Effect Of High-temperature Aging Research Articles

Effects of thermal aging on Cu nanoparticle/Bi-Sn solder hybrid bonding

The effects of high-temperature aging on a novel hybrid bonding layer were investigated. The hybrid layer, which consisted of Cu nanoparticles and a eutectic Bi-Sn solder powder, was formed by a sintering reaction of the solid-phase Cu nanoparticles and a chemical reaction involving the liquid-phase Bi and Sn in combination. The layer was used to bond a SiC chip to a direct bonded aluminum substrate. A conventional Cu nanoparticle-based bonding layer was also prepared as a reference. Samples with these bonding layers were evaluated using the thermal aging test (225 or 250°C, 100h). Bonding strength and synchrotron radiation computed laminography (SRCL) measurements were performed both before and after the thermal aging test. It was observed that thermal aging greatly decreased the bonding strength of the conventional layer. In contrast, the bonding strength of the hybrid layer was reduced only slightly by the thermal aging treatment. SRCL images showed that the conventional layer exhibited numerous cracks, which acted as passages for oxidation. On the other hand, in the hybrid layer, the liquid-phase Bi and Sn densified the Cu sintering phase through the formation of an alloyed Cu-Sn phase. As a result, the hybrid layer contained fewer passages for oxidation as compared to the conventional layer and maintained its bonding strength even against thermal aging. Therefore, the hybrid layer, which is highly stable against thermal aging, will be useful for the high-temperature operation of intelligent power modules.

Effects of high temperature aging on the microstructural evolution and mechanical behavior of SAC305 solder joints using synchrotron X-ray microdiffraction and nanoindentation

Isothermal aging causes degradation in the mechanical behavior of lead-free solder materials used in microelectronic packaging, leading to significant reductions in product reliability. In this work, we have characterized the aging-induced changes that occur in the mechanical properties and creep behavior of actual solder joints. These changes occur due to microstructure evolution and residual strains/stresses in the solder material, and measurement of these evolutions are critical to developing a fundamental understanding of solder aging phenomena. The enhanced high-energy X-ray microdiffraction beamline present at the synchrotron at the Advanced Light Source at Lawrence Berkeley National Laboratory was employed to characterize the solder joints after various aging times at 125 °C. Aging-induced changes in the Sn grain orientation, Sn grain distribution, and residual strain distribution were measured. The observed microstructural evolution was then correlated with changes in the mechanical response of the solder joints measured using nanoindentation.

Effect of High Temperature Aging on Microstructure and Mechanical Properties in an Environmental Barrier Coating

Effect of High Temperature Aging on Microstructure and Mechanical Properties in an Environmental Barrier Coating

Effect of high-temperature aging on microstructure and mechanical properties of Ni–Mo–Cr based superalloy subjected to simulated heat-affected zone thermal cycle

In the work, the effect of high-temperature (800–1100 °C) aging treatment on microstructural evolution and mechanical properties of the Ni–17Mo–7Cr based superalloy subjected to heat-affected zone (HAZ) thermal cycle. When the aging temperature is in excess of 800 °C, massive tiny MoC particles and a few chromium carbides are precipitated in the alloy. The lamellar-like structures grow in the alloy and tiny MoC are precipitated around them. In addition, some nano-sized chromium carbides with needle-like morphology are formed in the MoC. With increasing the aging temperature, the tensile and yielding strength decrease slightly due to increased precipitates in the alloy. In comparison with the alloy that does not go through the HAZ simulation, both of their mechanical properties share the close value at each temperature. The retention interval above 1300 °C during the HAZ simulation also influences the alloy's microstructure and mechanical properties. More lamellar-like structures are produced when elevating the retention interval over 5 s. Due to the increase of solidification defect and stress concentration, the tensile and yielding strength decrease sharply when the interval is increased from 5 s to 10 s. Further improving the interval has a limited influence on the alloy's mechanical properties.

Effect of high temperature ageing on microstructure and mechanical properties of a nickel-free high nitrogen austenitic stainless steel

The effect of ageing and oxidation at 850°C for different durations viz., 1, 10, 100 and 200h on microstructure and mechanical properties of a nickel free high nitrogen steel (Fe–Cr–Mn–N) was investigated. The microstructure of the alloy in as-received condition essentially consists of fine equi-axed austenite grains with annealing twins. However, ageing at 850°C has resulted in the formation of very fine, globular and discrete Cr2N precipitates initially at grain boundaries for an ageing time of 1h and subsequently within the grains with increasing ageing time beyond 1h. The size of these precipitates has progressively increased with further ageing. In addition, coarse intermetallic precipitates of (Fe,Mn)Cr type with body centred tetragonal structure were observed in the samples aged for ≥100h at 850°C. The effect of these precipitates on mechanical properties of the alloy was studied. It was noticed that the mechanical properties deteriorated on ageing, which has been attributed to the depletion of solid solution strengthening elements like nitrogen, chromium and manganese from the matrix to form nitrides and intermetallic precipitates. Moreover the alloy aged in air (i.e., oxidised) exhibits marginally inferior tensile properties as compared to unoxidised alloy.

Effect of high temperature aging on luminescence properties of 5D0 → 7F2 transition of 8YSZ:Eu powder and coating

Since the luminescence property of Eu3+-doped zirconia partially stabilized by 8wt% yttria (8YSZ:Eu) has been widely used in the thermal barrier coatings (TBCs), the effect of high temperature aging on the luminescence properties from 8YSZ:Eu powder and coating are studied in our research. The 8YSZ:Eu powder and free-standing 8YSZ:Eu coating were aged at 1400°C for 6h, 12h, 24h, 48h and 96h, respectively. The addition of Eu3+ ions can improve the phase stability of 8YSZ at high temperature due to the introduction of oxygen vacancies. Except the irregular change in the first several hours, the variations in the peak properties of 5D0→7F2 transition with the aging time prolongation at 1400°C for the 8YSZ:Eu powder and coating are as follows: the peak position is red shift, the peak width (FWHM) is increased and the peak intensity of the 5D0→7F2 transition is decreased.

Effect of high temperature aging on microstructure and mechanical properties of HR3C heat resistant steel

Microstructure and mechanical properties of the HR3C austenite heat resistant steel were investigated after artificial aging at 650°C for time up to 3000 h. The results show that as the aging time increased, the room temperature tensile and impact fracture mechanisms of the HR3C steel change from trans- to intergranular fracture. M23C6 type carbides and MX type carbonitrides continuously precipitate during aging, leading to the change of the mechanical properties and fracture mode of the steel. Moreover, the dissolution of the coherent twins and the transformation from the incoherent twins to the thermodynamically stable austenite subgrains have great effects on the mechanical properties of the aged steel, too. When increasing the aging time to ≧2000 h, the microstructure and mechanical properties of the steel are nearly constant, indicating a good thermal stability of the HR3C steel at elevated temperature.

Effect of Ageing at 700 °C on Microstructure and Mechanical Properties of S31042 Heat Resistant Steel

To investigate the effect of high temperature ageing on the microstructure and mechanical properties of S31042 steel, solid solution treatment at 700 °C was carried out for various time from 10 to 6000 h. Experimental results showed that the change of mechanical properties is closely related to the amount of precipitated phases. During ageing from 10 to 300 h, precipitation in the tested steel increases rapidly, and correspondingly, the high temperature yield strength and room temperature hardness of tested steel increase rapidly. Meanwhile, the thickness of the secondary phase on grain boundaries widens sharply and the room temperature Charpy impact absorb energy decreases. Ageing beyond 300 h, the precipitation in the steel increases gradually and the precipitates coarsen to a certain extent. The high temperature yield strength of the steel keeps stable, and the room temperature Charpy impact energy and hardness decrease slowly. Ageing beyond 3000 h, the mechanical properties of the steel tend to be stable. The main precipitates are M23C6, NbCrN and NbC in the tested steel.

Microstructural stability of Sn–1Ag–0.5Cu–xAl (x=1, 1.5, and 2wt.%) solder alloys and the effects of high-temperature aging on their mechanical properties

Abstract The effects of Al addition on the microstructural stability and mechanical properties of Sn–1Ag–0.5Cu (wt.%) solder alloy under high-temperature aging were investigated. The addition of Al refines the primary β-Sn dendrites and enlarges the interdendritic regions. The addition of Al also suppresses the formation of Ag 3 Sn and Cu 6 Sn 5 intermetallic compounds and leads to the formation of Ag 3 Al and Al 2 Cu intermetallic compounds. Moreover, the addition of Al leads to the segregation of an Al-rich phase. Tensile test results indicated that the addition of Al significantly increased the yield strength and ultimate tensile strength, whereas the elastic modulus increased only slightly and the total elongation decreased. Similar to the Sn–1Ag–0.5Cu solder alloy, the microstructures of Al-modified Sn–1Ag–0.5Cu solder alloys become notably coarsened after aging, which in turn significantly degrades their mechanical properties. Fracture surface analysis indicated that the addition of Al to the Sn–1Ag–0.5Cu solder alloy leads to a brittle fracture instead of a ductile fracture.

Investigating the effect of aging on transpassive behavior of Ni-based alloys in sulfuric acid with shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS)

The effect of high temperature aging on the electrochemical behavior of Ni superalloys has implications for their use in Generation IV nuclear reactors. Linear sweep voltammetry, shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS), and X-ray photoelectron spectroscopy (XPS) were used to interrogate the passivation layer formed on heat-treated and as-received samples of Inconel 617 and Haynes 230. Results demonstrate that heat treatment improves electrochemical corrosion resistance for both alloys. The improved electrochemical behavior is associated with differences in the spectra; specifically, the appearance of a mixed Cr(III/VI) oxide.

Effect of high-temperature aging on the fracture toughness of ytterbia-stabilized t′ zirconia

Dense t′ ZrO2–8 mol.% YbO1.5 candidate thermal barrier material was aged for 192 h at 1150 and 1250 °C. The high initial indentation toughness (∼87 J m−2) reduced by ∼56% in early-stage aging at both temperatures. The toughness increased gradually with aging at 1150 °C and more rapidly at 1250 °C. Precipitation of the cubic phase and its transformation to t″ during cooling was observed. Transformation toughening was activated by 192 h at 1250 °C. Ferroelastic toughening was dominant in the absence of transformation toughening.

Effect of high temperature aging on reliability of automotive electronics

In this paper, an investigation on the effect of high temperature aging on the thermomechanical properties, microstructure of the molding compounds and the reliability issues of the packages is presented. Experimental characterizations of aging effect on the packaging materials and the package were carried out. DMA, TMA and TGA were used to measure the moduli, coefficients of thermal expansion (CTE), and the shrinkage induced by the aging process. Construction analysis was performed to examine the aging effect on the microstructure of the aged samples. It is found that aging has significant influence on the rubbery modulus, the glass transition temperature (Tg) and the strength. Aging-induced shrinkage was also found. Oxidation is believed to be one of the main mechanisms for the degradation of the material properties. Finite element modeling is applied to investigate effect of aging on the reliability of the packages. An aging-dependent elastic model has been established to describe the material property evolution caused by aging. 2D finite element models were established to simulate the impact of the aging effect on the stress/strain of the package. Aging-induced shrinkage was also considered in the model, which was applied to the surface layer. The modeling results indicate that the aging of the compounds has a significant impact on the stress/strain status in the package. And the aging-induced shrinkage cannot be simply neglected. Further research work on the experimental aspects and improvement of the aging-related material models are needed.

Effect of lean/rich high temperature aging on NO oxidation and NOx storage/release of a fully formulated lean NOx trap

Commercial-intent lean NOx traps (LNTs) containing Pt, Pd, Rh, Ba, Ce, Zr, and other proprietary additives were thermally aged at 750, 880, 930, and 1070°C using lean/rich cycling and then investigated for effects of aging on NOx storage capacity, NO oxidation, NOx reduction, and materials properties. Additionally, DRIFTS analysis was used to determine the effects of high temperature aging on surface chemistry and NOx storage. As platinum group metal (PGM) dispersion decreases with aging, the NO turnover frequency (TOF) for NO oxidation at 200, 300, and 400°C is shown to increase. The fraction of stored NOx that is successfully reduced also increases with aging, and it is suggested that this is accounted for by a slower release of more stable NOx species resulting from thermal aging. NOx storage and NOx release experiments performed with DRIFTS at 200, 300, and 400°C indicate that a substantial amount of NOx is stored on Al2O3 as nitrates at 200 and 300°C before aging. However, almost no nitrates are seen on alumina after aging at 900 and 1000°C, resulting in a significant reduction in NOx storage capacity. This is most likely due to a 45% reduction in total surface area and a high temperature redispersion of Ba over remaining alumina sites. No evidence of BaAl2O4 was observed with XRD.

Effects of high temperature aging in an impure helium environment on low temperature embrittlement of Alloy 617 and Haynes 230

The effects of high temperature environmental damage on low temperature embrittlement of wrought nickel-base superalloys, Alloy 617 and Haynes 230 were evaluated. They were aged in an impure helium environment at 1000 °C for up to 500 h before tensile tested at room temperature. The tensile test results showed that the loss of ductility was associated with the increase in the inter-granular fracture with aging time. For Alloy 617, inter-granular oxidation and coarsening of grain boundary carbides contributed to the embrittlement. The significant loss of ductility in Haynes 230 was only observed after 500 h of aging when the globular intermetallic precipitates were extensively formed and brittle inter-granular cracking began to occur.

Improved activity of Rh/CeO2–ZrO2 three-way catalyst by high-temperature ageing

The effect of high-temperature ageing on the activity of Rh/CeO 2 –ZrO 2 for the NO–C 3 H 6 –O 2 reaction was quite different depending on the Ce/Zr molar ratio of CeO 2 –ZrO 2 support. The activity of Rh/CeO 2 –ZrO 2 with a Ce/Zr molar ratio of 74/26 (Rh/CZ-74/26) was significantly enhanced by high-temperature ageing, whereas that of the other Rh/CeO 2 –ZrO 2 was decreased. The promotion of the activity of Rh/CZ-74/26 by high-temperature ageing was considered to be due to the formation and stabilization of active reduced Rh species as well as the change in the surface properties of CeO 2 –ZrO 2 to inhibit the formation of formate species poisoning the catalytically active sites.

Effect of high-temperature aging on electrical properties of Hiperco® 27, Hiperco® 50, and Hiperco® 50 HS alloys

Some more electric aircraft concepts require soft magnetic FeCo materials to be stable at temperatures as high as 773 K for long periods of time. At this high operating temperature, aging related processes may occur that result in changes in material properties. The material supplier typically specifies only room-temperature properties, and only limited reports are available on properties at elevated temperatures. The change in properties as a function of time at 773 K will give information on the lifetime of the material to assist designers when selecting materials for high-temperature applications. We have conducted a study on the effects of long-term aging on the magnetic, mechanical, and electrical properties of Hiperco® 27, Hiperco® 50, and Hiperco® 50 HS FeCo soft magnetic alloys. Samples of each material were aged in argon for 100, 1000, 2000, and 5000 h at 773 K. Here, we report the changes in electrical resistivity after aging. Of the three alloys, high-temperature aging has the greatest effect on the resistivity of Hiperco® 50. The electrical resistivities for each sample are compared and conclusions are drawn on the relative thermal stability of each alloy. The changes in electrical resistivities for each alloy are also related to changes in other properties, such as total power loss and coercivity, that were observed during this study on aging.

Near-Threshold Fatigue Crack Growth at 63Sn37Pb Solder Joints

Fatigue tests were performed using single lap-joint specimens to obtain near-threshold fatigue crack growth data of solder joint under mode-II load. Attention was focused on the effect of high temperature aging and microstructures separately from the intermetallics. As a result, it was shown that the long cast time yielded the intermetallics and microstructures of the solder invariable regardless of aging condition. The granular micro-structure of the air-cooled specimens was shown to be inferior to the laminated micro-structure of the furnace-cooled specimens. Also, transition of fatigue crack behavior with ΔJ and the procedure of fatigue crack propagation from the pre-crack tip were discussed.

Effect of 900–1150 °C aging on the microstructure and mechanical properties of a DS casting Ni 3Al-base alloy IC6

The effect of high-temperature aging at 900–1150 °C on microstructure and mechanical properties of a recently developed directional-solidification (DS) casting Ni 3Al-base alloy has been studied in the present investigation. The microstructure change during aging in the temperature range 900–1150 °C for periods of 25 to 4400 h has been examined by optical microscope, SEM and TEM. The tensile and stress rupture properties of the specimens after aging at 900, 1000 and 1100 °C for periods of 25 to 1000 h have been determined. The experimental results showed that the mechanical properties slowly deteriorated with aging time. The deterioration of properties was attributed to the microstructure changes during aging, which include a volume fraction decrement of the main strengthening phase γ-Ni (Mo) solid solution due to the formation of γ-Ni Mo phase by the reaction of γ → Y-NiMo + γ′, the coalescence and growth of both γ and γ′ phase and a solution-hardening decrease due to the homogenization of Mo distribution in the γ and γ′ phases.

Effect of high temperature aging on ferrite transformation kinetics and tensile properties of type 316L stainless steel weld metal

Tensile samples of AISI type 316L weld metal, deposited by the gas tungsten arc welding process, were heat treated at 873,973, and 1073 K, before being subjected to tensile loading at an initial strain rate of 5·5 × 10−5 S−1 at a temperature of 427 K. The transformation kinetics of δ ferrite was studied in detail. The activation energy for the transformation of δ ferrite was found to be 272 kJ mol−1. Theferrite transformation kinetics datafor the above three temperatures were thenfitted into a master plot using the Dorn parameter, and its validity in this temperature range was verified by superimposing the ferrite transformation kinetics data at 948 and 1023 K on to the master plot. From examinations by optical microscopy, the weld metal was found to undergo competing transformation reactions during high temperature aging, namely, dissolution of δ ferrite, precipitation of carbidesj carbonitrides and σ phase, changes in σ phase morphology, and spheroidisation of σ phase. The effect of the ferrite transformation kinetics and σ phase precipitation kinetics on the tensile properties of the weld metal were also studied in detail. The yield stresses of all the aged weld metals were lower than that of the as deposited weld metal. The σ phase had no direct influence on changes in the yield stress. The ultimate tensile strength was affected only by the quantity and morphology of σ phase. All the competing processes (except changes in σ phase morphology) significantly influenced ductility. The increase in work hardening exponent n was dependent only on the amount of σ phase and not on its morphology.MST/1983

The high-temperature ageing of a low-alloy steel in the presence and absence of strain

The effect of high-temperature ageing in the presence and absence of strain was investigated for a high-temperature hot-rolled low-alloy steel. Mechanical tests were conducted on artificially aged material and material removed from operating plant. The steel investigated was developed for less critical elevated-temperature applications, which do not require heat-treated pressure-vessel-quality alloy materials, such as the Cr-Mo steels. Wide scatter in the high-temperature creep properties was observed. Due to a very high phosphorous content, reversible temper embrittlement at temperatures above 400°C results in Chapry V-notch values of less than 4 J cm −2 after exposure times of only a small fraction of the component's design life. There is a difference in creep mechanism for short-time creep-rupture tests and those executed beyond 10 000 h. Confidence can only be obtained in creep-rupture data if the test field is extended to temperatures and stresses below 480°C and 150 MPa, respectively, and also to yield rupture data for up to 30 000 h. The very low fracture toughness values at room temperature and the high ductile-to-brittle transition temperature of aged material necessitate that special design features be considered. From a utility point of view, the suitability and economics of this steel for large, high-temperature structural applications—where normal design, operating and maintenance philosophies are expected to be followed—are questioned.