Hardness Test Research Articles

Investigating the combined influence of rolling, ECAP processes, and intermediate annealing on mechanical and microstructural properties of beryllium copper alloy 25

A beryllium copper alloy 25 underwent a series of processing steps involving rolling, equal-channel angular pressing (ECAP), and subsequent annealing. This study delved into the combined effects of these processes on the microstructural evolution and mechanical properties of the deformed beryllium copper alloy 25. The investigation utilized optical microscopy, scanning electron microscopy, transmission electron microscopy, room temperature Vickers hardness testing, and tensile testing. The findings reveal a notable enhancement in the strength of the beryllium copper alloy 25 while preserving its ductility after subjecting it to six ECAP passes followed by annealing at 210 °C for 20 min, applied to the rolled sample. Initially, an increase in number of ECAP passes resulted in a gradual reduction in grain size and a weakening of the alloy's texture. This led to an increase in ultimate tensile strength up to 333.5% without reducing in percentage elongation. Notably, after six ECAP passes, the average grain size decreased from 48 µm to less than 1 µm, yielding exceptional comprehensive mechanical properties with significantly improved strength and plasticity. The resultant material exhibits promising potential for fabrication into bars and plates for a wide range of applications in aerospace and marine industries.

In-line porosity and hardness monitoring of tablets by means of optical coherence tomography

In-line monitoring of critical quality attributes (CQAs) during a tableting process is an essential step toward a real-time release strategy. Such CQAs can be the tablet mass, the API content, dissolution, hardness and tensile strength. Since dissolution testing is laborious and time-consuming and cannot be performed in-line, it is desirable to replace dissolution testing with predictive models based on other CQAs that affect the dissolution characteristics, such as the tablet porosity and hardness. Traditionally, porosity is determined offline via gas adsorption methods or other techniques, such as Terahertz spectroscopy or gas in scattering media absorption spectroscopy. Tablet hardness is typically established using a hardness tester. While these destructive tests can readily be performed at-line, they have limited applicability in in-line settings for a high-percentage inspection. Optical coherence tomography (OCT) has recently been proposed as a possible tool for determining quality attributes. This work describes the first application of OCT for the prediction of tablet porosity and hardness. OCT measurements of tablets produced in a ConsiGma 25™ tableting line and a Stylcam 200R compaction simulator in several compaction force settings were performed and correlated with the porosity and hardness. It was demonstrated that OCT can easily be installed in-line and provide real-time information about critical material attributes. These insights confirm the applicability of OCT as a real-time quality control tool and its potential to replace time-consuming and destructive offline measurements.

Tribological and mechanical behaviors of Fe3O4NPs reinforced UHMWPE biocomposite

Ultra high molecular weight polyethylene (UHMWPE) filled with diverse contents of magnetite nanoparticles (Fe3O4NPs) were produced via hot compression molding. The effect of Fe3O4NPs on the tribological and mechanical properties of the UHMWPE matrix was studied. Wear and friction behaviors were studied using a reciprocating pin-on-disc tribometer under a sliding speed of 0.03 m.s−1 and an applied normal load of 20N. Mechanical behavior was investigated using tensile and hardness tests. SEM technique was used to explore the surface morphology and to investigate wear mechanisms. Results showed that reinforcement with Fe3O4NPs improved UHMWPE matrix hardness and wear resistance. A maximum hardness and wear resistance in addition to a good mechanical behavior in traction were obtained when adding 1 wt% of magnetite nanofiller. Reinforcement increased the coefficient of friction but there is no obvious correlation between nanofiller contents and friction. SEM analysis showed that the reinforcing rate of UHMWPE influences wear mechanisms.

The effect of pulverized glass waste particle sizes on the mechanical properties of AA6061-T6 friction stir welded joints.

Abstract The study sought to investigate the effect of pulverized glass waste (PGW) particle size as reinforcement for AA6061-T6 joints produced by Friction Stir Welding. The study utilized three particle sizes of 15 microns, 45 microns and 75 microns of the PGW as reinforcement alongside the established process parameters ranges of 900-1400rpm, 25-63mm/min and 1-2.5° in a Taguchi L9 orthogonal array for the welding process experimental design. The welding experiments were repeated for each reinforcement particle size mentioned above. Parallel-hole reinforcement strategy was used on all joints for the application of the PGW, Tensile strength, Hardness tests and Microstructural Analysis were carried out on the welded joints and subsequently, analysis of the data. For tensile strength, several sample sets showed a trend of higher tensile strength the smaller the PGW particles size (Figure 6). For hardness, however, there was no overall, discernable trend/pattern of increase in hardness as the particle size decreased. The highest average tensile strength value obtained was 85.25MPa. The lowest tensile strength was 14.26MPa. A distinguishing feature between the highest and lowest value for tensile strength is that the former was obtained with a traverse speed of 25 mm/min while the latter was obtained using a 40 mm/min traverse speed. The higher the rotational speed of the tool pin, the greater the heat of friction generated while the lower the traverse/welding speed, the greater the heat of friction generated as the tool pin spends enough time per unit length to generate sufficient heat and cause plastic deformation sufficiently high enough to cause grain refinement. Using imageJ, percentage distribution of PGW for each crucial zone (Nugget/Stir zone, Thermo mechanically affected zone and Heat affected zone) of the FSWed joint was generated for samples selected for microstructural analysis. The average value for each sample was obtained as well. The highest tensile strength value (85.25MPa) was obtained with a sample using the smallest PGW size (15 µm), in line with the trend (figure 6) in which tensile strength was greater the smaller the PGW size used. The highest hardness value (90.90 BHN) was obtained with the sample having the highest average value for percentage distribution of the PGW (58.06%). A distinct trend was noted in which the greater the percentage distribution of the PGW, the higher the hardness value obtained (figure 30).

The impact of heat treatment process on the drilling characteristics of Al–5Si–1Cu–Mg alloy produced by sand casting

Aluminum–Silicon (Al–Si) based materials are commonly preferred in engineering studies requiring high mechanical performance as an alternative to steel materials. These alloys are especially preferred in the automotive industry, aerospace components and heavy machinery parts. In post-casting processes, machining operations are of great importance for high geometric precision, surface quality and longer fatigue life in mechanical environments. In this research, the microstructural, mechanical and machining characteristics of the Al–5Si–1Cu–Mg material produced by sand casting method in both as-cast (AC) and heat-treated (HTed) (Solid solution, quenching and aging-SQA) states were experimentally investigated. Microstructural examinations were carried out with optical microscope and SEM images. Mechanical properties were determined by tensile and hardness tests. Then, drilling experiments were performed in the CNC vertical machining center with 8 mm diameter uncoated HSS (High Speed Steel) cutting tools at constant cutting conditions (i.e., cutting speed-V: 125 m/min, feed rate-f: 0.05 mm/rev and depth of cut-DoC: 15 mm). In microstructural investigations, it was determined that the microstructure of the Al–5Si–1Cu–Mg material in AC state consists of α-Al, eutectic Si, β-Fe (β-Al5FeSi) and π-Fe (π-Al8Mg3FeSi6) intermetallics. After the SQA, the existing phases generally exhibited a spherical structure, and it was seen that the β phase in the microstructure transformed into the Ɵ (Al7FeCu2) phase. SQA improved the hardness, yield and tensile durability of the material, whereas decreasing the elongation to fracture. SQA process improved the machining characteristics of the material by decreasing thrust force, moment, surface roughness and built-up edge (BUE) formation. The machined subsurface structure of HTed alloy under constant cutting conditions was determined to be more stable and smooth and the machined surface microhardness of HTed alloy was higher compared to as-cast alloy due to the effect of solid precipitation hardening. In addition, shorter and more broken chips occurred in the machining of HTed alloys due to the effect of low elongation to fracture.

Electromagnetic interference shielding, mechanical, and flame retardant behaviors of Ti3C2Tx-MXene/glass fabric epoxy hybrid composites

This study investigates the manufacturability and electromagnetic shielding effectiveness (EMI-SE) of Ti3C2Tx/MXene-coated glass fabric laminated composites for aerospace applications. MXene-coated fabrics were produced using a dip-coating method. The effects of varying dipping counts (5 and 10) and different configurations of fabric arrangements on the EMI-SE of the composites in the X-band range (8.2–12.4 GHz) were investigated. Glass fabrics with 5 and 10 dips showed average surface resistances of 38.56 Ω/sq and 23.17 Ω/sq, respectively. In both the 5- and 10-dip composite sets, the total EMI-SE increased with the number of MXene-coated glass fabric layers in the composite. The 5MXC5 and 10MXC5 specimens, with conductive fabric in all layers, had average total shielding effectiveness (SET) of −18.75 dB and −23.21 dB, respectively. These values are 147.05 % and 205.80 % higher than the neat glass fiber-epoxy composite (C1). Flammability, bending, ILSS, and hardness tests were conducted on these composites. Increasing the MXene content reduced the burning rate, with 10MXC5 exhibiting a 26.31 % lower burning rate compared to C1. However, higher MXene content slightly decreased bending and ILSS values. Optical microscope examination of the fracture surfaces revealed that this decrease was due to delamination damage.

Heat Treatment Optimization and Nitriding Effects on Mechanical Properties of 32CrMoV12-10 Steel

32CrMoV12-10 steel is widely utilized in industries where high strength and toughness are crucial. This alloy is commonly used in manufacturing components like gun barrels, gears, and bearings, which demand exceptional mechanical properties. These parts typically undergo heat treatments, including hardening and surface enhancement techniques such as nitriding, to extend their fatigue life significantly. It is crucial to identify optimal heat treatment conditions to achieve desired material performance. In this study, commercial 32CrMoV12-10 steel was selected to investigate the impact of heat treatment parameters (temperature, duration time, and quenching media) on its mechanical properties. To analyse the effect of these parameters, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and the Taguchi Method were employed, facilitating a systematic examination of the process stages and subsequent mechanical testing outcomes, including Charpy V-notch impact, hardness, and tensile strength assessments. An optimal heat treatment protocol was established based on these analyses, and the nitriding depth of the optimally treated sample was examined using a micro-Vickers hardness tester. For comparative analysis, another sample with closely related outcomes was also evaluated. Results indicated that the surface hardness of the optimally treated Sample 10 reached 870 HV, with a core hardness of 417 HV, compared to non-nitrided Sample 3, which showed a surface hardness of 860 HV and a core hardness of 415 HV. Despite the proximity in their values, Sample 10 exhibited slightly higher micro-Vickers hardness than Sample 3. However, while Sample 3 fails to meet the specified tensile stress and hardness criteria, Sample 10, produced through optimization, meets criteria, ranging from 970 to 1040 N/mm², underscoring the efficacy of the optimization process facilitated by TOPSIS. This optimization was notable for its minimal experimental requirements, proving effective in conserving time, energy, and resources while investigating the processed material.

Effect of nanoparticles reinforcement of silicon dioxide derived from prosopis juliflora on Silver-Grey magnesium nanocomposite: utilization of silicon dioxide mechanical and tribological properties

Abstract The automotive and aviation industries require lightweight materials to enhance working efficiency. Composites combine materials such as aluminium, magnesium, titanium, steel, and copper with various forms of reinforcements to offer lightweight alternatives for a range of applications. The present investigation aims to fabricate a Silver-Grey Magnesium (Mg-25%Si) alloy-based nanocomposite with silicon dioxide (SiO2) nano reinforcement at weight % of 0, 3.25, 6.5 and 9.75 utilizing the two step stir casting method. Prosopis juliflora is utilized in the production of different weight percentages of SiO2 nano reinforcements. The microhardness, tensile, wear, and impact tests are performed on the Silver-Grey Magnesium nanocomposites (Mg-25%Si/SiO2) utilizing a computerized tensometer testing machine, a Vicker’s hardness tester, a pin-on-disc tribometer, and an Izod impact, respectively. The x-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and Energy-dispersive x-ray spectroscopy (EDAX) with elemental mapping microstructure were employed to scrutinize the tensile specimen fracture, EDAX, elemental mapping microstructure, wear, CoF, and worn surface characterization and impact strength analysis. When compared to the Silver-Grey Magnesium (Mg-25%Si) base alloy, the results of the Mg-25%Si/SiO2 nanocomposites demonstrated an increase in SiO2 nano reinforcements that significantly increased microhardness, tensile strength, wear resistance, and impact strength. The corresponding values are 113.36 VHN, yield and ultimate tensile strength of 603.25 MPa and 665.84 MPa, 0.00478 mm3 m−1, CoF of 0.38421 and 400 J m−1.

Mechanical and Metallurgical Assessment of a Submerged Arc Welded Surfaced Rail

The surfaces of rails are often damaged during constant loading, so it is essential to repair the damaged areas in a railroad network to get the best performance. However, the traditional methods of improving rails are expensive, time-consuming, and require excessive effort. Therefore, some creative ideas would be helpful in this process, one of which may be on-site overlay arc welding instead of exchanging the whole part of the rail. In this paper, the performance of such a method is assessed experimentally, and its results are interpreted.For the investigation, a worn part of the 136RE rail, used in the freight railway network in the U.S., was chosen. After milling and flattening the surface of the rail, a submerged arc welding process was applied to rebuild this rail by utilizing a 1/8-in Lincore 40-S depositing wire. This study used four destructive tests: 1) XRD residual stress measurement, 2) SEM/OM analysis, 3) hardness test, and 4) tensile test. The results showed that the required mechanical strength could be achieved. However, the repaired area seems more vulnerable to the forces encountered on a railroad network due to the more brittle structure due to high temperatures in this region. Considering this flaw is critical because forces are primarily dynamic in railway networks, especially in heavy rails, which are higher due to the extensive use of freight trains.

Mechanical properties and galling resistance of API grade steels: A comparative study

Galling is a type of wear that affects the oil and gas industry causing loss of profits due to unexpected stops in the exploration and extraction process. In the present work, the galling resistance of three API grade steels (L80 type 1, T95 type 2, and P110) and one proprietary steel (125HC) used in the industry was evaluated by means of cross-cylinder tests. The surfaces were analyzed, and a Galling Tendency number was computed in order to rank the materials. Additionally, tensile and hardness tests were conducted to analyze the influence of the mechanical properties on galling. It was found that P110 exhibited the worst response and T95 the best one. For materials with the same ductility, an increase in strength is associated with higher galling resistance. A new index, based on the ductility and yield strength of the material, is proposed to predict the galling performance, demonstrating a strong correlation with the galling tendency.

Investigation of the hybridization effect of glass fibers and diboron trioxide epoxy composites on some mechanical properties

Abstract The mechanical behavior was most important in industry, and one way to enhance the mechanical properties involves preparing hybridized epoxy composites. Different additives (glass fiber and B2O3 powder) have various concentrations (0, 5, 10, 20, and 30% wt.) for B2O3, while glass fibers have a fixed concentration (10% wt.). Hybrid epoxy composites have been manufactured by the hand lay-up method. Mechanical investigations involve tensile tests, impact tests, and hardness tests. According to the results, increasing the boric oxide concentration increased the examined mechanical characteristics (strength, stiffness, strain-at-break, hardness, toughness, and fracture toughness). Hybrid materials with a weight percentage of 20% B2O3 and 10% glass fibers had the best mechanical properties. These findings are most likely due to the reinforcing elements being evenly distributed and scattered, which enhances mechanical characteristics. A slight decrease in the mechanical properties of the composite at 30% weight percentage of B2O3 and 10% glass fibers, which is related to the presence of voids and agglomerations, is thought to be a sign that the material has reached the saturation level of reinforcement and that the mechanical properties of the structure will collapse if more reinforcing materials are added.

Synthesis and characterization of 4-layered functionally graded Al-Al2O3 MMC

Functionally graded materials (FGMs) have a gradient of properties along their dimensions. These materials are resistant to delamination, making them ideal for replacing conventional composites in various fields of engineering. Among FGMs, aluminium-based FGMs are receiving a lot of attention due to their versatility. Al-Al2O3 FGMs, in particular, are widely preferred in the aerospace and automobile sectors. This study involves synthesizing a 4-layered FG Al-Al2O3 MMC through PM. The material is subjected to impact, compression, and hardness tests, to assess its mechanical properties. To understand the characteristics of the material, Optical microscopy, SEM, and XRD are carried out. The powder metallurgy route produces FG MMCs with improved properties. The material exhibited an impressive hardness of 183 HV at the top layer, which is higher than similar FGMs and FGMs fabricated via Centrifugal Casting. The compressive strength of Al-Al2O3 FGM is 138 MPa and the impact strength is 16.25 kJ/m2. Owing to the improved properties and FGMs being resistant to delamination mode of failure the study recommends the material as a replacement for conventional Al-Al2O3.

Dispersoid evolution in Al–Zn–Mg alloys by combined addition of Hf and Zr: A mechanistic approach

Coherent Al3X-type L12-structured dispersoids have the potential of effectively stabilizing the grain structure and increasing strength. This concept has been successfully demonstrated for non-hardenable and rapidly solidified Al alloys. In precipitation-hardened Al alloys, effective dispersoid addition requires both controlling their high-temperature stability and minimizing their impact on precipitation hardening. The current study focuses on dispersoid-modified AlZn5.0 Mg1.2 alloys, which exhibit MgZn precipitation upon age-hardening and include less than 1 wt% of Zr and Hf for dispersoid formation. Heat treatments between 350 °C and 500 °C for varying times were applied to evaluate dispersoid formation, thermal stability and the related strengthening potential. The microstructure was assessed using transmission electron microscopy (TEM) and atom probe tomography (APT), and the mechanical response was evaluated by hardness testing. TEM after heating at 500 °C reveals Ostwald ripening for the dispersoids. APT results on the dispersoids reveal a core–shell structure development upon longer annealing times. The Zr–Hf-modified alloy exhibits a higher initial strength than the Zr-modified alloy but the latter displays greater strength retention even after prolonged exposure to 500 °C. This effect is attributed to a destabilization of the mixed Zr–Hf dispersoids that arises from lower enthalpic benefits of Al3Hf formation over Al3Zr.

Enhancing the machinability and formability of tool steels through spheroidizing annealing heat treatment

This research focuses on enhancing the machinability and formability of tool steels by applying different heat treatment scenarios. Machinability is the process of cutting metals with the least energy effort, while formability is the ability of a metal to be shaped into different forms without severe damage. Enhancing machinability and formability improves dimensional tolerance and surface finish and increases the lifetime and reliability of tool steels. This research will use two tool steel materials, “D2” and “O1,” which are widely used in industry. They contain high percentages of carbon by weight (1.55% and 0.95%, respectively). The “O1” tool steel is used in blanking dies and room-temperature cutting tools, whereas the “D2” tool steel is used for carpentry cutting tools and gauges. The different heat treatment scenarios are based on the latest literature, which shows excellent results with other materials. The heat treatment plan is set to cover various scenarios to determine the most effective treatment for machinability and formability. The experimental work will include several mechanical tests: tensile tests, compression tests, hardness tests, and toughness tests. The conclusions regarding the different heat treatments will be based on the test results.

Influence of the material properties on the clinching process and the resulting load-bearing capacity of the joint

This study focuses on the phenomenological change in material strength caused by a specific heat treatment and the subsequent analysis of the influence on the clinching process and the resulting joint properties. For this purpose, three series of tests were performed. In the first series of tests, the influence of heat treatment up to 340 °C on the mechanical properties of an age-hardenable AlMgSi alloy was investigated. Holding time and temperature were varied and the material strength was evaluated by tensile and hardness tests. Two strength-increasing and two strength-reducing heat treatment parameters were identified. In the second series of tests, selected heat treatment parameters were applied to a larger number of specimens and the joint strength was investigated by shear and head tensile tests. In the shear tensile test, mainly the properties of the punch-side material have an influence on the resulting joint strength. A change in strength of the die-side material can be neglected. In contrast, the properties of both sheets are important in the head tensile test. The strength of the joint will only increase if the strength of both sheets is increased. In general, a strength increasing heat treatment resulted in higher joint strength. In the third series of tests, the factor of punch displacement was considered, which was demonstrated to directly influence the formation of the clinched joint geometry.

Failure of a tantalum lined tee induced by hydrogen embrittlement

A lined tee leaked a high temperature mixture of HCI gas and steam from the inner tantalum liner into the external carbon pipe. The main causes of failure have been proposed based on several analysis methods, including macroscopic examination, metallographic inspections, chemical composition analysis, hardness test, scanning electron microscopy analysis and energy dispersive spectrometry test. On the basis of experimental analyses, computational fluid dynamics simulations were employed to explore the flow fields of HCI gas and steam in pipelines. It was found that the failure region of the tantalum liner was coincidence with the mixture zone of two media. The root cause of failure was the formation of liquid hydrochloric acid during the start-up of equipment, causing that hydrogen ions in liquid hydrochloric acid penetrated into tantalum, resulting in hydrogen embrittlement cracks. Meanwhile, pitting corrosion was caused in mixing areas. Adjusting the structure of tee pipe from T-type to Y-type was put forward to prevent equipment failure.

Regulating hardness homogeneity and corrosion resistance of Al-Zn-mg-cu alloy via ECAP combined with inter-pass aging

The novel processing strategies of Equal Channel Angular Pressing (ECAP) combined with inter-pass aging was designed, and XRD, SEM, TEM, electrochemical testing, and hardness testing were used to evaluate the relationship between microstructure and performance of alloys in this work. The results indicate that the hardness uniformity of the circular cross-section perpendicular to the extrusion direction was improved by combining ECAP with inter-pass aging, resulting in a hardness inhomogeneity factor (~0.030) that was lower than that achieved by peak aging and double-stage aging alloys. Polarization curves and electrochemical impedance spectra show that a more negative corrosion potential and a smaller corrosion current density were possessed by the alloy, with the maximum intergranular corrosion depth (IGC) being reduced to 38 μm. Microstructure observation indicates that the improvement in hardness uniformity is due to the uniformity of grain size and the improved distribution and size of the η’ phase, which is attributed to the interaction between the pinning and shear effects of precipitates and dislocations during deformation. The enhanced corrosion resistance was attributed to an orderly combination of deformation and aging that increases the grain boundary volume and disrupts the η phase continuity within grain boundaries.

Fluorinated B-72 hybrid silver doped modified nanoparticle as a coating for biological corrosion protection of ancient bricks

In this paper, a superhydrophobic organic-inorganic composite coating containing fluorinated B72 hybrid methyl-modified silica/(Ag doped TiO2) by hexamethyldisilazane (HMDS) (H-SiO2/Ag/TiO2) was prepared by means of a mild and an environmental friendly method. Transparency, adhesion, hardness tests and photocatalytic performance were measured to determine the content of Ag in TiO2 which the TiO2/AgNO3 ratio is 0.008 g/mL. The synthesized Ag/TiO2 nanoparticles were characterized by X-ray diffraction (XRD), Raman spectra and transmission electron microscope (TEM). The highest contact angle of coated ancient bricks was 148.66° and the color change value of ΔE⁎ before and after coating was <5 which is within an acceptable range. The physical properties such as apparent porosity and water vapor permeability (ΔMp) were studied. After weathering from acid, alkali, salt, water and ultraviolet radiation, the bricks coated by the composite coatings still have good hydrophobicity that the contact angle were >120° and minor degree of surface corrosion comparing with the ancient bricks. The inhibitory effect of the composite coating on Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), and that on algae (Chlamydomonas and Dunaliella) were studied through bacteriostasis test and algae comparative experiments, respectively. Finally, the mechanism of the composite coating on antibacterial and anti-algae was studied. The results showed that the appearance of the ancient bricks was not changed after coating, and the anti-weathering, antibacterial and anti-algae properties of the ancient transformation were increased.

Sn and Cu influence on Mg:Si ratios evolution in clusters based on DFT and its impact on precipitation hardening of pre-aged Al-1.0Mg-0.6Si alloys

Using atom probe tomography (APT), transmission electron microscopy (TEM), and hardness tests, the effect of Sn and Cu on the evolution of Mg:Si ratios in clusters and subsequent precipitation hardening behavior of pre-aged Al-1.0Mg-0.6Si alloys are investigated, and the underlying mechanism is revealed by density functional theory (DFT) calculation of interaction energy. It is shown that, the doping of Sn and/or Cu increases the average Mg:Si ratio in clusters. This increase is attributed to the strong interaction of Sn/Cu with Mg solutes, which enhances the binding of Mg to Si-rich clusters and results in a higher proportion of clusters with Mg:Si ratios near 1 (0.75 ∼ 1.25). Consequently, the enhanced precipitation of β" precipitates during artificial aging is observed in Sn and/or Cu doped alloys, due to the ease of clusters with Mg:Si ratios near 1 transform into β" precipitates, leading to an improved hardening response. Notably, the combined doping of Sn and Cu exhibits the strongest aggregation tendency towards Mg solutes, yielding the most pronounced strengthening effects on precipitation and hardening response during artificial aging. Furthermore, a schematic model detailing the evolution of Mg:Si ratios in clusters is proposed, based on the APT results and DFT calculation of interaction energy.

Effect of Vinyl Acetate, Glass Fibers Contents, and Buffer Space on EVA's Mechanical Property and Shock Absorption Ability.

The aim of the study was to evaluate the mechanical properties and impact absorption capacity of prototype materials comprising ethylene vinyl acetate (EVA) of different hardness reinforced using different amounts of glass fibers (GFs), considering a buffer space. Six prototype materials were made by adding E-GFs (5 and 10 wt%) to EVA with vinyl acetate (VA) contents of 9.4 wt% ("hard" or HA) and 27.5 wt% ("soft" or SO). Durometer hardness and tensile strength tests were performed to evaluate the mechanical properties of the materials. Moreover, an impact test was conducted using a customized pendulum impact tester to assess the impact absorption capacity (with or without a buffer space) of the specimens. The mechanical properties of the prototypes, namely, durometer hardness, Young's modulus, and tensile strength, were significantly higher in the HA group than in the SO group, regardless of the presence or added amount of GFs. The addition of GFs, particularly in a large amount (10 wt%), significantly increased these values. In terms of the impact absorption capacity, the original hardness of the EVA material, that is, its VA content, had a more substantial effect than the presence or absence of GFs and the added amount of GFs. Interestingly, the HA specimens with the buffer space exhibited significantly higher impact absorption capacities than the SO specimens. Meanwhile, the SO specimens without the buffer space exhibited significantly higher impact absorption capacities than the HA specimens. Moreover, regardless of the sample material and impact distance, the buffer space significantly improved impact absorption. In particular, with the buffer space, the impact absorption capacity increased with the added amount of GFs. The basic mechanical properties, including durometer hardness, Young's modulus, and tensile strength, of the EVA prototype were significantly increased by reducing the amount of VA regardless of the presence or added amount of GFs. Adding GFs, particularly in large amounts, significantly increased the values of aforementioned mechanical properties. Impact absorption was significantly affected by the hardness of the original EVA material and enhanced by the addition of the buffer space. The HA specimen had a high shock absorption capacity with the buffer space, and the SO specimen had a high shock absorption capacity without the buffer space. With the buffer space, impact absorption improved with the amount of added GFs.