Vickers Microhardness Tester Research Articles

Study on microstructure and thermal shock resistance of plasma sprayed Cr2O3/8YSZ composite coating

In order to explore the high temperature performance of Cr2O3/8YSZ composite coating, four kinds of Cr2O3/8YSZ composite coatings were prepared on the surface of Q235 steel by using the plasma spraying technology (the content of 8YSZ is 50%, 30%, 20% and 0%, respectively). The morphology of the coating was characterized through thermal field emission scanning electron microscopy, and the distribution of elements in the section of the coating was scanned by using EDS line. The phase composition of the composite coating was analyzed by using X-ray diffractometer, and the surface roughness of the composite coating was measured by using surface profilometer. The microhardness of the coating was measured by using automatic micro-Vickers hardness tester, and the scratch resistance of the coating was compared by using scratch tester. The thermal shock resistance of the coating was tested in Gleeble-3800 thermal physical simulator, and the cross section morphology after thermal shock was observed and analyzed. The results show that when the ratio of Cr2O3 to 8YSZ is 7∶3, the sample coating has good thermal shock resistance due to the deflection effect of 8YSZ on the vertical cracks and the thermal stress release effect of the pores and cracks in the coating.

Behavior of free-standing atmospheric plasma sprayed Al2O3–Cr2O3 solid solution-based coatings under cyclic heating at 1000 °C

This paper investigates the cyclic heating behavior of free-standing atmospheric plasma sprayed Al2O3 - Cr2O3 coatings containing a solid-solution phase. The coatings are deposited on steels by spraying mechanically blended Al2O3 - Cr2O3 powder mixture with variable Cr2O3 content (2–6 wt%) in the feedstock. The tests are performed up to 50 cycles at 1000 °C temperature in a muffle furnace in a normal atmosphere. After each cycle, the weight gain of the coatings is measured, and the oxidation rate constant (Kp) for each material is estimated. The microstructure and phases of the coatings are studied by using scanning electron microscopy (SEM) and X-ray diffractometry (XRD) techniques respectively. The porosity and crack length are estimated by image analysis (Image J) technique. The hardness of the coatings is measured by Vickers microhardness tester. After 50 cycles, all the free-standing coatings are found to be intact without fragmentation. At higher cycles, the Al2O3 - Cr2O3 coatings form α-Al2O3 and (Al0.9Cr0.1)2O3 solid-solution phase only. The Al2O3 - Cr2O3 coatings gain much less weight than the pure Al2O3 coating due to the major presence of oxidation resistant α-Al2O3 phase in the former. However, among the Al2O3 - Cr2O3 coatings with an increase in Cr2O3 content, the Kp value tends to increase due to the high presence of metastable (Al1.8Cr0.05)2O3 solid-solution phase. On the other hand, the (AlxCr1-x)2O3 phase helps to reduce crack formation due to its high fracture toughness properties. With the highest amount of solid-solution phase content, the Al2O3-4 wt% Cr2O3 coating shows the highest fracture toughness among all. The micro-porosity of the coatings is increased with an increase in the heating cycle, and the coating hardness is reduced accordingly.

Investigation of the mechanical properties of lead-free Sn-58Bi solder alloy with cobalt addition through flux doping

PurposeThis study aims to investigate the effect of incorporating cobalt (Co) into Sn-58Bi alloy on its phase composition, tensile properties, hardness and thermal aging performances. The fracture morphologies of tensile-tested solders are also investigated to correlate the microstructural changes with tensile properties of the solder alloys. Then, the thermal aging performances of the solder alloys are investigated in terms of their intermetallic compound (IMC) layer morphology and thickness.Design/methodology/approachThe Sn-58Bi and Sn-58Bi-xCo, where x = 1.0, 1.5 and 2.0 Wt.%, were prepared using the flux doping technique. X-ray diffraction (XRD) is used to study the phase composition of the solder alloys, whereas scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are used to investigate the microstructure, fractography and compositions of the solders. Tensile properties such as ultimate tensile strength (UTS), Young’s modulus and elongation are tested using the tensile test, whereas the microhardness value is gained from the micro-Vickers hardness test. The morphology and thickness of the IMC layer at the solder’s joints are investigated by varying the thermally aging duration up to 56 days at 80°C.FindingsXRD analysis shows the presence of Co3Sn2 phase and confirms that Co was successfully incorporated via the flux doping technique. The microstructure of all Sn-58Bi-xCo solders did not differ significantly from Sn-58Bi solders. Sn-58Bi-2.0Co solder exhibited optimum properties among all compositions, with the highest UTS (87.89 ± 2.55 MPa) at 0.01 s−1 strain rate and the lowest IMC layer thickness at the interface after being thermally aged for 56 days (3.84 ± 0.67 µm).Originality/valueThe originality and value of this research lie in its novel exploration of the flux doping technique to introduce minor alloying of Co into Sn-58Bi solder alloys, providing new insights into enhancing the properties and performance of these solders. This new Sn-Bi-Co alloy has the potential to replace lead-containing solder alloy in low-temperature soldering.

Effect of shade and thickness on the microhardness of resin-based composite specimens at different points considering curing light beam’s inhomogeneity

BackgroundRecent studies have reported the inhomogeneity in the light emitted by dental light-curing units (LCUs). It is essential to understand how this uneven light distribution affects the physical properties of resin-based composites (RBCs) at various points across their surfaces. This study aimed to evaluate the effect of LCU beam’s inhomogeneity on the microhardness of RBCs with different shades and thicknesses.MethodsFour body (A1B, A2B, A3B, and A4B), one dentin (A3D), and one enamel shade (A3E) of RBC (Filtek Z350 XT) were examined. The specimens were fabricated in four thicknesses (1, 2, 3, and 4 mm) and subjected to a 40-second light-curing. Vickers microhardness testing was performed at the center point, and 3 mm left and right from the center at the bottom surface of each sample. The LCU beam profile was characterized using a beam profiler, while irradiance after specimen passage was measured using a spectrometer. One-way analysis of variance (ANOVA) and Tukey’s post-hoc tests were used to analyze the effects of shades and thicknesses on irradiance and microhardness, respectively. One-way repeated-measures ANOVA was used to compare the microhardness across different points. Pearson’s correlation analysis examined the relationship between irradiance and microhardness.ResultsThe beam profile of LCU revealed inhomogeneous light distribution. Light irradiance was decreased with both the increase in thickness and darker shade of the specimens (p < 0.05). Microhardness was found to decline with an increase in sample thickness (p < 0.05), and was consistently higher at the center point compared to the periphery, particularly in thicker (3 and 4 mm) and darker shades (A3B, A4B, and A3D). A positive correlation was found between the irradiance and microhardness across all evaluated points (p < 0.05).ConclusionsInhomogeneous light emission from LCU significantly influences the microhardness of RBC samples, depending on the thicknesses and shades. The findings underline the importance of considering LCU beam inhomogeneity in clinical settings to ensure optimal polymerization of RBC.

Effects of Different Zinc Content on Solidification, Microstructure, and Mechanical Properties in Tin–Bismuth Alloy

The present aims to evaluate the effect of adding Zn (0.5% and 9.0% in wt%) on phase transformation temperatures, microstructure coarsening, solidification parameters (cooling rate‐L and growth rate‐VL), macrosegregation, and mechanical properties of directionally solidified Sn‐34wt%Bi‐xZn alloys. The samples have been characterized by optical microscopy, scanning electron microscopy, X‐ray fluorescence, and X‐ray diffraction, in addition to Vickers microhardness and tensile tests. The CALPHAD method has been used for thermodynamic computations via Thermo‐calc software, in order to obtain thermodynamic data. The microstructure of Sn–Bi–Zn alloys is mainly dendritic, composed of a Sn‐rich matrix (β‐Sn) with Bi precipitates inside and surrounded by a Sn+Bi eutectic mixture of phases, predominantly observed at the coarse scale. Coarse Zn needles are also observed in the Sn‐34wt%Bi‐9wt%Zn alloy due to the high Zn content. On the whole, Zn provoked a coarsening of the dendritic arrangement. Moreover, Zn additions cause inverse segregation of Bi, as compared to the rather constant macrosegregation profile observed in the binary Sn–Bi alloy. On the whole, both additions of Zn (0.5 and 9.0) promoted increase in Vickers microhardness, yield strength (σY), and ultimate tensile strength (σu), however, causing an overall reduction in elongation‐to‐fracture (δ).

The cell membrane as biofunctional material for accelerated bone repair

The cell (plasma) membrane is enriched with numerous receptors, ligands, enzymes, and phospholipids that play important roles in cell-cell and cell-extracellular matrix interactions governing, for instance, tissue development and repair. We previously showed that plasma membrane nanofragments (PMNFs) act as nucleation sites for bone formation in vivo, and induce in vitro mineralization within 1 day. In this study, we optimized the methods for generating, isolating, and applying PMNFs as a cell-free therapeutic to expedite bone defect repair. The PMNFs were isolated from different mouse cell lines (chondrocytes, osteoblasts, and fibroblasts), pre-conditioned, lyophilized, and subsequently transplanted into 2 mm critical-sized calvarial defects in mice (n = 75). The PMNFs from chondrocytes, following a 3-day pre-incubation, significantly accelerated bone repair within 2 weeks, through a coordinated attraction of macrophages, endothelial cells, and osteoblasts to the healing site. In vitro experiments confirmed that PMNFs enhanced cell adhesion. Comparison of the PMNF efficacy with phosphatidylserine, amorphous calcium phosphate (ACP), and living cells confirmed the unique ability of PMNFs to promote accelerated bone repair. Importantly, PMNFs promoted nearly complete integration of the regenerated bone with native tissue after 6 weeks (% non-integrated bone area = 15.02), contrasting with the partial integration (% non-integrated bone area = 56.10; p < 0.01, Student's test) with transplantation of ACP. Vickers microhardness tests demonstrated that the regenerated bone after 6 weeks (30.10 ± 1.75) exhibited hardness similar to native bone (31.07 ± 2.46). In conclusion, this is the first study to demonstrate that cell membrane can be a promising cell-free material with multifaceted biofunctional properties that promote accelerated bone repair. Statement of significance•For the first time, the cell (plasma) membrane is used as material for bone repair.•The plasma membrane from chondrocytes promoted rapid bone repair within 2 weeks, with complete integration of the newly formed bone with the surrounding native tissue.•The plasma membrane from chondrocytes presented multifaceted effects, strongly promoting the attraction of macrophages, endothelial cells and osteoblasts to the healing site.

Evaluation of the cumulative effect of photodynamic therapy and local fluoride on the microhardness and topography of demineralized enamel and cementum surfaces

BackgroundThe present study aimed to determine the cumulative effect of two photodynamic therapy methods with methylene blue and indocyanine green and two topical fluoride therapy methods with fluoride varnish and silver diamine fluoride alone and in combination on the microhardness and topography of demineralized enamel and cementum surfaces. Materials and methodsSeventy-two sound human teeth were selected, and their buccal and lingual surfaces were assigned to two main groups of enamel and cementum using simple randomization. The initial surface hardness (SH) of the enamel and cementum in each sample was determined using a micro-Vickers hardness tester using a 200-g force in 10 s. Then artificial caries was induced by immersion in a demineralizing/remineralizing solution (i.e., each tooth provided two samples, one on the buccal aspect and the other on the lingual aspect). Each enamel/cementum main group was divided into two subgroups using simple randomization based on the local fluoride type (fluoride varnish and silver diamine fluoride) and the type of the photosensitizer agent (methylene blue and indocyanine green). Finally, 16 groups were achieved (n = 9). The final surface hardness of the enamel and cementum samples was determined as described above. Finally, the sample surfaces were prepared for the surface topography evaluation under a scanning electron microscope. The baseline microhardness was compared between the 16 study groups in the first step using one-way ANOVA. Then, three-way ANOVA was used to evaluate the effect of fluoride, laser, and surface (enamel and cementum) on microhardness. ResultsAll the groups exhibited decreased microhardness due to the induction of artificial caries. In both main groups of enamel and cementum, the lowest decrease in microhardness was recorded with combined photodynamic therapy and methylene blue photosensitizer material and fluoride varnish (15.1 % for cementum and 16.7 % for enamel), and the highest decrease in microhardness was recorded in the methylene blue group (35.7 % for cementum and 34.9 % for enamel). ConclusionThe combination of photodynamic therapy with the photosensitizer substance methylene blue or indocyanine green together with fluoride varnish or silver diamine fluoride is effective on the remineralization of demineralized enamel and cementum. Although there is no difference between the combination of photodynamic therapy with fluoride varnish compared to fluoride varnish alone, both of these treatments are more effective than using photodynamic therapy alone.

Studies on the physico-chemical properties of semi-organic nonlinear optical (NLO) material: 2-CPPC [2-CNPyH][ClO4]

Semi-organic NLO single crystals 2-cyanopyridinium perchlorate (2-CPPC) were successfully grown by the method of slow evaporation of solvent at room temperature (27 °C) by using acetone as a solvent and of dimension 15×12×3mm3. The powder X-ray diffraction (XRD) of the grown crystal has been investigated. The UV–vis study estimates the transmission range, refractive index, extinction coefficient, band gap, and reflectance of the grown 2-CPPC crystal. The fluorescence spectra of the grown crystal were also recorded. The presence of different functional groups and the vibrational modes were confirmed by using FTIR analysis. The crystal's mechanical properties were studied by a Vickers microhardness tester. Single beam Z-scan technique using He–Ne laser is used to study the third-order NLO properties.

Development of High Strength and Super Electrical Conductive Cu-3Ti-2Si-1.5Ni-xNb Alloys

The study explored the mechanical and electrical behavior of niobium-doped Cu-3Ti-2Si-1.5Ni alloys by Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), micro-Vickers hardness, and electrical conductivity tests. The stir-casted alloys underwent solution treatment at 900 °C/5 h and cooled in air. Results showed that niobium additions led to significant improvements in the properties of the parent alloy. The ultimate tensile strength, yield strength, hardness, and electrical conductivity reached maximum values of 528 MPa, 437 MPa, 358 HV, and 58.5 %IACS, respectively, at 1.1 wt% Nb addition. The enhancements were attributed to increased precipitation of second phases and refined grain structure. However, the percentage elongation decreased with niobium addition. These findings demonstrate that Cu-3Ti-2Si-1.5Ni alloys with niobium nanopowder exhibit a promising balance of mechanical and electrical performances, making them suitable for advanced engineering applications.

Effectiveness of chitosan nanoparticles, and novel chemical irrigants with surfactant on smear layer removal and microhardness alteration

ObjectiveThis current study was designed to compare and correlate between smear layer eradication and reduction in microhardness by natural 0.2%chitosan nanoparticles and novel chemical irrigants with surfactant at the apical root third. Materials and methodOne hundred and twenty straight single-rooted extracted lower premolars were decoronated and working length obtained with #10 K-file. Pro-taper rotary files were used till apical size F3. The canals were simultaneously flushed with assigned irrigant containing surfactant [(ChX-Ultra, NaOCl-Extra, Pro-EDTA, 0.2%chitosan nanoparticles, Biopure MTAD]. The samples were randomly divided into two equal groups (n = 60). InGroup S (n = 60), the residual smear layer was examined by scanning electron microscope and in Group M(n = 60) microhardness was determined by Vickers Microhardness Tester. Further both groups were divided into six equal groups (n = 10 each) according to assigned irrigating solutions.For smear layer removal; Kruskal-Wallis tests followed by pair wise comparison using Mann Whitney U test was done. For change in microhardness ANOVA and post hoc Tukey tests was done. ResultsMaximum smear layer removal was recorded in Biopure MTAD (1.8 ± 0.63), followed by pro-EDTA (2.2 0 ± 0.63) then 0.2%chitosan (2.6 ± 0.51), then NaOCL Extra (3.5 ± 0.53)and least in CHX-Ultra (4.4 ± 0.52) and saline (5.0 ± 0.00). Pro-EDTA group (12.8 ± 2.47) revealed significant highest reduction in microhardness followed by Biopure MTAD (8.01 ± 3.06), 0.2%chitosan nanoparticles (5.48 ± 2.87), NaOCl-Extra (5.44 ± 1.62) and least recorded in CHX-Ultra (4.94 ± 1.43) and saline (3.04 ± 0.63). ConclusionThe elimination of the smear layer is always accompanied by a reduction in microhardness. Moreover, irrigant with surfactant and chelators enhanced smear layer removal, with best perceived in Biopure MTAD.

Performance Analysis of U3Si2-Al Fuel with Density of 2.96 gU/cm3 and Burnup of 56%

Post-irradiation examination (PIE) of a low-enriched-uranium silicide fuel plate, irradiated in the Indonesian Reaktor Serba Guna–Gerrit Augustinus Siwabessy (RSG-GAS) multipurpose reactor, was successfully conducted. The objective of the PIE project was to evaluate the performance and integrity of the fuel under radiation exposure and, furthermore, to explore the potential for increasing the burnup level, enhancing its efficiency and effectiveness. The targeted fuel plate, identified as IDA0045, was extracted from the experimental silicide fuel element RI-SIE2, which had a burnup level of approximately 56% loss of 235U. A scanning electron microscope combined with energy dispersive X-ray spectroscopy microstructural examination and a Vickers microhardness test were conducted for the top, middle, and bottom sections of the fuel. The PIE results indicated minimal occurrence of fuel swelling and good fuel integrity under irradiation, suggesting the possibility of increasing the burnup level.

Effects of NaF versus SDF treatment on microhardness of artificial radiation caries at cervical and root areas.

This study aimed to compare the effect of silver diamine fluoride (SDF) and fluoride varnish (NaF) on the Vickers microhardness (VHN) of enamel and dentin after radiotherapy and pH-cycling. Human premolars were cut longitudinally, embedded and serially polished. The VHN of enamel/dentin and irradiated enamel/dentin were evaluated. The irradiated specimens were treated with either NaF or SDF, subjected to pH-cycling then VHN test for 4 days. Consequently, they were subjected to energy-dispersive X-ray (EDX) analysis. Radiation adversely affect enamel VHN (p<0.05), whereas dentin VHN was not affected (p>0.05). After pH-cycling, a significant decrease in dentin VHN was observed on day 2 for all groups, whereas enamel VHN was significantly decreased in the control group on day 4. SDF-treated enamel demonstrated higher VHN than that of NaF on day 3. Caries prevention effect of SDF and NaF were observed on enamel, where SDF was proved to be superior to NaF.

Effect of seawater salinity, pH, and temperature on external corrosion behavior and microhardness of offshore oil and gas pipeline: RSM modelling and optimization

This research aims to investigate the effects of seawater parameters like salinity, pH, and temperature on the external corrosion behaviour and microhardness of offshore oil and gas carbon steel pipes. The immersion tests were performed for 28 days following ASTM G-1 standards, simulating controlled artificial marine environments with varying pH levels, salinities, and temperatures. Besides, Field emission scanning electron microscopy (FESEM) analysis is performed to study the corrosion morphology. Additionally, a Vickers microhardness tester was used for microhardness analysis. The results revealed that an increase in salinity from 33.18 to 61.10 ppt can reduce the corrosion rate by 28%. In contrast, variations in seawater pH have a significant effect on corrosion rate, with a pH decrease from 8.50 to 7 causing a 42.54% increase in corrosion rate. However, the temperature of seawater was found to be the most prominent parameter, resulting in a 76.13% increase in corrosion rate and a 10.99% reduction in the microhardness of offshore pipelines. Moreover, the response surface methodology (RSM) modelling is used to determine the optimal seawater parameters for carbon steel pipes. Furthermore, the desirability factor for these parameters was 0.999, and the experimental validation displays a good agreement with predicted model values, with around 4.65% error for corrosion rate and 1.36% error for microhardness.

Effect of sliding speed and sliding distance on wear behavior of AZ31-B4C composite

Emphasis of current research is to investigate the dry sliding behavior of AZ31 magnesium alloy and AZ31–1.5B4C magnesium metal matrix composites (MMCs) at varying sliding speeds and sliding distances. Magnesium alloy and composite are fabricated through ultrasonic assisted stir casting method. Optical microscope (OM), scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDAX) are used to characterize developed materials. Microhardness of all materials is measured using a Vickers microhardness tester. Wear-friction behavior is investigated in dry sliding mode using pin-on-disc tribometer at room temperature. Magnesium alloy and composite are tested over a range of sliding speeds (0.25–1.25 m s−1) and distances at a moderate normal load (20N). Wear morphology is finally investigated for composites and alloy under SEM and EDAX. SEM micrographs of as-cast AZ31-1.5B4C composite reveals uniform distribution of B4C particles with noticeable refinement in grain structure. EDAX spectra of AZ31-1.5B4C composite depict the presence of boron and carbon along with existing elements of AZ31 alloy. Microhardness has enhanced around 30% for Mg-MMC by incorporating 1.5 wt% B4C in AZ31 alloy. Furthermore, the use of B4C as reinforcement increases the density of the composite. Wear rate is reduced by around 20% and COF is reduced by around 25% for AZ31-1.5B4C composite compared to AZ31 alloy for all experimental conditions. Abrasion, oxidation, adhesion and delamination wear mechanisms are observed as dominant mechanism for varying sliding speeds and distances.

Preparation and Characterization of Biowaste Derived Zn, Sr Co‐substituted HAP/Lignin Biocomposite for Potential Biomedical Applications

AbstractThis present study deals with the facile synthesis of Zinc (Zn), Strontium (Sr) Co‐substituted hydroxyapatite (M‐HAP)/lignin composite for biomedical applications. For composite formation, HAP was isolated from egg shell through wet precipitation method, biopolymer of lignin was extracted from neem wood through organosolve technique then HAP composites (HAP, HAP/lignin, Zn‐HAP/lignin, Sr‐HAP/lignin, Zn, Sr‐HAP/lignin) were obtained using freeze drying performance. The synthesized HAP composites were characterized using X‐ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy‐dispersive X‐ray analysis (EDAX). The antibacterial behavior of the HAP composites was investigated against E. Coli, B. Subtilies, P. Aeruginosa and S. Aureus pathogens. Then the mechanical property of the HAP composites was carried out using Vicker's microhardness test which reveals a better improvement in mechanical hardness. The antibacterial activity confirms that the HAP composite exhibits enhanced antibacterial activity. Further, the cell viability analysis shows that the co‐substitution of Zn and Sr in HAP lattice improved cell viability analysis, which indicates that the obtained Zn, Sr co‐substituted HAP/lignin biocomposite acts as a potential biomaterial for better biomedical application.

Sustainable microwave processing and surface characterization of powdered tungsten reinforced copper metal matrix (Cu-Wx) castings

The present work focuses on in-situ melting and casting of powdered copper metal matrix composites using a microwave hybrid heating approach. The composites of copper metal matrix are developed in such a way that the conductivity is least affected and related mechanical properties like flexural strength, tensile strength and hardness can be improved. Present work reports the processing and characterization of tungsten (W) powder reinforcement copper metal composites with weight percentages of W varied from 1%, 3% and 5%. The complete mechanism of interactions of Cu-Wx (x = 1%, 3% and 5% weight of copper powder) based composite powders with microwave heating is explained. The processed composite castings are characterized metallurgically through metallurgical microscope, SEM/EDS and XRD analysis; which reveals even dispersion of W particles in Cu matrix phase with some agglomerations. Some intermetallic formations are observed due to intense heating characteristics of microwaves. Further, mechanical and electrical characterizations of developed castings are carried out through Vicker's microhardness testing and electrical conductivity tests respectively. Addition of reinforced particles in metal matrix leads to an increase in microhardness on the expense of conductivity of composite. The 5% W addition led to 1.5 times increase in microhardness and 18.25% increase in resistivity. The mechanical testing revealed that the 5% W reinforced casting led to ∼22% higher ultimate tensile stress in comparison to pure copper casting. However, there was a significant decrease in ductility of metal matrix composites.

Investigation of the structural and magnetic properties of rapidly solidified Nd–Fe–B–Ce alloys

This study introduces the first literature report of rapidly solidified Nd–Fe–B–Ce alloys fabricated using the melt-spinning technique at varying disc rotation speeds. The resulting alloy images are then analyzed using various image processing techniques, and their structural and magnetic characteristics are described. The alloys are characterized using a variety of methods, including x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDX), differential thermal analysis (DTA), vibrating sample magnetometry (VSM), and Vickers microhardness tests. By using XRD, the tetragonal hard magnetic Nd2Fe14B phase is detected in the Nd30Fe65B0.9Ce5 alloy. The FE-SEM microstructure analysis shows that the grain structure of the ingot alloy is indistinct, and the tetragonal symmetric structure begins to appear at disc rotation speeds of 20 m/s and 40 m/s. The analysis of FE-SEM images using histogram analysis, the image segmentation technique, and VSM method reveals that the coercivity values of the sample produced at the 80 m/s solidification speed increased by approximately 34% when compared to the ingot alloy.

Effect of friction time on the mechanical properties of AA 6061-T6 continuous drive friction welded joints

Continuous drive friction welding (CDFW) is a solid-state method used to join solid cylindrical metals. This process involves several key parameters that influence the strength of the connection, including friction time, friction pressure, and machine speed. The aim of this research was to determine the effect of different friction times on the mechanical properties of Aluminium 6061 CDFW joints. Friction time variations of 2, 3, 4, 5, 6, 7, 8, 9, and 10 seconds were used in the welding process, while other parameters remained constant: friction pressure at 30 MPa, upset pressure at 70 MPa, upset time at 2 seconds, and engine speed at 1000 rpm. Microstructure observations, Vickers microhardness testing, and tensile testing were conducted to assess the impact of friction time on the joint results. Analysis of the microstructure revealed changes, such as recrystallization, in the joint area. It was observed that the grain size in the joint area was smaller compared to that of the heat-affected zone (HAZ) and the parent metal. Hardness testing showed a decrease in hardness value with increasing distance from the joint. In the tensile test, the highest tensile strength of 215.76 MPa was achieved with a friction time of 6 seconds, while the lowest tensile strength of 78.60 MPa was obtained with a friction time of 2 seconds

Mechanical properties of aluminum /SiC bulk composites fabricated by aggregate accumulative press bonding and stir-casting process

Today, the emergence of composite structures can be considered a huge transformation on an industrial scale, especially in the transportation industry. Among all the structures made by the composite process, aluminum-based composites (AMMCs) are particularly popular both in the scientific and industrial fields. These structures are very light in weight and, at the same time, have significant strength. The ability to work with the machine in these structures is very high, and their plastic deformation is so high that they can be used in different industry sectors. Today, various methods are used to induce plastic deformation in aluminum-based composites (AMMCs). One of these methods is called aggregate accumulative press bonding (APB). The advantage of this method compared to other methods is that this method can create a homogeneous nanocomposite with ultra-fine grains. In the present study, the investigation of mechanical properties (MP's) of AA5083/5%SiC bulk composites fabricated via APB vs. pressing temperature (Temp) was conducted. All primary composite samples were fabricated via the stir-casting process (SCP). APB process was done on composite samples as a supplementary process. Finally, the effect of pressing Temp on the MP and microstructural properties (MSP) was investigated. The pressing Temp was varied between the ambient Temp's up to T = 300 °C. The MP were measured in this study by the Vickers micro-hardness (VMH) test, tensile test, and scanning electron microscopy (SEM). It was realized that the pressing Temp has a prominent effect on the MS and MP of fabricated 400°C. Samples fabricated at the ambient Temp have low ductility and high strength while for samples fabricated at T = 300 °C, the elongation and toughness values were higher than others. The TS of samples after 2 steps of APB at T = 200°C is 1.31 times more than that of fabricated at T = 300°C. Elongation was reduced sharply to 1.8% after the two steps at the ambient Temp, while it was 21% for the annealed AA5083.

Impact of calcium hydroxide and 2-hydroxyisocaproic acid on the microhardness of root dentine: an in vitro study.

To evaluate and compare the effect of calcium hydroxide [Ca(OH)2] and 2-hydroxyisocaproic acid (HICA) on the microhardness of root dentine. Fifty-one matured maxillary central incisors with straight root and type I canal configuration were decoronated to a standardized length of 16mm. The root canals were cleaned and shaped using rotary instruments up to size F5. The tooth samples were then randomly assigned into three groups (n = 17) based on the intracanal medicament placed. Group A: control group with no intracanal medicament, Group B: root canals placed with Ca(OH)2, and Group C: root canals placed with HICA. After 1week, the intracanal medicaments placed within the root canals were removed and the canals were dried. Subsequently, the specimens were split longitudinally into two halves and subjected to the Vickers microhardness test with indentations made at the coronal, middle, and apical-third root regions. The data were analyzed using one-way ANOVA and Tukey's post hoc tests. The control group showed significantly highest microhardness value (P < 0.001), followed by HICA and finally, Ca(OH)2 at the coronal, middle, and apical-third root regions, respectively. Nonetheless, there were no statistically significant differences in microhardness values across different root regions within each group. HICA was found to have a significantly lesser reduction in root dentine microhardness which could be a potential alternative to Ca(OH)2. Nevertheless, future studies are warranted to verify the present outcomes in the clinical setting.