Artificial Aging Process Research Articles

Investigation on the deformation behavior and post-formed microstructure/properties of AA7075-T6 alloy under pre-hardened hot forming process

In this study, a refined hot forming process for age-hardened aluminum alloys that is referred to as the pre-hardened hot forming (PHF) process was investigated. The ductility of the AA7075-T6 alloy was significantly improved during this process, which was evaluated through hot tensile tests ranging from 200 °C to 400 °C. Based on these results, hot stamping tests for automotive components were successfully conducted, and mechanical property testing of post-formed parts were carried out. The results indicate that under the forming temperature of 200 °C, the tensile strength of the formed component maintained more than 92% of the original T6 sheet blank tensile strength and more than 93% of the yield strength. Moreover, the post-formed strength did not decrease monotonically with increasing forming temperature. There was an abnormal drop in the strength of the component formed at 300 °C, which is obviously lower than that of the vicinal temperatures (250 °C and 350 °C). Microstructure observations and differential scanning calorimetry (DSC) analysis were conducted to explore the microstructure of the formed components. The results showed that there was no obvious difference among the grain sizes of the formed components under different forming temperatures. The sample formed at 250 °C maintained a large amount of the η′ phase, while the coarse η phase was the dominant precipitate in the microstructure of the sample formed at 300 °C. The contributions of grain boundary strengthening and precipitation strengthening were evaluated based on the Hall-Petch equation and Orowan strengthening theory, respectively. The calculation results showed good agreement with the experimental data. All the results indicated that direct forming of the AA7075-T6 alloy was achieved by the PHF process and that the forming temperature should be limited below 300 °C to obtain satisfactory mechanical properties without a subsequent artificial aging process.

Sobre el secuestro de hidrocarburos aromáticos policíclicos en suelos añejados

The fate of polycyclic aromatic hydrocarbons is a major environmental concern that has attracted much attention in current literature. The physicochemical properties of contaminants, along with soil characteristics and ageing, translate into an unusual sorption that leads to high sequestration and low bioavailability. In the present study, fresh (non-sterile) and aged (sterile) synthetic soils (sand-perlite 1:1 v/v) were characterized and spiked (hexadecane, phenanthrene and pyrene 2:1:0.5) to evaluate sequestration extents. Hydrocarbons extraction differed for sand and perlite in fresh samples, on the contrary, the artificial ageing process affected equally the extraction in the synthetic soil components. In the synthetic soil, the extractability of hexadecane and phenanthrene were 80% and 60%, respectively, in fresh samples, but for both hydrocarbons it was only 20% in aged samples. Pyrene extractability was not affected by the components of the synthetic soil or by ageing, and this may be related to an in-situ crystallisation process. The characteristics of the soil and its contaminants, coupled with long-term interactions, significantly modified the PAHs environmental fate, leading to the formation of non-extractable residues, also known as sequestered contaminants. This study expands current knowledge about the fate of these contaminants and should serve as motivation for further experimental and theoretical research on this subject.

Influence of Light-Curing Units on Color Stability of Composite Resins After Aging

Background and AimOne of the most important problems with composite restorations is the loss of consistency between the composite and tooth color. The present study aimed to compare the color stability of two types of nanohybrid composites cured with different light-curing devices after aging.Materials and MethodsIn this study, the color stability of 40 disc-shaped specimens (10 mm in diameter and 2 mm in height) from two types of enamel and dentin nanohybrid composites (IPS Empress Direct, Ivoclar Vivadent) was investigated. A group of 10 samples of each composite was cured by light-emitting diode (LED) Bluephase device (Ivoclar, Vivadent) at 1200 mW/cm2 for 20 seconds, and another group of 10 specimens was cured by a quartz-tungsten-halogen (QTH) device (Coltolux 2.5, Colten, USA) at 600 mW/cm2 for 40 seconds. The initial color of the samples was determined by the Konica Minolta spectrophotometer (CS2000, USA), and then, the composite samples were subjected to an accelerated artificial aging (AAA) process in the QUV/SPRAY device. Then, the color of the samples was reassessed. Two-way analysis of variance (ANOVA) was used to compare the color changes in the study groups at a significance level of P=0.05.ResultsThe specimens cured by the LED device showed significantly lower color change compared to QTH (P=0.047). However, there was no significant difference in color stability between enamel and dentin composites cured by a fixed apparatus (P=0.474).ConclusionThe curing of nanohybrid composites with LED devices causes lower color change compared to QTH.

Experimental and Numerical Investigation on Strengthening Behavior of 7075 Aluminum Alloy Sheets in Hot Forming–Quenching Integrated Process

Abstract 7xxx-Series aluminum alloys have a wide application prospect in the automotive industry due to its higher strength than other series of aluminum alloy. However, little literature has been reported on the formability and strengthening behavior of 7xxx-series aluminum alloys for the structural components of body in white (BIW). In this paper, the formability and strengthening behavior of 7075-T6 were investigated systematically under hot forming–quenching (HFQ) integrated process. First, compound dies with rod-heated blank holder and water-cooled lower punch and upper die were set up for experiment. For low adhesion friction and high cooling rate, the optimum blanking temperature was determined as 400 °C. Second, forming state, thickness distribution, and temperature field were investigated through experiment and finite element simulations. A-pillar reinforcement panel was successfully manufactured based on the simulation results. The simulation data showed that the maximum thinning rate of the whole part is about 14.25%, and the maximum thickening rate is about 1.95%. Third, the formability and quench sensitivity of u7075-T6 were achieved through time–temperature–transformation (TTT) curves and continuous cooling precipitation (CCP) diagrams combined with the thermo-mechanical coupling simulation. Finally, the strengthening was measured by testing the tensile strength and Vickers hardness at different positions of formed parts after artificial aging process. The testing result showed that the strength of the formed parts after artificial aging at 120 °C for 24 h were 162.7–172.2 HV and 505–528 MPa, respectively.

Interactions between a Buffered Amine Oxide Impregnation Carrier and an Acrylic Resin, and Their Relationship with Moisture

Wood used outdoor is subjected to different sources of degradation and should be protected properly. In this study, acrylic resins were added to a wood impregnation system using amine oxides and propiconazole, an organic fungicide, to create a two-part wood protection preservation treatment. Since amine oxides can diffuse readily into wood, this treatment protected both the surface and inner structure of the treated wood following a simple dipping. Many aspects of the treatment were studied: the adhesion of the acrylic coatings, their permeability to water, and the impregnation depth of the propiconazole. In each case, a particular attention was accorded to the interactions between the resins and the impregnation system. Adhesion and permeability tests were coupled with an artificial aging process simulating severely wet conditions. Amine oxides reduced the adhesion of the coatings but did not impair their aging properties. Because of their hydrophilic nature, they also increased the permeability to liquid water, although they did not affect the air moisture permeability. The penetration of the propiconazole, estimated with a dye, decreased with the resin. Overall, the two parts of the treatment lightly impaired each other, but the practical aspect of this treatment may overcome these disadvantages.

Achievement of High Strength and Ductility in Al-Si-Cu-Mg Alloys by Intermediate Phase Optimization in As-Cast and Heat Treatment Conditions.

In order to obtain high-strength and high-ductility Al–Si–Cu–Mg alloys, the present research is focused on optimizing the composition of soluble phases, the structure and morphology of insoluble phases, and artificial ageing processes. The results show that the best matches, 0.4 wt% Mg and 1.2 wt% Cu in the Al–9Si alloy, avoided the toxic effect of the blocky Al2Cu on the mechanical properties of the alloy. The addition of 0.6 wt% Zn modified the morphology of eutectic Si from coarse particles to fine fibrous particles and the texture of Fe-rich phases from acicular β-Fe to blocky π-Fe in the Al–9Si–1.2Cu–0.4Mg-based alloy. With the optimization of the heat treatment parameters, the spherical eutectic Si and the fully fused β-Fe dramatically improved the ultimate tensile strength and elongation to fracture. Compared with the Al–9Si–1.2Cu–0.4Mg-based alloy, the 0.6 wt% Zn modified alloy not only increased the ultimate tensile strength and elongation to fracture of peak ageing but also reduced the time of peak ageing. The following improved combination of higher tensile strength and higher elongation was achieved for 0.6 wt% Zn modified alloy by double-stage ageing: 100 °C × 3 h + 180 °C × 7 h, with mechanical properties of ultimate tensile strength (UTS) of ~371 MPa, yield strength (YS) of ~291 MPa, and elongation to fracture (E%) of ~5.6%.

A basic study on artificial aging in Mg-10Al12Si+1Pb alloy

In this study, research has been made on the aging of metal matrix composite materials produced by the in situ casting system. Mg matrix composite material was produced by the in situ casting system. In this study, 90%Mg + 10% Al12Si (wt) ingot casting was performed for alloy formation and 1% Pb was added as an alloying element to the melted structure. This study aims to examine the effect of the artificial aging (AA) process on hardness and microstructure after alloying and composite of Mg metal. The in situ casting system was used in the casting of Mg alloy under the Ar gas atmosphere. The material after required casting homogenization process; for the AA process, they were embedded in a powder graphite filled vessel and kept at 350 °C for 1 h and then quenched (with 25 °C water). Later; after quenching, the materials were kept at 150 °C for 2, 4, 12, 16 and 24 h and aged samples were obtained. Microstructure images were obtained from the samples by scanning electron microscope (SEM) and light optical microscope (LOM) and then the hardness values of the micro hardness device were measured. Grain structure because of AA heat treatment; showed changes according to un-aging material. The hardness value is directly proportional to the increasing aging time of the materials applied to the AA process; it was found that the levels increased approximately to 45% (86HV to 125HV) compared to the un-aging material and passed to the fixing phase.

Prediction of long-term volumetric parameters of asphalt concrete binder course mixture using artificial ageing test

Ageing of asphalt mixture occurs during the production and construction, and it will continue until the end of the pavement lifetime. Modified Butonic bitumen consists of petroleum bitumen and extracted bitumen from natural asphalt was used as a binding material to produce asphalt concrete binder course (AC-BC). This study purposed to predict the effect of long-term ageing on volumetric parameters of asphalt concrete binder course mixture using an artificial laboratory test. Three different treatments were conducted, the first treatment without the ageing process as the control specimen, the second and third treatments used oven heating as the artificial ageing process for 2 and 4 days 85°C. After ageing process completion, the volumetric parameters were determined by the value of the void in the mixture (VIM), void of mineral aggregates (VMA) and the void filled with asphalt binder (VFB).

Evaluation of the Precipitation Process of a Clad Pipe by the Thermoelectric Potential Technique

The article reports a study carried out on metallic samples extracted from a metallurgically bonded clad pipe (API 5L X65 steel-Inconel 825 alloy) subjected to a solution heat treatment at 1200 °C and a subsequent aging treatment at 650 °C for different times in order to promote microstructural changes in thermo-metallurgical bonded materials. The non-destructive thermoelectric potential (TEP) technique was used to monitor microstructure changes due to the artificial aging process. In addition, micro-hardness tests were carried out on the metallic materials and micrographs were obtained by means of an optical and scanning electron microscope (SEM). The TEP value changed with solution treatment temperature and reached a maximum value for solution treatment at 1200 °C. The changes in TEP during solution treatment were caused by changes in the solubility of the alloying elements. In the artificial aging process, the TEP value decreased with increasing aging time due to the precipitation process, but exhibited distinct characteristics for the different zones at the clad pipe samples.

Optimization of Age Hardening Behaviour of AA2024 Hybrid Composite Reinforced with Red Mud and Fly Ash through RSM

Hybrid AA2024 Metal Matrix composite find explicit application, so important factors like Hardness, lightweight is considered and hybrid composite was synthesized by stir casting route. In this investigation, the effects of age hardening on Hardness of AA2024 reinforced with industrial wastes is measured by using a Vickers hardness test and the influence of different process parameters are studied using Design Expert. A Response Surface Methodology is an effective technique used to observe the impact of age hardening parameters and their interconnection on surface hardness of the prepared hybrid AA2024 composite. A mathematical model was created to optimize the weight percentage of reinforcement and artificial ageing process parameters for maximum Hardness. Adequacy and lack of fit of the developed model were checked using the Analysis of variance Technique. Hardness is taken as the response and optimum parameters are obtained by using the quadratic model. Based on the results, it can be perceived that the weight percentage of Red mud, ageing temperature and ageing time has shown a notable effect on the response. For a specifically optimized parameter, the hardness is improved and it was observed that ageing temperature is the most influencing factor based on the RSM. The optimized parameters for the desired response are Ageing Temperature is 198.87ᵒC, Ageing time is 6.82884 hours, and Red mud wt % is 4.2865 respectively. A confirmation test is carried out with the optimized parameters experimentally and its error is less than the 5 % which shows good results with RSM. Surface morphological studies are carried for the optimized Age Hardened hybrid composite and it showed the uniform distribution of reinforcements in the matrix. Because of the increased hardness, these hybrid composite would perceive real time applications like Orthopaedic braces, aircraft structures and manufacturing crew machine products.

Modulation of the natural aging effect on subsequent artificial aging in Al–Mg–Si aluminum alloys with alloying content ∼ 1 wt% through temperature tuning

In this paper, the influence of the natural aging (NA) on the subsequent artificial aging (AA) process in Al–Mg–Si aluminum alloys with alloying content ∼1 wt% was studied. Methods including various aging, hardness testing, transmission electron microscope (TEM), atom probe tomography (APT) etc, were employed. The results show that the NA before AA affects the AA precipitation process adversely under lower AA temperatures, e.g. 150 °C, by suppressing the peak aging hardness, while such effect can be modulated to be positive by increasing AA temperature to over 175 °C. Under higher AA temperatures, transformation of clusters into main strengthening precipitates, β″ phase for example, is promoted. The nucleation probability of these phases is enhanced, through lowering the nucleation energy barrier. As a result, the NA clusters facilitate nucleation and growth of the main precipitates during AA. The overall results proved that the NA effect on the subsequent AA process in the Al–Mg–Si aluminum alloys with alloying content about 1% can be modulated by tuning the AA temperature.

Effects of Holding Time During Artificial Aging Process on AA6061 to the Mechanical Properties

Materials that have been frequently used for automotive or construction equipment are Aluminum Alloys (AA) 6061. Artificial aging is one of the processes to obtain optimal strength and hardness values. In this process, depending on the temperature and holding time. In this study, experiments have been carried out on the effects of holding time during the artificial aging process. Heating a solid solution at 300C for 1 hour is the first step. The holding time variations used are 1, 2, 3, 4, and 5 hours. Experiments have been made on impact strength, hardness values and microstructure. For hardness values decrease with increasing holding time. When holding time for 1 hour has a value of 80.8 HVN while the holding time of 5 hours has a hardness value of 47.4 HVN. But in impact testing, the impact strength increases with increasing holding time. Both of these have been supported by microstructure observation data.

Structural and property changes of silk fibroin determined by an immunoassay during an artificial aging process

Recently, increasing interest has been focused on the origin and transmission of silk. However, ancient silks have usually undergone severely deterioration and investigations of the sequential and spatial structural changes in the degradation process have rarely been reported. In this paper, a novel immunoassay was proposed for investigating the structural changes of silk fibroin (SF) at sequential level during an alkali aging process. Three polyclonal and one monoclonal antibodies, i.e., HAPJ0449, HAPH1223, HAPJ0409, and HAMK0111, were accurately prepared through animal immunization. Next, a sensitive indirect enzyme-linked immunosorbent assay (ELISA) based on the antibodies was performed to characterize the aged silks. The ELISA results indicated that the macromolecular structure of silk fibroin degraded gradually with an increase in the alkali aging time interval. The antibodies produced by immunizing rabbits with hapten-keyhole limpet hemocyanin (KLH) conjugate exhibit superior sensitivity to those obtained by immunization with silk fibroin. Moreover, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and attenuated total reflectance—Fourier transform-infrared spectroscopy (ATR-FTIR) results showed the molecular weight and crystallinity index of silk samples decreased during the aging process. Thus, combined with conventional analytical tools, the immunological method has the potential to provide an accurate and reliable quantitative index for aging assessment of severely degraded silks, which may serve as a reference for studying the origin and transmission of these materials.

Progress of Bamboo Recombination Technology in China

At present, China is the world's largest producer of bamboo resource possessor and bamboo processing. The main processing method of bamboo recombination technology is rolling and compaction, by which a reconstituted material with bamboo fibrotic veneer as matrix and phenolic resin as reinforcement is prepared. It has excellent physical and mechanical properties and can replace high-quality wood to manufacture various engineering structural materials and building decoration materials. This paper reviewed the research process and progress of bamboo recombination technology, the existing technical problems and prospects, in order to provide references for future research on bamboo recombination theory and production practice. In recent years, as a new material with controllable properties, designable structures, and adjustable dimensions, bamboo reconstituted materials have been comprehensively studied from the aspects of pressing process parameters, physicochemical mechanical properties evaluation system, and microstructure characterization, but the research is not comprehensive and has not in-depth view. In the future, the relationship between microstructure and performance should be emphatically studied to clarify the law of mechanical performance change and ultimate mechanical performance under synergistic enhancement effect, as well as the performance change and interface formation of the resin during the entire molding process. Meanwhile, the reliability and relevance of applied research should be further expanded, and the integration of natural and artificial aging environment, process and performance, and macro- and microscales should be strengthened.

Hardness improvement of aluminum alloy 2024 t3 after artificial aging treatment

The needs of having strong and light material for many construction is increasing. Aluminum is one of materials that fulfill this requirement with other advantages such as corrosion resistant and easily formed. Generally, hardness of aluminum and its alloys is lower than ferrous metal such as iron and steel. Aluminum hardness improvement can be conducted by heat treatment namely artificial aging. Artificial aging in aluminum alloy type 2024 T3 in this study was conducted in 2 phases that is solution treatment in 500 °C for 1 hour and continued with artificial aging process in 180 °C by holding time 2, 4 and 6 hours. From the conducted research, it was found that there was hardness improvement on aluminum type 2024 T3 in line with the increasing of aging time. The gained microstructure was getting smooth which means the precipitation hardening process was getting perfect.

Post-Weld Heat Treatment Effects on Mechanical Properties and Microstructure of AA6061-T6 Butt Joints Made by Friction Stir Welding at Right Angle (RAFSW)

Friction stir welding (FSW) provides users with many advantages over fusion welding techniques. Nevertheless, it is not widely employed in current industry mainly due to high equipment costs and royalties. To overcome these issues, a low-cost FSW technique operated at a right angle, called RAFSW, has recently been developed by our research team. To make the RAFSW technique reliable for potential users, we are going to analyze the effect of various post-weld heat treatments (PWHT) on the mechanical and physical properties of the RAFSW joints. To this end, optimized process parameters are used to weld butt joints of an AA6061-T6 alloy. The joints were characterized using a tensile test, a micro-hardness test, and metallography techniques. The most efficient aging time was obtained for various aging temperatures. Moreover, it was found that artificial aging at 220 °C for 30 min could be used as a fast and cost-effective artificial aging PWHT for the industrial sector. In addition, the repeatability of the PWHTs were demonstrated by studying the effect of waiting time prior to the artificial aging. Finally, it was revealed that a single fast artificial aging process is more beneficial than solubilizing followed by an artificial aging process in terms of tensile properties, consumed time, and cost.

Influence of natural aging on the mechanical properties of high pressure die casting (HPDC) EN AC 46000-AlSi9Cu3(Fe) Al alloy

Abstract The standard aluminum alloy AlSi9Cu3(Fe) is the most common Al alloy used to produce castings by means of high-pressure casting technology and has wide application in the automotive industry, especially for motor mounts, gearbox housings, filter housings, generator housings, turbocharger housings, etc. The advantages of AlSi9Cu3(Fe) alloy are relatively good mechanical properties, strength and hardness, although it shows slightly lower elasticity and corrosion resistance. The artificial aging process or stabilization annealing can be used to improve the dimensional stability of castings, with the aim of achieving better mechanical properties as soon as possible. In this paper, the influence of natural aging time on the mechanical properties of AlSi9Cu3(Fe) alloy as well as on microstructure development was investigated. Specimens were prepared by high pressure die casting technology under optimized parameters. Chemical content was determined by optical emission spectroscopy. Thermodynamic calculation was performed by Thermo-Calc 5 software and transformation temperatures during dynamic measurement were followed by differential scanning calorimetry. Tensile properties after 3 and 30 days of aging, as well as 7 months, were determined by a tensile test at an MTS 810 instrument. Metallographic analysis was carried out by optical microscope and field-emission scanning electron microscope. Results showed a significant increase in tensile strength, yield strength and elongation with aging time and formation of (αAl + βSi), Alx(Fe,Mn)ySiz, Al2Cu-Si, Al5FeSi and Al-Mg2Si-Cu phases.

Estudio de tejidos alternativos al Tetex TR para uso como material de refuerzo en la restauración de soportes de tela pintados: primeros resultados

The present work shows the outcomes from a first experimental analysis that aimed to find a support fabric with the functional features of Tetex TR (a polyester fabric), which, currently, is no longer produced. The study is divided in different stages: on the one hand, four different fabrics were selected and tested by a visual exam under a microscope in order to determine their main structural features; on the other hand, several mock-ups were prepared to compare and evaluate the mechanical behavior, chemical stability and reversibility of the fabrics, before and after an artificial ageing process. The results show the possibility of replacing Tetex TR some of the tested fabrics for local interventions on textile support, introducing new accessible and affordable materials into the field of canvas painting restoration.

Improvement of Hardness of Short Fork (6082 Alloy)-A Case Study

Abstract The short fork is made of 6082 Aluminium alloy and used in propeller shaft of small or mini trucks. The objective of the current investigation is to find the influence of t-6 heat treatment on the hardness of short fork (yoke). The effect of aging time on hardness and Microstructural changes is investigated. The test samples of the 6082-aluminum alloy were initially forged into the short fork at temperature 450°C and then solutionizing at 540°C for 15 min followed by water quenching. Furthermore, it was artificially aged at 190°C for 60-240 minutes. Rockwell hardness test was performed to find out the relationship between hardness and aging time. The optical microscope was used to investigate the Microstructural changes of the Aluminium alloy with different aging time. The result revealed that the change in grain size and microstructure during solutionizing heat treatment and artificial aging process are responsible for the change in hardness of the alloy. Aging at 190°C for 240 minutes gives the desired hardness of the component. These process parameters will be helpful to achieve maximum hardness of short fork and will be useful to other gorging industries.

Ageing of Zirconia Dedicated to Dental Prostheses for Bruxers Part 2: Influence of Heat Treatment for Surface Morphology, Phase Composition and Mechanical Properties

Abstract Purpose: This part of the study focuses on the influence of zirconia heat treatment for surface morphology, phase composition and mechanical properties Methods: Zirconia samples was prepared with ISO 13356:2013 and ISO 14704:2008 recommendations. X-ray diffraction, observations (SEM) and (AFM), microhardness (Olivera & Phara method), and static bending test (4PBT) were taken. Results: characterization of YSZ and high temperature heat treatment has clearly shown that the aging process influences the change in phase composition of the material, significantly worsening the topography. In turn, re-treatment of the high temperature made after the artificial aging process results in reverse transformation of the desired tetragonal phase, but does not affect the improvement of surface morphology. Conclusions: The research made it possible to assess the negative impact of the zirconium oxide aging simulation process. Because of the failure to achieve the intended results, it was also proved that the high-temperature re-processing was not appropriate.