyapatite (FHA) solid solution. In this paper, FHA nanoparticles were successfully synthesized by a sol-gel method. Also, the influence of aging temperature on formation of FHA powder was studied. Equimolar solutions of calcium nitrate tetrahydrate, triethyl phosphite and ammonium fluoride in ethanol were used as Ca, P and F precursors. After aging at different temperatures, the synthesized powders were heat treated at 550 degrees C. The powders were investigated with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), selected area electron diffraction pattern (SAED), energy dispersive analysis of X-ray (EDAX) and zetasizer measurement. The results of XRD proved the presence of fluorapatite (FA) and HA in all samples. In addition, the formation of FHA was confirmed by FT-IR results. XRD studies also showed that the crystallites were in nanometric scale. At the same time, this result was in good agreement with the result of zetasizer analysis.

Influence of Aging Temperature on Rheological and Chemical Properties of Asphalt Binders

Four asphalts used in field pavements were aged at a laboratory in a pressure-aging vessel (PAV) at several temperatures for various lengths of time. The chemical (infrared spectra) and rheological properties of these aged asphalts were compared. Results showed that the same PG graded asphalts from different crude sources had significant differences in their rheological behavior and chemical properties after long-term oxidative aging. Asphalt per se had approximately the same aging rheological pattern regardless of aging temperature. Laboratory PAV aging at 80°C for 504 h was found to produce stiffer material than the same material subjected to the same PAV aging at 100°C for 100 h. The plot of G* complex modulus versus phase angle was found particularly useful for characterizing the asphalt binder rheology in terms of long-term aging characteristic. Additionally, the aging shift factor, generated from the aging master curve, was used to characterize the modulus changes with respect to aging and to compare effects of aging on different materials. Furthermore, results indicated a linear relationship between the change of rheological property and the change of chemical property (carbonyl index) with respect to long-term aging. It was verified that sulfoxide was formed easily with aging. However, sulfoxides also decomposed at longer aging times.

The Effect of Aging Parameters on Properties of Maraging Steel

In this article, an investigation of aging parameter (temperature and time) effects on mechanical properties and dimensional changes of Maraging 15 10 5 steel is presented. Aging tests were carried out in a dilatometer accompanied by simultaneous registration of forthcoming alterations of size. The results indicate a significant influence of aging temperature and aging time duration on achieved hardness values, as well as on dimensional changes, which is caused by diffusion of alloyed elements from Ni-martensite matrix during aging. On the basis the tests, optimal aging temperature and aging time duration of Maraging 15 10 5 steel are determined.

Influence of aging temperature, time, and environment on thermo-oxidative behavior of PMR-15: nanomechanical characterization

A series of PMR-15 resin specimens were isothermally aged at 288, 316, and 343 °C over a range of time. For PMR-15 aged at 288 °C, the samples were also subjected to different aging environments including: ambient air, dry air, inert (argon), and pressurized air (0.414 MPa). Nanoindentation was performed to characterize localized mechanical properties as well as the development and growth of the oxidative layer. The measured increase in stiffness in the specimen surface oxidation layer is a manifestation of the chemical changes in the polymer occurring during oxidation. The average elastic modulus in the oxidized region is relatively insensitive to variations in aging temperature, time, and the environments. The thickness of the oxidative layer is observed to increase in the early stages of oxidation and the oxidation process eventually approaches an auto-retardation state. Aging under elevated pressure increases the thickness growth rate of the oxidation layer, while there is no significant difference in growth rate for specimens aged in dry air versus those aged in ambient air. It is shown that the measured average thickness of the oxidation layer and the transition region determined by the nanoindenter is in good agreement with optical microscopy measurements for all conditions considered.

Structure and Mechanical Properties of Ni-P-Nano Al2 O3 Composite Coatings Synthesized by Electroless Plating

Ni-P-nano Al2 O3 composite coatings were deposited by electroless plating, and their microstructures were observed by SEM (scanning electron microscope). The microhardness and the wear resistance of the Ni-P-nano Al2 O3 composite coatings were measured using microhardness tester and block-on-ring tribometer, respectively, and the comparison with those of Ni-P coatings or Ni-P-micro Al2 O3 coating was given. The influences of aging temperature on their hardness and wear resistance were analyzed. The results showed that the nano Al2 O3 particles were distributed uniformly in the Ni-P-Al2 O3 coatings. Among three kinds of Ni-P based coatings, the hardness and wear resistance of Ni-P-nano Al2 O3 coatings were largest, and the maximum values could be obtained at 400 °C. This indicated that the precipitation of nano Al2 O3 particles would improve the hardness and wear resistance of the Ni-P coatings.

Influence of Aging Temperature on the Microstructure and Stress Rupture Property of DZ951 Alloy

Effect of different aging temperatures on microstructure and stress rupture properties of DZ951 alloy were investigated in this paper. The results show that the shape of carbide changed from script-like in as-cast alloy to block during different aging treatments. MC carbide degrades into M23C6 at the aging temperature of 970°C, which made alloy have a better combination of strength and ductility than that at other aging temperatures. The size of γ′ phase increases and the shape of γ′ phase changed from sphere (870°C) to quasi-cuboid (920°C) and cuboid (970°C) with the increasing aging temperature. The stress rupture life of DZ951 alloy at 1100°C/60MPa improves with the increased of aging temperature. The fractographs at different conditions showed a ductile fracture mode.

Aging temperature and abrasive wear behaviour of cast Al–(4%, 12%, 20%)Si–0.3% Mg alloys

In the present paper, influence of aging temperature during artificial age hardening treatment ( T 6) of cast Al–(4, 12, 20%)Si–0.3% Mg on abrasive wear behaviour has been reported. Alloys were prepared by controlled melting and casting. Cast alloys were given age hardening treatment having sequence of solutionizing, quenching and artificial aging. All the alloys were solutionized at 510 °C for 8 h followed by water quenching (30 °C) and aging hardening at 150, 170, 190, 210 and 230 °C for 12 h. Abrasive wear tests were conducted against of 320 grade SiC abrasive medium at 5 and 10 N normal loads. It was observed that the silicon content and aging temperature significantly affect the wear resistance. Increase in aging temperature improves the wear resistance. Hypereutectic alloy showed better wear resistance than the eutectic alloy under identical conditions. Optical microstructure study of alloys under investigation has shown that cast dendritic structure is destroyed besides the spheroidization of eutectic silicon crystals after the heat treatment. The extent of change in structure depends on aging temperature. Scanning electron microscopy (SEM) of wear surface was carried to analyze the wear mechanism.

Influence of aging on discontinuous dissolution in Al-22at.% Zn alloy

The influence of prior aging and volume diffusion on the kinetic parameters of discontinuous dissolution were studied in al-21.55at.%Zn alloy. The following kinetic parameters were considered: the critical temperature of discontinuous dissolution T cr, the rate of discontinuous dissolution V d 1, the diffusivity KD b,m λ at the boundary of receding cells, and the activation energy of discontinuous dissolution. A new method of calculation of KD b,m λ is proposed. It is concluded that T cr, V d 1, and KD b,m λ are strongly affected by the conditions of prior aging. The estimated diffusivities for discontinuous dissolution are more than two orders of magnitude smaller than those for diffusion at stationary grain boundaries. This result is caused by volume diffusion ahead of the precipitation front and within α-phase lamellae. However, the discontinuous dissolution is still controlled by diffusion at the boundary of receding cells. The influence of aging temperature and volume diffusion on KD b,m λ values was found to be connected with the change in pre-exponential factor in the Arrhenius equation.

Aspects of degradation and stability of ABS copolymers. I. Effect of β‐carotene as antioxidant

AbstractThe oxidative degradation of polybutadiene–styrene–acrylonitrile (ABS) copolymer was extensively investigated. Three factors were studied: the influence of ageing temperature on the rate of the oxidation of the copolymer; the efficiency of β‐carotene as chain breaking antioxidant; and the effect of butadiene content on the rate of the oxidative degradation of the ABS copolymer.

Influence of aging temperature and time on hardness and electrical conductivity of Cu–Cr alloys

AbstractSpecimens of cold-rolled Cu–0·44Cr and Cu–0·94Cr were solution treated and water quenched. Their hardness and electrical conductivity were measured after quenching and aging. Thin foils of Cu–0·94Cr were prepared and examined in the electron microscope. The sizes of coherent particles in the foils were measured and from these results it was deduced that particle growth is controlled by volume diffusion. Both coherently precipitated and non-dissolved chromium particles with a bee lattice were observed in aged Cu–0·94Cr. Empirical formulae for the influence of aging temperature and time on hardness and coruiuctivity were established.

Influence of γ-Fe precipitates on physical and mechanical properties of Cu–Fe alloys

AbstractThe object in this work was to investigate the influence of aging temperature and time and chemical composition on the mechanical and electrical properties of Cu–Fe alloys. Polycrystalline specimens of Cu–0·5–3Fe alloys after solution treatment at 950°C for 1h were aged at temperatures of 400°, 500°, 600°, and 700°C for times of 0·5, 1, 3, and 10h. The methods used for the investigations were: optical and electron microscopy, Mossbauer spectroscopy, electrical resistance measurements, and mechanical tests. The aging of supersaturated solid solutions of iron in copper has a great influence on the structure and properties of Cu–Fe alloys. However, a change in alloy composition does not cause a change in electrical resistance, but influences only the mechanical properties and precipitation kinetics. In the initial stage of aging there are iron clusters present, which grow with aging time into dispersive, coherent γ-Fe particles. The size of the γ-particles increases with temperature and time of aging...

Properties of TiN xfilms reactively sputtered in an argon-nitrogen atmosphere

The dependence of the resistivity and temperature coefficient of resistivity (TCR) of TiN x films on nitrogen pressure is described. The partial nitrogen pressure was varied from 10 −5 Torr to 2×10 −4 Torr. The maximum value of the resistivity (216 μΩ cm) and the lowest negative value of TCR (−33 ppm K −1) were obtained in the nitrogen pressure range (2−4)×10 −5 Torr. The minimum value of the resistivity (44 μΩ cm) and the highest positive value of the TCR (1160 ppm K -1 were obtained in the nitrogen pressure range (4−10)×10 −5 Torr. The influence of aging temperature up to 573 K on the resistance changes are shown. X-ray diffraction analysis indicated the presence of oriented or non-oriented TiN in these films.

On the influence of aging temperature and pre-strain on the stress corrosion cracking of Al-Zn-Mg alloy

Studies were made on the effects of aging temperature and pre-strain on the stress corrosion cracking of ternary Al-Zn-Mg alloys containing 4.5wt.%Zn-3wt.%Mg, 4.5wt.%Zn-2wt.%Mg, and 4.5wt.%Zn-1wt.%Mg.The results obtained were summarized as follows:(1) The alloys aged at low temperature were sensitive to the stress corrosion cracking. The fact would be due to small proof stress and high corrosion rate. The alloys aged at temperatures higher than G. P. solvus were insensitive to the stress corrosion cracking.(2) When the aging temperature was higher, the alloy having lower content of additional elements promptly turned to be more insensitive to the stress corrosion cracking as compared with that of higher content.(3) The specimen as pre-strained was more sensitive to the stress corrosion cracking than that as no prestrained. The sensitivity was greater with the increase of pre-strain.

A resistometric study of pre-precipitation in Al-10% Zn

An extensive investigation of the influence of quenching and aging temperatures upon the preprecipitation phenomenon in Al-10% Zn has been carried out by means of resistivity measurements at liquid nitrogen temperature. It has been found that an appreciable clustering of solute atoms takes place during the quenching itself and that the rate of pre-precipitation during isochronal or isothermal aging increases greatly with quenching temperature; the energy of formation of vacancies in the alloy, evaluated by the dependence of the rate of clustering on the quenching temperature, is 0.70 ± 0.02 eV, as compared with the value 0.76 ± 0.04 eV previously reported for pure aluminum. The final size of zones during isothermal aging at 40°C is larger after quenching from 350°C and decreases both for lower and for higher quenching temperatures. The presence of a “slow reaction” after quenching from 600°C has also been detected. Concerning the influence of aging temperature it has been found that the amount of increase in resistivity decreases greatly by increasing the aging temperature and that the activation energies of the phenomenon (derived from the times to reach the maximum in resistivity) are 0.43 ± 0.02 eV after quenching from 300°C, and 0.38 ± 0.02 eV after quenching from 450°C. Other miscellaneous results on the effect of varying the aging temperature and on the reversion phenomenon are reported. The results are interpreted in terms of a simple picture of the pre-precipitation phenomenon; the role of vacancies appears to be a fundamental one in determining the rate of pre-precipitation which is stopped only when all the excess of quenched-in vacancies is eliminated; the mechanism of elimination of vacancies appear to be, roughly, the same as in pure aluminum. The variation of the maximum increase in resistivity against the various aging temperatures has been explained in terms of a variation of the number of zones which form; in this way it appears that the number of zones is higher the lower the aging temperature, and that if the aging temperature is changed also the number of zones tends to change so as to establish the new equilibrium number; however this can be accomplished only if an excess of quenehed-in vacancies is still present. Finally other related questions such as the reversion phenomenon, the “slow reaction” and the meaning of the activation energies are discussed.