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This study examined the electrophoretic deposition (EPD) of titanium nitride (TiN) on AISI D2 tool steel, analyzing coating properties and TiN nanoparticle stability in the presence of polyethyleneimine as a dispersant in isopropyl alcohol. The parameters investigated were deposition time (5, 10, and 15 minutes), electric field strength (0.2, 0.5, 1, 1.5, and 2 V/m), and suspension concentration (0.2, 0.3, and 0.4 mg/L). Results indicated that a deposition time of 10 minutes with an electric field strength of 0.5 V/m and a suspension concentration of 0.2 mg/L provided optimal results in terms of thickness and micro-hardness. Higher deposition time led to increased thickness but decreased micro-hardness, while increasing electric field intensity for a constant deposition time led to increased deposition mass and thickness but lower quality at higher concentrations. Microstructural examination and micro-hardness testing confirmed these findings. [ABSTRACT FROM AUTHOR]

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Weld strength and quality are mostly affected by process parameters, which, in turn, influence the mechanical properties of weld metal and heat affected zone. In this research work, effect of electrode wire preheating on different responses including electrode wire melting rate, wire and plate melting efficiency, width of heat affected zone, microhardness, and corrosion rate of weld metal was studied. The experiments were carried out to accumulate the response data using the optimisation techniques. Then, the quadratic mathematical models were developed and checked the significance using the tests such as ANOVA, F-test and lack of fit. The preheat current is found to be the most contributing parameter, which efficiently enhanced the wire melting rate, wire melting efficiency and microhardness of weld metal whereas reduced the plate melting efficiency, heat affected zone (HAZ) width and corrosion rate. In addition, micrographs and micro-hardness results also confirmed the significant influence of preheat current. [ABSTRACT FROM AUTHOR]

Machining of electrically insulating ceramic materials has been a challenging task for ceramic industries. Assisted electrode method (AEM) based wire electrical discharge machining (WEDM) process emerged as an advanced option to machine insulating ceramics. This study deals with the machining of yttrium (Y2O3) stabilised zirconia (ZrO2) ceramic using copper (Cu) and stainless steel (SS) assisted electrode (AE) in presence of alumina (Al2O3) powder, ethylene glycol and demineralised water mixed dielectric fluid. The effect of different AE materials, pulse on time (TON), peak current (IP) on length of cut (LC), surface roughness (Ra), and average micro-hardness (MH) were investigated. Further, the comparison was made between minimum and maximum LC, and Ra (case-(i) and case-(ii)), respectively. SEM and EDS were carried out to analyse the surface characteristics and distribution of elements of the machined surface. Experimental results show that machining with SS AE at high levels of TON and IP provides high spark energy that results in higher value of LC (1300.910 µm), Ra (24.520 µm) and MH (1401.713 HV). Increasing TON and IP significantly increases the LC and Ra. Moreover, hardness near the lower junction was higher than the hardness near the upper junction and middle region of the machined surface. [ABSTRACT FROM AUTHOR]

In this study, the influence of the applying repeated thermal cycling during welding on the microstructural transformations and mechanical properties in Austenitic Stainless Clad-Steel Plates (ASCSP) has been investigated, particularly in the substrate. For this purpose, a novel methodology was used, by filling the entire groove length and gradually shortening the subsequent passes. Afterwards, microstructural characterization of different zones in the welded joint was conducted using optical microscope. Results showed a decrease in acicular ferrite (AF) in the Weld Metal Substrate (WM-S) from the root pass (10 kJ/cm) to the second pass (13.5 kJ/cm). This decrease continued until a total disappearance by the third pass due to a heat input of 17.8 kJ/cm. Vickers micro-hardness test was used to investigate the effect of the subsequent passes on the mechanical properties of the joint. Micro-hardness examination confirms the metallurgical results. It was revealed that micro-hardness variations are influenced by AF percentage and pro-eutectoid ferrite levels. [ABSTRACT FROM AUTHOR]

Public transport via trams has become increasingly important in daily life to meet the growing demand for economic and environmental considerations. In order to ensure the safety of the railway system and reduce service costs, it is necessary to understand the tribological behavior of the system. There are various types of damage such as fatigue, wear, and cracking that can harm the wheels and rails. To determine the wear mechanisms and identify the situations in which wear movements occur, it is crucial to monitor factors such as temperature, surface roughness, and contact micro-hardness between the wheel and the rail. The objective of this study is to analyze the tribological behavior and the impact of climatic conditions on the wheel–rail contact system in the desert area of the Ouargla tramway in Algeria. To achieve this, an intelligent sensor programmed by a microcontroller was utilized to measure the temperature of the wheel–rail contact. Additionally, a hardness tester was used to measure the micro-hardness of the rail, and a roughness tester was utilized to monitor the surface condition of the rail. The measured temperature values during the passage of the tramway varied between ambient temperature and a temperature of 450∘C. The micro-hardness values ranged from 270 Hv to 440 Hv, and the roughness values varied between 0.4 μ m and 2.7 μ m. [ABSTRACT FROM AUTHOR]

In this article, the effect of activating flux powders viz., Silicon Dioxide (SiO2), Chromic Oxide (Cr2O3), Titanium Dioxide (TiO2) and Vanadium Pentoxide (V2O5) on Flux-Bound TIG (FB-TIG) welding of UNS S32760 Super Duplex Stainless Steel (SDSS) is investigated. Also, conventional TIG welding is done for a comparative study with the FB-TIG welds. The macrographs of the welds are obtained to analyze the depth, width and aspect ratio. The depths obtained with all the fluxes are found to be superior relative to the conventional TIG welds. The highest penetration of 6 mm is obtained for V2O5 welds. Then the microstructure and composition of the welds are analyzed using Optical Microscopy and Area-Mapping analysis. The authors observed the presence of three forms of austenite viz., Grain Boundary Austenite, Intragranular Austenite and Widmanstatten Austenite in the weldment zones. The micro-hardness profiles of the welds are also analyzed, and the profiles obtained with all the FB-TIG welds are found to be relatively smoother without any abrupt variations. Through this investigation, it is delineated that FB-TIG welding can increase the overall productivity in the welding of SDSS, as the penetration obtained is up to thrice relative to the conventional TIG welding. [ABSTRACT FROM AUTHOR]

This study investigates how welding travel speed and spindle speed influence the quality of welds in 270 mm diameter AISI 316L stainless steel pipes joined through friction stir welding (FSW). The FSW process was performed with spindle speeds of 250 rpm and 300 rpm, and travel speeds of 50 mm/min and 100 mm/min, utilizing a PCBN-coated W–Re tool in position control mode. Axial force, spindle torque and penetration depth were evaluated. The microstructure was analyzed using an optical microscope to understand the effects of spindle and travel speeds. High-resolution microscopy was employed to identify variable grain sizes across different weld zones. Vickers micro-hardness tests showed higher hardness in the stir zone and adjacent thermo-mechanically affected regions. The joint welded at 300 rpm and 100 mm/min displayed the highest hardness in the stir zone at 254 HV, indicating grain refinement confirmed by microstructural evaluation. [ABSTRACT FROM AUTHOR]

The enhancement of nuclear and high-temperature applications largely depends on the cladding procedure for the composition of bimetallic sheets made of stainless steel. The current study presents a modified version of a unique experimental set-up for a perforated substrate sheet with ball-milled, nano-scale clad powder reinforcement. To create the clad material, Al2O3, SiC nano-sized grain powders and Mg coarse grain powder were combined with fine Al powder particles using a ball milling technique. In parallel, SS316L substrate sheets were utilised to fabricate bimetallic composite sheets and were perforated at regular intervals for a specific area. In an inert gas environment, a conventional heating process with mild initial compaction was offered for the sintering process to progress upon. The influence of the processing on the interfaces is suggested by the microstructure, energy-dispersive X-ray (EDX) and micro-hardness results from different sites in the synthesised bimetallic composite sheet. The processing methods and how they affect the diffusion behaviour of the clad intersection and perforation zone are described in depth in this experimental study. [ABSTRACT FROM AUTHOR]

In the present work, copper mould casting is used to prepare Ti-6Al-4 V alloy in the form of a cylindrical rod of dimension 7.5 mm ∅ × 33 mm L . Microstructural and grain size changes are observed in different regions along the length of the rod sample suggesting the influence of cooling rate during solidification. The present study is undertaken to investigate the microstructural changes in three different regions along the length of the sample. Cooling rates calculated using standard empirical method at different regions are found to be in the range of ~ 1.53 × 104–4.3 × 104 K/s. The obtained alloy is analysed using micro-indentation to determine the hardness. The present study also probes into the understanding of chemical interaction among the participating elements resulting in bond formation to explain the micro-segregation effect. Grain size variation is observed in the range of 149–411 µm within the same rod sample along the longitudinal direction. This study helps to understand the formation of graded microstructure in Ti-6Al-4 V useful in load-bearing applications. [ABSTRACT FROM AUTHOR]

The present work deals with the relationship between the degree of cold plastic deformation (up to 55.3% in the neck area in the tensile test and up to 66.6% in the compression test) and the parameters of the Indentation Size Effect (ISE). The tested material consists of 97% wrought copper. The Hanemann tester (Carl Zeiss, Jena, Germany) was used to measure micro-hardness. The loads applied during the micro-hardness test were between 0.09807 N and 0.9807 N. The influence of the load on the degree of the micro-hardness and simultaneously on the ISE, expressed by the Meyer's index n, was significant. The influence of load on the ISE parameters was also evaluated using the Meyer's index n, the PSR method, and the Hays–Kendall approach. For the undeformed sample, the Meyer's index was close to 2, with the increase in the degree of tensile and compressive deformation increasing its "reverse" character (n > 2). [ABSTRACT FROM AUTHOR]

In recent years, the industry has demanded high hardness, wear resistance, corrosion resistance, and other properties for critical components made of steel and its alloys. Enhancing the surface properties of a part by applying modification techniques to its surface is considered to be an economical and efficient method. Laser hardening, as a new surface modification technology, has received more and more attention due to its high hardening efficiency, fast cooling rate, and excellent surface properties. Laser hardening technology has good application prospects in surface modification, and significant progress has been made in the exploration of laser hardening strengthening mechanisms, optimization of process parameters, high-quality preparation of hardened layers, and theoretical simulation. However, some problems need to be addressed in the practical application of the technology. This paper reviews the research progress of the laser surface hardening process for steel and its alloys, including numerical investigation, process optimization, hardening performance analysis, and external field-assisted laser hardening technology. It also discusses the problems and challenges faced by the technology and gives an outlook on its development trend. [ABSTRACT FROM AUTHOR]

Nano-ferrites of Cu1–xNixFe2O4 (x = 0 to 1 with step 0.2) system was synthesized utilizing the flash auto combustion process annealed at 600oC for 3 h. The structural characterization for synthesized samples was carried out using x-ray Diffraction (XRD), Fourier transition infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The hardness of the prepared material was measured using micro-indentation creep technology. XRD pattern verified the creation of a single-phase cubic spinel structure. The undesired CuO phase forms around for pure Copper ferrite and decreases with increasing Ni content. The average crystalline size decreases from 27.92 nm to 13.28 nm by doping process from x = 0.2 to x = 1 which retards the growth of crystalline size. FTIR spectra are distinguished by the presence of two prominent absorption bands, ν2 for the octahedral site and ν1 for the tetrahedral site, in the range of approximately 593 and 471 cm− 1, respectively. FTIR analysis verified the formation of the ferrite system's spinel structure. The TEM images show a nanocrystalline nature with some agglomeration and the crystallites are spherical in shape which their sizes are agrees well with that obtained from XRD measurements. The hardness decreases as the dwell time increases. The hardness and yield strength (Y) values were significantly improved due to the decrease in the crystallite size after Ni doping. The stress exponent (n) value increases by increasing Ni content which means that the mechanical properties improved due to increment of resistance. [ABSTRACT FROM AUTHOR]

An investigation into the optical and mechanical properties of a novel borate glasses with the chemical composition of 70 B2O3-10 Li2O-10ZnO-5Bi2O3-5CaO-xEu2O3 was conducted. The glassy specimens of Eu3+-doped borate were prepared by the melting-quenching technique. An enhanced density from 3.0860 to 3.2176 g cm−3 and reduced molar volume from 29.27819 to 29.17447 (cm3 mol−1) are the outcome of increasing the concentration of Eu3+ in glasses. Plotting the extinction coefficient, dielectric constant (ε1, ε2), and refractive index (n) against wavelength reveals that they all rise as level of Eu3+ elements in the glass lattice increases. An increase in Eu3+ concentration results in a decrease in both the volume (VELF) and surface (SELF) energy loss functions. Also, all elastic-mechanical moduli (such as Young's, Bulk, Shear, and Elongation) increase with increasing the quantity of Eu3+ ions in the glass lattice. The Young's modulus (Y, GPa) of the glassy specimens was 34.512, 36.089, 36.504, 36.730 and 37.114 GPa for x equal 0, 0.25, 0.5, 0.75 and 1 mol ratio in the glass system, and coded by Eu-0.0, Eu-0.25, Eu-0.5, Eu-0.75 and Eu-1.0, respectively. Growing Eu2O3 levels resulted in an increase in Micro-Hardness from 2.050 to 2.146 GPa. Poisson's ratio values for Eu-0.0, Eu-0.250, Eu-0.5, Eu-0.75 and Eu-1.0 were 0.273, 0.275, 0.277, 0.277 and 0.278, respectively. [ABSTRACT FROM AUTHOR]

In the present global scenario, manufacturing industries are trying to make the process more sustainable by improving economic feasibility, machining efficiency, environment, and operator's safety as prescribed by ISO-14000 standards. The present study investigates the machining efficiency and sustainability analysis of the single wall carbon nano tube (SWCNT) mixed rotary electric discharge machining (EDM) process by utilizing waste vegetable oil (WVO) as a dielectric medium. Peak current, pulse on time, pulse off time, powder concentration, and tool rotation are taken as an input variable. The result reveals that SWCNT mixed rotary EDM utilizing WVO as a dielectric fluid exhibit 119.91% higher material removal rate (MRR) and 61.23% lower surface roughness (SR) as compared to the EDM process using EDM oil as a dielectric medium. Further, due to the superior thermo-physical properties of WVO, the proposed dielectric shows better surface morphology, lower recast layer thickness, better wear resistance, and low micro-hardness of machined surface as compared to EDM oil. Finally, the sustainability index analysis result concludes that WVO could be a better replacement of hydrocarbon-based oils in the EDM industry to make the process more sustainable in terms of cost, performance, ecological balance, and operator's safety. [ABSTRACT FROM AUTHOR]

Nano-ferrites of Cu1–xNixFe2O4 (x = 0 to 1 with step 0.2) system was synthesized utilizing the flash auto combustion process annealed at 600oC for 3 h. The structural characterization for synthesized samples was carried out using x-ray Diffraction (XRD), Fourier transition infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The hardness of the prepared material was measured using micro-indentation creep technology. XRD pattern verified the creation of a single-phase cubic spinel structure. The undesired CuO phase forms around for pure Copper ferrite and decreases with increasing Ni content. The average crystalline size decreases from 27.92 nm to 13.28 nm by doping process from x = 0.2 to x = 1 which retards the growth of crystalline size. FTIR spectra are distinguished by the presence of two prominent absorption bands, ν2 for the octahedral site and ν1 for the tetrahedral site, in the range of approximately 593 and 471 cm− 1, respectively. FTIR analysis verified the formation of the ferrite system's spinel structure. The TEM images show a nanocrystalline nature with some agglomeration and the crystallites are spherical in shape which their sizes are agrees well with that obtained from XRD measurements. The hardness decreases as the dwell time increases. The hardness and yield strength (Y) values were significantly improved due to the decrease in the crystallite size after Ni doping. The stress exponent (n) value increases by increasing Ni content which means that the mechanical properties improved due to increment of resistance. [ABSTRACT FROM AUTHOR]

The primary design property necessary to ensure the longevity and durability of manufactured materials is the material hardness. The primary objective of this study was to investigate the effect of cutting parameters, namely feed rate, cutting speed, and depth of cut, on the surface hardness generated during the turning process of aluminum alloy 6061. The turning experiments were conducted using a Taguchi L27 orthogonal array arranged for three-level cutting parameters. The Analysis of Variance (ANOVA) was employed to determine the relative importance of each parameter on surface hardness. Additionally, an Artificial Nural Network (ANN) predictive model using the back-propagation learning algorithm was created to predict surface hardness levels at each level of the cutting parameters. The results revealed that increasing the values of all the turning parameters resulted in an increase in hardness, and it was concluded that the feed rate was the most critical factor (53.41%) in achieving high surface hardness, followed by the depth of cut (27.89%), whereas cutting speed had a lower impact (18.7%). This study also suggests a simple equation for estimating the surface hardness from the cutting parameters. The ANN model could accurately estimate the surface hardness with a coefficient of correlation (R) higher than 0.98 between the predicted and experimental values. The predicted values of hardness by ANN were more precise (R² =0.973839) than those predicted by ANOVA (R²=0.893). [ABSTRACT FROM AUTHOR]

Abstract An investigation into the optical and mechanical properties of a novel borate glasses with the chemical composition of 70 B2O3-10 Li2O-10ZnO-5Bi2O3-5CaO-xEu2O3 was conducted. The glassy specimens of Eu3+-doped borate were prepared by the melting-quenching technique. An enhanced density from 3.0860 to 3.2176 g cm−3 and reduced molar volume from 29.27819 to 29.17447 (cm3 mol−1) are the outcome of increasing the concentration of Eu3+ in glasses. Plotting the extinction coefficient, dielectric constant (ε1, ε2), and refractive index (n) against wavelength reveals that they all rise as level of Eu3+ elements in the glass lattice increases. An increase in Eu3+ concentration results in a decrease in both the volume (VELF) and surface (SELF) energy loss functions. Also, all elastic-mechanical moduli (such as Young’s, Bulk, Shear, and Elongation) increase with increasing the quantity of Eu3+ ions in the glass lattice. The Young’s modulus (Y, GPa) of the glassy specimens was 34.512, 36.089, 36.504, 36.730 and 37.114 GPa for x equal 0, 0.25, 0.5, 0.75 and 1 mol ratio in the glass system, and coded by Eu-0.0, Eu-0.25, Eu-0.5, Eu-0.75 and Eu-1.0, respectively. Growing Eu2O3 levels resulted in an increase in Micro-Hardness from 2.050 to 2.146 GPa. Poisson’s ratio values for Eu-0.0, Eu-0.250, Eu-0.5, Eu-0.75 and Eu-1.0 were 0.273, 0.275, 0.277, 0.277 and 0.278, respectively.

BACKGROUND: Micro-abrasion, at-home whitening combined with infiltration resin have a good effect on dental fluorosis, but the effect of this method on micro-cracks in dental fluorosis is still unclear. OBJECTIVE: To explore the effect of micro-abrasion, at-home whitening combined with infiltration resin on micro-cracked dental fluorosis. METHODS: (1) Clinical research: A total of 23 patients with micro-cracked dental fluorosis, including 255 micro-cracked dental fluorosis, were selected from July 2020 to March 2021 in the Department of Prosthodontics, Stomatology Hospital, Tianjin Medical University. All of them received combined treatment of tooth micro-abrasion, at-home whitening and infiltration resin. The tooth color, tooth sensitivity, and tooth pain threshold were compared before treatment and 1 week and 1 month after treatment. (2) In vitro experiment: 60 teeth with fluorosis with at least one crack on the tooth surface were collected and randomly divided into three groups for treatment. The control group was treated without any treatment. The whitening group was treated with micro-abrasion and at-home whitening, and the combined group was treated with micro-abrasion, at-home whitening, and infiltration resin, with 20 teeth in each group. The microhardness of the three groups of teeth samples after treatment was measured. RESULTS AND CONCLUSION: (1) Clinical study: 6 months after treatment, among 255 teeth with micro-cracked dental fluorosis, whitening treatment for 207 teeth was significantly effective and whitening treatment for 48 teeth was effective, and the overall treatment efficiency was 100%. With the extension of treatment time, the proportion of moderate and severe dental sensitivity showed a decreasing trend. At 6 months after treatment, 255 teeth with dental fluorosis had no severe sensitivity, 15 with moderate sensitivity, 125 with mild sensitivity, and 115 with no sensitivity, and the difference was significant compared with the sensitivity before treatment (P < 0.05). There was no significant difference in the threshold of tooth pain before treatment and 1 week and 6 months after treatment (P > 0.05). (2) In vitro experiment: The tooth microhardness of the whitening group was lower than that of the control group and the combined group (P < 0.05), but there was no significant difference between the control group and the combined group (P > 0.05). (3) The results show that the methods of micro-abrasion, at-home whitening combined with infiltration resin have good clinical efficacy in the treatment of micro-cracked dental fluorosis. [ABSTRACT FROM AUTHOR]

This study examines the impact of both constant and pulsed current on the tensile characteristics, micro-hardness of weld surface, and metallurgical properties of the Inconel 718 and SS316L weldments. The Tungsten Inert Gas (TIG) welding process utilized two distinct arc modes to combine incompatible metals. The pulse frequency was systematically adjusted within the range of 2 Hz–6 Hz in order to investigate its impact on the welding parameters. A tensile test was performed using a universal testing equipment under various temperature conditions, including room temperature and an elevated temperature of 350 °C. When the samples were welded at a frequency of 4 Hz, both the Ultimate Tensile Strength (UTS) and Yield Strength (YS) were greater compared to when the samples were welded at 2 Hz, 6 Hz, or a continuous arc mode. Furthermore, it was noted that the YS-to-UTS ratio was higher for the weldments produced at 4 Hz pulse frequency. The UTS of current and pulsed (4 Hz) modes at a temperature of 350 °C were determined to be 505 and 524 MPa, respectively. Pulse welding demonstrated a higher hardness number compared to steady welding due to the regulated rate of heat. The TIG weldments of Inconel 718 and SS316L demonstrated superior mechanical and metallurgical qualities when exposed to elevated temperatures. The practical implications of these findings are relevant to the fabrication of turbine discs and shafts.

In this investigation, rolled plates of AZ31 Mg alloy were successfully friction-stir welded. It was found that the process leads to the microstructural refinement in the NZ due to the dynamic recrystallization with a global microstructural heterogeneity through the weld. The maximum microhardness values were attributed to the finest microstructure. The obtained results revealed that the cathodic behavior of the grain boundaries improves the corrosion resistance of the NZ. Thus, the corrosion resistance enhancement was ascribed to the most homogeneous microstructure and the finest grains.

Transient liquid phase (TLP) bonding was used to bond an IN939 superalloy utilizing a traditional, two-step heating process. The bonding process was carried out using BNi-2 foil with a 70-µm thickness as the interlayer in the first step at 1160 °C for 1 min and then at 1120 °C for different isothermal solidification times (50, 65, 80, and 95 min) in the second, also at 1120 °C for 80 min in conventional TLP bonding under vacuum furnace at a pressure of 10-5 torr. All the bonded specimens are then subjected to heat treatment and examined before and after heat treatment. A single-phase (isothermal solidification) was generated at the centerline after 80 minutes using a two-step technique. Due to insufficient bonding times, eutectic-products consisting of (gamma solid-solution), (Cr rich-boride), and (Ni rich-boride phases) formed in the centerline. The diffusion-affected zone also contained blocky- and needle-shaped boride precipitates in addition to the eutectic phases. The Vickers micro-hardness, and shear tests were done on the joints to evaluate their mechanical quality. The duration of isothermal solidification was shortened by using two-step TLP bonding. The hardness profile across the bond area was better than the conventional method and became more uniform after the heat treatment, and the shear strength was 631 MPa, and became 885 MPa after heat treatment, while about 479 MPa with the conventional TLP after heat treatment for the specimen with the isothermal solidification time of 80 min. After being subjected to a two-stage post-bond heat treatment, the microstructure becomes close to the base metals, as a result, a homogenizing microstructure forms across the joint. With increased bonding times, all of the bonds' shear strengths increased, and the hardness distribution across the bond area was better than the conventional technique and following the heat treatment, became more uniform. The bond shear strength was enhanced after the heat treatment because a significant γ-'phase developed in the bond area. [ABSTRACT FROM AUTHOR]

In today's living environment, employing green, clean, and sustainable energy to produce each kind of product is a necessity. The use of microwaves in the processing of materials has grown more prevalent in recent years. In this research, we theoretically and practically investigate the heating characteristics of a charge (Al-7075 alloy) in a microwave environment since microwave technology has numerous benefits that directly safeguard many factors linked to the environment. Microwave in-house setups at 2.45 GHz and 2.4 kW are used for in-situ charging. In-situ pouring of charge into the mould cavity is done for 15 min at melting temperature. The COMSOL Multiphysics 5.6 version is used to model and heat the charge using the finite element approach. With a maximum inaccuracy of 7.24%, the simulated heating curve for 15 min of microwave exposure agreed well with the actual heating curve of charge in the time temperature plot. Al-7075 alloys were characterized both in their as-received and as-cast states. Corrosion resistance qualities of the as-cast Al-7075 alloy was found to be superior to those of the as-received alloy, with a microhardness value that was 8% higher. [ABSTRACT FROM AUTHOR]

This study proposed the dynamic modeling and control strategy for GMAW and FCAW processes using two parallel-connected inverters in the power supply to weld an HSLA X70 steel pipeline using short-circuiting and spray transfer modes. The obtained results showed a great similarity between the welding current and voltage of the simulation model and the experimental process. A novel technique, the single-sided enveloped spectrum (SSES), proved highly efficient in estimating droplet detachment frequency (DDF). Mesh area calculations confirmed the high arc stability due to optimized welding parameters. The microstructure of a GMAW pass consisted primarily of coarse acicular ferrite, Widmanstätten ferrite, and polygonal ferrite, with minor traces of bainite. In contrast, the FCAW passes exhibited a wider variety of ferrite morphologies. Grain boundary ferrite (GBF) morphology was prevalent, while the capping passes showed a distinct feature: very fine grains of bainite and acicular ferrite. Vickers micro-hardness measurements revealed a significant reduction in hardness within the Heat Affected Zone and Weld Zone of the GMAW process, down to approximately 180 ± 5 HV. Conversely, the capping pass exhibited the highest micro-hardness, reaching around 230 HV. This increase is attributed to the presence of a fine, columnar microstructure composed of Widmanstätten and polygonal ferrite. [ABSTRACT FROM AUTHOR]

Titanium (Ti) and its alloys are frequently employed in the biomedical industry because they have a high corrosion resistance in addition to being lightweight, non-toxic, and having excellent biocompatibility. In this work, the microstructure and some required properties were evaluated for binary Ti-15Zr alloy produced by powder metallurgy (PM) for biomedical applications; the obtained results were also compared to that of commercially pure Ti (CP-Ti). The major goal of this paper is to study the impact of Zr addition on the microstructure, micro-hardness, and corrosion resistance of Ti alloy.

The present experimental work is carried out on SAE 420 steel to optimize process parameters of low-power laser hardening to improve surface micro-hardness and wear resistance for dry sliding for bio-medical applications. Laser power is the most significant factor for micro-hardening and wear resistance. Rank two for scanning speed and three for standoff distance, respectively. The experiments show that the surface micro-hardness of treated samples varies from 711 to 833 Vickers Pyramid Number by optimized process parameters such as laser beam power of 300 W, laser scan speed of 1.0 mm/s, and standoff distance of 225 mm. In comparison, the base material micro-hardness is 208 Vickers Pyramid Number as the predictive equation generated for finding micro-hardness value for the above three laser hardening process parameters. The dry sliding wear test is conducted on all laser-treated samples and a comparison is made with the untreated sample. A significant improvement in wear resistance was observed for treated as compared to untreated samples. The wear of laser hardened sample of SAE 420 steel was 3.67 x10-9 g/cm compared to untreated base metal wear rate of 139.00 x 10-9 g/cm at an applied load of 30 N and sliding speed of 300 revolutions per minute. The scanning electron microscopy analysis of wear samples (untreated, treated maximum, and minimum hardness) is observed for investigating material removal patterns.

This research aims to analyze the welding of 1 mm thick NiTinol sheets using an autogenous double pulse tungsten inert gas (DPTIG) welding process. The effect of heat input (HI) on bead geometry, microstructure, hardness, tensile strength, phase transformation temperature (PTT), and corrosion behavior was studied. The lower (111.25 J/mm), and higher (120.14 J/mm) HI produced an average grain size of 26 μm and 36 μm, respectively. The microstructure of the fusion zone (FZ) had coarser columnar grains with intermetallic phases such as Ni3Ti, and TiO2. The grain size in the FZ increased with the increase in HI. Sample P (111.25 J/mm) showed a higher hardness of 280.54 HV and tensile strength of 566 MPa due to a higher proportion of austenite phase (99.4%), the smaller grain size of 26 µm, a larger fraction of high angle grain boundary (HAGB) of 75.8%, and higher kernel average misorientation (KAM) value of 4.93. Compared to base metal (BM), sample P (111.25 J/mm), and sample S (120.14 J/mm) exhibited a reduction in tensile strength of 19.14% and 32.29%, respectively. The decline in hardness and tensile strength was attributed to the formation of intermetallic phases, a decrease in the Ti/Ni ratio, coarser grain formation, and a decrease in HAGB fraction and KAM values. The fractured tensile samples showed a mixed mode of fracture with dimples and cleavage facets. Compared to BM, Sample Q (118.05 J/mm) exhibited lesser variation in temperature hysteresis values for austenite and martensite temperatures, with a deviation of 0.4°C and 3.1°C, respectively. All the welded samples had better corrosion behavior than the BM due to a higher Ti/Ni ratio. [ABSTRACT FROM AUTHOR]

LIn this research, a new technique for severe plastic deformation (SPD) was proposed, entitled as non-uniform simple shear extrusion (NUSSE). The larger strains can be obtained in the non-uniform simple shear extrusion (NUSSE) method without repetition of the process. But, in pure shear extrusion (PSE) and simple shear extrusion (SSE) processes, to achieve larger strains, it is necessary to repeat the processes. In this study, the technique was investigated experimentally and numerically using ABAQUS software. The maximum plastic strain, inhomogeneity in deformation, filling frac- tion and micro-hardness parameters were researched after NUSSE process. Also, the obtained results were compared to the SSE and PSE processes. After this technique, due to the specific design of deformation channel, filling fraction was increased by about 44.92% and 41.84% in comparison with SSE and PSE processes, respectively. Also, the micro-hardness was significantly increased compared to annealing process. [ABSTRACT FROM AUTHOR]

This work aims to study the influence of heat treatment on the microstructure of laser metal deposited multi-layered Inconel 718 alloy. As-deposited samples were subjected to standard heat treatment, and the resulting microstructure and mechanical properties are studied. When observed under optical microscope and scanning electron microscope, the microstructure revealed microstructural homogenisation. In this case, the grain morphology shows that Nb-rich Laves phase in as-deposited sample is converted to small irregular granules in post heat treatment. The main finding of this study is that after heat treatment, the continuous bands of Nb-rich Laves phase are dissolved into small patches, as observed in elemental mapping through Energy Dispersive Spectroscopy. Also, Nb and Ti are distributed uniformly in the microstructure forming γ´ (Ni3Ti) and γ´´ (Ni3Nb) strengthening precipitates in Ni matrix. The precipitates developed has resulting in 50–60% higher hardness (419 HV) in the heat-treated sample compared to as-deposited sample. [ABSTRACT FROM AUTHOR]

Additive mixed friction stir welding can be an innovative and novel method for enhancing the friction stir welding process. Thus, this research aimed to investigate nano Al2O3 effects on the mechanical and microstructure of FSWed joints using Al alloys AA2024-T351/AA7075-T651. The experiments were performed based on response surface approach based CCD twenty run with varying three factors: tool rotational speed (A: 800-1,200 rpm), welding speed (B: 20-60 mm/min), tool plunge depth (C: 0.2-0.4 mm) and fixed volume percentages of Al2O3 nano-particles (8%). Mechanical performances such as tensile, yield, and hardness tests have been performed and microstructural properties have been analyzed through SEM and microscopy. The statistical analysis shows that the tensile strength can be significantly affected by rotational speed (A), welding speed (B), tool plunge depth (C), interaction (AB, BC, AC), and quadratic term A², B² in the FSW process; yield strength was influenced considerably by main, interaction, and quadratic terms; main factors and quadratic terms A², B² and C² significantly influenced hardness values. The fracture test revealed that the joints with Al2O3-reinforced AA2024-T351/AA7075-T651 alloys were more ductile and less brittle. The optimal conditions for FSW, tool rotational at 1,146 rpm, weld speed at 60 mm/min, and 0.4mm plunge depth were responsible for higher tensile strength of 169 MPa, yield strength of 145 MPa, and micro-hardness values of 89 HRB due to the uniform nano-particle dispersions and better material mixing. [ABSTRACT FROM AUTHOR]

The automobile industry relies primarily on spot welding operations, particularly resistance spot welding (RSW). The performance and durability of the resistance spot-welded joints are significantly impacted by the welding quality outputs, such as the shear force, nugget diameter, failure mode, and the hardness of the welded joints. In light of this, the present study sought to determine how the aforementioned welding quality outputs of 0.5 and 1 mm thick austenitic stainless steel AISI 304 were affected by RSW parameters, such as welding current, welding time, pressure, holding time, squeezing time, and pulse welding. In order to guarantee precise evaluation and experimental analysis, it is essential that they are supported by a numerical model using an intelligent model. The primary objective of this research is to develop and enhance an intelligent model employing artificial neural network (ANN) models. This model aims to provide deeper knowledge of how the RSW parameters affect the quality of optimum joint behavior. The proposed neural network (NN) models were executed using different ANN structures with various training and transfer functions based on the feedforward backpropagation approach to find the optimal model. The performance of the ANN models was evaluated in accordance with validation metrics, like the mean squared error (MSE) and correlation coefficient (R2). Assessing the experimental findings revealed the maximum shear force and nugget diameter emerged to be 8.6 kN and 5.4 mm for the case of 1–1 mm, 3.298 kN and 4.1 mm for the case of 0.5–0.5 mm, and 4.031 kN and 4.9 mm for the case of 0.5–1 mm. Based on the results of the Pareto charts generated by the Minitab program, the most important parameter for the 1–1 mm case was the welding current; for the 0.5–0.5 mm case, it was pulse welding; and for the 0.5–1 mm case, it was holding time. When looking at the hardness results, it is clear that the nugget zone is much higher than the heat-affected zone (HZ) and base metal (BM) in all three cases. The ANN models showed that the one-output shear force model gave the best prediction, relating to the highest R and the lowest MSE compared to the one-output nugget diameter model and two-output structure. However, the Levenberg–Marquardt backpropagation (Trainlm) training function with the log sigmoid transfer function recorded the best prediction results of both ANN structures. [ABSTRACT FROM AUTHOR]

This work optimizes the current (I), voltage (V), flow rate (F), and arc gap (G) of the gas tungsten arc welding (GTAW) of the Ti40A titanium alloy to decrease the heat input (HI) and improve the ultimate tensile strength (TS) and micro-hardness (MH). The radial basis function network (RBFN) was utilized to present performance measures, while weighted principal component analysis (WPCA) and an adaptive nondominated sorting genetic algorithm II (ANSGA-II) were applied to estimate the weights and generate optimal points. The evaluation via an area-based method of ranking (EAMR) was employed to determine the best solution. The results indicated that the optimal I, V, F, and G are 89 A, 23 V, 20 L/min, and 1.5 mm, respectively. The improvements in the TS and MH were 1.2 % and 19.8 %, respectively, while the HI was saved by 18.4 %. The RBFN models provided acceptable accuracy for prediction purposes. The ANSGA-II provides better optimality than the conventional NSGA-II. The HI, TS, and MH of the practical GTAW Ti40A could be enhanced using optimality. The optimization method could be utilized to deal with optimization problems for not only other GTAW operations but also other machining processes. [ABSTRACT FROM AUTHOR]

In this work, magnetic field-assisted autogenous gas tungsten arc welding (GTAW) of low carbon steel has been studied. The external magnetic field was generated by custom made rectangular shaped samarium cobalt permanent magnets which were arranged in a manner to generate a cusp-type magnetic field (CMF). The impact of CMF on the morphology and microstructural evaluation of the weld joints were examined prudently using optical microscope, Field-emission scanning electron microscope and X-Ray Diffraction technique. The experimental results exhibited that the CMF assisted GTAW produce joints with better mechanical and metallurgical properties compared to conventional GTAW. In CMF assisted welds, width of weld beads was reduced by an average of 4% and depth of penetration was increased by 13%. Temperature measurement on the work piece showed a significant amount of temperature decrease for the same amount of heat input under the influence of the CMF. An improvement in grain refinement was observed in the heat-affected zone (HAZ) adjacent to fusion boundary by 12% and HAZ adjacent to base metal by 15% compared to conventional GTAW, which in turn promoted a considerable increase in hardness. The tensile properties in CMF assisted welds were enhanced by 3% and 8%, respectively, for an increase of heat inputs from 0.34 to 0.45 kJ mm−1. [ABSTRACT FROM AUTHOR]

Filler powder plays an important role during microwave hybrid heating-based joining process. In this work, nano-size nickel powder has been taken as filler material for preparing SS304-SS304 butt joints. Effects of size of nickel powder on mechanical properties (strength and hardness) of joints have been investigated. Scanning electron microscope tests show that the joints possess uniform microstructure. Energy dispersive spectroscopy tests demonstrated the presence of elements (Chromium, iron, carbon, silicon, manganese, phosphorus) other than filler powder (Nickel) in the joint region thereby confirming complete melting of joint region and also transfer of carbon from graphite separator sheet to joint region during microwave processing. Micro-hardness test results showed that nano-size filler powder-based joints are less prone to surface wear than corresponding micro-size filler powder-based joints. Micro-tensile strength of nano-size nickel powder-based joints is also far better than micro-size filler powder-based joints. [ABSTRACT FROM AUTHOR]

In recent years, the implementation of rotary friction welding technology in the industrial sector has made significant progress, especially in the automotive industry, where multiple sheets forming the bodywork of a single vehicle are now assembled using this process. In this study, we utilized the phenomenon of rotary friction to enhance the quality of welded parts at different rotational speeds. Measurements of stress values, microhardness, and temperature were conducted in the welding zones for the following combinations: A60 steel/A60 steel, A9 aluminum/A9 aluminum, and their combination A60/A9. The results from each pair of welded plates were compared to achieve a comprehensive characterization. [ABSTRACT FROM AUTHOR]

Titanium (Ti) and its alloys are frequently employed in the biomedical industry because they have a high corrosion resistance in addition to being lightweight, non-toxic, and having excellent biocompatibility. In this work, the microstructure and some required properties were evaluated for binary Ti-15Zr alloy produced by powder metallurgy (PM) for biomedical applications; the obtained results were also compared to that of commercially pure Ti (CP-Ti). The major goal of this paper is to study the impact of Zr addition on the microstructure, microhardness, and corrosion resistance of Ti alloy. [ABSTRACT FROM AUTHOR]

This study proposes a hybrid process method based on Cryogenic Minimum Quantity Lubrication and Ultrasonic Rolling Strengthening Process (CMQL-URSP) to improve the surface integrity and enhance the mechanical properties of blade surface. First, the principle of the CMQL-URSP hybrid process was described. Second, the TEM experiments were conducted to clarify the influence of the CMQL-URSP hybrid process on aircraft engine blades. Finally, the blade processing experiments were performed to demonstrate the effectiveness of the CMQL-URSP hybrid process on the blade surface micro-morphology, micro-hardness and residual stress. The results indicate that the CMQL-URSP hybrid process effectively overcomes the limitations inherent to the solitary application of URSP. The CMQL process inhibits work hardening, thereby allowing the URSP to achieve better low-plastic surface improvement. Grain refinement governed by the continuous dynamic recrystallization mechanism leads to the formation of nanocrystals, which significantly improves mechanical properties of blade surface. The CMQL-URSP hybrid process results in a reduction in surface roughness from Ra 2.644 μm to Ra 0.055 μm, an increase in surface residual compressive stress from 321 MPa to 657 MPa, and the formation of a reinforced layer with a depth of 3.7 mm on the blade, thereby enhancing the surface integrity of the blade.

The present work deals with the relationship between the degree of cold plastic deformation (up to 55.3% in the neck area in the tensile test and up to 66.6% in the compression test) and the parameters of the Indentation Size Effect (ISE). The tested material consists of 97% wrought copper. The Hanemann tester (Carl Zeiss, Jena, Germany) was used to measure micro-hardness. The loads applied during the micro-hardness test were between 0.09807 N and 0.9807 N. The influence of the load on the degree of the micro-hardness and simultaneously on the ISE, expressed by the Meyer’s index n, was significant. The influence of load on the ISE parameters was also evaluated using the Meyer’s index n, the PSR method, and the Hays–Kendall approach. For the undeformed sample, the Meyer’s index was close to 2, with the increase in the degree of tensile and compressive deformation increasing its “reverse” character (n > 2).

Electron beam melting and vacuum refining (EBMR) is a modern metallurgical method that has proven advantages in terms of environmental sustainability and efficiency for recycling refractory and reactive metals and alloys with unique physical, chemical, and mechanical properties. In this work, the effectiveness for removing impurities from technogenic molybdenum, titanium, and hafnium metals using EBMR method is investigated. The thermodynamic and kinetic process conditions and their influence on the possibility of impurities’ removal from the studied technogenic materials are discussed. It has been established that there are no thermodynamic limitations for the removal of silicon, antimony, iron, aluminum, and copper impurities at EBMR of molybdenum and the maximal overall removal efficiency is 58 %. In the case of titanium technogenic material, the highest refining efficiency and maximal overall impurity removal level of 99.97 % and 100 % for some inclusions (such as Fe, Cu, Ta, and Cd) are achieved. The studies show that impurities (metallic and non-metallic) can be effectively removed from technogenic hafnium using single e-beam refining processing and the highest refining effectiveness is 52.21 %. The obtained results allow formulating the conditions of the refining process aiming to obtain metal materials with high purity, better structures and properties and demonstrate high effectiveness of the EBMR method. [ABSTRACT FROM AUTHOR]

The resistance spot welding (RSW) process is still widely used to weld panels and bodies, particularly in the automotive, railroad, and aerospace industries. The purpose of this research is to examine how RSW factors such as welding current, welding pressure, welding time, holding time, squeezing time, and pulse welding affect the shear force, micro-hardness, and failure mode of spot welded titanium sheets (grade 2). Resistance spot welded joints of titanium sheets with similar and dissimilar thicknesses of 1–1 mm, 0.5–0.5 mm, and 1–0.5 mm were evaluated. The experimental conditions were arranged using the design of experiments (DOE). Moreover, artificial neural network (ANN) models were used. Different training and transfer functions were tested using the feed-forward backpropagation approach to find the optimal ANN model. According to the experimental results, the maximum shear force was 5.106, 4.234, and 4.421 kN for the 1–1, 0.5–0.5, and 1–0.5 mm cases, respectively. The hardness measurements showed noticeable improvement for the welded joints compared to the base metal. The findings revealed that the 0.5–0.5 mm case gives the highest nugget and heat-affected zone (HAZ) hardness compared to other cases. Moreover, different failure modes like pull-out nugget, interfacial, and partial failure between the pull-out nugget and interfacial failure were noticed. The ANN outcomes based on the mean squared error (MSE) and coefficient of determination (R2) as validation metrics demonstrated that using the Levenberg–Marquardt (Trainlm) training function with the log sigmoid transfer function (Logsig) gives the best prediction, where R2 and MSE values were 0.98433 and 0.01821, respectively. [ABSTRACT FROM AUTHOR]