Microhardness Tests Research Articles

Creep rupture and microstructural analysis of dissimilar welded joints of P92 steel and Alloy 617

Advanced ultra-supercritical plants are recognized for their efficiency and effectiveness in energy production, particularly when operating at elevated steam temperatures (700–720 °C). High-temperature components within these plants, including turbines, pipes, headers, and tubes, typically employ nickel-based alloys like Alloy 617, renowned for their outstanding resistance to corrosion and oxidation. Nevertheless, lower-temperature components (below 620 °C) frequently use less expensive ferritic-grade steels like P91 and P92. Welding these disparate materials balanced the plant’s performance and cost-effectiveness. This study focuses on the creep rupture behaviour of a dissimilar welded joint made through a gas tungsten arc welded joint between P92 steel and Alloy 617, utilizing a Ni-based Inconel 617 filler, at a test temperature of 650 °C under a stress of 140 MPa. A light microscope and a field emission scanning electron microscope were used for microstructural study. The investigation looks at how creep ruptures happen and how the microstructure changes inside the DWJ, and microhardness testing to comprehensively assess the joint’s performance under specific stress and temperature conditions. At 140 MPa and 650 °C, the sample demonstrated a creep rupture time of 54.5 h.

Innovative Solid-State Recycling of Aluminum Alloy AA6063 Chips Through Direct Hot Rolling Process

In this paper, the feasibility of an innovative solid-state recycling process for aluminum alloy AA6063 chips through direct rolling is studied, with the aim of offering an environmentally sustainable alternative to conventional recycling processes. Aluminum chips, produced by milling an AA6063 billet without the use of lubricants, were first compacted using a hydraulic press with a 200 kN load and subsequently heat-treated at 570 °C for 6 h. The compacted chips were directly hot-rolled through several successive passes at 490 °C. The bulk material underwent the same rolling schedule to allow comparison of the samples and assess the process, in terms of mechanical properties and microstructure. All the rolled samples were tested by tensile and microhardness tests, whereas the microstructure was observed by an optical microscope and the EBSD-SEM technique. The fracture surface of all tested samples was analyzed by SEM. Recycled samples exhibited good mechanical properties, comparable to those of the bulk material. In particular, the bulk material showed an ultimate tensile strength of 218 MPa, in contrast to 177 MPa for the recycled chips, and comparable elongation at break. This study demonstrates that direct rolling of compacted aluminum chips is both technically feasible and has environmental benefits, offering a promising approach for sustainable aluminum recycling in industrial applications within a circular economy framework.

Preliminary Evaluation of Nickel Silicide (NiSi12-wt%) Laser Cladding for Enhancing Microhardness and Corrosion Resistance of S355 Steel

S355 construction steel, a commonly used mild steel due to its exceptional strength, is prone to environmental degradation, especially pitting corrosion in highly corrosive marine environments. To address this vulnerability, applying a surface layer of nickel silicide (NiSi) cladding on such components could offer a solution, given that NiSi-based alloys are known for their high corrosion resistance and exceptional mechanical properties. Thus, the present study has investigated the corrosion resistance and microhardness of the NiSi12-wt% cladding deposited onto substrates of S355 steel using laser metal deposition. An accelerated ASTM G48 corrosion test and a Vickers microhardness test were conducted in a solution of 6% ferric chloride (FeCl3) solution at room and elevated temperatures to represent marine environments, with uncladded sheet substrates exposed to the same test environments as a reference. All exposed S355 steel samples, with and without cladding, underwent microhardness testing and were characterized using light optical microscopy (LOM) and low-voltage field emission scanning electron microscopy (LVFESEM). The findings indicate that the NiSi12-wt% cladding significantly enhances the corrosion resistance and mechanical properties of the S355 steel samples, showcasing its potential for use in marine and industrial environments where corrosion and mechanical wear are expected.

Results of metallographic studies of cutting parts of cultivator paws made of 30MnB5 steel

Rationale. Cultivators are widely used in our country for surface tillage. Moreover, their most common working organ is the pointed paw. In recent years, foreign manufacturers of agricultural machinery have begun to use boron-containing steels in the manufacture of working parts of agricultural machinery, which can increase the wear resistance and durability of machine parts. The article presents the results of metallographic studies of the structure and properties of the cutting parts of pointed cultivator paws made of boron-containing steel 30MnB5. The purpose of the work is to study the structure and properties of boron-containing steels after surfacing relit and subsequent hardening. Materials and methods. When carrying out metallographic studies, we used the cutting parts of the paws of the KPIR-3.6 and KPU-5.4 cultivators, mass-produced according to OST 23.2.164-87 at the Buinsky Machine-Building Plant of the Republic of Tatarstan. These working bodies were made of steel grade 30MnB5 DIN EN 10083-3. To ensure heterogeneity of the structure, a layer of relit was fused to one side of the cutting blade of the cultivator paw, after which the entire working element was hardened. The macro- and microstructure of the metal part was studied using a microsection cut out to the cutting edge. For macrostructural studies, a stereoscopic microscope from MEIJI RZ with a magnification of up to 7 times was used. The microhardness of the part was measured using the Vickers method (GOST R ISO 6507-1-2007) at different loads on a MicroMet 5104 microhardness tester. Contamination of the base metal of the part with non-metallic inclusions was assessed using the “Ш4” method according to GOST 1778-70. Results. The proposed manufacturing technology for cultivator blades made of 30MnB5 steel made it possible to obtain a cutting part that is heterogeneous in structure and hardness, which ensures self-sharpening of the blade during the friction of the cultivator blade on the soil. The steel base of the cultivator paw after heat treatment has a troostomartensite structure with a microhardness of ~ 564 HV 0.3. The deposited layer of relit has a dendritic cast structure of tungsten with a microhardness of 900...1020 HV 0.05 and tungsten carbides with a microhardness of 2315...2460 HV 0.05. The wear of paws made of 30MnB5 steel turned out to be 9.5% less than that of working bodies made of 65G steel. The cost of manufacturing working parts using the proposed technology was reduced by 14.3%. Conclusion. The practical value of the study lies in the fact that the results of studies of the cutting parts of self-sharpening cultivator paws, made of 30MnB5 steel using the proposed technology, are used in the production process of Buinsky Machine-Building Plant OOO in the Republic of Tatarstan. The paws manufactured using the proposed technology are installed on cultivators KPIR-3.6 and KPU-5.4. The presence of the self-sharpening effect of the paws made it possible to increase the quality of products required by consumers and its high competitiveness.

Remineralising enamel caries with a novel peptide: An in vitro study

ObjectiveTo evaluate the antibacterial and remineralising effects of GAPI peptide on artificial enamel caries. MethodsHuman enamel blocks were exposed to Streptococcus mutans biofilm to create artificial carious lesions. The blocks were randomly assigned to either the GAPI treatment group or the deionised water control group, treated twice daily for 21 days. The viability, growth kinetics, and morphology of S. mutans biofilms were assessed using confocal laser scanning microscopy (CLSM), colony-forming unit (CFU) counting, and scanning electron microscopy (SEM). Lesion depth, mineral loss, calcium-to-phosphorus ratio, Knoop hardness, enamel surface morphology, and crystal characteristics of enamel lesions were determined using micro-computed tomography (Micro-CT), SEM-energy dispersive spectroscopy (EDS), a microhardness tester, SEM, and X-ray diffraction (XRD). ResultsCLSM showed that the dead-to-live ratio of S. mutans was 0.8±0.1 in the GAPI group and 0.4±0.1 in the control group (p<0.001). The Log CFUs were 6.9±0.7 in the GAPI group and 8.1±0.5 in the control group (p=0.002). SEM revealed confluent growth of S. mutans in the control group but not in the GAPI group, which also exhibited cell damage. Micro-CT showed that the lesion depth (µm) was 142±11 in the GAPI group and 178±20 in the control group (p<0.001), with mineral loss (gcm⁻³) of 1.1±0.1 and 1.5±0.1, respectively (p<0.001). SEM-EDS indicated that the calcium-to-phosphorus ratio was 1.71±0.02 in the GAPI group and 1.67±0.03 in the control group (p=0.006). Additionally, Knoop hardness was 302±22 in the GAPI group and 242±17 in the control group (p<0.001). SEM revealed an orderly pattern of enamel rods in the GAPI group, and XRD showed better crystallisation of hydroxyapatite in the GAPI group compared to the control group. ConclusionGAPI exhibits antibacterial and remineralising properties against artificial enamel caries. Clinical SignificanceIf the anti-caries properties of GAPI are confirmed in clinical studies, it could be used for caries prevention.

Influence of Ti element on the microstructure and crack of modulated WC-strengthened Ni-based alloy coatings by laser cladding

For laser cladding of WC reinforced Ni50A Ni-based alloy coatings can cause cracks and porosity. Cracks and pores will restrict the application and performance of the coating. In order to improve the crack condition of the coating, the influence of alloying element Ti on the crack was investigated by introducing it. Cracks in the coatings were eliminated. When the addition amount of Ti is 3wt%, the morphology and properties of the coating are the best. The phase composition, microstructure, elemental distribution and grain orientation of the coatings were characterised using X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS), Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM). The hardness and abrasion resistance of the coatings were tested using microhardness tester and friction tester. The results show that a large number of second phases are present in the coating when Ti particles are not added. The introduction of Ti element disperses the localised stresses in the Ni50A-WC coating. The macroscopic morphology of Ni50A-WC coating was improved. The introduction of Ti reduced the area of the second phase within the coating. The introduction of Ti generated TiC/TiWC2 in situ. However, the introduction of Ti increased the dilution rate and decreased the strength of the coating. Therefore, the microstructure of the coating can be controlled and the macroscopic defects of the coating can be improved by adjusting the addition ratio of Ti elements.

The Microstructure and Wear Properties of Ni-coated and Agglomerated-Sintered WC-10Ni/316 Composite by Laser Melting Deposition

WC-10Ni particle-reinforced stainless steel matrix composites have potential applications in aerospace, energy engineering, automotive manufacturing, and marine engineering equipment. However, there is currently insufficient research on the integrated manufacturing and comparative analysis of Ni-coated (WC-10Ni)1.5/316 and agglomerated-sintered (WC-10Ni)1.5/316 composites using Laser Melting Deposition (LMD) technology. In this work, the fabrication and examination of the LMDed specimens are conducted to determine the influence of the forming process of particle reinforcement on the microstructure and wear properties of WC-10Ni/316 composites. The microstructure, phase composition, composition distribution, microhardness, and wear resistance of the two composites were comparatively analyzed using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), microhardness tester, X-ray diffraction(XRD), energy-dispersive spectroscopy (EDS), and a reciprocating wear tester. The results indicate that the microstructure of Ni-coated (WC-10Ni)1.5/316 composite specimen contains a higher quantity of undecomposed Ni-coated WC-10Ni particles, with a lower proportion of precipitates, and dendrites predominantly exhibit an elongated dendrite morphology. In contrast, the agglomerated-sintered (WC-10Ni)1.5/316 composite specimen features a greater content of decomposed agglomerated-sintered WC-10Ni particles, a higher content of precipitates, and dendrites mainly present as slender dendrites. Both composites consist of phases such as γ-(Fe, Ni, Cr), WC, W2C, Fe6W6C, M6C, and Cr23C6. The undecomposed WC-10Ni particles and tungsten precipitates significantly enhance the microhardness and wear resistance of the specimen. Specifically, the Ni-coated (WC-10Ni)1.5/316 composite specimen displays a microhardness of 350.2±3.3 HV1.0, with a wear rate of 1.5797±0.0455mg/(N·km). Meanwhile, the Agglomerated-sintered (WC-10Ni)1.5/316 composite specimen reveals an average microhardness of 410.9±6.1 HV1.0 and a wear rate of 0.8057±0.0352mg/(N·km).

Efficacy of combining soluble calcium and pyrophosphate with sodium fluoride in inhibiting enamel caries progression: an in vitro study

ObjectiveThis study aimed to compare the effects of a combination of sodium fluoride, soluble calcium, and pyrophosphate (FCaP) versus fluoride alone in inhibiting enamel caries progression. DesignDifferent FCaP solutions were prepared, and two were selected for testing (FCaP-1: F = 76mmol/L, Ca = 7.6mmol/L, P = 7.6mmol/L, FCaP-5: F = 76mmol/L, Ca = 23mmol/L, P = 23mmol/L). Fluoride solution (F = 76mmol/L) was used as a control. Fluoride and calcium bioavailability in the solutions were measured, and NMR analysis was used to identify fluorine-containing complexes. Sound bovine enamel samples (n = 24 / group) underwent a 4-day pH cycling protocol followed by an additional 3 days of demineralization. Micro-hardness testing and fluoride concentration measurements were performed. ResultsFCaP-1 and FCaP-5 demonstrated nearly 100% fluoride and calcium bioavailability. NMR analysis confirmed the formation of fluorine-containing complex. Enamel treated with FCaP-5 exhibited significantly less reduction in subsurface hardness after pH cycling and additional demineralization compared to fluoride alone. Interestingly, fluoride concentration and acid resistance on enamel surfaces treated with FCaP-5 was lower than with fluoride alone (Steel’s multiple comparison test, p < 0.05). ConclusionsFCaP effectively inhibits caries progression in subsurface enamel layers under pH cycling conditions by providing bioavailable calcium, indicating that FCaP increases the effectiveness of fluoride in caries management. FCaP may be a valuable addition to clinical practice, particularly for improving the effectiveness of fluoride-containing oral care products in individuals with low salivary calcium levels.

Development of engineering coating based on alumina nanoparticles incorporated into a Ni-Co alloy matrix: Effect of current density and alumina bath loading on microstructure and electrochemical corrosion behavior

The construction of electrodeposited coatings (EDCs) with enhanced microstructural characteristics and superior electrochemical corrosion behavior is of enduring concern for the industrial applications. In this study, alumina (Al2O3) nanoparticles were incorporated into a Ni-Co alloy matrix to improve its morphological and electrochemical behaviors. The primary objective was to assess the impact of varying electrodeposition current densities (20, 40, and 60 mA/m2) and different contents of alumina (3, 5, and 7 g/L) on the properties of a ternary Ni-Co-Al2O3 composite coating. EDX analysis was employed to investigate the effects of deposition current density and alumina bath loading on cobalt/nickel (Co/Ni) ratio and alumina content in the coatings. The results revealed that both the Co/Ni ratio and alumina content in the coatings increased with increasing current density and bath loading, but only up to certain thresholds (40 mA/m2 and 5 g/L). XRD analysis was conducted to assess the phase composition, crystal structure, crystallite size values, and preferred orientation of the fabricated EDCs. The mechanical properties of the deposited coatings were also evaluated using Vickers microhardness testing. The electrochemical corrosion behavior of the as-prepared EDCs was assessed using potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) techniques. The 40 mA/cm2 and 5 g/L samples exhibited lower corrosion current density (jcorr), higher charge transfer resistance (Rct), and lower double layer capacitance (CPEdl) values, suggesting that the increased cobalt and alumina particles in the coatings improved the corrosion resistance. Consequently, the optimal current density and alumina bath content for achieving the most favorable properties were found to be 40 mA/m2 and 5 g/L, respectively.

Surface Cladding of Mild Steel Coated with Ni Containing TiO2 Nanoparticles Using a High-Temperature Arc from TIG Welding

This study explores the use of a high-temperature arc generated during tungsten inert gas (TIG) welding to enhance the mechanical properties of the surface of AISI 1020 steel. An innovative two-step process involves using the high-temperature arc as an energy source to fuse a previously electrodeposited Ni/TiO2 coating to the surface of the substrate. The cladded surface is characterised by a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), an optical microscope (O.M.) equipped with laser-induced breakdown spectroscopy (LIBS), Vicker’s microhardness testing, and pin-on-plate wear testing. The treated surface exhibits a unique amalgamation of hardening mechanisms, including nanoparticle dispersion strengthening, grain size reduction, and solid solution strengthening. The thickness of the electrodeposited layer appears to strongly influence the hardness variation across the width of the treated layer. The hardness of the treated layer when the Ni coating contains 30 nm TiO2 particles was found to be 451 VHN, validating an impressive 2.7-fold increase in material hardness compared to the untreated substrate (165 VHN). Similarly, the treated surface exhibits a twofold improvement in wear resistance (9.0 × 102 µm3/s), making it substantially more durable in abrasive environments than the untreated surface. Microstructural and EDS analysis reveal a significant reduction in grain size and the presence of high concentrations of Ni and TiO2 within the treated region, providing clear evidence for the activation of several strengthening mechanisms.

Insights Into the Effects and Implications of Acidic Beverages on Resin Composite Materials in Dental Restorations: An InVitro Study.

Dental composite resins are commonly used due to their excellent physical and mechanical properties. However, exposure to beverages like Coca-Cola, Apple juice, and Black coffee can negatively impact these materials. This study examined the effects of these drinks on the surface microhardness and surface roughness of Nanohybrid, Giomer, and Dual-Cure Bulk-fill resin composites. Seventy-two disc-shaped resin composite specimens were prepared and divided into four groups (n = 18) based on immersion liquid: Group 1 (Coca-Cola), Group 2 (Apple juice), Group 3 (Black coffee), and Group 4 (Distilled water). The composites were further categorized into NeoSpectra (Subgroup 1), Beautifil II (Subgroup 2), and Predicta (Subgroup 3). Specimens were immersed for 14 days, alternating 18 h in beverages and 6 h in distilled water daily. Microhardness was measured using a Vickers microhardness tester, and surface roughness was analyzed by atomic force microscopy. Data were assessed using one-way ANOVA and Tukey's post hoc test, with significance set at p < 0.05. All groups experienced significant decrease in microhardness and surface roughness. Coca-Cola led to the highest roughness and hardness reduction. Among composites, the Nanohybrid resin (NeoSpectra) showed the least alteration. NeoSpectra ST, a nanohybrid composite, demonstrated superior resistance to acidic beverages compared to Giomer and Bulk-fill composites. The study finds that out of three composite materials, nanohybrid composites are the most acid resistant which provides a suitable material for patients who consume acidic beverages more frequently. In this way, clinicians can use this information to help optimally increase the longevity of their restorations by selecting materials according to oral exposure levels of acids in their patients.

Microstructure degradation and creep failure study of the dissimilar metal welded joint of heat-resistant steel and Inconel 617 alloy tested at 650 °C and applied stress range of 100–150 MPa

The advanced ultra-supercritical (A-USC) power plant system is anticipated to become India's next-generation base-load power station. To adopt AUSC technology, dissimilar welded joints (DWJs) between heat-resistant steels and the nickel-based alloys, using the nickel-based fillers, will need to be implemented. However, failure of dissimilar welded joints from P92 steel base metal or the heat affected zone (HAZ) has been commonly observed under high-temperature creep conditions. In the present study, the creep rupture behaviours and rupture mechanisms of DWJ between the Ni-based alloy Inconel 617 and heat-resistant P92 steel with Inconel 617 (ERNiCrCoMo-1) filler metal were investigated. Creep tests were conducted at 650 °C in the stress range of 100–150 MPa. To examine the creep rupture behaviour of the DWJ samples, optical microscopy (OM), scanning electron microscopy (SEM) and microhardness tests were performed. Cross-sectional images of the fractured creep specimens tested under various operating conditions revealed failures originating from distinct locations, including the P92 base metal and the inter-critical heat affected zone (HAZ). The specimen tested at 650 °C/150 MPa exhibited failure originating from the P92 base metal, whereas the specimen tested at 650 °C under the stress range of 100–130 MPa showed failure from the inter-critical heat affected zone (ICHAZ). The failure from P92 BM was primarily governed by plastic deformation, with the growth and coalescence of dimples ultimately resulting in trans-granular fracture. The specimens tested at 650 °C/100–130 MPa, which failed from the ICHAZ, exhibited a typical Type IV inter-granular failure. This failure mode is primarily attributed to matrix softening in HAZ, weakening of the boundaries, coarsening of the precipitates, and the evolution of intermetallic Laves phases. The specimen that failed in the stress range of 100–130 MPa exhibited a high density of microvoids in the ICHAZ, along with a few microvoids in the FGHAZ. The weld metal showed negligible degradation in microstructure, while the hardness study revealed a significant increase in hardness with an increase in rupture time, i.e., a decrease in applied stress and it was attributed to evolution of the new carbide phases in weld metal. Coarsening of the carbide precipitates was observed in each zone of the HAZ of P92 steel as well as in the base metal. The EDS study of the fracture tip and the FGHAZ/ICHAZ of the specimen that failed under stresses of 100 MPa and 120 MPa confirmed the evolution of intermetallic Laves phases. High magnification SEM images confirmed that triple boundaries are preferential locations for microvoid nucleation. The failed specimen showed the presence of microvoids near the carbide precipitates, with a large density of both coarse and fine precipitates confirmed all around and inside the microvoids. The ICHAZ and FGHAZ confirmed the formation of fine prior austenite grain boundaries (PAGBs) during the welding thermal cycle, which exhibited a lower density of carbide precipitates and this played a major role in Type IV failure.

High strength‐ductility combination in low‐density dual phase high entropy alloys

High strength and good ductility combination make it appealing for advanced structural and functional applications. However, enhancing strength typically reduces ductility due to their inverse correlation. FCC, BCC, L12, and B2 phases are most commonly found in high-entropy alloys (HEAs), which are the subject of extensive research to tweak their mechanical properties. We present a systematic microstructure-oriented mechanical property investigation for a newly developed low-density dual-phase high entropy alloy (LDDP-HEA) with varying phase fractions. In this study, Al15Cu20Fe25Ni30Ti10 HEA was designed by phase formation rules and heat treated at 800, 900, and 1000 °C for 24 h, followed by water quenching to investigate phase stability and their effect on mechanical properties. A combination of FESEM, EBSD, EDS, XRD, microhardness, and compression tests were carried out to investigate the microstructural characteristics and mechanical properties of the HEAs. The LDDP-HEA exhibited an excellent combination of mechanical properties with a high yield strength of ∼1675 MPa, ultimate compressive strength of ∼2250 MPa, and elongation to fracture of ∼10 % in the as-cast condition. The strength and low density of the alloy lead to superior specific compressive yield strength of 240 MPa g−1 cm3 and 121.70 MPa g−1 cm3 in as-cast and heat treated at 1000 °C conditions, respectively.

Effect of sodium hypochlorite and EDTA pretreatment on the resin infiltration efficacy and acid resistance of enamel white spot lesions: an in vitro study

BackgroundThis in vitro study aimed to evaluate the effect of sodium hypochlorite (NaOCl) and ethylene diamine tetraacetic acid (EDTA) as pretreatments on the resin infiltration efficacy and acid resistance of enamel white spot lesions (WSLs).MethodsEnamel blocks prepared from the buccal surfaces of sound human premolars were placed in a demineralisation solution for 3 days to establish artificial enamel WSLs. All the blocks with WSLs were randomly divided into four groups (n = 40 per group): RI (Control): resin infiltration only. N/RI: 5.25% NaOCl pretreatment + resin infiltration; E/RI: 17% EDTA pretreatment + resin infiltration; NE/RI: combined pretreatment of 5.25% NaOCl with 17% EDTA + resin infiltration; Enamel pore exposure was measured by using SEM observation and Image J software in each group after pretreatment prior to resin infiltration (n = 8 per group). Resin penetration depth and enamel surface microhardness were assessed after resin infiltration (n = 8 per group for each test) by a confocal laser scanning microscope and a Vickers’ microhardness test respectively. The remaining specimens were subjected 7 days of pH cycling after which surface enamel roughness and microhardness were assessed by an atomic force microscope and a microhardness test respectively.ResultsCompared to the control group, the enamel surface pore exposure (p = 0.007), resin penetration depth (p = 0.011) and enamel surface microhardness (p < 0.001) were all significantly increased after the pretreatment of 5.25% NaOCl alone or combined with 17% EDTA by one-way ANOVA. After pH cycling, no significant differences were found in enamel surface roughness or microhardness among the four groups (p = 0.55) by two-way ANOVA.ConclusionsEnamel surface pretreatment of 5.25% NaOCl or combined with 17% EDTA improved the efficacy of the resin infiltration of WSLs, but might be useless in enhancing the acid resistance of resin-infiltrated WSLs.

Microstructure, precipitates and mechanical properties of Cu-3Ni-1Ti alloy by two-stage cold rolling and aging treatment

The effects of two-stage cold rolling and aging treatment on the mechanical and electrical properties of Cu-Ni-Ti alloy were investigated. The microstructure evolution, precipitation behavior, and strengthening mechanism of the alloy after two-stage cold rolling and aging treatment were analyzed using microhardness, tensile strength, and electrical performance tests, combined with transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques. The research results show that the alloy after two-stage cold rolling and aging treatment exhibits excellent comprehensive properties, tensile strength reaches 635 MPa, yield strength is 597 MPa, hardness is 182 HV, conductivity is 62.1 % IACS, and elongation is 14.5 %. This processing method facilitates the precipitation of more nanoscale Ni3Ti phases and the formation of smaller cellular substructures. Consequently, the alloy maintains its exceptional mechanical properties through the combined effects of dislocation and precipitation strengthening. This study provides a novel preparation process and a solid theoretical foundation for enhancing the mechanical and electrical properties of Cu-Ni-Ti alloys.

Investigating impact of in-process cooling mediums on microstructural and mechanical properties of FSWed AA2219 T6 joints

This study investigates the influence of various in-process cooling techniques on the microstructural characteristics and mechanical properties of the friction stir-welded AA-2219-T6 alloy. The in-process cooling methods used include normal air, dry fan, an oil-water mixture (20:80), and water. The primary objective is to determine the optimal cooling strategy for enhancing the quality of the weldment. The characterization included light microscopy, tensile testing, X-ray diffraction (XRD), microhardness testing, and scanning electron microscopy (SEM) analysis of fractured surfaces to evaluate the microstructure and mechanical properties. It was seen that in-process cooling methods significantly affect the microstructural features and mechanical properties of AA 2219-T6 alloy weldments. Findings indicated that the water-cooled method at 55 °C resulted in the highest density of Al2Cu particles, leading to superior hardness and mechanical properties compared to other in-process cooling methods. Specifically, the water-cooled samples exhibited a ~ 17% increase in hardness compared to air-cooled samples and achieved an ultimate tensile strength equivalent to 65.4% of the base metal. Furthermore, a notable volume of second-phase particles was observed on the fractured surfaces in the water-cooled condition, attributed to the lower in-process temperatures, thus underscoring the effectiveness of water cooling in friction stir welding.

Development and optimization of parameters for HVOF sprayed Al2O3 and ZrO2 blended aluminum coating on 316L SS

Abstract A significant number of gas turbines, aircraft engines, bearings, and automotive engines operating under a wide temperature range fail frequently due to fatigue and surface oxidation. Thus, a new coating formulation 40Al-35Al2O3-25ZrO2 was deposited on 316L SS substrate through the high velocity oxygen-fuel (HVOF) thermal spray coating method. The number of passes, spray distance and oxygen flow rate were varied by using Taguchi L9 array to achieve an optimized coating with higher hardness, less porosity, and roughness. The coating phase analysis, microstructure, elemental composition, microhardness and nano hardness were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), Vickers microhardness and nano indentation testing. The sample 5 prepared at spray distance of 20 cm and oxygen/acetylene ratio of 2 exhibited optimal hardness (1972 HV1), tensile strength (6.463 GPa), porosity (0.75%) and roughness (6.2 μm) due to α-Al2O3 and t-ZrO2 phases. Oxygen flowrate was the influential parameter contributing 48.71% to microhardness and 42.41% to roughness, while spray distance with contribution 51.62% was influential parameter for porosity.

Highly reflective ZrC-Cu-based metal matrix composite coatings deposited via cold-spray for laser protection applications

Lasers are very powerful and can produce high temperatures, capable of melting materials when projected with an appropriate power, exposure time, distance, and beam width. High energy lasers are used for attacking enemy aircraft and missiles; however, the same threat is inevitable to the allied aircraft and missiles. Surface coatings have proven to be a viable solution to reduce damage from such laser attacks. In the present work, ZrC-Cu-based highly reflective coatings were deposited on Al-6061 alloy using the cold spray to develop laser damage resistance. Microstructural characterization, XRD, micro-hardness, reflectivity measurements, and laser ablation tests were conducted on the developed materials. The results showed improved ceramic retention and mechanical properties along with minimal porosity in the coating with increasing ZrC content in the feedstock. Additionally, the XRD analysis revealed that Cu-ZrC composite coatings could be produced by cold spray, without decarburisation of ZrC or oxidation of Cu. Owing to the exceptional purity in coatings, highly reflective coatings were obtained. At the target wavelength of 1080 nm, Cu-30 %ZrC composition achieved a remarkable reflectivity of 75 % (85 % of bulk copper). The coatings with compositions of Cu-30 %ZrC, Cu-50 %ZrC and Cu-70 %ZrC remained undamaged under laser irradiation, whereas Cu-85 %ZrC exhibited a laser ablation pit. These findings provide valuable insights into developing optimized ZrC-Cu coatings against laser irradiation.

Effect of thermal history on performance of bulk metallic glass spacecraft components

Bulk metallic glasses (BMGs) are multi-element metal alloys with attractive properties for spacecraft applications. With recent advances in the BMG supply chain and commercialization, understanding the effects of thermal history associated with the manufacturing, integration, and service on performance of BMG components is critical for infusion. In this study, a Cu43Zr43Al7Be7 (at. %) BMG-forming composition, an alloy developed for gears for extreme-environment applications, was investigated. The thermal properties and structural glassy states resulting from different thermal treatments were studied with differential scanning calorimetry, microhardness, and four-point bending tests. It is shown that the thermal history and resulting structural states have a pronounced effect on some mechanical properties, highlighting the necessity of qualifying parts in different glassy states for their intended practical applications.

Analysis of Mechanical Properties and Printing Orientation Influence of Composite Resin for 3D Printing Compared to Conventional Resin.

This study aimed to compare the flexural strength, surface roughness, and microhardness of a resin for three-dimensional (3D) printing and a conventional composite resin and to evaluate whether the printing orientation influences these properties. To evaluate the flexural resistance, test specimens were produced and divided into four groups: three groups of resins for 3D printing with inclinations of 0°, 45°, and 90° and one group of conventional composite resin. Forty discs were produced and subjected to a sandpaper-polishing sequence, and the surface roughness was measured using a roughness meter. The Vickers microhardness (HV) test was performed at three different points, and the average was obtained. The results were subjected to ANOVA statistical analysis and Tukey's test. There were statistical differences in the flexural strength and microhardness between the conventional resin and the resin used for 3D printing. No statistical difference in surface roughness was observed. The resin for 3D printing exhibited lower flexural strength and microhardness than conventional composite resins. We concluded that the resin for 3D printing had lower flexural strength and HV than the conventional composite resin but similar surface roughness. The printing orientation did not affect the flexural strength, whereas the hardness increased as the printing angle increased.