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Purpose: To evaluate the effect of different lithium-disilicate (LiSi) glass-ceramic surface decontamination procedures on the shear bond strength (SBS) to resin cement. Materials and Methods: Seventy CAD/CAM LiSi ceramic specimens (IPS e.max CAD, Ivoclar) were cut and sintered. Fifty specimens were treated with 5% hydrofluoric acid (HF) for 20 s, while 20 were left untreated. All 70 specimens were then contaminated with human saliva and try-in silicone paste. The following surface cleaning methods were investigated (n = 10): C: water rinsing (control); PA: 37% H3PO4 etching for 20 s; E: 70% ethanol applied for 20 s; CP: cleaning paste (Ivoclean, Ivoclar) brushed for 20 s; HFSEP: self-etching ceramic primer (Monobond Etch&Prime, Ivoclar) rubbed for 20 s; HF: 5% HF applied for 20 s or no HF etching prior to contamination; SEP: self-etching ceramic primer rubbed for 20 s and no HF etching prior to contamination. Composite cylinders were created and luted with an adhesive resin cement to the decontaminated surfaces. After storage for 24 h at 37°C, the SBS test was conducted. Two fractured specimens per group were observed under SEM to perform fractographic analysis. The data were statistically analyzed with p set at <0.05. Results: The type of surface cleaning approach influenced bond strength (p < 0.001). HFSEP, SEP, and HF attained higher SBS (p < 0.001) compared to other groups. None of the approaches were able to completely remove contaminants from the ceramic surfaces. SEM images showed residual traces of contaminants on CP-treated surfaces. Conclusions: The self-etching ceramic primer enhanced bond strength to contaminated LiSi ceramic surfaces, irrespective of previous treatment with hydrofluoric acid. [ABSTRACT FROM AUTHOR]

Two clinical cases involving the fracture of a natural tooth and one of a ceramic crown are presented and discussed based on fractography principles. In the first case, a patient reported intense pain in a sound third molar where a longitudinal fracture was identified, and the tooth was extracted. In the second case, a posterior rehabilitation using a lithium silicate ceramic crown was carried out, and the patient returned after 1 year with a fractured piece of the crown. Both were analyzed under microscopy to identify the origins of fractures and their causes. The fractures were critically analyzed so that relevant information could be generated from the laboratory to the clinic. [ABSTRACT FROM AUTHOR]

Purpose: To inves)gate the op)mal combina)on of factors (finish line, scanning, and ceramic processing) to achieve the best values of both adapta)on and fracture load for lithium disilicate crowns (LD). Materials and Methods: Two abutment prepara)ons, chamfer (C) and rounded shoulder (S), were produced with a den)n analog material and scanned with either extraoral (E) or intraoral (I) scanners. Images were processed using CAD soEware to design a premolar. Blocks of LD were milled using a CAD/CAM system (CAD). For the press technique (PRE), crowns were first 3D printed using a polymeric material, then heat-pressing protocol was performed. Design of experiments was used to plan four experimental groups (n = 10): CAD-CI, CAD-SE, PRE-CE, and PRE-SI. Two dependent variables were analyzed: adapta)on, measured using the replica technique; and fracture load of the cemented crowns. Fractographic analysis was performed. Data were analyzed using ANOVA and regression sta)s)cal analyses. Results: There was no significant effect of the scanning method and finish line on the gap thickness in the different regions. For the processing method, CAD resulted in larger gap thickness in the occlusal, axial angle, and marginal areas and a smaller gap in the axial area (P < .001). The inves)gated factors had no effect on the fracture load. Yet, PRE-CE was considered the op)mum design because it achieved 100% of the desired fracture load (>1000 N) and 40% adapta)on (< 200 µm). Conclusions: The op)mum combina)on of factors for all-ceramic crowns is chamfer abutment prepara)on, extraoral scanning, an d the press technique (combined w 3D prin)ng). [ABSTRACT FROM AUTHOR]

Ultrasonic metal welding machines are suitable for various complex applications (e.g., battery tabs) through unique mechanical design, special pressure application methods and high-precision welding. This work reports the weldability, forming quality and fractographic analysis of copper multilayered welded joints which were studied by SEM-EDS characterization, micro-hardness testing and tensile testing based on ultrasonic double roller welding (UDRW). Three groups of process parameters (A, B and C) were established to investigate the performance, production quality and welded joint surface interconnections. The tensile testing results of sample under parameter 3 in group A [S-P3(A)] indicate the maximum tensile strength of 69.859 N in T-peel test while the average tensile strength has increased by 58.525 N due to rise in welding time from 2 sec to 5 sec. The results analysis indicates that welding quality features in S-P3(A) joints under 4 bar, 100 mm/s, 45 % have been exploited. The over-welded zone was transformed into good-welded zone. The micro-cracks, fatigue stations and peeling texture in multilayers were reduced. It was found that when the welding energy was 10000 J then the tearing edges and interlayers cracks were minimized while keeping the other parameters constant. Moreover, when the amplitude increased up to 50 %, then numerous micro-cracks and micro-fissure stations were created, which leads to the occurrence of fracture in multi-layer welded joint. The EDS study investigated that the complex features are formed at the interface junction of sample 3 S3(A) in multilayer welds. The complex multilayer microstructures can induce and produce unique hardness properties for battery manufacturing. It leads to high quality and durable welds. Eventually, it is experimentally demonstrated that robust 40 layer welded joints can be obtained by the UDRW process. The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request. • Low amplitude used to minimize the damage of a workpiece, reduce metal debris and heat. • The study reports 40 layers of 0.2mm Cu thin foils welded joints using ultrasonic seam welding technology. • Tensile testing of S-P3(A) indicate maximum strength with 69.859N due to incremental upturn in time from 2sec to 5sec. • Welding quality features in S-P3(A) joints under 4bar, 100mm/s, 45%: (a) inside cross-sectional view were investigated. • Weldability, forming quality and fractographic analysis of Cu welded joints were studied by SEM-EDS characterization. [ABSTRACT FROM AUTHOR]

This paper analyses the notch effect in the fracture behaviour of acrylonitrile–styrene–acrylate (ASA) material manufactured by fused filament fabrication (FFF). The research is performed on 72 single-edge-notch bending (SENB) specimens containing U-notches with nominal notch radii varying from 0 mm (crack-like defects) up to 2.0 mm, and fabricated with three different raster orientations (0/90, 45/−45, 30/−60). Apparent fracture toughness values are obtained for the different conditions and the resulting notch effect is analysed through the Theory of Critical Distances. A fractographic analysis is also performed using Scanning Electron Microscopy (SEM) in order to justify the fracture (macroscopic) behaviour from the observed fracture micromechanisms. The notch effect observed in the three ASA raster orientations is very similar, and lower than that observed in other FFF polymeric alternatives (ABS, PLA). [ABSTRACT FROM AUTHOR]

This study investigates the effect of laser treatment parameters on the tensile behavior of H13 tool steel in both quenched and tempered conditions. The effects of varying laser parameters on ultimate tensile strength and elongation at fracture which is the aim of this research were explored by employing a bionic unit to apply laser treatment with two parallel lines on the steel surface. These parameters are crucial for understanding material performance under tensile stress. Statistical analysis, including an analysis of variance (ANOVA), and fractographic analysis using SEM were conducted to analyze the results. The findings reveal a significant enhancement in the ultimate tensile strength of the laser-treated samples, with values ranging between 1342.27 and 1497.25 MPa, surpassing the non-treated substrate's strength of 1247.23 MPa. However, a decrease in elongation at fracture was observed, indicating increased brittleness post-laser treatment, with elongation values notably lower than the non-treated sample's 14.71%. The hardness values within the laser-treated zone exhibited a high variance, with the highest values found in the hardened zone ranging from 65.7 to 61.4 HRC, suggesting the formation of fine carbides and lath martensite due to rapid cooling and martensitic transformation. Furthermore, the depth of the laser-transformed zone, significantly influenced by laser power, varied between 1.30 and 1.9 mm, highlighting the critical role of laser parameters in affecting material properties. The study highlights a critical balance between ductility and strength in laser-treated H13 tool steel, which is essential for optimizing the material's performance for industrial applications. [ABSTRACT FROM AUTHOR]

Large gas engines are typically applied to compensate for peak loads and grid instabilities in the electric power supply. A key component of these engines is the spark plug. Because of the harsh conditions encountered in their use, the spark plug electrodes are subject to significant wear. Conventional electrodes are expensive due to the precious metal alloys they contain. As an alternative, ceramic materials from the groups of silicide, carbides, and nitrides were selected for preliminary experiments that investigate functional as well as mechanical properties and wear behavior. Because of the harsh conditions during operation, the new materials must have a high melting temperature, good thermal shock resistance, high thermal conductivity, and high corrosion/oxidation resistance as well as high density. It was found that the mechanical and thermomechanical properties of certain ceramic candidates are sufficient for application as spark plug electrodes. Furthermore, the chosen ceramic materials achieve an adequate performance in terms of secondary voltage trace and ignition behavior. However, wear resistance may not be sufficient for service times longer than the service time of existing spark plugs and further research is still necessary before ceramic electrodes may be established as a commercial alternative to existing electrodes. [ABSTRACT FROM AUTHOR]

A high-entropy alloy with an atomic composition of Fe40Mn15Cr20Ni22Ti3 with outstanding strength–ductility synergy induced by titanium additions was successfully developed. At room temperature, its ultimate tensile strength can reach 1089 MPa and still maintain 21% elongation. Moreover, at low temperature of 77 K, its ultimate tensile strength and elongation have been increased to 1285 MPa and 35%, respectively. After careful analysis, it is found that the cause for the large increase in elongation is the decrease of the stacking fault energy at low temperature, which leads to the deformation mechanism of the alloy to change from dislocation wave slip to plane slip. In addition, the precipitation strengthening and grain boundary strengthening induced by chrome-rich σ precipitates are the main strengthening contribution. [ABSTRACT FROM AUTHOR]

The purpose of the article was to analyze the influence of print orientation, using the direct metal laser sintering (DMLS) method, on the strength of the tested material before and after heat treatment. The heat treatment involved heating the material to 490 °C and subsequently cooling it within the furnace for four hours. Experimental research involves the X3NiCoMoTi 18-9-5 tool steel. Analysis of the test results indicates a strength increase following heat treatment. Additionally, a numerical study was conducted to investigate the mechanical characteristics of the X3NiCoMoTi 18-9-5 tool steel fabricated via 3D printing. Fractographic analysis of specimen failure was performed, and the results were subsequently compared. [ABSTRACT FROM AUTHOR]

This work investigated the tensile and fatigue strength, fatigue crack propagation rate and corresponding mechanism, and fracture behavior (under the tensile and cyclic loading) of the extruded CaO-AM30 alloy. The microstructure observations shown that the average grain size of AM30 base alloy was 7.8 μm, which decreased to 3.5 μm in the CaO-AM30 alloy. In both alloys, Mg17Al12 and Al6(Mn, Fe) phases were present, and C15 ((Mg, Al)2Ca) phases were additionally present in the CaO-AM30 alloy. Also, the average size of the Mg17Al12 and Al6(Mn, Fe) phases was much smaller in the CaO-AM30 alloy than those in the AM30 alloy. As a result of the smaller grains and fine evenly distributed second phases, CaO-AM30 alloy shown an improved tensile strength along with a 25% increase in the elongation. Accordingly, the CaO-AM30 alloy showed higher fatigue strength (168 MPa) than the AM30 alloy (130 MPa) after ~ 107 number of cycles. Nevertheless, fatigue crack growth test revealed that the CaO-AM30 alloy has a lower threshold ∆Kth value than the AM30 base alloy. Also, the calculated value for m (log slope of da/dN and ∆K) was 13.64 for AM30 alloy, which increased to 14.15 for the CaO-AM30 alloy. The relatively higher crack propagation rate of the CaO-AM30 was most likely related to the presence of larger plastic deformation zone in it than its grain size, causing the suppression of fatigue crack closure mechanism during the unloading half of the cycle. Hence, this study suggested that the fine grains improve the strength and high-cycle fatigue properties of the Mg alloys, but adversely affect the fatigue crack propagation resistance. [ABSTRACT FROM AUTHOR]

ABSTRACT The milled surface of TC4 titanium alloy was treated by laser shock peening (LSP) and laser shock wave planishing (LSWP) to investigate the effect of compressive residual stress (CRS) and surface roughness (SR) on the vibration fatigue performance. The results demonstrate that although the amplitude of CRS induced by LSWP is lower than that of LSPed specimens, the vibration fatigue life of LSWPed specimens increased by 63.78% due to a significant reduction in SR from Sa 14.1 μm to Sa 4.21 μm. When the SR is low, increasing the amplitude of CRS is more advantageous to enhance fatigue life. The fractographic analysis further confirmed that compared with LSPed and T0.2‐LSWPed specimens, T0.1‐LSWPed specimens have considerably less initial fatigue crack initiation, and the crack initiation location is deeper. The fatigue striation spacing of T0.1‐LSWPed specimens is the smallest (0.25 μm), greatly lowering the fatigue crack growth rate. [ABSTRACT FROM AUTHOR]

The effect of plastic deformation on the hydrogen embrittlement behavior of high-strength martensitic steels was investigated using a U-bend test. The hydrogen embrittlement susceptibility appeared to be enhanced with increasing plastic strain. Based on fractographic and stress-strain analyses, the maximum principal stress dominated the hydrogen embrittlement fracture. Although an apparent enhancement with increasing plastic deformation was observed, the origin of this enhancement was increased residual stress arising from the evolution of graded plastic strain during U-bending. We conclude that residual stress, rather than plastic strain induced by plastic deformation strongly affects hydrogen embrittlement susceptibility in deformed high-strength steel components. • Hydrogen embrittlement susceptibility of U-bend specimens was independent of plastic strain. • Maximum principal stress was the primary criterion for the hydrogen embrittlement susceptibility. • The apparent decrease in hydrogen embrittlement resistance with reduced bending radii was due to increased residual stress. [ABSTRACT FROM AUTHOR]

In this research, a smart manufacturing approach was used to enhance the mechanical properties of aluminum (Al) for lightweight applications. The smart manufacturing involved cryomilling of Al powders with and without 5 wt.% magnesium (Mg) powders for varying durations followed by a high-pressure cold spray (HPCS) additive manufacturing process to prepare bulk components. The morphological changes, crystallite size, and composition of the cryomilled powders and cold sprayed (CS'ed) components were examined using scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The results showed that the crystallite size reduces with an increase in cryomilling time and the addition of Mg dopant. To test the mechanical properties of the bulk CS'ed components, microhardness tests were performed using a Vickers microhardness tester. Uniaxial tensile tests were also carried out to ascertain the material's tensile properties. The mechanical testing results showed great improvement in the hardness and tensile strength of CS'ed Al–Mg samples as compared to pure Al samples. Subsequently, fractography analysis of the tensile failed samples was carried out to determine the nature of the failure. The research article also discusses the inherent mechanisms for the improvement in mechanical properties of smart manufactured components as a result of Mg doping and cryomilling. [ABSTRACT FROM AUTHOR]

This paper presents a comparative assessment of hygrothermal effects on the mechanical and thermomechanical properties of resin‐infused thermoplastic E‐glass fiber‐reinforced composites (FRC) in the marine environment. The thermoplastic FRCs were immersed in seawater at two different aging temperatures, that is, 35 and 70°C. The quasi‐static tests were conducted on unaged and aged FRCs, followed by scanning electron microscopy (SEM) to determine the effect of the marine environment on the mechanical properties and damage progression. The specimens immersed at 70°C showed a significant drop of 46.7%, 39.7%, 22.6%, and 16% in mechanical properties (tensile, compression, flexural, and ILSS) mainly due to plasticization, matrix cracking, and fiber/matrix debonding. The specimens immersed at 35°C showed a reduction in tensile, compressive, and flexural strength of 10%, 14.7% and 1.9% respectively, with no significant effect on ILSS. In addition, dynamic mechanical analysis (DMA) reveals that prolonged aging induces an increase in glass transition temperature Tg due to polymerization reactions. This work is intended to reveal the effect of extreme marine environment on the resin‐infused thermoplastic FRC and to provide a useful reference for their potential structural applications in the marine industry. Highlights: Influence of aging conditions on the long‐term performance of FRCs.Hygrothermal aging leads to an increase in the glass transition temperature.The marine environment degrades mechanical properties of FRCs by up to 50%.Matrix cracking and fiber‐matrix debonding evolved as dominant failure modes. [ABSTRACT FROM AUTHOR]

This experimental work involves characterization and fractography of a bio‐based epoxy and an in‐situ polymerisable thermoplastic polymer matrix based non‐crimp glass and carbon fiber composites under compressive loading. The laminates are characterized under compression loading using a combined loading compression (CLC) fixture. Laminates made using the thermoplastic matrix exhibit higher compressive strength (approx. 20% along fiber direction) compared to the bio‐epoxy based laminates. Further, both composites exhibit comparable compressive modulus characteristics. The tested composites are subjected to fractography analysis using Scanning Electron Microscopy (SEM) and Computed tomography (CT). SEM results indicate a difference in fiber‐matrix interface characteristics between the thermoplastic matrix and the bio‐epoxy matrix. Additionally, the CT scans reveal a difference in failure modes due to fiber orientations. A difference between failure mode of the exterior and interior plies of the specimens was also noticed. However, no specific influence of matrix type was observed on the overall macroscopic failure behavior. Highlights: Bio‐epoxy and thermoplastic based laminates were characterized in compression.Post‐test fractography was performed using SEM and x‐ray CT scans.Use of thermoplastic matrix exhibits better fiber‐matrix adhesion compared to bio‐epoxy.Both laminates performed well in compression under laboratory test conditions. [ABSTRACT FROM AUTHOR]

This paper reports improvement in the tensile, flexural and interlaminar shear strength (ILSS) properties of ADG‐NH2/Epoxy/CFRP composites at low filler content. Five symmetrical CFRP composite laminates were prepared through wet layup process assisted by vacuum bagging technique with varying wt% proportions (0.25, 0.5, 0.75 and 1) of ADG‐NH2/Epoxy. Tensile tests, short beam shear test and flexural tests were carried out as per ASTM D3039, ASTM D2344 and ASTM 790‐10 respectively to assess the effect of the ADG‐NH2 functionalized nano additives on their mechanical properties. The variation in ILSS were studied for varying temperatures (room temperature, 35, 50, 75, 85, & 100°C for each type of ADG‐NH2/Epoxy wt% (neat, 0.25, 0.5, 0.75 & 1)) of ADG‐NH2/Epoxy/CFRP composites. The ILSS was enhanced up to ∼27% for 0.5 wt% of ADG‐NH2 reinforced CFRP at room temperature but reduced with the higher concentrations (0.75 wt% & 1 wt%). It was observed that ILSS reduced with gradual temperature variations up to 100°C w.r.t room temperature. But an increment was observed up to 0.5 wt% for ADG‐NH2 for all temperature. Form the test results, it has been recorded an improvement in mechanical properties that is, the elastic modulus by ∼18%, ultimate tensile strength by ∼21%, % elongation at break by∼19% and toughness by∼28% for the 0.5 wt% of ADG‐NH2 graphene nano additive reinforced CFRP composite laminates as compared to neat epoxy CFRP laminates. Results also show the augmentation in the Max load by ∼24%, flexural strength by ∼33%, flexural modulus by ∼43%, and flexural strain by ∼26% were observed for the 0.5 wt% of ADG‐NH2 graphene nano additive reinforced CFRP composite laminates as compared to neat epoxy CFRP composite laminates. Fractographic studies of fractured surface using SEM analyses shows better adhesion mechanisms which supports the augmentation in mechanical properties with addition of amine functionalized graphene to CFRP laminate. Highlights: Reinforcement of amine functionalized (ADG‐NH2) graphene in the epoxy matrix and incorporation with carbon fibers to enhance the interfacial and flexural properties.Evaluation of temperature effects on interlaminar shear strength properties of amine functionalized CFRP compositesImprovements in tensile, ILSS and flexural properties observed for a low percentage (0.5 wt%) of ADG‐NH2 graphene reinforced CFRP composite laminates.Use of aerospace grade epoxy and resin with amine functionalized graphene for further use in aerospace industry applications. [ABSTRACT FROM AUTHOR]

The hydrogen embrittlement behavior of a prerolled Fe–15Mn–0.65C–2Al–2Si high‐Mn steel with various cut‐edge properties is studied via hydrogen precharging and slow strain rate test. In the presence of hydrogen, samples prepared by laser cutting under atmosphere of N2 exhibit the best total elongation at about 39%. Press blanking produces severe shear deformation, tensile residual stresses, and strain‐induced martensite, resulting in a high risk to hydrogen‐induced cracking. With compressive residual stresses produced from waterjet, corresponding samples exhibit the lowest elongation loss against hydrogen. Despite hydrogen charging, the fracture surfaces show transgranular quasi‐cleavage features, for which mechanical twinning from prerolling plays a critical role. The hydrogen‐enhanced decohesion mechanism accounts for cleavage fracture since hydrogen segregation reduces cohesive stress at twin boundaries. [ABSTRACT FROM AUTHOR]

The current framework for managing construction waste, guided by European Union regulations, calls for an integrated waste management system. However, the reuse of old plaster waste, particularly from deteriorated facades, remains underexplored. This study investigates the potential of repurposing old plaster waste as a substitute for aggregates and cement in mortars, with the aim of promoting environmental sustainability and resource efficiency. Three mortar mixes were analyzed: a control mix, a mix with 45% waste replacing aggregates, and a mix with 10% waste replacing cement. Results show that replacing 45% of aggregates with plaster waste led to a 30% reduction in flexural strength, while the 10% cement replacement increased flexural strength by 6%. Compressive strength dropped by 27% and 38% for cement and aggregate replacements, respectively. Despite these reductions, the waste replacement remained within acceptable limits for structural integrity. Further microscopic analysis revealed that the incomplete integration of portlandite particles from the waste contributed to non-uniform bonding and crystal formation, weakening the mortar's structure. This research demonstrates the feasibility of reusing old plaster waste, offering a novel approach to reducing construction waste and promoting a circular economy. It contributes to filling the knowledge gap on the reuse of plaster mortars while aligning with sustainable construction goals. [ABSTRACT FROM AUTHOR]

Highlights In actual service conditions, the composite structures are subjected to the combined effect of Mode‐I and Mode‐II loadings. It has great significance in the aerospace, defense, military, automobile, and marine sectors. This study aims to determine the Mixed Mode‐I/II interlaminar fracture toughness (ILFT) of plain and twill woven carbon, Kevlar monolithic, and interyarn hybrid textile composites under several hybridization schemes. The tailored properties are obtained using the interyarn hybridization of high stiff carbon yarn and high tough Kevlar yarn. The effect of individual yarn in the length direction in different hybrid composite laminates is carefully investigated. The Mixed Mode‐I/II ILFT characterization is experimentally performed using a mixed mode bending (MMB) test specimen on the Instron 8862 system under 45%, 55%, and 65% Mixed Mode ratios (MMRs). The increase in mode mixture percentage decreases the lever length, increases the load‐bearing capacity, and increases the Mixed Mode‐I/II ILFT of the MMB test specimen. Plain woven composites exhibited a higher ILFT than twill woven textile composites. The plain woven carbon–Kevlar hybrid composite laminate with carbon yarn‐in‐length direction shows the highest Mixed Mode‐I/II ILFT after CP laminates. Hybridization significantly increases the Mixed Mode‐I/II ILFT compared to monolithic Kevlar fabric‐reinforced composites. Moreover, the failure mechanisms are investigated using scanning electron microscopy. Mixed Mode‐I/II ILFT of carbon–Kevlar interyarn hybrid textile composites. ILFT at nonlinearity (NL), VIS, and 5%/Max load points for 45%, 55%, and 65% MMR. Advantage of placing carbon yarn‐in‐length direction in hybrid configurations. Effect of carbon–Kevlar interyarn hybridization on Mixed Mode‐I/II ILFT. Fractography of tested specimens to investigate several failure mechanisms. [ABSTRACT FROM AUTHOR]

The fatigue crack growth properties of G20Mn5QT cast steel and corresponding butt welds, using compact tension specimens, were monitored and investigated via acoustic emission (AE) techniques. Fatigue crack growth is a combination of cyclic plastic deformations before the crack tip, tensile crack fractures, and shear crack fractures. The cyclic plastic deformations release the maximum amount of energy, which accounts for half of the total energy, and the second-largest number of AE signals, which are of the continuous-wave type. The tensile crack fractures release the second-largest amount of energy and the largest number of AE signals, which are of the burst-wave type. The shear crack fractures release the least amount of energy and the lowest number of AE signals, which are similar to the burst type, albeit with a relatively longer rise time and duration. Crack tip advancement can be regarded as a discontinuous process. The critical area before the crack tip brittlely ruptures when the fatigue damage caused by cyclic plastic deformations reaches critical status. The ruptures produce a large number of tensile crack fractures and rare shear crack fractures. Through fractography observation, the shear crack fractures occur probabilistically around defects caused by casting or welding, which lead to stress and strain in the local complex. [ABSTRACT FROM AUTHOR]

The current research aims to investigate how processing parameters influence the mechanical properties and microstructure development of dissimilar AA7075/AA6061. These alloys were friction stir welded (FSWed) at varied traverse rates (ranging from 20 to 60 mm/min) while maintaining a constant rotation rate of 708 rpm. Several characterization techniques, such as electron microscopy and optical microscopy, were utilized to quantify the microstructure evolution of these dissimilar FSWed joints. A universal testing machine and a Vickers microhardness tester were used to evaluate the mechanical characteristics. The field emission–scanning electron microscope was used to examine the fracture surfaces of the fractured tensile specimens. The experiment revealed that the grain size within the nugget zone decreased as the tool traverse rate increased from 20 to 60 mm/min. Specifically, the grain size in the nugget zone measured 5.82 µm at a speed of 20 mm/min, whereas it reduced to 3.64 µm at 60 mm/min. Furthermore, the FSWed sample processed at 60 mm/min demonstrated a superior ultimate tensile strength of 251 MPa. The hardness values exhibited a similar increasing trend as the traverse speed increased. The heat-affected zone of the AA6061 side achieved the lowest hardness at a traverse rate of 20 mm/min. A ductile fracture mode predominated for most of the dissimilar joint fracture surfaces investigated. [ABSTRACT FROM AUTHOR]

The presence of α casing in beta titanium can be detrimental to various forming applications and can be eliminated through chemical milling. The effect of the chemical milling process on the removal of alpha casing from the surface of beta titanium has been investigated extensively. Chemical milling is performed at different solution concentration ratios, and the specimens are characterized using Vickers hardness and surface roughness. The optimum results for chemical milling with a high material removal rate of 3.85 mm3/min are obtained with HF (10%) and HNO3 (10%). The effect of chemical milling on the mechanical strength of beta titanium is studied through tensile tests at room temperature and at increased temperature (200 °C). The maximum percentage of elongation obtained after chemical milling is around 24.4%, compared to 1.7% observed with the as-received specimen. Comprehensive analysis through optical microscopy, XRD, and EBSD confirmed the successful removal of the α casing from the β-Ti alloy at both 0.7- and 0.5-mm chemical milling depths. The effectiveness of the chemical milling process is further investigated through fractography analysis of the tensile-tested specimens. Chemical milling with the specified solution proves to be an effective method for enhancing α casing removal and mechanical performance of β-Ti alloys, making it a promising technique for various industrial applications. [ABSTRACT FROM AUTHOR]

Highlights Graphene (nano) platelets (GPs) are cost‐effective and possess high structural integrity, but their limited surface functional groups hinder their compatibility with polymers. In this study, an eco‐friendly, water‐based mechanochemical approach was developed to modify GPs with polyacrylamide (PAM), creating PAM graphene platelets (PAM‐GPs) with a grafting ratio of approximately 15%. The platelet was measured to be a few nanometers in thickness, and the grafted PAM provides abundant functional groups, including amide groups, which enhance compatibility with polymers. A typical polymer, bisphenol‐A epoxy, was compounded with PAM‐GPs, resulting in a high degree of exfoliation and dispersion of PAM‐GPs within the matrix. The resulting epoxy/PAM‐GP composites exhibited significantly improved mechanical properties, including an 18% increase in Young's modulus and a substantial enhancement in fracture toughness, with a 71% increase at a low filler fraction of 0.5 wt%. These improvements are attributed to the effective interfacial interaction between the PAM‐GPs and the epoxy matrix, facilitated by the grafted functional groups. This study highlights the potential of PAM‐GPs as toughening fillers for epoxy composites, emphasizing their applicability in enhancing the durability and performance of structural components in industrial applications. Polyacrylamide (PAM)‐modified graphene platelets by a water‐based approach. A strong interface promoted exfoliation and dispersion of platelets. PAM‐modified platelets improved epoxy modulus and toughness. Fractographic analysis unveils toughening mechanisms. [ABSTRACT FROM AUTHOR]

This study employs a custom hollow specimen setup to investigate the HE in API 5L X60 pipeline base and welded materials exposed to pure hydrogen and a 20% hydrogen–natural gas blend at 2.07 MPa. Results indicate embrittlement with increasing hydrogen concentration. The base material showed a hydrogen embrittlement index (HEI) of 11.6% at 20% hydrogen and 12.4% at 100% hydrogen. For the welded material, the HEI was 14.6% at 20% hydrogen and 18.0% at 100% hydrogen. Fractography analysis revealed that the base and welded materials exhibited typical ductile fracture features in the absence of hydrogen, transitioning to a mixture of quasi-cleavage and micro-void coalescence (MVC) features in hydrogen environments. Additionally, with hydrogen, increased formation of secondary cracks was observed. Notably, the study identified the Hydrogen-Enhanced Localized Plasticity (HELP) mechanism as a probable contributor to hydrogen-assisted fracture. [ABSTRACT FROM AUTHOR]

Post-processing techniques can efficiently improve the surface quality, address microstructural defects, and optimize mechanical properties in additively manufactured parts. Surface severe plastic deformation processes such as ultrasonic nanocrystal surface modification (UNSM) integrated with localized laser heating were explored to enhance the surface properties, microstructure as well as the fatigue crack growth properties (FCG) in both directions of built. We successfully induced greater plasticity flow and achieved beneficial refinement of the surface grain structure by precisely controlling the heat and impact energies during surface treatment process. The LA-UNSM process, with the parameters utilized in this study considerably decreased the FCG rates of treated samples, when compared to samples without surface treatment. Improved fatigue crack growth properties along vertical and horizontal orientations after the post-process treatment were attributed to the induced-microstructural changes, improved surface quality, induced compressive residual stresses through gradient structure deformation layer that was prepared on the surface of the material. The fractographic analysis revealed that the cracks mostly originated from the pores in the as-produced state. This observation shows a clear correlation between the surface treatment performed and a substantial improvement in fatigue crack growth resistance. [ABSTRACT FROM AUTHOR]

The effect of platinum (a rare metal)–aluminide coating parameters on the tensile properties of nickel-based superalloy Rene®80 was evaluated at 871 °C. For this purpose, initial layers of platinum with different thicknesses (2, 4, 6 and 8 μm) were coated on tensile samples. Then, low-temperature high-activity (LTHA) and high-temperature low-activity (HTLA) processes were used for aluminizing. Results of microstructural evaluations using scanning electron microscope (SEM) and phase analysis by X-ray diffraction (XRD) showed a three-layer structure coating for different platinum layer thicknesses and both aluminizing processes. Increasing the thickness of the platinum layer from 2 to 8 μm led to the improvement in the final coating thickness from 91.6 to 102.1 μm in HTLA. This increase was from 128.1 to 148.6 μm in LTHA. The results of hot tensile tests at 871 °C showed a decrease in strength properties of the coated samples compared to the uncoated ones. However, HTLA and high thicknesses of the initial platinum layer showed an intense reduction. The results of fractographic evaluations about uncoated samples showed a ductile fracture. On the other hand, coated samples showed a simultaneous ductile and brittle fracture failure mechanism. But the main fracture morphology was brittle cleavage fracture which was for the HTLA. [ABSTRACT FROM AUTHOR]

AbstractThis study compares dip brazing and TIG welding operations carried out under optimal conditions on the parameters of strength, deformation, and ability to resist shocks for Al-64430 joints, which find extensive use in automobile and telecommunication industries. The fabricated samples were tested for bump test, surface deformation, microhardness and tensile strength, and the joint properties were studied through SEM, EDAX mapping and EDX. Compared to the dip-brazed samples, the TIG welded samples achieved 161% greater strength and 1000% greater elongation but subsequently 1330% higher surface deformation. Both joints were able to pass the bump test; however, some degree of cracks were observed post testing in both samples. Both samples achieved similar joint microhardness values, but notably, compared with the TIG welded sample, the brazed sample showed no HAZ zones in terms of microhardness variation, where a substantial decrease in microhardness was recorded. This absence of the HAZ region was also confirmed through the microstructure. Both primary and secondary silicon were observed in brazed samples, which had finer grain sizes than did the welded samples. Dendrite formation was observed for the brazed samples, whereas a uniform distribution of aluminium was observed for the welded samples. Fractographic analysis revealed brittle intergranular fracture with small dimples present at the fracture point for the brazed joints, while out-of-plane fracture with sharp edges indicated a more ductile nature for welded joints. [ABSTRACT FROM AUTHOR]

The influence of acetone vapor bath smoothing on the fatigue lives of 3D printed acrylonitrile butadiene styrene test specimens was investigated using a rotating bending cantilever beam test. The results show that the vapor bath treatment improved the fatigue life by a factor of two on average, but the variability in the specimen lifetime increased. Investigation of the fracture surface via optical and scanning electron microscopy reveals a complex fracture path with crack nucleation at multiple sites. Based on the observations from the study, suggestions are made to improve the fatigue lives of 3D printed ABS polymer components. [ABSTRACT FROM AUTHOR]

Passive non-destructive evaluation tools such as acoustic emission (AE) testing and acousto-ultrasonics (AU) approach present a complex problem in damage localisation in complex and nonhomogeneous geometries. A novel AU-guided AE frequency interpretation approach is proposed in this research work which aims at overcoming this limitation. For the experimental evaluation, the damage sources from a geometrically complex clear dental aligners are tested under cyclic compression load and their origins are evaluated. Despite the rapid worldwide diffusion of the clear aligners, their mechanical behaviour is poorly investigated. In this work, the frequency characteristics of the artificially simulated stress wave, generated from different dental positions of the clear aligners, are studied using the AU approach. These frequency characteristics are then used to analyse the AE signals generated by these aligners when subjected to cyclic compressive loading. In addition, the time domain characteristics of the AE signals are studied using their Time of Arrival (ToA). The Akaike Information Criterion (AIC) is used to estimate the ToA. These frequency and time domain characteristics of the AE signals are used to estimate the local damage origin in the clear dental aligners. This will help in identifying localised damage sources during the usage period of the aligners. Experimental results revealed significant damages in the left maxillary premolar and right maxillary third molar of the aligners. [ABSTRACT FROM AUTHOR]

Highlights Restoration of the structural integrity of damaged CFRP composite through thermally reversible Diels–Alder bonds with the exact interfacial healing between matrix/fiber is extremely desirable for manufacturing of high‐performance self‐healing laminates. This article demonstrates the fabrication of amine‐functionalized maleimide‐grafted MWCNT (with different weight ratios 0.5 wt%, 1.0 wt%, and 1.5 wt%) reinforced thermally reversible self‐healing CFRP composite. The morphological changes, functional elements, elemental groups, and thermal degradation of functionalized‐MWCNTs were characterized by FESEM/HR‐TEM, FTIR, XRD, and TG‐DTA analysis. The results demonstrated that CFRP reinforced with silane/maleimide grafted MWCNT enhanced the dispersion, exhibited 82% healing efficiency and improvement in flexural strength‐67.11%, tensile strength‐64.75% concerning pure‐CFRP. FE‐SEM fractography of composites indicated that nanotube pullout was predominant failure‐criteria in CFRP‐pristine‐MWCNTs whereas strong interfacial adhesion dominated in CFRP‐maleimide‐MWCNTs. The purpose of this article is to investigate matrix/fiber/nanofillers interface healing properties of CFRP‐composite before and after damage. Furthermore, it is intended to reform structural integrity and examines average healing efficiency. Amine‐functionalized maleimide‐grafted MWCNT, CFRP composite fabrication. Characterized, morphological changes functional elements thermal degradation. Improvement in healing efficiency (82%), flexural strength‐(67.11%). The enthalpy of 0.5 wt% MWCNTBm enhanced to 10.91 J/g. Fractographic examinations show extensive intralaminar/interlaminar deformation. [ABSTRACT FROM AUTHOR]

Rapid evolution in engineering and manufacturing demands light weight material with enhanced mechanical properties. Aluminium metal matrix composites with ceramic reinforcement particulates serve this demand due to their reduced density, improved strength and hardness along with higher resistance to wear and corrosion. However, the material cost and reduced machinability hinders the full potential of utilization. To overcome these challenges, in this work cupola slag, an industrial waste generated as by product of cast iron production, has been incorporated as reinforcement of aluminium composites using low cost stir casting method. The enhancement of material properties and machinability by cupola slag inclusion on base alloy has been investigated in detail. Moreover, introspection about the underlying mechanisms responsible for the improvement in material properties has been studied using detailed microstructure and fractographic analysis. The results show improvement of in material properties and machinability up to 7 wt.–% cupola slag inclusion, beyond which the reduced wettablity prohibits sound castings. The ultimate tensile strength and specific strength observed to be improved by 18.20 % and 33.23 % respectively for 7 wt.–% slag reinforced composites when compared with base alloy. This work can be a successful addition to the knowledge pool of ongoing research on low‐cost novel material with enhanced properties. [ABSTRACT FROM AUTHOR]

We study Inconel 718 refractory alloy produced by using different modes of electron beam melting. The phase composition and specific features of the microstructure of alloy are analyzed both in the initial state and after hardening heat treatment. The fracture surfaces of the samples of alloy are analyzed after uniaxial tensile tests. It is shown that the fracture of the material occurs according to the ductile mechanism. However, fracture surfaces contain significant amounts of defects in the form of unmolten areas and porosity, which is typical of the products obtained by using additive technologies from powder materials. It is shown that the fracture of the analyzed alloy is provoked by the presence of unmolten areas and intermetallic particles of the δ-phase in the structure. [ABSTRACT FROM AUTHOR]

The microstructure and impact toughness of high-strength low-alloy steels joined by friction stir welding are studied. The hardened steel samples are tempered at a temperature of 600–650°C for 1 hour, followed by warm rolling to a total strain of 1.5 at the same temperature. The resulting steels are characterized by an ultrafine-grained lamella-type microstructure. The as-processed steel plates are joined by friction stir welding. A martensitic microstructure is formed in the stir zone. The steel samples with a carbon content of 0.15% show high impact toughness of 68 J/cm2 at room temperature with a gradual decrease to 16 J/cm2 at a temperature of –196°C, while the steel samples with a carbon content of 0.36% exhibit an impact toughness of 10 J/cm2 at room temperature. The 0.36% carbon steel joints are tempered at a temperature of 650°C for 1 hour, which increases their room-temperature impact toughness to 67 J/cm2. [ABSTRACT FROM AUTHOR]

The permeability evolution of fractures in geologic media plays a pivotal role in various geo-mechanical activities, ranging from energy resources recovery to the deep geologic disposal of hazardous materials. This paper presents both laboratory and computational investigations into the evolution of fracture permeability under the influence of varying confining stress levels in a crystalline granitic rock from the Canadian Shield. Steady state permeability experiments were conducted to assess variations in fracture permeability in areas where stress conditions may significantly change due to large-scale underground excavations. A high accuracy laser scanner was used to capture the geometric features of the fracture surface, enabling the numerical simulation analysis of stress-induced hydromechanical behavior. The fracture permeability evolution was systematically investigated under both isotropic stress and deviatoric stress conditions, including four loading–unloading sequences and a series of sequentially increased deviatoric stresses. Simulations of fracture closure under increasing confining pressure and corresponding fluid flow process were performed incorporating a model constructed from fracture elevation data obtained through scanning. The results demonstrate a reduction in permeability exceeding 50% as the triaxial confining stress increases from 5 to 40 MPa. Additionally, permeability hysteresis during stress relief was observed. These findings are relevant to deep geological construction activities where excavation leads to the development of an excavation damage zone and stress alterations, affecting overall fluid flow process. Highlights: The fracture permeability evolution in Lac du Bonnet granite under four loading–unloading sequences has been systematically investigated. Stress-induced fracture closure process and its corresponding fluid flow process were simulated based on a model constructed from fracture elevation data obtained through scanning techniques. Fracture permeability showed a clear dependence on stress level and permeability hysteresis was observed during the stress relief. [ABSTRACT FROM AUTHOR]

This study aims to develop thermoplastic (TP) and thermoset (TS) based mixed matrix composite using design dependent physical compatibility. Using thermoplastic-based (PLA) skeletal lattices with diverse patterns (gyroid and grid) and different infill densities (10% and 20%) followed by infiltration of two different thermoset resin systems (epoxy and polyurethane-based) using a customized FDM 3D printer equipped with a resin dispensing unit, the optimised design and TP-TS material combination was established for best mechanical performance. Under uniaxial tensile stress, the failure modes of TP gyroid structures with polyurethane-based composites included 'fiber pull-out', interfacial debonding and fiber breakage, while epoxy based mixed matrix composites with all design variants demonstrated brittle failure. Higher elongation (higher area under curve) was observed in 20% infilled gyroid patterned composite with polyurethane matrix indicating the capability of operation in mechanical shock absorption application. Electron microscopy-based fractography analysis revealed that thermoset matrix properties governed the fracture modes for the thermoplastic phase. This work focused on the strategic optimisation of both toughness and stiffness of mixed matrix composite components for rapid fabrication of construction materials. [ABSTRACT FROM AUTHOR]

In this research work, a real case of failed ASTM A860 WPHY 65 long elbow pipe coated with inorganic zinc ethyl silicate primer is collected from a treatment facility to investigate the root causes of its failure, which was reported after approximately 28 months of use. The failure was investigated using visual observations, metallurgical analysis using optical emission spectroscopy, mechanical testing, X‐ray diffraction of corrosion product, chemical analysis of sewage and corrosion rate test of the elbow using a three‐electrode potential technique, fractographic analysis using scanning electron microscope along with computational analysis to confirm the results. Through the testing, it was observed that severe depletion in the strength can be attributed to erosion–corrosion caused by various impurities present in the sewage, leading to the generation of corrosion pits and turbulent eddies and stresses generated due to sudden changes in fluid flow direction along with gases present in sewage reacting with a base metal. Various failure mechanisms that have led to pipe failure are discussed in this paper, along with a listing of preventive measures to delay it. [ABSTRACT FROM AUTHOR]

To assess the influence of calcination process on the properties of minimally processed recycled 3Y-TZP, and to compare it with its commercial counterpart. Non-milled 3Y-TZP waste was collected, fragmented and ball-milled to a granulometric < 5 µm. Half of the recycled powder was calcined at 900 °C. Recycled 3Y-TZP disks were uniaxially pressed and sintered to create two recycled groups: 1) Calcined and 2) Non-calcined to be compared with a commercial CAD/CAM milled 3Y-TZP. The microstructure of experimental groups was assessed through density (n = 6), scanning electron microscopy (n = 3) and energy-dispersive X-ray spectroscopy (n = 3); and the crystalline content was evaluated through X-ray diffraction (XRD) (n = 3). Optical and mechanical properties were investigated through reflectance tests (n = 10), and Vickers hardness, fracture toughness (n = 5), and biaxial flexural strength tests (n = 16), respectively. Fractographic analysis was performed to identify fracture origin and crack propagation. Statistical analyses were performed through ANOVA followed by Tukey´s test, and by Weibull statistics. Particle size distribution of recycled powder revealed an average diameter of ∼1.60 µm. The relative density of all experimental groups was > 98.15 % and XRD analysis exhibited a predominance of tetragonal-phase in both recycled groups, which were similar to the crystallographic pattern of the control group. Cross-section micrographs presented flaws on the non-calcined group, and a more homogeneous microstructure for the calcined and commercial groups. Commercial samples showed lower contrast-ratio and higher translucency-parameter than the recycled groups, where non-calcined presented higher translucency-parameter and lower contrast-ratio than its calcined counterpart. The commercial group presented higher fracture toughness and characteristic strength than the recycled groups. Moreover, the calcined group exhibited higher hardness, characteristic strength, and probability of survival at higher loads than the non-calcined group. Fractographic analysis depicted the presence of microstructural flaws in the non-calcined group, which may have acted as stress-raisers and led to failures at lower flexural strengths values. The calcination process improved the microstructure, optical, and mechanical properties of the recycled 3Y-TZP. • Effect of calcination on minimally processed recycled zirconia powder was assessed. • Calcination enhanced the microstructure, optical, and mechanical features of the recycled 3Y-TZP. • Calcination did not promote alterations to the crystalline structure of the recycled 3Y-TZP. • Calcined powder resulted in a more homogeneous microstructure. • Recycled 3Y-TZP demonstrated a potential for applications in reconstructive dentistry. [ABSTRACT FROM AUTHOR]

Thin-laminate composites with thicknesses below 200 μm hold significant promise for future, larger, and lighter deployable structures. This paper presents a study of the time-dependent failure behavior of thin carbon-fiber laminates under bending, focusing on establishing a fundamental material-level understanding of this type of failure. A novel test method was developed, enabling in-situ micro-CT imaging during long-term bending. Time-to-rupture experiments revealed the stochastic nature of failure, prompting a statistical approach to account for initial imperfections. The total probability of failure was calculated using separate Weibull functions for instantaneous and delayed time-dependent failures. The resulting function, dependent on curvature and aging time, is a design guideline for the design of future deployable space structures. Time-lapse micro-CT imaging identified kink bands and fiber–matrix debonding as primary failure mechanisms, providing essential insights for the design optimization of composite laminates. [ABSTRACT FROM AUTHOR]

This study identified a cracking that occurred continuously in the built direction of an additive manufactured part of alloy 718 by the laser metal deposition method and clarified the cracking behavior. The solidification microstructure of alloy 718 was evaluated by EDS, EPMA, and extraction residue, and it was found that Laves phase, Ti carbides, and Al oxides were formed between the dendrite microstructures. A fracture surface analysis of the cracks revealed that the cracking in the additive manufacturing was hot cracking associated with the liquid film and that the cracking occurred along the grain boundaries. The fracture surface at the beginning of the cracking showed a solidification cracking fracture surface. The experimental investigation for crack propagation during additive manufacturing and the analytical evaluation of the mechanical state around the cracking using thermal elastic-plastic analysis elucidated the cracking behavior during additive manufacturing. If the cracking exists at the fusion boundary, it is suggested that the cracking initiates from the solid-liquid interface towards the solidification direction. Moreover, tensile strain occurred around the cracks during additive manufacturing, particularly the strain was biggest at the crack edge on the fusion boundary. Therefore, the continuous cracking that occurred beyond each layer in the additive manufacturing of alloy 718 in this study can be considered solidification cracking, and its behavior can be further explained as a notch extension cracking that starts from the solidification cracking and continuously occurs in the solid-liquid coexistence temperature region. [ABSTRACT FROM AUTHOR]

Aluminium metal matrix composites (AMMCs) are replacing the monolithic alloys for advance engineering applications in industries. Present work appraised the use of fragmented aluminium with the reinforcement of SiC, ZrO2 and NiTi mixture. Mechanical and microstructural properties of fabricated AMMCs were evaluated, and it was found that fabricated composites have finer grain structure compared to the base alloy. Tensile strength of base alloy was enhanced by 44.8% due to refinement of the grains, shear lag and bowing of dislocations. The maximum value of compressive strength, microhardness and impact strength was found in composite with 3wt% reinforcement of each of SiC, ZrO2 and NiTi. The transformation of ductile to cleavage fracture was confirmed by fracture morphology. Tribological analysis reveals that the material loss due to wear and roughness of worn-out surfaces was decreased by the accumulation of reinforcement. [ABSTRACT FROM AUTHOR]

The current study deals with mechanical and microstructural analyses of Al6061/GNPs/CeO2 hybrid composites. Hybrid aluminum metal matrix composites (HAMMCs) were manufactured using the 2-step stir-casting method, with the addition of GNPs and CeO2 at varying weight percentage ratios (1:3, 3:3, and 3:1). The highest tensile strength, flexural strength, and impact strength were 113.666 MPa, 73.08 MPa, and 13.062 J, respectively. The hardness increased by 21.47 percent with a reduced particle grain size of 6.36 nm. The FESEM study verified fine grain refinement and homogeneous reinforcement distribution, whereas surface fractography of the tensile specimens determined the failure caused by the formation of cracks, pores, debonding, and large-sized dimples in the stir-cast alloy and HAMMCs. [ABSTRACT FROM AUTHOR]

The present study deals with the development of a harmonic structured commercially pure Ti using a novel and newly designed press-milling method to surface-deform the Ti powder particles and subsequent sintering. The harmonic structure is a bimodal distribution of fine and coarse grains where a continuous network of fine grains (shell) surrounds discrete clusters of coarse grains (core). A harmonic structured Ti featuring a shell with an average grain size of ~ 4.3 μm and a core with an average grain size of ~ 12 μm is obtained. The HCP crystal structure in the XRD patterns indicates the absence of any phase transformation due to press-milling. The hardness of the shell region improves ~ 2.5 times that of core regions. The compression studies also show an improved combination of strength and ductility in the harmonic structured Ti. [ABSTRACT FROM AUTHOR]

Al2618 high-strength aluminum alloy was subjected to precipitation hardening at T6 tempering conditions to improve its mechanical properties for employing it as the spacecraft skin material. Nine specimens of Al2618 artificially aged alloy were prepared according to the ASTM-E606/E606M-12 standard and tested through the S-N curve method. It resulted in the fatigue strength of Al2618 being 150 MPa, which is better than the existing Al2024-T3 alloy by about 8.7%. An increment of 59.9% and 3.2% of fatigue life and fatigue strength for the infinite fatigue life of the alloy was identified through the Basquin Equation and Kohout-Věchet method, respectively, in correspondence with Al2024-T3. The fractographic analysis of the broken materials was investigated with the support of SEM images; the failure mechanism and causes for the failures were discussed. [ABSTRACT FROM AUTHOR]

The structure and tensile properties of A380 aluminum alloy were modified by intensive melt shearing for different shearing speeds. Three different speeds, including 600, 1200, and 1800 rpm, were employed to evaluate the effect of melt shearing speed on the macrostructure, microstructure, and tensile properties of A380 aluminum alloy. It was found that the size of grains decreased with increasing the shearing speed while porosity increased, especially beyond 1200 rpm. Moreover, the grain size of the alloy became more uniform. The microstructure of the alloy was also modified so that shearing led to the change of harmful coarse eutectic Si to fibrous Si and decreased both the length and aspect ratio of the brittle β-phase. These modifications caused the alloy to be more ductile and stronger, i.e., the strength and elongation percentage of the alloy increased up to shearing at 1200 rpm. [ABSTRACT FROM AUTHOR]

Friction stir welding was used to join ME20 magnesium alloy. The effect of tool material, pin configuration, spindle speed, and feed rate on the mechanical characteristics and surface finish of the joint was studied with the aid of Taguchi's design of experiments. Statistical analysis of test results and scanning electron microscopic fractography revealed that H13 tool material and a threaded pin configuration led to marked improvements in the properties. An optimum speed of 1600 rpm of the spindle led to favorable weld strength and surface finish. The optimized parametric combination developed through the grey relational approach improved weld strength by 17.78%, joint hardness by 6%, and surface finish by 12.8%. [ABSTRACT FROM AUTHOR]

An arc is used as a heat source in the manufacturing process known as wire arc additive manufacturing (WAAM), which uses layer-by-layer cladding to fuse wire. In the current work, Wire Arc Additive Manufacturing (WAAM)-fabricated Inconel 625 alloy has been examined. The research was done on the microstructure, mechanical characteristics, and impact of the solidification rate on the characteristics of the manufactured specimens for the Inconel 625 alloy. Microstructural analysis has shown that the specimen’s layers have varying microstructures. The bottom layer exhibits a blocky or equiaxed microstructure because of the faster solidification rate, while the upper zone generated elongated and discontinuous dendrites because of the slower solidification rate. This difference in the microstructure in the top and bottom zones directly influence the ultimate tensile strength, where the bottom zone has more tensile and yield strength than the top zone. Also, the presence of cracks in the top zone, which is found during the fractography test, also correlated the top zone’s ultimate tensile strength.

Bio-polymer composites are emerging as a feasible substitute for conventional polymers in various major fields of applications. In the current research, the impact of hybridization of inter and intra-woven natural engineering fibers namely, brown flax, white flax, and jute of different amalgamations along with commingled SCF and novel nano IW filler has been studied. The composites are manufactured by hand layup process and physical and thermomechanical characteristics of the composites are experimentally studied. The composites mingled with IW filler demonstrated better dimensional stability and mechanical properties such as maximum tensile strength of 36.74 MPa, bending strength of 82.53 MPa, and hardness of 84.89 D compared to other composites. However, elastic and flexural modulus are maximum for composite without any filler. The composites mingled with SCF filler demonstrated the highest impact strength, energy absorption, and elongation. Thermogravimetric analysis and thermal conductivity study demonstrated that the composite with SCF filler exhibited better thermal stability and thermal resistance than the other hybrid composites. Fourier transform infrared spectroscopy study confirms the interaction of hydrogen bonds with different polymers, matrices, and fillers. It is established that the weaving pattern and the filler types greatly influences the mechanical and thermal characteristics of the composites. Filler addition and fabric hybridization optimizes the catastrophic failures and enhances the thermal stability, hence becoming more suitable for small interior structural components in aerospace and automobile applications. [ABSTRACT FROM AUTHOR]

High and very high cycle fatigue tests were performed to examine the microstructure and fracture mechanism of GH4169 superalloy in combination with techniques including electron‐backscatter diffraction (EBSD). Fractographic analysis revealed that surface failures are induced by surface flaws, whereas internal failures are caused by pores, facets, and inclusions. The three‐dimensional observation shows that fracture surfaces exhibit an irregular texture due to crystallographic mismatch of grains and plastic deformation at the crack tip. Based on EBSD analysis, Euler angles exhibited a complex geometry of grain orientation at the crack tip area, hindering crack propagation as evidenced by lower values of the Schmid factor and misorientation at the crack tip. Furthermore, the threshold values of small and long cracks decrease, whereas the transformation sizes from small to long crack growth increase from surface to internal failure. Finally, a novel microstructure defect‐based life prediction model is established, and the predicted results demonstrate a close resemblance to experimental outcomes. [ABSTRACT FROM AUTHOR]