Early Stage Of Aging Research Articles

Effects of Sn addition on precipitation of Al–Zn–Mg alloy at early stage of natural aging

The effect of Sn addition on the natural aging behavior of Al–Zn–Mg alloy was investigated using atom probe tomography (APT) experiments and density functional theory (DFT) calculations. The results demonstrate that Sn retards the natural aging behavior by facilitating the preferential formation of Mg–Sn clusters, which suppress the formation of Guinier-Preston zones (I) during the earliest aging stage. Quantitative solute analysis conducted by APT has suggested increasing amount of Mg–Sn clusters in Sn-contained alloy due to their high binding energy, supported by DFT calculations on the Sn.

Effect of Mg Content and Cooling Rate After Solidification on the Mechanical Properties of T5-treated Al-Si-Mg Alloy

The effects of Mg content and cooling rate on the T5 treatment of Al-Si-Mg alloys have been investigated using Avrami kinetics and transmission electron microscopy. The alloys were super-heated at 800 oC for 1 hr followed by degassing treatment at 720 oC for 15 min, and poured into a metallic mold preheated to 250 oC. The as-cast alloys were then T5-treated at a temperature of 190 oC. As the Mg content and/or cooling rate increased, the strength of the T5-treated alloys increased while the elongation decreased over the entire aging time. However, some T5 treatment conditions were effective to at enhancinge elongation as well as strength. The alloy with low Mg content showed excellent elongation in the early stage of aging. B, but as the aging time increased, h. However, the elongation decreased rapidly so that there was showed no significant difference from with the alloy with high Mg content in the over-aging stage. This was due to a coarse and agglomerated precipitate structure, which were likely to be formed by the rapid precipitation and agglomeration of the β′ phase. The alloy with a high cooling rate exhibited superior strength with similar elongation over the entire aging time compared to the slowly cooled alloy. The reason for the decrease in strength for in the slowly cooled alloy was attributed to the coarsening of precipitates and suppression of the formation of fine precipitates during cooling.

MicroRNAs-mediated regulation of insulin signaling in white adipose tissue during aging: Role of caloric restriction.

Caloric restriction is a non-pharmacological intervention known to ameliorate the metabolic defects associated with aging, including insulin resistance. The levels of miRNA expression may represent a predictive tool for aging-related alterations. In order to investigate the role of miRNAs underlying insulin resistance in adipose tissue during the early stages of aging, 3- and 12-month-old male animals fed ad libitum, and 12-month-old male animals fed with a 20% caloric restricted diet were used. In this work we demonstrate that specific miRNAs may contribute to the impaired insulin-stimulated glucose metabolism specifically in the subcutaneous white adipose tissue, through the regulation of target genes implicated in the insulin signaling cascade. Moreover, the expression of these miRNAs is modified by caloric restriction in middle-aged animals, in accordance with the improvement of the metabolic state. Overall, our work demonstrates that alterations in posttranscriptional gene expression because of miRNAs dysregulation might represent an endogenous mechanism by which insulin response in the subcutaneous fat depot is already affected at middle age. Importantly, caloric restriction could prevent this modulation, demonstrating that certain miRNAs could constitute potential biomarkers of age-related metabolic alterations.

Research on the Aging Properties of HTPB Propellant under Vacuum

The space environment has high vacuum, rapid temperature alternations and other extreme conditions, which can affect the energy, ignition rate and ignition performance of solid propellants in the space environment. In order to obtain the space aging performance of HTPB propellant, this paper investigates the aging performance of HTPB propellant in vacuum environment and compares it with atmospheric pressure, and analyses the oxidative cross-linking, degradation chain scission and “dehumidification” behaviour based on the mechanical properties, cross-sectional state and infrared spectra of propellant before and after aging. The research results show that the anhydrous environment under vacuum prevents the occurrence of the chain scission degradation of HTPB propellant, and HTPB propellant is basically only affected by the oxidative cross-linking reaction, where the reaction rate is slow. The mechanical properties show that the breaking strength increases slightly in the first stage, in the later stage of aging, the oxidative cross-linking reaction was intensified due to the decomposition of AP, and the breaking strength increased obviously compared with the initial value. Under the atmosphere, the HTPB propellant was mainly affected by oxidative cross-linking reaction in the early stage of aging, and the breaking strength increased. In the later stage of aging, due to the chain scission degradation of OA moisture absorption, the breaking strength showed an opposite trend and decreased. In addition, an obvious “dehumidification” phenomenon occurs inside the propellant after aging, which is more obvious under a vacuum.

Comparative analysis of rheological and microscopic performance of SBS modified asphalt based on field aging and laboratory aging

In this study, the correlation and difference of Styrene-Butadiene-Styrene (SBS) modified asphalt rheological and microscopic performance under field aging and laboratory aging were analyzed. The asphalt recovery experiment obtained SBS modified asphalt after construction aging (CA), 1 year field aging (1A), and 5 years field aging (5A) as field aging samples. The SBS modified asphalt samples were obtained by laboratory aging methods: ultraviolet aging (UV), rotating film oven test (RTFOT), and pressure aging vessel (PAV). Dynamic shear rheometer (DSR) and bending beam rheometer (BBR) experiments were applied to test the SBS modified asphalt rheological performance, and infrared spectroscopy (IR) and fluorescence microscopy (FM) were applied to test the SBS modified asphalt microscopic performance. By contrasting the SBS modified asphalt correlation and difference in rheological and microscopic performance during field aging and laboratory aging, the conclusion demonstrates that the degree of rheological and microscopic performance after CA treatment is not significantly different from that after RTFOT treatment. However, from the micro performance analysis, the micro performance indexes of PAV (10H) and PAV (20H) were significantly lower than those of 1A and 5A, and the rheological and micro properties are different after accelerated aging. This suggests that accelerated aging can recover and simulate the behavior in the early stages of field aging, but with increasing age, accelerated aging cannot fully simulate the aging behavior in more complex situations, resulting in a lower degree of accelerated aging than in the mid- to late-stage field aging.

Age-hardening Behavior in <i>γ</i>′-phase Precipitation-hardening Ni-based Superalloy

Dislocations are often introduced in Ni-based superalloys to impart sufficient strength at both room temperature and high temperatures prior to their use in automobile exhaust gaskets. However, the interaction between the representative γ′ (Ni3(Al, Ti))-phase precipitates and dislocations in high temperature remains unclear. Therefore, this study examined the effect of cold rolling on age-hardening behavior and microstructure evolution, focusing on the formation of γ′-phase Ni3Ti during aging at 700°C for up to 400 h after 60% cold rolling of solution-treated specimens. During the early stage of aging, at 0.03 h, the hardness rapidly increased from 401 HV to 496 HV. Age-hardening continued until 3 h and reached its peak of 536 HV, followed by gradual decrease with aging time. 3D atom probe investigation revealed that the γ′-phase was confirmed after 0.3 h of aging. However, the composition-modulated structure speculated to be caused by spinodal decomposition was observed in the 0.03 h aged specimen. The change in strength with aging time was considered by calculating the contribution of each strengthening mechanism. In the initial stage of aging (0–3 h), dislocation and solid-solution strengthening dominated along with spinodal strengthening. Strengthening by spinodal decomposition in the 0.03 h aged specimen is presumptively accelerated by the introduced dislocations, which is followed by further precipitation strengthening caused by γ′-phase precipitates. In the later stage of aging (3–400 h), precipitation strengthening became dominant and reached its peak at 20 h aging, while dislocation strengthening decreased with aging time.

Influence of substructures on precipitation behavior and mechanical properties of cryogenic rolled Al–Mg–Si alloys during aging treatment

Cryogenic rolling is a promising method to improve the mechanical properties of Al–Mg–Si alloys. In this paper, the effect of artificial aging treatment on the mechanical properties and microstructures of cryogenic rolled Al–Mg–Si sheet is investigated. The hardness and yield strength of cryogenic rolled alloys decrease at the early aging stage, but the hardness and yield strength of room temperature rolled alloys increase at the early aging stage. Besides, substructures (such as dislocations) are observed in cryogenic rolled alloys but not in room temperature rolled alloys after solution treatment, the degree of recrystallization in the cryogenic rolled alloy is inferior to that in room temperature rolled alloy. The differences lead to the difference in strength between cryogenic rolled alloys and room temperature rolled alloys at the early aging stage. A precipitation mechanism is proposed to explain how these substructures promote precipitate nucleation and growth during artificial aging treatment. Based on the precipitation strengthening theory, a precipitation model is used to explain the strengthening contribution from precipitation during aging treatment, the capacity of precipitation strengthening in cryogenic rolled alloy is much higher than that in room temperature rolled alloy.

The challenge of risk prevention in home healthcare-An interview study with nurses in municipal care.

Safety in home healthcare has garnered increased attention as more people are receiving care for complex conditions at home. The prerequisites for providing safe care at home differ from those in hospitals. Malnutrition, falls, pressure ulcers and inappropriate medication commonly follow poor risk assessments, causing unnecessary suffering and costs. Therefore, risk prevention in home healthcare needs to be prioritised and studied more closely. To describe nurses' experiences of performing risk prevention in municipal home healthcare. Qualitative inductive approach, using semi-structured interviews with 10 registered nurses in a municipality in southern Sweden. Data underwent qualitative content analysis. The analysis resulted in three main categories and one overarching theme describing nurses' experiences of risk prevention in home healthcare. Getting everyone onboard comprises the categories: Managing safety while respecting the patient's self-determination, which covers patient participation, the strategic importance of respecting different views of risks and information and the fact that healthcare workers are guestsin the patient's home. Finding ways to make it work touches upon the relational aspect, including next-of-kin and promoting a common understanding to prevent risks. Being squeezed between resources and requirements refers to ethical dilemmas, teamwork, leadership and organisational prerequisites. Patient habits, living conditions and limited awareness of risks is a challenge in risk prevention in home healthcare, where patient participation plays a pivotal role. Risk prevention in home healthcare needs to be initiated at an early stage of disease and ageing and should be seen as a process where early health-promoting interventions can prevent the development and accumulation of risks over time. Long-term cross-organisational collaborations and patients' physical, mental and psychosocial conditions also need to be taken into account.

Improving Precipitation in Cryogenic Rolling 6016 Aluminum Alloys during Aging Treatment.

This study systematically investigated the performance and microstructure characterization of cryogenic rolling (CR) and room-temperature rolling (RTR) Al-Mg-Si alloys. The result showed that the hardness of the CR alloys decreased at the early aging stage, but that the hardness of the RTR alloys increased at the early aging stage. Retrogression phenomena were apparent in the CR alloys at the early aging stage. Despite undergoing the same solid solution treatment, a few substructures were still observed in the CR alloys, and the degree of recrystallization in the CR alloys was significantly inferior to that in the RTR alloys. After aging for 50 h, the strength and precipitates' density in the CR 75 alloy were higher than that in the other alloys; this indicated that the substructures were beneficial to precipitation and precipitate growth. A precipitation strength model was employed to illustrate the precipitation contribution at different aging stages. The results showed that the CR 75 alloy obtained the strongest precipitation strengthening.

Rapid drop in ductility of the bimodal-structured Mg–15Gd binary alloy during early aging

A bimodal-structured Mg–15Gd binary alloy with 45% volume fraction of elongated grains and 55% of dynamically recrystallized (DRXed) grains is fabricated by the extrusion process. The precipitating behavior correlating with the evolution of mechanical properties is systematically characterized during the subsequent aging treatment at 200 °C. The extruded alloy presents an outstanding strength with tensile yield strength of 466 MPa and ultimate tensile strength of 500 MPa at peak aging condition, while the elongation drops from 9.2% in extrusion state to 3.1%. It is found there obviously exist a rapidly decreasing range of ductility at the early stage of aging. Just during this time, the nano precipitates form preferentially at lamellar dislocation boundaries (LDBs) within the elongated grains, but there is no dense and uniform precipitation in the matrix. The results suggest that the low elongation in the aged Mg–15Gd alloy is mainly attributed to the nano precipitates prior formed at the LDBs with a high density in the elongated grains. The related mechanism has been clarified.

Effects of Cu Addition on Age Hardening Behavior and Mechanical Properties of High-Strength Al-1.2Mg-1.2Si Alloy.

In this study, the effects of Cu addition on artificial age hardening behavior and mechanical properties of Al-1.2Mg-1.2Si-(xCu) alloy was investigated quantitatively and qualitatively by Vickers hardness, tensile test, and transmission electron microscope. The results indicated that Cu addition enhanced the aging response of the alloy at 175 °C. With the increase in Cu content, the time for the alloys to reach peak aging decreased from 12 h to 10 h and 8 h. The tensile strength of the alloy was obviously improved with Cu added in which was 421 MPa of 0Cu alloy, 448 MPa of 0.18Cu alloy, and 459 MPa of 0.37Cu alloy. The results of TEM observation revealed that the addition of 0.37Cu changed the aging precipitation sequence of the alloy, in which the precipitation sequence of 0Cu and 0.18Cu alloy was SSSS→GP zones/pre-β″→β″→β″ + β', 0.37Cu alloy was SSSS→GP zones/pre-β″→β″ + L→β″ + L + Q'. Moreover, with the addition of Cu, the number density and volume fraction of precipitates of the Al-1.2Mg-1.2Si-(xCu) alloy was evidently increased. The number density was increased from 0.23 × 1023/m3 to 0.73 × 1023/m3 in the initial aging stage and from 1.9 × 1023/m3 to 5.5 × 1023/m3 in the peak aging stage. The volume fraction was increased from 0.27% to 0.59% in the early aging stage and from 4.05% to 5.36% in the peak aging stage. It indicated that Cu addition promoted the precipitation of strengthening precipitates and boosted the mechanical properties of the alloy accordingly.

Early changes in elderly food habits related to reduced protein intake

Age-related loss of muscle mass and function is a leading cause of frailty in elderly people. Changes in adult lifestyle (diet and physical activity) are highlighted as some causes and modifiable factors that can be challenged. The objective of this work was to analyze the changes in food-related habits that occur during the early stages of aging, focusing on those related to protein intake, and the reasons behind these changes. The study was carried out in Spain. Four discussion groups were held with 60–75 years old participants, to generate the list of changes in food-related habits and products consumed. These changes among the young elderly population were quantified through a questionnaire completed by 346 participants (65–75 years old, 50 % women). Factor analysis revealed seven dimensions of change in food habits: 1) eating healthier, 2) more time cooking and eating lunch at home, 3) buying/eating gourmet or indulgent products, 4) reducing the amount of food and having light meals, 5) shopping online, 6) shopping more frequently and in small stores, and 7) quick/easy to prepare dinners. Concerning changes in products consumed, three groups were observed: 1) group with no changes (23 %), 2) reduced certain protein foods (mainly meat and sausages) (37 %), and 3) also reduced the meat, sausages, and dairy desserts but increased others (fish, chicken, dairy products, and pulses) (40 %). The search for health was the main reason for avoiding certain foods, reducing the amount and portions, and for reducing the consumption of protein food products.

Promotion of astrocyte-neuron glutamate-glutamine shuttle by SCFA contributes to the alleviation of Alzheimer's disease

The brain is particularly susceptible to oxidative damage which is a key feature of several neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease. The shuttling of glutathione (GSH) precursors from astrocytes to neurons has been shown to be instrumental for the neuroprotective activity. Here, we revealed that short chain fatty acids (SCFA), which have been related to AD and PD, could promote glutamate-glutamine shuttle to potentially resist oxidative damage in neurons at cellular level. Furthermore, we performed nine-month-long dietary SCFA supplementations in APPswe/PS1dE9 (APP/PS1) mice, and showed that it reshaped the homeostasis of microbiota and alleviated the cognitive impairment by reducing Aβ deposition and tau hyperphosphorylation. Single-cell RNA sequencing analysis of the hippocampus revealed SCFA can enhance astrocyte-neuron communication including glutamate-glutamine shuttle, mainly by acting on astrocyte in vivo. Collectively, our findings indicate that long-term dietary SCFA supplementations at early aging stage can regulate the neuroenergetics to alleviate AD, providing a promising direction for the development of new AD drug.

The Regulation of the AMPK/mTOR Axis Mitigates Tendon Stem/Progenitor Cell Senescence and Delays Tendon Aging.

Age-related tendon disorders are closely linked with tendon stem/progenitor cell (TSPC) senescence. However, the underlying mechanisms of TSPC senescence and promising therapeutic strategies for rejuvenation of TSPC senescence remain unclear. In this study, the senescent state of TSPCs increased with age. It was also verified that the AMPK inhibition/mTOR activation is correlated with the senescent state of TSPCs. Furthermore, a low dose of metformin mitigated TSPC senescence and restored senescence-related functions, including proliferation, colony-forming ability, migration ability and tenogenic differentiation ability at the early stage of aging. The protective effects of metformin on TSPCs were regulated through the AMPK/mTOR axis. An in vivo study showed that metformin treatment postpones tendon aging and enhances AMPK phosphorylation but reduces mTOR phosphorylation in a natural aging rat model. Our study revealed new insight and mechanistic exploration of TSPC senescence and proposed a novel therapeutic treatment for age-related tendon disorders by targeting the AMPK/mTOR axis at the early stage of aging.

Influence of trace silicon addition on the strengthening precipitates, mechanical properties and stress relaxation resistance of Cu-Cr alloy

First-principles calculations and experimental studies, including transmission electron microscopy (TEM), electrical conductivity measurements, and yield strength and stress relaxation resistance tests, were carried out to determine the influence mechanism of trace Si on the precipitates and stress relaxation resistance of a Cu-Cr alloy. TEM observation and aging precipitation kinetic analysis showed that the addition of trace Si significantly refined the Cr-rich precipitates of the Cu-Cr alloy but did not appreciably promote the nucleation of the precipitated phase. The influence of trace Si on the Cr-rich precipitates was assessed in terms of the Si-Cr and Si-vacancy interactions. The first-principles calculations reveal that there exists a strong attraction between Si and Cr with an interaction energy of − 0.27 eV for the nearest neighbor, which could promote the formation of Si-Cr clusters in the early aging stage that serve as heterogeneous nucleation particles for precipitates and induce the refinement of body-centered cubic (bcc) Cr-rich precipitates, resulting in an increase in the yield strength of the Cu-Cr alloy. The strengthening precipitates of the Cu-Cr-Si alloy mainly consisted of fcc Cr-rich precipitates and bcc Cr-rich precipitates, the strengthening mechanisms of which were the dislocation shear mechanism and dislocation bypass mechanism, respectively. In terms of performance, the conductivity of the Cu-Cr alloy decreased with the addition of trace Si from 94.5% IACS to 92.5% IACS, the yield strength increased from 178 MPa to 193 MPa, and the stress relaxation rate decreased from 18.93% to 15.27%. The improvement in the stress relaxation resistance of the Cu-Cr alloy with the addition of trace Si was mainly attributed to the drag effect of the element on dislocation movement and the refinement effect of the element on Cr-rich precipitates.

Evolution of precipitate and precipitate/matrix interface in Al-Zn-Mg-Cu (-Ag) alloys

• The phase evolution of Al-Zn-Mg-Cu alloys with and without Ag addition during ageing at 120 °C and over-ageing at 180 °C is revealed. • The mechanism controlling the early-stage solute clustering and the promoting effect of Ag are elucidated systematically. • The role of solute clusters on the formation of η’ precipitates is clarified by in-situ STEM heat treatment. • With longer ageing time, the precipitate/matrix interface shows an evolution from Zn dominating for the interface between early-stage η’ and Al matrix to Zn and Mg co-segregating for η’/Al and η 2 /Al interfaces. • The role of precipitate/matrix interface in the growth of η’ and η 2 is revealed. • The exact positions of Ag and Cu atoms are specified. Evolution of precipitate and precipitate/matrix interface in artificially aged Al-Zn-Mg-Cu (-Ag) alloys has been systematically studied. In the early stage of ageing, Ag, as a fast diffuser, can promote the formation of solute pairs and small clusters. Solute clusters are further demonstrated to be able to act as precursors for η’ precipitates by in-situ STEM heating. With prolonged ageing time, the precipitate/matrix interface evolves from the Zn-dominated interface between early-stage η’ and Al matrix to the Zn and Mg co-segregated η’/Al and η 2 /Al interfaces. The η’/Al interfacial layers are shown to precede the formation of η’, while the η 2 /Al interface is found to be closely related to the thickening process of η 2 and the involved particular atomic movements are specified. Experimental observations and DFT calculations reveal that for η’ and η 2 , Ag can dissolve into the precipitate as well as locate at the precipitate/matrix interface without showing preference. For Cu, its dissolution in the precipitate and segregation on the interface mainly occur for η 2 rather than η’. The incorporation of Ag and Cu does not change the defined precipitate structure.

Mathematical Model for Early-Aged UHPFRC Compressive Strength Changes

Compressive strength is the most important mechanical index of ultra-high performance fiber-reinforced concrete (UHPFRC). The rule of changes in compressive strength in early-aged UHPFRC is of great significance to guide concrete curing, formwork removal, and prestress stretching. Therefore, it is very necessary to study an accurate mathematical model to describe the change in compressive strength of UHPFRC at an early age. For this purpose, a new mathematical model of compressive strength age is proposed in this work for predicting the long-term strength of UHPFRC according to a few test data from early-aged UHPFRC. This new model can overcome the shortcomings of the existing models, such as the exponential model, logarithmic model, and polynomial model. The proposed model is first demonstrated by using four groups of compressive strength test data compiled from previous research studies. Subsequently, an experiment of early-aged UHPFRC compressive strength was carried out to further verify the proposed mathematical model. The mixed proportion used in the UHPFRC compressive strength test was 10.87:0.82:1 (powder:steel fiber:water), and the design strength grade was 120 MPa. Based on the UHPFRC experimental data, it was shown that the average fitting error and standard deviation of the new model were about 10%~20% of that of the logarithmic model and the polynomial model. The proposed model can precisely predict the compressive strength of UHPFRC, with a determination coefficient (R2) of 0.9974. The research results show that the average fitting error and standard deviation of this new model were significantly reduced when compared to the existing models, and the predicted compressive strength by the new model on the 60th day is the closest to the actual design strength grade of concrete. The greatest advantage of the proposed method lies in its simple formula, fast implementation, and no need for complex mathematical operations. It has been shown that the proposed model is superior to the existing models due to its higher fitting accuracy and prediction accuracy, and it can be better used to predict the later strength of UHPFRC by using only a few compressive strength test data taken at the early age stage.

Post‐curing and structural relaxation of epoxy networks during early stages of aging for civil engineering applications

AbstractIn this work, epoxy networks used for civil engineering constructions are aged at ambient temperature, and the impact of the early stages of aging on mechanical properties is analyzed. It is observed that Young's modulus and the yield stress increase with the aging time whereas the strain at break and the toughness decrease. The structural causes for these variations are investigated by swelling experiments, infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. By combining experimental results, it is deduced that the aging process occurs in two stages. During the first 7 days of aging, the change in mechanical properties should essentially be attributed to the postcuring, which results in additional crosslinking reactions. When increasing the aging time to 21 days, the crosslinking density reaches a plateau, but a second stage emerges, in which the mechanical properties continue evolving in the same way, with variations of the mechanical parameters being of comparable amplitude. This second stage is attributed to the evolution of the thermodynamic state of the glass, leading to a densification of the epoxy network through minimization of the free volume, and favoring the creation of physical interactions between polymer segments. Therefore, structural relaxation is shown to have a significant impact on the mechanical properties.

Hydroxyl radical production by abiotic oxidation of pyrite under estuarine conditions: The effects of aging, seawater anions and illumination

Pyrite is widely distributed in estuarine sediments as an inexpensive natural Fenton-like reagent, however, the mechanism on the hydroxyl radical (HO·) production by pyrite under estuarine environmental conditions is still poorly understood. The batch experiments were performed to investigate the effects of estuarine conditions including aging (in air, in water), seawater anions (Cl−, Br− and HCO3−) and light on the HO· production by pyrite oxidation. The one-electron transfer dominated the process from O2 to HO· induced by oxidation of pyrite. The Fe (oxyhydr)oxide coatings on the surface of pyrite aged in air and water consumed hydrogen peroxide while mediating the electron transfer, and the combined effect of the two resulted in a suppression of HO· production in the early stage of aging and a promotion of HO· production in the later stage of aging. Corrosion of the surface oxide layers by aggressive anions was the main reason for the inhibition of HO· production by Cl− and Br−, and the generation of Cl· and Br· may also play a role in the scavenging of HO·. HCO3− increased the average rate of HO· production through surface-CO2 complexes formed by adsorption on the surface of pyrite. The significant enhancement of HO· production under light was attributed to the formation of photoelectrons induced by photochemical reactions on pyrite and its surface oxide layers. These findings provide new insights into the environmental chemical behavior of pyrite in the estuary and enrich the understanding of natural remediation of estuarine environments.

Acceleration of aging behavior and improvement of mechanical properties of extruded AZ80 alloy through (10–12) twinning

The effects of pre-existing {10–12} extension twins on the precipitation behavior of an extruded AZ80 material during aging and on its mechanical properties after peak aging are investigated. The material containing {10–12} twins—which are formed by compression before aging (twinned material)—has a finer grain size and higher dislocation density than the extruded material. Although the peak hardnesses of the twinned and extruded materials are almost the same, the time to reach the peak hardness is considerably shorter in the former material than in the latter (4 h and 24 h, respectively). In the twinned material, the high dislocation density of the {10–12} twins promotes continuous precipitation, which results in the formation of numerous fine Mg17Al12 precipitates within the twins in the early stage of aging. The formation of these continuous precipitates reduces the driving force for discontinuous precipitation, which consequently suppresses the formation and growth of coarse Mg17Al12 precipitates at the grain boundaries. Despite its shorter peak-aging time, the 4 h-peak-aged twinned material shows higher tensile strength and elongation than the 24 h-peak-aged extruded material. These higher mechanical properties of the former material are attributed primarily to the presence of more abundant fine continuous precipitates, which are effective in strengthening the material, and less abundant coarse discontinuous precipitates, which can act as crack initiation sites. These results demonstrate that the introduction of {10–12} twins into wrought Mg–Al-based alloys can accelerate the Mg17Al12 precipitation kinetics considerably and improve the strength and ductility of the peak-aged alloys simultaneously.