Long-term Natural Aging Research Articles

Effect of natural aging on biochar physicochemical property and mobility of Cd (II).

This project utilized both field experiment and laboratory analyses to address the gap in understanding regarding the alterations in properties and functions of biochar, and the impact of heavy metal passivation in soil over long-term natural field aging. The study aimed to examine the changes in the physical and chemical characteristics of biochar over an extended period of natural aging. Additionally, it sought to analyze the impact and mechanisms of biochar in reducing of the harmful effects of the heavy metal cadmium (Cd) during the aging process. Both original and aged biochar conformed to the pseudo-second-order kinetics model and the Langmuir model. The aging process enhanced the adsorption of Cd by biochar and mitigated the leaching of Cd2+ into the soil. These findings provide a scientific basis for evaluating biochar's environmental behavior and its potential use in the remediation of soil contaminated with heavy metals.

Assessment of chemical degradation of epoxy resin binder used in the service of the Qin terracotta warriors

Since the Qin terracotta warriors were unearthed, polyamide 650 cross-linked E-44 epoxy resin binder has been employed to bond and restore them. In this paper, the chemical aging of the binders service in indoor natural environment during the past 30 years in the terracotta warriors was studied by means of infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The results indicated that the binders did not emerge the characteristic peak of carbonyl stretching vibration at 1700 cm−1 in the IR spectra of all determined binders, and their thermal decomposition curves did not emerge any abnormal changes, and the thermal decomposition mainly occurred above 300 °C. There are evident ceramic grains attached to the surface of the binders being peeled off for sampling. These results that the binders service in the Qin terracotta warriors did not exhibit an observable chemical aging and still has strong adhesion. Generally, discrepancies were observed between natural aging and accelerated artificial aging due to the ineffectiveness of the latter to reproduce the effects of complex weather conditions. Compared to artificially accelerated aging, the evaluation results in a long-term natural aging of the binder which is used for restoration of the life-size Qin terracotta warriors, providing in the present investigation, are more reliable in terms of predicting the safety of restored terracotta warriors.

Understanding the differential precipitation behavior of friction stir welded Al-Zn-Mg-Fe alloy during long-term natural aging

Al-Zn-Mg-Fe (HE700) is a new generation cast alloy based on dilute Al-Fe hypoeutectic system. Being a new member, the precipitation behavior of the HE700 alloy is not fully understood unlike its conventional 7xxx series counterparts. Moreover, presence of Fe and friction stir welding (FSW) used to join such alloys add to the complexity of the precipitation phenomenon. The present study captured the microstructural features with atomic-scale resolution that provided new insights into the nature, distribution, and evolution of precipitates in this alloy. The stir zone (SZ) and heat-affected zone (HAZ) exhibited significantly different natural aging behavior. Finer precipitates identified as GPI and GPII (Guinier Preston zones) were found to coexist with very fine zinc-rich solute clusters in the SZ. The GP zones evolved gradually and transitioned into strengthening precipitates. The HAZ, on other hand, exhibited heterogeneous distribution of coarse pre-existed particles and fine MgZn2 precipitates that were heterogeneously nucleated by localized solute supersaturation and thermally induced dislocations. Hardness variations can be correlated to precipitates evolution thereby helping design a suitable post-weld heat treatment (PWHT) process.

Clustering behaviour of pre-aged Al-Mg-Si alloy during subsequent natural ageing and paint baking

The clustering behaviour of a pre-aged Al-Mg-Si alloy during natural ageing (NA) and paint baking (PB) was systematically investigated by hardness measurements and atom probe tomography (APT). The results show that pre-ageing (PA) can effectively retard the negative effect of NA and enhance the paint-baking response even after long-term NA (up to one year). The pre-aged alloy shows a good resistance against clustering within a short NA period of one week, and the capability is enhanced with increasing pre-ageing time. However, the clustering becomes significant after prolonged NA, especially for one year. The increasing number density of clusters containing 10–30 solute atoms contributes most to the hardness increase after prolonged NA. The mechanism about two synergistic processes of ‘vacancy trap’ and ‘vacancy escape’ is introduced to explain the phenomenon. The alloy with a prior PA above 2 h exhibits a good PB response even after one-year NA. Such performance is attributed to large-size precipitates (GP zones or pre-β″ precipitates) formed during PA, which can serve as nuclei for β″ due to a similar composition. Moreover, a strength model has been established to predict the different strengthening effect and evaluate contributions from clusters, GP zones and pre-β″/β″ precipitates during multi-stage ageing in the Al-Mg-Si alloy.

Механические характеристики стальных конструкций длительного срока эксплуатации при пожаре

The problem of fire resistance of metal building structures with a long service life is considered. The results of a study of the influence of a long service life of steel structures on the physical, chemical and mechanical characteristics (tensile strength, yield strength, relative elongation) at the elevated temperatures in relation to a steel structure with a service life of 92 years are presented. The steel structure was operated under stress conditions — bending under the load of a reinforced concrete flight of stairs. Due to long-term use, traces of the corrosion process are noticeable on its surface over its entire area. The results of the chemical analysis of test samples № 1, 2 are presented. According to GOST 27772—2021, it can be established that the steel under study corresponds to the standard content of the chemical composition of steel of strength class C345, with the exception of a 2-fold increased S content and an insufficient amount of manganese content. With increased sulfur content, steel becomes less strong and the steel resistance to brittle fracture decreases. This is confirmed by earlier work, which showed that increased sulfur content helps to reduce the mechanical characteristics of steel by 2 times. For the first time, the tests were carried out to assess changes in the mechanical characteristics of long-term steel structures under conditions of increased temperature (fire). A comparative analysis of the results of studies of mechanical tests at elevated temperatures for various steel grades was performed. It was established that for the studied samples of steels № 1, 2, long-term natural exposure at temperatures of 500 °C and 600 °C, the yield strength decreases by 23 % and 46 %, and the ultimate strength decreases by 42 % and 50 %, respectively. A tendency for a more intense loss of mechanical characteristics for steel structures of long-term natural aging under fire conditions was revealed.

Analysis of static stiffness properties of column-architrave structures of ancient buildings under long term load-natural aging coupling

The column-architrave structures were widely used in the Yingxian wooden pagoda and pagoda has been in service for many years. Over time, it has been subjected to stress and the effects of natural aging. In order to analysis the ability of the structures to resist deformation under specific static excitation, a study of the static stiffness properties of column-architrave structures in ancient buildings considering long term load-natural aging coupling was carried out. Based on the Gerhards model, a strength degradation model has been developed for column elements and architrave elements, taking into account long-term loading and natural aging effects; By constructing a regular model and a realistic model, the deformation of the regular model under long term self weight load and the deformation of the realistic model under long term self weight load and aging are simulated by finite element model; The relationship between deformation values and static stiffness as a function of time is investigated through multiple points of the column-architrave structures, and the reliability of the proposed model is verified by extracting and comparing data from the automated real-time 3D monitoring system of the wooden pagoda. The results show that the numerical simulations of both models show that the middle of the architrave is more easily deformed than the mortise and tenon joint structures; The deformation resistance of the realistic model is lower than the deformation resistance of the regular model, and the natural aging effect has a non-negligible deterioration effect on the deformation of the column-architrave structures; For the column and architrave elements, they are likely to become unstable at 3330 AD and 3543 AD respectively, which means that after 1307 and 1520 years, the static stiffness of both elements tends to decrease with time in service, with the decrease in static stiffness of the architrave elements being less than that of the column elements.

Prim-O-glucosylcimifugin ameliorates aging-impaired endogenous tendon regeneration by rejuvenating senescent tendon stem/progenitor cells

Adult tendon stem/progenitor cells (TSPCs) are essential for tendon maintenance, regeneration, and repair, yet they become susceptible to senescence with age, impairing the self-healing capacity of tendons. In this study, we employ a recently developed deep-learning-based efficacy prediction system to screen potential stemness-promoting and senescence-inhibiting drugs from natural products using the transcriptional signatures of stemness. The top-ranked candidate, prim-O-glucosylcimifugin (POG), a saposhnikovia root extract, could ameliorate TPSC senescent phenotypes caused by long-term passage and natural aging in rats and humans, as well as restore the self-renewal and proliferative capacities and tenogenic potential of aged TSPCs. In vivo, the systematic administration of POG or the local delivery of POG nanoparticles functionally rescued endogenous tendon regeneration and repair in aged rats to levels similar to those of normal animals. Mechanistically, POG protects TSPCs against functional impairment during both passage-induced and natural aging by simultaneously suppressing nuclear factor-κB and decreasing mTOR signaling with the induction of autophagy. Thus, the strategy of pharmacological intervention with the deep learning-predicted compound POG could rejuvenate aged TSPCs and improve the regenerative capacity of aged tendons.

Effect of long-term natural aging on the microstructural characteristics of an extruded WE54 alloy

The microstructure and the corresponding crystallographic texture of the as-extruded WE54 alloy after natural aging for 11 years at room temperature have been characterized by the Electron backscatter diffraction (EBSD) technique. Before natural aging, the as-extruded WE54 exhibited equiaxed microstructure with a strong splitting basal texture and the presence of second particles along the extrusion direction (ED). Unexpectedly, long-term aging led to the formation of elongated deformed grains along ED having {11–20}<10-10> and {0001}<10-10> orientations with a partial development of fine static recrystallized grains by continuous and discontinuous mechanisms. It is believed that the origin of such grain structure development is the residual stored strain during the extrusion processing and the strain field induced from the solute Nd and Y atoms diffusion through the long-term natural aging. Artificial aging at 400 °C for 60 min demonstrated that the elongated deformed grains disappeared and left behind a heterogeneous recrystallized microstructure with a weak basal texture.

Effects of natural aging on the artificial aging kinetics and responses of Al–5Mg–3Zn–1Cu (wt.%) alloy

Effects of natural aging (NA) on artificial aging (AA) behavior of Al–5Mg–3Zn–1Cu alloy were studied from the perspectives of kinetics and microstructure evolution. The results show that short-term NA (24 h) has marginal effects on AA at any temperature, as well as long-term NA (>240 h) on low-temperature AA (120 °C), but long-term NA can accelerate aging kinetics and alleviate severe hardening ability attenuation at high temperatures (>150 °C). Analysis of the precipitates evolution demonstrates that such attenuation is primarily attributable to coarsening and reduction of intragranular precipitates and is also slightly related to the formation of precipitate-free zone (PFZ). Three main factors cause the unfavorable microstructure in NA-free alloy at high temperatures AA: (1) Insufficient nucleation of intragranular precipitates induced by weakened nucleation driving force, larger critical nucleation radius, and rapid vacancy annihilation; (2) The nucleated precipitates are prone to coarsening; (3) The precipitation near grain boundary is obstructed due to the depletion of vacancies and solutes. Clusters formed during NA can inhibit the unfavorable microstructure by delaying the annealing out of excess vacancies, promoting the nucleation of precipitates, and elevating the activation energy for precipitation coarsening, thereby enhancing the hardening potential. This work is instructive for the formulation of heat treatment strategies for Al–Mg–Zn–Cu alloys with high Mg/Zn ratios.

Long-term natural-aging-induced alleviation of attenuation of artificial-aging hardenability in an Al-5Mg-3Zn-1Cu (wt.%) alloy

Effects of long-term natural aging (NA, 2400 h) on the artificial aging (AA) responses of Al-5Mg-3Zn-1Cu alloy at various temperatures (120–175 °C) were scrutinized. The results show that the hardenability of the alloy without NA (NA-free) deteriorates seriously at high AA temperatures (>150 °C). Such decay of AA hardenability is primarily induced by the larger and sparser intragranular precipitates and is also associated with the wide precipitation-free zone. Compared with NA-free alloy, long-term natural pre-aging improves the nucleation conditions in the early stage of subsequent AA, thus preventing these unfavorable microstructures and thereby mitigating the decay of hardening potential.

Effect of Cu/Sn additions on the precipitation and property in Al-Mg-Si alloys

The effects of Cu and Sn additions on the precipitation hardening of Al-Mg-Si alloys were systematically studied by performance testing and microscopic characterisation. Sn addition can retard the onset of natural aging (NA), while after long-term NA, the NA hardening is enhanced. Although Cu and Sn can promote the NA hardening, the Cu and Sn combination addition results in NA hardness lower than the individual Cu addition. Compared with Sn, Cu addition is more efficient in promoting the artificial aging hardening of these alloys. Both of the Sn and Cu atoms can incorporate in the interior of the β′′ phase and produce disordered structure. The results are expected to provide new insight for designing new aluminium alloys for automotive application.

Long-Term Leaching Behavior and Geochemical Modeling of Cement Solidified Incineration Fly Ash Containing Waste Tires and Wood Biomass

Waste incineration is a widely used treatment method, and sustainable approaches are required to properly recycle large volumes of incineration ash to reduce environmental impacts and landfill space consumption. Studies have focused on the potential of recycling incineration ash as a replacement for natural aggregates in civil engineering applications, such as road construction. However, industrial waste incineration ash, such as waste tire incineration ash, contains hazardous heavy metals, such as lead and zinc that pose potential environmental threats. Moreover, few studies have investigated the leachability of these hazardous metals after long-term natural aging. This study investigates the long-term evolution of leachate chemistry, mineralogical transformation, and heavy metal fixation performance of a recycled roadbed material using ash from industrial waste incineration of waste tires and biomass (SFA). Additionally, field samples from a five-year pilot test site utilizing SFA were also examined. Regulatory leaching tests showed that the concentrations of Cd, Pb, As, T-Cr, and Ni were all below permissible limits even after five years of utilization. Long-term column leaching experiment results indicated that, compared to the total content of the SFA material, the leaching ratios of Pb, T-Cr, Cu, and Zn were 27%, 12%, 5%, and 0.1%, respectively. The SFA pH-stat leaching test results demonstrated that the mass release of the total content of heavy metals was relatively minimal, even under acidic pH conditions (pH &lt; 4). Finally, profiles of pH and major ions in leachate from the column leaching experiment were simulated using HYDRUS HP1, implementing a dual-porosity modeling approach. In conclusion, despite containing hazardous heavy metals, SFA exhibits significantly low leaching rates over a long-term period.

Improvement of UV aging resistance of PBAT composites with silica-immobilized UV absorber prepared by a facile method

Prolonging the service life of polymer materials by enhancing their aging resistance is an effective and practical way to reduce the polymer waste. In this work, to improve the migration resistance and thermal stability of commercial UV absorber used in polymer composites, a solvent & coupling agent-free method with only one-step reaction was proposed to immobilize a commercial UV absorber 2‑hydroxy-4-(octyloxy)benzophenone (UV-531) onto the surface of silica nano particles (SiO2). UV-531 was chemically bonded on the surface of SiO2 with the loading weight of 12%. The as-prepared immobilized UV-531 (SiO2–531) could be homogeneously dispersed in the matrix of poly(butylene adipate-co-terephthalate) (PBAT) and showed significantly improved migration resistance and thermal stability compared with free UV-531. For example, the initial decomposition temperature of SiO2–531 is about 200 °C higher than that of free UV-531. Therefore, PBAT/SiO2–531 composites showed even better anti-UV aging performance than PBAT/SiO2 composites with twofold added free UV-531 during accelerated ultraviolet weathering and long-term natural climatic aging tests. For example, PBAT/SiO2–531 composites can maintain higher retentions of tensile strength and elongation at break than PBAT/SiO2 composites with free UV-531 does after accelerated UV aging. Hopefully, the proposed facile method to enhance the anti-UV aging efficiency of commercial UV absorber may potentially uncover an extensive family of building blocks for constructing highly anti-aging plastic composites.

Effects of Natural Aging and Discontinuous Cyclic Loading on High Cycle Fatigue Behavior of Steels

Metallic components may not be used immediately and are stored for several months or years after fabrication in some cases, which experience long-term natural aging. Moreover, the fatigue-beared components commonly suffer discontinuous cyclic loadings in service. In this paper, the effects of natural aging and discontinuous loading on high cycle fatigue life and failure mechanism were investigated through rotating bending fatigue tests. The long-term natural aging (e.g., more than 20,000 h) reduced the fatigue life of both 25CrMo4 and 30CrMnSiA steels, and this effect was irrespective of the roughness of the specimen surface. The effect of natural aging on the failure mechanism was related to the microstructure of materials. The natural aging promoted the probability of multi-site crack initiation for 25CrMo4 steel, but had no influence on the crack initiation mode of 30CrMnSiA steel. The discontinuous cyclic loading had no harmful influence on the fatigue life of 25CrMo4 steel, and it had no influence on the failure mechanism. The specimens under continuous and discontinuous cyclic loadings both failed from single-site crack initiation or multi-site crack initiation at the specimen surface.

Deterioration of Microstructures and Properties in Ancient Architectural Wood from Yingxian Wooden Pagoda (1056 AD) during Natural Aging

The Yingxian Wooden Pagoda (1056 AD), located in Shanxi province, China, is a unique architectural pure-wooden artifact standing for a millennium. Despite its longevity, the structures and properties of the ancient architectural woods used in its construction have been significantly degraded due to long-term natural aging, which has profoundly impacted the preservation of this valuable cultural heritage. To better understand this degradation, we studied the deterioration of a baluster (Larix principis-rupprechtii Mayr.) from Yingxian Wooden Pagoda. The study employed various analytical techniques, including optical microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, solid-state 13C nuclear magnetic resonance spectroscopy, X-ray diffraction, and nanoindentation technology, to evaluate the microstructures and properties of the ancient architectural woods. Results indicated that the destruction of wood cell walls was primarily transverse transwall destruction and interfacial debonding and that the degradation of chemical components was primarily in the hemicellulose (xylan) and amorphous region of cellulose. The reduced elastic modulus and hardness of tracheid cell walls in the ancient architectural woods were higher than in recent larch woods. This study would help deepen understanding of wood deterioration during long-term natural aging for the subsequent preservation and protection of wooden cultural heritages and longer use of ancient timber constructions.

Molecular Dynamics Study on Crack Propagation in Al Containing Mg-Si Clusters Formed during Natural Aging.

The crack propagation behavior of Al containing Mg-Si clusters is investigated using molecular dynamics (MD) simulations to demonstrate the relationship between the natural aging time in Al-Si-Mg alloys and ductility. Experimental results show that the elongation at failure decreases with natural aging. There are few studies on the relationship between natural aging and ductility because of the difficult observation of Mg-Si clusters. To solve the difficulty, cracked Al containing Mg-Si clusters of varying sizes are assumed for the MD simulations. A larger Mg-Si cluster in Al results in earlier crack opening and dislocation emission. Moreover, as the Mg-Si cluster size increases, the stress near the crack tip becomes more concentrated. This causes rapid crack propagation, a similar effect to that of crack tip sharpening. As a result of long-term natural aging, the cracks expand rapidly. The influence of geometry is also investigated. Crack lengthening and thickness reduction negatively impact the fracture toughness, with the former having a larger impact than the latter. Although there are several discrepancies in the practical deformation conditions, the simulation results can help to more thoroughly understand natural aging in Al-Si-Mg alloys.

Физико-химические и термические превращения газонаполненной полимерной теплоизоляции естественного старения

Introduction. In the process of operation, various materials are subjected to prolonged exposure to environmental factors, which can lead to irreversible physical and chemical changes that affect not only their service life, but also fire safety. In this regard, the study of the influence of natural ageing on the features of the combustion process, fire hazard characteristics of thermal insulation materials is relevant. Aims and objectives. The aim of the work is to evaluate the physicochemical and thermal transformations of polymer gas-filled thermal insulation (expanded polystyrene foam) of long-term natural ageing. Methods. A set of physicochemical methods, namely X-ray phase analysis, infrared spectroscopy and thermal analysis methods (TG, DTG, DSC) were used to study the physicochemical nature and thermal stability of naturally aged polystyrene foam. Results and discussion. In the work the technical condition of polymer thermal insulation was assessed on the objects: cinema "Udarnik" (Russia, Moscow), 1927-1930 year of construction and a residential building (Tajikistan, Vahdat), 2014 year of construction. The method of X-ray phase analysis for polystyrene foam of natural ageing revealed a decrease in crystallinity. The change in the phase state of polymer thermal insulation indicates the thermal fluctuation nature of the processes associated with its natural aging and leading to a change in the ordering of the arrangement of individual macromolecular sites of aromatic hydrocarbon. At the same time, under the conditions of natural ageing there is a decrease in the apparent density of polystyrene foam by 20-41 %. By method of infrared spectroscopy the greatest changes are established in areas of characteristic absorption bands 3057...2846 cm-1, and also 1500...1450 cm-1, that testifies to destabilisation of hydrocarbon chains of macromolecules of polystyrene foam of natural ageing. The character of thermo-destructive transformations is established for the investigated samples, the tendency of expansion of the main section (335...470 °С) in comparison with the samples without natural ageing (360...450 °С) is revealed. The identified features of physicochemical and thermal transformations of naturally aged polystyrene foam can lead to changes in the intensity of the combustion process and heat release. Conclusion. According to the results of the study it is established that in the process of natural ageing in gas-filled polymers irreversible physical and chemical changes occur under the influence of environmental factors. Deterioration of the technical condition of polymer thermal insulation during its operation can lead to changes in the characteristics of fire hazard, features of its combustion and heat release when exposed to fire. Keywords: thermal insulation; polymers; polystyrene foam; fire hazard; service life; natural ageing.

Rapid Simulation of Decade-Scale Charcoal Aging in Soil: Changes in Physicochemical Properties and Their Environmental Implications.

In situ aging can change biochar properties, influencing their ecosystem benefits or risks over time. However, there is a lack of field verification of laboratory methods that attempt simulation of long-term natural aging of biochar. We exploited a decade-scale natural charcoal (a proxy for biochar) aging event to determine which lab-aging methods best mimicked field aging. We oxidized charcoal by ultraviolet A radiation (UVA), H2O2, or monochloramine (NH2Cl), and compared it to 10-year field-aged charcoal. We considered seven selected charcoal properties related to surface chemistry and organic matter release, and found that oxidation with 30% H2O2 most representatively simulated 10-year field aging for six out of seven properties. UVA aging failed to approximate oxidation levels while showing a distinctive dissolved organic carbon (DOC) release pattern. NH2Cl-aged charcoal was the most different, showing an increased persistent free radical (PFR) concentration and lower hydrophilicity. All lab oxidation techniques overpredicted polycyclic aromatic hydrocarbon release. The O/C ratio was well-correlated with DOC release, PFR concentration, surface charge, and charcoal pH, indicating the possibility to accurately predict biochar aging with a reduced suite of physicochemical properties. Overall, our rapid and verified lab-aging methods facilitate research toward derisking and enhancing long-term benefits of biochar application.

Synchronous improvement of mechanical properties and stress corrosion resistance by stress-aging coupled with natural aging pre-treatment in an Al-Zn-Mg alloy with high recrystallization fraction

Enhancing the strength of Al-Zn-Mg alloys is critical to the weight-lightening of structural components in the application of high-speed trains and aerospace industries, while high stress corrosion cracking (SCC) susceptibility of Al-Zn-Mg alloys (especially the alloy with high recrystallization fraction) with high strength makes it difficult. In this study, the influence of tensile stress-aging coupled with natural aging pre-treatment on the mechanical properties and SCC resistance of Al-Zn-Mg alloy with high recrystallization fraction has been investigated. The results show that tensile stress-aging at 160 ℃ can inhibit the dissolution of clusters/Guinier-Preston (GP) zones formed during long-term natural aging pre-treatment, which increases the number density of matrix precipitates (MPts), narrow the width of precipitate free zone (PFZ), and dramatically improve the mechanical properties of the experimental Al-Zn-Mg alloy. Meanwhile, the precipitation of the high density of MPts within the matrix will assume a large number of solute atoms during artificial aging, which will reduce the supplement of solute atoms to grain boundaries. As a result, the volume of anodic active grain boundary precipitates (GBPs) and the content of free solute atoms at grain boundaries are reduced, which reduces the possibility of initial nucleation and propagation of SCC crack. The coupled treatment method proposed in this study proves efficient in resolving the contradiction between the strength and SCC resistance in Al-Zn-Mg alloy.

Effect of long-term natural aging on the tensile and fracture properties of aluminum alloy AA2219-T87 parent and weldments at room and cryogenic temperatures

Aluminum alloy (AA2219) is widely used for the fabrication of earth storable and cryogenic propellant tanks. To ensure flight safety, it is important to understand the effect of long-term storage on the mechanical properties, which are dependent on the microstructure. Therefore, the present work is carried out to understand the effect of long term (11 years) ambient storage on the tensile and fracture properties of AA2219-T87 in parent material and weld joint. The tensile test results of naturally aged AA2219-T87 material for 11 years in both parent and weldments indicate an increase in tensile strength at room and cryogenic (77 and 20 K) temperatures. STEM-HAADF and TEM analysis revealed the presence of well-oriented densely populated CuAl2 precipitates (plate-like θ’ and θ” precipitates). The changes in mechanical and fracture properties were understood from the quantification of precipitate distribution, that can be attributed to the natural aging phenomenon taking place at ambient conditions, during the extended period of storage. Here, we report the mechanism towards understanding the increase in strength of AA2219-T87, by the growth of the finer θ” precipitates during natural aging. Since tensile (RT, 77 K, and 20 K) and fracture properties (RT) of welds have improved, with no significant reduction in ductility, long-term naturally aged (up to 11 years) fabricated products of AA2219-T87 are flightworthy.