Microhardness Tests Research Articles

Effect of fast multiple rotation rolling on friction surfaced Al[sbnd]Si[sbnd]Cu alloy

In this study, the impact of four linear speeds (75, 95, 115, and 135 mm/min) during fast-multiple rotation rolling (FMRR) on the A390 coating applied via friction surfacing (FS) on the AA1050 substrate was investigated. The microstructure, mechanical properties, and wear resistance were examined using optical microscopy, scanning electron microscopy, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), nanoindentation tests, microhardness tests, and pin-on-disc tests. Results showed that as the linear speed increased to 135 mm/min, the FMRR-treated layer became 48.6 % thinner. At a linear speed of 135 mm/min, the grain size reduced to 1.24 ± 0.15 μm, and the sizes of Al2Cu and Si particles decreased to 0.51 ± 0.02 μm and 3.45 ± 0.11 μm, respectively. The nano-hardness and Young's modulus increased to 9.11 GPa and 218.9 GPa, respectively. Moreover, the wear rate decreased by 43.53 % compared to the consumable rod and by 65.96 % compared to the AA1050 substrate at a linear speed of 135 mm/min. EBSD results indicated the presence of recrystallization and shear texture components in the FMRR-treated layer. TEM analysis confirmed the presence of nanometer-sized Si particles (<10 nm) and grains (100–500 nm) in the FMRR-processed layer.

253MA heat-resistant stainless steel by wire arc additive manufacturing: microstructure and mechanical properties

ABSTRACT The 253MA stainless steel fabricated via wire arc additive manufacturing displays a mixed austenite and ferrite microstructure. It features many dislocations, minimal inclusions, and carbides, observed through TEM. Notably, CeO2 spherical inclusions enhance its high–temperature and oxidation resistance. Microhardness test 2 shows average values of 187.9 HV0.2 and 183.9 HV0.2 in transverse and longitudinal directions, respectively. Mechanical properties at room temperature include a yield strength of 388 MPa, a tensile strength of 681 MPa, 18.89% elongation, and 34% area reduction post–fracture. Impact toughness measured 89.7J and 133.7J in transverse and longitudinal directions, respectively. At 600°C, the steel's yield strength and tensile strength drop to 208 MPa and 412 MPa, with elongation increasing to 32.06% and area reduction to 53%. The stress–strain curve at 600°C shows serrated flow, suggesting dynamic strain ageing. SEM analysis indicates ductile fracture with larger dimples at elevated temperatures.

Influence of distal-end heat treatment in the properties of heat-activated NiTi archwires.

The aim of this study was to evaluate the extent of property changes caused by heating the distal portion of heat-activated nickel-titanium (NiTi) wires. Forty preformed heat-activated NiTi archwires (3MUnitek, Monrovia, CA, USA) with anominal cross-section of 0.018″ were used in this study. The archwires were divided into acontrol group, not submitted to heat treatment and, thus, maintaining the as-received properties, and an experimental group, in which the archwires were submitted to heat treatment for distal bending at one end. Wire segments of control and experimental groups were submitted to differential scanning calorimetry (DSC) and Vickers microhardness measurements. The DSC results suggest local recrystallization and precipitate dissolution at the heat-treated tip, which decreases as the distance to the wire's tip increases. Vickers microhardness tests revealed significant changes for distances between 6and 8 mm from the wire's tip. Heating the distal portion of heat-activated NiTi archwires should be performed with care since this clinical procedure may compromise the performance of these wires to a distance of 8 mm from the archwire end. Heat treatment for distal bending in heat-activated NiTi archwires may be performed, with little impact on the areas adjacent to heat treatment. In cases presenting molars requiring significant orthodontic corrections, it should be preferred to apply other techniques to avoid archwire sliding, such as crimpable stops, or to have flame control to avoid placing aheat-treated section in the tubes of these molars.

Microscale channels produced by micro friction stir channeling (μFSC)

The current literature lacks comprehensive research on the processing limits of the Friction Stir Channeling process (FSC) for creating the smallest continuous and integral channels, using tools with threaded probes 2 mm in diameter or smaller. This study pioneers the exploration of the extreme limits of the microscale FSC process, with potential applications in the development of ultra-compact heat exchangers, seeking to enhance the efficiency and sustainability of these systems. Customized tools were designed and manufactured, with predefined dimensions and geometries to establish a set of parameters that consistently produce continuous microchannels, maximizing the hydraulic diameter within the constraints of each tool's specifications and geometry. Comprehensive evaluations—including continuity, watertightness, micro-computed tomography, neutron computed tomography, microhardness testing, and thermal measurements—were conducted to ensure the channels' structural integrity and suitability for super-compact heating and cooling applications. Internal channels were successfully created using tools with threaded probes measuring 2.0, 1.0, and 0.5 mm in diameter, and corresponding shoulder diameters of 5, 4, and 3.5 mm, within 5 mm thick AW1050-H111 aluminum alloy plates. The smallest channel achieved a hydraulic diameter of 191 μm, using a 0.5 mm diameter threaded probe, thus qualifying it as a microchannel. The thermal performance of a compact heat exchanger model was also tested, demonstrating that despite the high cost associated with tool production, particularly due to the specialized manufacturing processes required, the FSC process remains viable, reliable, and repeatable for the production of mini- and micro-channels.

Thermal, chemical and mechanical characterization of Azadirachta indica tree gum

This study focuses on the comprehensive thermal, chemical, and mechanical characterization of neem gum, a natural, colorless, tasteless polysaccharide obtained from Azadirachta indica tree’s trunk. The collection process of gum involves manual extraction from crude neem tree exudates, followed by thorough cleaning and homogenization with water. A portion of the resulting gum is then filtered, allowed to thicken, and naturally dried for subsequent mechanical testing. Various analytical techniques, such as thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to determine the thermal properties, Fourier transform infrared spectrometry (FTIR) to find the functional groups, scanning electron microscopy (SEM), and micro-X-ray fluorescence analysis (µ-XRF) to decide the elemental composition, microhardness, tensile, flexural, and compression tests to determine the mechanical properties, are employed in this study. The thermal and mechanical properties of neem gum have been relatively unexplored, and this highlights the novelty and importance of this research. The results are analyzed and compared with other natural tree gums. The pH of 5.07 shows that the gum is slightly acidic in nature, and the peaks obtained from thermal analysis demonstrate that it doesn’t have a melting point. The microhardness value, tensile strength, flexural strength, and compressive strength of neem gum are 238.64 MPa, 1.0155 MPa, 1.899 MPa, and 1.1023 MPa, respectively. This research provides valuable insights into the diverse characteristics and potential applications of neem gum in various fields. It is being used in the pharmaceutical industry. It can also be used as a cap for cutting tools, such as drill bits, after manufacturing, during transportation to protect their sharp edges from damage.

Research on microstructure, mechanical property and wear mechanism of AlCoCrFeNi/WC composite coating fabricated by HVOF

In this study, HVOF spraying technology was utilized to prepare AlCoCrFeNi/WC composite coatings with varying WC content on 40CrMnMoA steel substrate. The microstructure, elemental distribution, phase structure and chemical valence states of wear scratches of the composite coatings were analyzed using the SEM, EDS, XRD and XPS. Microhardness was measured using single-point digital microhardness tester, while nanohardness and elastic modulus were determined using a nano-indenter. The bonding strength of the composite coatings was evaluated using a tensile tester. Friction and wear tests were conducted to assess the wear behavior of the composite coatings. The results indicated that the microstructure, microhardness, nanohardness and elastic modulus of AlCoCrFeNi HEA coating increased with the addition of WC, attributed to the hard phase effects of WC. However, the bonding strength first decreased and then increased. Compared to the W 0 coating, the wear rates of the other composite coatings decreased by 30.5 %, 46.1 %, 65.3 %, and 82.1 %, respectively, which demonstrating that the effect strengthening of WC. After the friction and wear tests, the wear mechanism of the W 0 and W 1 coatings represents adhesive wear, abrasive wear and severe oxidation wear. In contrast, the W 2 and W 3 coatings exhibited slight adhesive wear, slight abrasive wear and slight oxidation wear, while the W 4 coating showed the slightest abrasive wear, the slightest adhesive wear and the slightest oxidation wear.

Interfacial assessment of cention forte vs. equia forte and two forms of calcium silicate cements at two time intervals

AimAssessment of interfacial gaps and mechanical impact of the materials layering between Cention Forte and Equia Forte restorations with two forms of Calcium Silicate Cements (CSCs) at the interfacial surface at two-time intervals.MethodologySix groups of 72 primary molars were categorized by restorative material type and CSCs: Cention Forte(C), Cention Forte without primer (Cx), and Equia Forte (EQ). All were applied over MTA Angelus powder (M) or Bio-C Repair putty (P). Restorative materials were applied immediately (subgroup A) or delayed (Subgroup B). SEM was used to detect interface gaps. EDX measured element migration from the interface at specific distances. Vickers Microhardness Tester assessed microhardness.ResultsRegarding SEM, there were no gaps between CSCs interfaces of both types (Powder and Putty) with all restorations at two-time intervals. Microhardness, there was a statistically nonsignificant difference between subgroups A & B in all groups except at 200 µm in the Cention groups (subgroup A) was significantly lower than (subgroup B) (P = 0.002, 0.03) respectively. At 400 µm in the MTA Angelus powder Group Cx, subgroup A was significantly higher than subgroup B (P = 0.003*). While Bio-C Repair putty in Group EQ (subgroup A) was significantly higher than (Subgroup B) (P < 0.0001*).ConclusionsThe delayed application of Cention Forte over two types of CSCs is useful in getting the maximum HV and, in turn, the long survival rate of the filling. Immediate application of Cention Forte without primer is better over both types of CSCs. The delayed application of Equia Forte over MTA angelus powder is more considerable.

Fracture toughness and cavitation erosion behavior of Fe-based amorphous composite coatings with Ni-coated Al2O3 addition

Fe-based amorphous composite coatings were prepared on 304 stainless steel substrates using atmosphere plasma spraying (APS), aiming to investigate the effect of Ni-coated Al2O3 particles addition on fracture toughness and cavitation erosion behavior of Fe-based composite coatings. The microstructure, phase composition, elastic modulus, microhardness and fracture toughness of the coating were characterized using scanning electron microscopy with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness tester and nanoindentation. The cavitation erosion behavior of Fe-based coatings was investigated by ultrasonic vibration cavitation method. Fe-based amorphous composite coatings exhibit a characteristic lamellar microstructure and reveal the presence of amorphous phases along with α-(Fe, Cr), NiO, Ni and Al2O3 crystalline phases. When the content of Ni-coated Al2O3 in coating increases from 0 wt% to 3 wt%, there is slight deterioration in porosity from 3.64 % to 4.75 % and fracture toughness from 2.579 MPa·m1/2 to 2.392 MPa·m1/2, yet an increase in microhardness from 925.4 HV0.5 to 1090.3 HV0.5. The composite coating with 3 wt% Ni-coated Al2O3 demonstrates the peak cavitation resistance and its cumulative mass loss is significantly reduced by 36.4 % compared to the pure Fe-based coating. The cavitation erosion failure of Fe-based amorphous composite coatings is predominantly characterized by the brittle fracture mechanism. The fundamental process driving cavitation erosion damage involves the material peeling and coating delamination instigated by intense micro-jet impact and shock wave propagation. The proposed Fe-based amorphous composite coatings can be applied to improve the anti-cavitation performance of components in contact with high-speed fluids, such as ship propellers and centrifugal pump blades.

FABRICATION AND CHARACTERIZATION OF AA6082-T6 PRODUCED BY FRICTION STIR ADDITIVE MANUFACTURING

The machinability of aluminum alloy (Al-6082) has the scope of enhancement by integrating Friction Stir Processing (FSP) with tool geometry, tool shape and different tool materials. In this research, the role of tool pin shape has been studied by experimenting on various tool shapes (square, hexagonal and octagonal) with the aim of machinability improvement. In FSP, the tool rotation speed is 930[Formula: see text]rpm and tool travel speed is 26[Formula: see text]mm/min. The specimens have undergone tensile, microhardness and microstructure testing using optical microscope and scanning electron microscopy. The percentage elongation has been increased from 15% to 29% in the case of the octagonal-shaped tool pin; similarly, the (Vickers’) microhardness value is 14.6% higher than the square- and hexagonal-shaped tool pins. Among these tool pin shapes, the octagonal-shaped tool pin succeeded in providing the best-in-class machinability performance on Al-6082 T6 alloy with FSP. It may unveil the newer scopes of FSP on Al-6082 for automotive components assembly and other similar applications.

Influence of ultrasonic power on microstructure and performance of electroless deposited Ni-W-SiC nanocoatings

This study reports the deposition of Ni-W-SiC nanocoatings on the 45-steel using the ultrasound-assisted electroless deposition (UELD) technique. The hardness and corrosion resistance of the nanocoatings were evaluated through microhardness tests and electrochemical analyses. The surface, cross-section, phase composition, and abrasion morphologies of the coatings were studied using scanning electron microscopy and X-ray diffraction. The findings indicated that the Ni-W-SiC coating obtained at 200 W showed a compact, fine, and flat microstructure with a porosity of only 0.03 %. As the ultrasonic power during the UELD process increased from 0 W to 200 W, the SiC content in the coating rose from 2.77 to 4.16 wt% The maximum bonding force of the coating synthesized without ultrasound was approximately 89.8 N. However, the bonding force of the coatings significantly decreased with increasing ultrasonic power. The coating’s thickness also increased, from 11.09 μm at 0 W to 14.97 μm at 300 W. At 200 W ultrasonic power, the diffraction peaks of the coating were both the lowest and broadest among all the coatings. Further, the coating achieved the highest microhardness value of 676 HV. At 200 W ultrasonic power, the coating's corrosion current density was 1.63×10−7 A/cm2, which is only one-twelfth that of 45 steel, demonstrating exceptional corrosion resistance. The electrochemical impedance spectroscopy (EIS) testings indicated that an excellent corrosion resistance of Ni-W-SiC coating was deposited by using a 200 W ultrasonic power. This study provides a technical support for the preparation of nickel-based composite coatings.

Study of strengthening mechanisms in Al-Cu and Al-Cu-Mg systems subjected to plastic deformation and T6 treatment

ABSTRACT A series of Al-4Cu and Al-2Cu-2Mg wt.% alloys were synthesized through casting and subjected to plastic deformation to evaluate the interaction and contribution of the different strengthening mechanisms since the experimental Vickers microhardness test. The plastic deformation was performed by cold-rolling to achieve a 50% thickness reduction. The results show that solid solution strengthening is the main mechanism responsible for the total hardness enhancement of the alloys, and the Mg presents a higher hardening capacity for the solid solution strengthening than the Cu. For Al-4Cu alloy, competition between the annihilation of dislocations and the formation of precipitates generates an apparent low response precipitation hardening. Nevertheless, for Al-2Cu-2Mg alloy, the Mg addition allowed retard the dislocation annihilation induced an apparent higher response precipitation hardening.

Effect of Stearyl Methacrylate Comonomer on the Mechanical and Physical Properties of Dimethacrylate-Based Dental Resins.

This study evaluated the effect of stearyl methacrylate addition on the physical and mechanical properties of bisphenol A glycidyl methacrylate- and triethylene glycol dimethacrylate-based polymers, which are traditionally used in dental applications. Methacrylate-based monomer compositions are polymerized under the visible blue light spectrum. An analysis of double bond conversion, surface microhardness test, three-point bending test and water sorption and water solubility were tested to determine the physical and mechanical properties of the dental polymers. The results indicated that stearyl methacrylate addition up to 25 wt% reduced the water sorption of the polymers. At amounts of stearyl methacrylate higher than 25 wt%, the solubility of the polymer in water increases due to the monofunctional structure. Mechanical properties are negatively affected by the increasing stearyl methacrylate ratio. Further, the addition of stearyl methacrylate slightly increased thermal stability. As such, the amount of stearyl methacrylate in a polymer composition is critical for the optimization of its mechanical and physical properties. According to the results, the amount of stearyl methacrylate has to be between 12.5-25 wt%.

Effect of WC content on the microstructure and wear resistance of Laser-cladded WC/Ni60A composite coatings

In this study, WC/Ni60A composite coatings with various WC contents were prepared on the surface of the TC4 titanium alloy using laser cladding. SEM, EDS, XRD, microhardness testing, and friction-wear performance testing were performed to characterize the coatings. The results revealed that an increase in the WC content reduced the coating dilution rate and increased its porosity. The microstructure of the composite coating included WC, Ni3Ti, Ni17W3, and TixW1−x species as well as carbides and borides. With increasing WC content, the wear rate decreased, and the wear mechanism changed from microabrasion and adhesive wear to localized adhesive wear. The coating with 45 wt.% WC showed the best wear resistance for the denser and more uniform distribution of its hard phase.

Crucial effects of plasma gas on the weld and microstructural characteristics of plasma arc welded aero engine Ti6Al4V alloy joints

This study explores the influence of plasma gas flow rate (PGFR) on the defects, microstructure evolution and mechanical properties during plasma arc welding of Ti6Al4V titanium alloy thin sheets using microscopic analysis, spectroscopic analysis, tensile and microhardness tests. The variation in PGFR affects the welding arc in terms of its stability, pressure and constriction which results in transformation of arc from conduction mode to keyhole mode and changes in microstructure as well. All the other welding process parameters were kept constant except for PGFR which was varied to investigate its significance. Excess weld metal was observed under the weld bead is an attribute of keyhole formation. Macrographs exhibits increments in weld geometry measurements whereas weld defects such as lack of penetration and porosity decreased with increased PGFR. The microstructural examination showed a variety of phase formations that includes majorly with acicular α and Widmanstätten α morphologies. Tensile strength and hardness at the weld region of the welded joints increases with increase in PGFR. An oxygen rich brittle subsurface layer called α-case morphology was observed at the weld region of 1 L/min joint causes significant reduction in ductility.

Improvement of AISI 316L laser cladding properties by high-frequency vibration process

In the present paper, a unique laser cladding-assisted high-frequency vibration device was applied to prepare the AISI 316L cladding layer by laser cladding on the surface of the AISI 316L stainless steel substrate. The macroscopic morphology, microstructure, microhardness, and wear resistance of the cladding layer were analyzed by optical microscope, scanning electron microscope, Vickers microhardness tester, friction and wear tester, and three-dimensional optical profiler. The laser cladding-assisted high-frequency vibration device uses a high-frequency oscillator with a fixed frequency (20 KHz) to transfer vibration energy through the probe in contact with the substrate and close to the molten pool. This paper explores the effect of different laser powers on the dilution rate of the cladding layer, compares and observes the cross-sectional morphology and microstructure of the cladding layer with and without high-frequency vibration, and analyzes the reasons for the different results.

Physical characteristics identification of the concrete interfacial transition zone via 3D image scanning

The interfacial transition zone (ITZ) is the weakest link in concrete materials. The physical characteristics of the ITZ, such as its microhardness and thickness, significantly influence the mechanical properties and durability of concrete. Typically, microhardness testing is employed to identify the physical features of the ITZ through line measurements with a certain degree of randomness. In order to accurately describe ITZ physical characteristics, this study proposes a novel physical characteristics identification method via three-dimensional (3D) image scanning. The fundamental principle of this method lies in the varying hardness of each concrete phase, resulting in different surface elevations after polishing. As the polishing abrasiveness changes from coarse (240 mesh) to fine (800 mesh), the ITZ can be clearly observed in the 3D point cloud images of the experimental concrete. The ITZ geometrical information (thickness and different surface heights) can be easily identified using 3D scanned images. It was also found that there was a considerable linear regression relationship between the height difference and the relative microhardness variation; thus, the ITZ microhardness could be indirectly recognized through surface measurements. The physical characteristics of ITZ can be statistically analysed, effectively mitigating the bias inherent in traditional test results and significantly improving identification efficiency and accuracy.

Effect of scanning strategy and laser peening on microstructure and fatigue properties of laser-directed energy deposition-built 15-5 PH stainless steel

PurposeThe aim of this paper is to study the effect of laser shock peening (LSP) on mechanical behaviour of the laser-directed energy deposition (LDED)-based printed 15-5 PH stainless steel with U and V notches. The study specifically concentrates on the evaluation of effect of scan strategy, machining and LSP processing on microstructural, texture evolution and fatigue behaviour of LDED-printed 15-5 PH steel.Design/methodology/approachFor LSP treatment, 15-5 PH steel was printed using LDED process with bidirectional scanning strategy (XX [θ = 0°) and XY [θ = 90°]) at optimised laser power of 600 W with a scanning speed of 300 mm/min and a powder feed rate of 3 g/min. Furthermore, LSP treatment was conducted on the V- and U-notched fatigue specimens extracted from LDED-built samples at laser energy of 3.5 J with a pulse width of 10 ns using laser spot diameter of 3 mm. Post to the LSP treatment, the surface roughness, fatigue life assessment and microstructural evolution analysis is performed. For this, different advanced characterisation techniques are used, such as scanning electron microscopy attached with electron backscatter diffraction for microstructure and texture, X-ray diffraction for residual stress (RS) and structure information, Vicker’s hardness tester for microhardness and universal testing machine for low-cycle fatigue.FindingsIt is observed that both scanning strategies during the LDED printing of 15-5 PH steel and laser peening have played significant role in fatigue life. Specimens with the XY printing strategy shows higher fatigue life as compared to XX with both U- and V-notched conditions. Furthermore, machining and LSP treatment led to a significant improvement of fatigue life for both scanning strategies with U and V notches. The extent of increase in fatigue life for both XX and XY scanning strategy with V notch is found to be higher than U notch after LSP treatment, though without LSP samples with U notch have a higher fatigue life. As fabricated sample is found to have the lowest fatigue life as compared to machines and laser peened with both scan strategies.Originality/valueThis study presents an innovative method to improve the fatigue life of 15-5 PH stainless steel by changing the microstructure, texture and RS with the adoption of a suitable scanning strategy, machining and LSP treatment as post-processing. The combination of preferred microstructure and compressive RS in LDED-printed 15-5 PH stainless steel achieved with a synergy between microstructure and RS, which is responsible to improve the fatigue life. This can be adopted for the futuristic application of LDED-printed 15-5 PH stainless steel for different applications in aerospace and other industries.Graphical abstract

Improved wear and corrosion protection of Ni–P alloy coating by an electrodeposited Ni–Co–P alloy coating

To improve the comprehensive protection performances of steel C1045 surface, the Ni–Co–P alloy coatings with varying CoSO4·7 H2O concentration (0, 10, 20, 30, 40, 50, 60 and 70 g·L–1) were successfully prepared by an electrodeposition technique on a steel C1045 surface. The effect of the addition of CoSO4·7 H2O in the plating solution on the surface microstructure, elemental composition, crystallite size, microhardness, wear and corrosion resistance of the Ni–Co–P alloy coatings were analyzed by using a scanning electron microscope, an energy dispersive spectroscopy, an X-ray diffraction, a microhardness tester, a friction wear tester and an electrochemical workstation, respectively. The results indicated that the Ni–Co–P alloy coating exhibited a flatter morphology, compact microstructure and more excellent properties compared with Ni–P alloy coating, and the addition and variation of CoSO4·7 H2O in the plating solution had significant effects on the surface microstructure and comprehensive protection performances Ni–Co–P alloy coating. Notably, when the mass concentration of CoSO4·7 H2O in the plating solution was 50 g·L–1, the Ni–Co–P alloy coating had the highest content of Co element (22.67 wt·%), smallest crystallite size (20.41 nm) and highest microhardness (716.2 HV0.1). Furthermore, its wear resistance and corrosion resistance were considerably improved compared to that of the Ni–P alloy coating. The minimum average dynamic friction coefficient, wear scar width and depth of Ni–Co–P alloy coating at 50 g·L–1 were 0.47±0.02, 450.9 µm and 14.1 µm, respectively. The corrosion current density (Icorr) of Ni–Co–P alloy coating was the smallest (0.68 µA·cm–2), the corrosion rate (Rcorr) was slowest (8.25 µm·year–1), and the polarization resistance (Rp) of the Ni–Co–P alloy coating was highest (29.83 kΩ·cm2). The corrosion resistance of Ni–Co–P alloy coating was best.

Investigating the microstructure and mechanical properties of Al–Ag-Sc ultra-fine grain alloy processed by accumulative rolling bonding method

The aim of the present study is to investigate the effect of accumulative roll bonding (ARB) and precipitation hardening on the microstructure development and there of mechanical properties of ultrafine grained Al–Ag-Sc alloy. For this purpose, the samples were heated to a temperature of 600 °C for 24 h, and then they were quenched in water. In order to carry out the two-stage precipitation hardening process, the samples were placed in the furnace at a temperature of 350 °C for 5000 s in the first stage, which was followed by quenching in water. In the second stage, they were heated to 250 °C for 5000 s following by water quenching too. Following, the samples were subjected to the ARB for up to 8 cycles. Scanning Electron Microscope (SEM) equipped with Electron Backscatter Diffraction (EBSD) and energy dispersive spectroscopy (EDS) techniques, and X-Ray Diffraction (XRD) was used to verify the microstructure and phase analysis of the prepared samples. Also, tensile and microhardness tests were conducted to confirm the mechanical properties, and pin-on-disk tests were done to check wear behavior. Microstructural parameters such as crystallite size, microstrain, and density of dislocations in rolled sheets were estimated using the Rietveld method. The Results have shown that applying various cycles of the ARB process leads to the development of ultra/nano grain structure. In that sense, performing 8-cycle of the ARB transformed the low angle grain boundaries (LAGBs) of the 4-cycle ARB condition to high angle grain boundaries (HAGBs). Results showed that there is proper welding between different layers, except for the layers created in the last cycle. Similarly, the obtained size of the crystallites demonstrates that the samples become finer when ARB cycles are increased. The results of the mechanical tests indicated that after 8 cycles, there is approximately 3.5-fold and 2.5-fold increase in the tensile strength and hardness compared to the original (annealed) sample, respectively. While the elongation decreased slowly and reached 1.5% in the 8th cycle. A fractography of the fracture surface of the original sample included deep and coaxial dimples, indicating a ductile fracture. Analysis of wear surface degradation showed that scratch wear occurred for all samples.

Microstructure and Corrosion Study on Friction Surfaced Aluminum Alloy Coatings over Mild Steel

In this study, the low-carbon steel (AISI 1018 mild steel) substrate is coated with the aluminum alloys AA6082-T6, Al-20Zn, and Al-2Si-15SiC to improve its corrosion resistance by the friction surfacing (FS) technique. To produce a high-quality coating, friction surfacing process variables including spin speed, speed of travel, and the rate of feed are crucial. This experiment examines twelve friction-surfaced plates with different parameter combinations. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) examinations were carried out in order to comprehend the microstructure and chemical composition of the coating deposits and the area in contact between the coated surface and the substrate. Microstructure investigation reveals that the intermetallic combination of Fe-Al at the coating interface region is an effect of the elemental diffusion of Fe to aluminum at the contact interface. Then a uniform and fine-grained coating deposit is observed as a result of the continuous recrystallization of the consumable rod under frictional stress and heat generation. According to the outcomes of the microhardness test, the coated surface is roughly 15–16% harder than the consumable rod. The coating bond strength was measured using a ram tensile test, and it ranged from 102 MPa to 135 MPa. Finally, evaluation of corrosion behavior through immersion testing and pitting corrosion testing reveals that the coatings made of Al-20Zn and Al-2Si-15SiC exhibit good corrosive resistance in an alkaline environment.