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The current study aims to explore the impact of friction stir welding (FSW) parameters on the tensile strength of dissimilar joint materials. A copper grade CDA 101 and an AISI-SAE low-carbon steel grade 1010 were selected as the dissimilar materials to analyze the tensile strength of the weld joints. The axial force, tool rotational speed, and welding speed were selected as process parameters for the weld joint fabrication process. The influence of the process constraints was investigated using the Taguchi technique, which is based on the L9 orthogonal array. Investigation of variance and signal-to-noise ratio were considered to forecast the ideal welding process constraints, and their percentage of contribution was computed by comparing the anticipated and actual welding process parameters. The test results revealed that the speed of the tool and the downward force (axial) exerted on the joint played a substantial impact on the joint strength. The maximum tensile strength of the Cu-steel dissimilar weld joints is found as 189 MPa which is determined during optimal welding process parameter values having tool rotating speed of 1100 rpm, welding speed of 40 mm/min, and an axial force of 6 kN. The FSW joints were inspected under a scanning electron microscope (SEM) and with an EDAX to identify the micro patterns and fracture surface of the joints. [ABSTRACT FROM AUTHOR]

This article outlines the development and examination of the properties of an asymmetrical dissimilar metal joint produced using friction welding (FW). Friction welding involving dissimilar materials, specifically a 50 mm (length) × 45 mm (width) × 20-mm (thickness) electrolytic tough pitch copper (ETP-Cu) plate and a 12.5-mm-diameter SS304L rod, was carried out. The assessment of the asymmetrically welded components encompassed ultrasonic testing, high-pressure helium gas testing, leak testing, tensile testing, scanning electron microscopy, optical microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, hardness measurements, and elemental mapping via X-ray. Significantly, there was an observed increase in tensile strength, resulting in a joint efficiency of 86.50% compared to the ETP-Cu base material, following FW between an asymmetric ETP-Cu plate and SS304L rod. The study unveiled notable variations in the microstructure near the joint interface on the ETP-Cu material side. Intermetallic compounds, such as FeCu4 and Cu9Si phases, were detected within the reaction layer at the interface between ETP-Cu and SS304L, exhibiting a variable thickness ranging from 30 to 50 μm. [ABSTRACT FROM AUTHOR]

The global construction industry faces a crucial challenge reconciling economic growth with environmental sustainability, notably due to the significant environmental impact of cement production, particularly in countries like Pakistan. As the demand for cement grows, so does the carbon footprint and environmental degradation, necessitating the exploration of sustainable alternatives like sugarcane bagasse ash (SBA), a byproduct of sugarcane processing, to mitigate these issues while also addressing rising costs in concrete production. Embracing SBA offers a promising avenue to alleviate environmental concerns and enhance the sustainability of the construction sector. This study investigated the SBA properties and effectiveness as a viscosity modifying agent (VMA) in self-compacting concrete (SCC), examining varying SBA content effects on fresh and hardened SCC properties. The hydration and microstructure properties were evaluated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) to investigate SBA-based SCC. The results indicate that SBA has the potential to enhance mechanical and microstructural properties by possibly increasing the formation of Calcium Silicate Hydrate (CSH) gel. Adding 5% SBA demonstrated favorable fresh properties while incorporating up to 15% SBA showed improvements in compressive strength. Overall, adding SBA to cement manufacturing during clinkerization can reduce environmental pollution and lower production costs. [ABSTRACT FROM AUTHOR]

AbstractThis study aimed to develop engineered geopolymer composites (EGCs) having considerably greater ductility than that of the engineered cementitious composite (ECC) for similar compressive strength. For this, three groups of fly ash (FA)-based EGC mixtures with different total binder (AL+FA) and alkali liquids/fly ash (AL/FA) were produced. After observing similar workability characteristics for EGCs and ECC, EGCs were subjected to three different initial curing conditions: 48 h at 100 °C, 24 h at 100 °C, and 24 h at 70 °C. The test results showed that almost all of EGCs exhibited the strain-hardening behaviour. While the curing temperature and time increased, the compressive strength and flexural strength of EGCs improved as well as the decreasing ductility. Moreover, mechanical properties including ductility were enhanced by the increment of AL+FA. EGCs cured at 70 °C for 24 h showed ultra-ductile behaviour. The results were also supported by XRD, TGA/DTA and FTIR. [ABSTRACT FROM AUTHOR]

Abstract The global construction industry faces a crucial challenge reconciling economic growth with environmental sustainability, notably due to the significant environmental impact of cement production, particularly in countries like Pakistan. As the demand for cement grows, so does the carbon footprint and environmental degradation, necessitating the exploration of sustainable alternatives like sugarcane bagasse ash (SBA), a byproduct of sugarcane processing, to mitigate these issues while also addressing rising costs in concrete production. Embracing SBA offers a promising avenue to alleviate environmental concerns and enhance the sustainability of the construction sector. This study investigated the SBA properties and effectiveness as a viscosity modifying agent (VMA) in self-compacting concrete (SCC), examining varying SBA content effects on fresh and hardened SCC properties. The hydration and microstructure properties were evaluated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) to investigate SBA-based SCC. The results indicate that SBA has the potential to enhance mechanical and microstructural properties by possibly increasing the formation of Calcium Silicate Hydrate (CSH) gel. Adding 5% SBA demonstrated favorable fresh properties while incorporating up to 15% SBA showed improvements in compressive strength. Overall, adding SBA to cement manufacturing during clinkerization can reduce environmental pollution and lower production costs.

In the present work, the effect of the Sn addition (0.01 to 0.118) wt.% on the mechanical and microstructural properties of the copper base gray cast iron alloys has been investigated, and the fracture surface obtained from the tensile test was examined. The results show that the Sn alloying improved and refined the pearlitic structure in the alloys and causes graphite flakes to thin. The optimum pearlitic content in the microstructure is obtained with the 0.076 wt. % Sn-alloyed gray cast iron (T3). The T3 alloy also shows the optimum mechanical properties such as tensile strength of 380 MPa, hardness of 225 BHN, and impact strength of 3.2 Joules. The wear resistance is also high in the T3 alloy compared to all the samples. The fracture analysis shows that the Sn alloying causes more brittle fractures in the gray cast irons compared to the without alloying condition. [ABSTRACT FROM AUTHOR]

The construction sector has undergone significant reforms towards increased sustainability in recent decades. Therefore, there has been a great interest in developing alternative binders for stabilising expansive clay subgrades and improving their mechanical properties while mitigating their swelling and shrinking behaviour. One such alternative binder is vinyl acetate-ethylene (VAE) polymers. However, there are only a few studies on utilising polymers, especially VAE polymers, for clay stabilisation. Specifically, there is a lack of research on using VAE polymer-stabilised clays for road subgrade purposes. This study aims to address this knowledge gap by evaluating the potential of using a VAE solid powder polymer to stabilise expansive clay subgrade through a comprehensive series of mechanical tests as well as physicochemical and microstructural analyses. The results of the experiments provide evidence that the introduction of the polymer considerably improved the mechanical strength and swell and shrinkage behaviour of the expansive clay. [ABSTRACT FROM AUTHOR]

As fuel prices rise and environmental rules become more stringent, there is pressure on the aerospace sector to create lighter, more efficient aircraft. Fuel usage is significantly reduced as a result of using lightweight alloys to make the aircraft as a whole lighter. Composites prepared from aluminium matrix are widely employed in the automotive and aeronautical sectors because of their excellent strength and wear rate characteristics. This study describes the mechanical, corrosion and wear characteristics of hybrid aluminium composites utilized in aeronautical applications. The aircraft industry needs aluminium alloys with better mechanical properties if it is to use them successfully. According to published studies, adding reinforcing particles repeatedly can increase mechanical attributes of prepared composites. As a result of soft and hard reinforcing particles incorporation, the resulting hybrid composites are less brittle and have higher wear resistance. Commonly used ceramic particulates inclusion such as silicon carbide, alumina, zirconium oxide (ZrO2) and aluminium nitride would induced a substantial strength and wear resistance as well as egg shell, coconut shell ash, bagasse ash and groundnut shell ash derivative from agro wastes. Hybrid composites with different types of reinforcement percentage were found to be homogenous and uniform distribution. In conclusion, the analysis reveals that hybrid composites based on aluminium have enormous potential in aircraft sector to replace aluminium alloy as well as composite with single reinforcement where less weight, high performance strength and minimum wear rate are required.

Brass materials are categorized in the copper alloys sub-groups with prevailing Zinc element. These materials are utilized from drinking water systems to automotive in a wide range of industrial applications due to superior properties such as strength, formability and corrosion resistance. This study aims to characterize and analyze smart and popular conducted manufacturing processes influences on the mechanical and microstructural properties of eco-friendly brass alloy. In this regard, microstructural, hardness, tensile and impact charpy tests have been carried out on extruded, extruded+annealing, forged and forged+annealing eco-brass CuZn40Pb2, CuZn38AS, CuZn21Si3P specimens. The experimental results have demonstrated that the manufacturing process type extremely influences the materials mechanical and microstructural properties. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to develop a fly ash+blast furnace slag (FA+BFS)-based engineered geopolymer composite (EGC) mixture having similar bearing strength and deformation capacity to the standard engineered cementitious composite (ECC) known with the M45 code in the literature. For this purpose, in addition to ECC, two different EGC mixtures incorporating different ratios of FA and BFS were produced. The compressive strength, modulus of elasticity, air dry unit volume weight, structural efficiency, ultrasonic pulse velocity (UPV), fracture toughness and flexural performance were determined on the 7th and 28th day as well as the fresh and rheological properties of these three mixtures. Finally, an EGC mixture having much higher compressive strength and ductility was obtained than that of ECC. Moreover, it was determined that increasing amount of BFS improved mechanical strength and toughness, but decreased ductility. The reasons of these situations were investigated microstructurally by XRD, TGA/DTA and FTIR analyzes. [ABSTRACT FROM AUTHOR]

In this work, nanokaolin (K) and nanometakaolin (MK) were synthesized from waste paper via planetary ball milling and characterized by means of X-ray diffraction (XRD), Fourier transform infrared vibrational spectroscopy (FTIR), and scanning electron microscopy (SEM). Suspensions of carboxymethyl cellulose (CMC) and the synthesized nanominerals at 1.5, 3, 6, and 9% led to nanocomposites 30, 60, 90, and 120 μm thick. Nanocomposites coated papers were analyzed by means of XRD, FTIR, SEM, tensile index, strain rate, burst index, and air passage resistance. The highest tensile index, burst index, and air permeability resistance values of 80.78 N. m g , 5.24 k P a. m 2 g , and 286.66 m l / m i n , respectively, were obtained for CMC-9%MK-120. These results indicated that paper coated with CMC nanometakaolin composite is suitable for packaging. [ABSTRACT FROM AUTHOR]

Yerba mate industrial processing produces tons of powder as a by-product, this yerba mate powder (YMP) is an excellent source of biomass to develop biodegradable materials. Cassava starch modified with 1,2,3,4-butane tetracarboxylic acid (BA) in the presence of sodium propionate as a catalyst is an eco-friendly option to obtain bioadhesives. This work aimed to develop sustainable laminates from starch-based adhesives and yerba mate powder and to study their physico-chemical, structural, and mechanical properties. Blends of bioadhesive and YMP were prepared (1:1, adhesive:YMP). Monolayer materials were obtained by thermo-compression and later assembled with adhesive to obtain bilayer laminates. Bioadhesive was able to bind the yerba mate by-product fibers, as evidenced by SEM microstructure analysis, the interactions of adhesive:substrate were elucidated by ATR-FTIR and supported by chemometrics analysis. The incorporation of the catalyst decreased the rugosity of materials and their mechanical performance was improved by the action of both acid concentration and catalyst presence, requiring higher energy for puncture. Thus, it was feasible to obtain mono and bilayer laminates as an eco-compatible alternative for the design of sustainable tray-like materials based on the industrial by-product of yerba mate. [Display omitted] • Yerba mate by-product can be used as raw material to produce thermo-compressed trays. • Cassava starch-based adhesives allowed the sustainable tray development. • The combined action of the acid and the catalyst led to better mechanical behavior. • The chemometric analysis confirmed the crosslinking between components. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the mechanical behavior, and the microstructure of NiTiCu shape memory alloy wires joined with silver-coated copper ferrules via ultrasonic spot welding. Therefore, the electrical resistance was measured during tensile testing, and the joints were analyzed by scanning electron microscopy. Energy-dispersive X-ray spectroscopy has determined the compounds of the developed welding zones. Furthermore, the influence of the ultrasonic welding on the transition temperatures of the NiTiCu wires was examined via differential scanning calorimetry. Tensile tests have shown that the ultimate tensile strengths of the joints reached almost 100% of that of the base material. An additional heat treatment rebuilt the typical shape memory alloy behavior after the ultrasonic welding process detwinned the martensitic wires. In addition, the B19′ structure of the welding zone and the ultrasonic spot-welding process did not affect the transition temperatures of the shape memory alloy.

This study applies a new method of mixing colloidal nano-silica (CNS). Previous studies have used powdered nano-silica or colloidal nano-silica and applied a binder weight substitution method. In this study, we tried to use ordinary Portland cement (OPC) as a binder and replace CNS with weight of mixing water. CNS was replaced by 10%, 20%, 30%, 40%, and 50% of the mixing water weight. The flow value, setting time, compressive strength, hydration reactant (X-ray diffractometer; XRD), pore structure (mercury intrusion porosimetry; MIP), thermal analysis, and scanning electron microscopy (SEM) analysis were performed. Experimental results show that the new substitution method improves the mechanical and microstructural properties through two effects. One is that the weight substitution of the mixing water shows a homogeneous dispersion effect of the nano-silica particles. The other is the effect of decreasing the w/b ratio when the CNS is substituted because the CNS is more dense than the mixing water. Therefore, we confirmed the applicability of mixing water weight replacement method as a new method of mixing CNS. [ABSTRACT FROM AUTHOR]

In this article, a novel stirring method has been developed for producing metal matrix nanocomposites, in which two different stirring methods, i.e. mechanical and electromagnetic stirrings, have been used simultaneously. Mechanical stirring might not be sufficient enough to break nano-agglomerations properly. Moreover, this method makes some unwanted porosities and gas entrapments in the composites. On the other hand, the electromagnetic stirring as a sort of body force (with no considerable shear stresses) could be used up to solidification decreasing the dendritic microstructures, gas entrapments, and undesirable agglomerations and impurities. Applying these both stirring methods simultaneously as an electromagnetic-mechanical stirring method, the distribution of reinforcing nanoparticles throughout the matrix phase would be more desirable due to better stirring conditions. In addition, since it is a simple and applicable approach, it can be used for mass production. Magnesium/Al2O3 nanocomposite with volume fractions of 0.5, 1.0, and 1.5% have been fabricated accordingly and then hot-extruded at 350°C using 20 : 1 extrusion ratio. According to the scanning electron microscopy (SEM) results, the nanoparticles have an appropriate distribution in the matrix. Also, comparing the results of microstructural evaluation and Vickers microhardness, tension and compression tests, it was observed that the grain size was decreased and the hardness and yield stress (in both tension and compression tests) were improved by adding more nanoparticles to magnesium matrix. [ABSTRACT FROM AUTHOR]

Abstract In this work an experimental method to determine the limit strain by means of digital image correlation is proposed. This method analyzes the variation of the thickness of a sheet metal through the temporal evolution of the strains, assuming incompressibility during the plastic strain process. To achieve this objective, the center and the edge of the necking area are identified with the strain history and the strain rate, respectively. The limit strain is thus determined when a non-homogeneous decrease in the thickness necking area begins, in contrast with existing methods based on performing analysis of surface strains. The proposed method is applied to determine the forming limit curve of commercial stainless steel and compared with other approaches. The results indicate that the proposed methodology is more reliable for determining the forming limit curve of the sheet, because it captures the heterogeneity of the strain distribution at the local necking site. The microstructure and the textures of the initial material are characterized via optical microscopy, x-ray diffraction and electron backscattering diffraction. The mechanical properties of the material are discussed in the light of the microstructural analysis. [ABSTRACT FROM AUTHOR]

Reinforced Inconel625 coatings have been successfully deposited by means of cold gas spray (CGS). Alumina has been simultaneously sprayed achieving a homogeneous distribution along the deposit with good cohesion between particles. The aim of this study was to investigate whether ceramic reinforcement could improve the mechanical and tribological properties of Inconel625 cold-sprayed coatings, while keeping the oxidation and corrosion resistance capacity. Furthermore, alumina particles were found to improve the spraying feasibility, by avoiding WC nozzle clogging during the process. A proper optimization of the spraying conditions was carried out in order to obtain the lowest possible porosity and best embedment of the alumina. Then, the mechanical and tribological properties as well as corrosion and oxidation behavior were characterized. Alumina acts as a reinforcement, improving the effects of abrasive and sliding wear. Regarding the oxidation and corrosion behavior, the coatings exhibit reasonably good oxidation resistance at temperatures up to 900 °C. The electrochemical corrosion performance in NaCl solution showed potentially lower noble corrosion values and corrosion current densities than bulk Inconel.

Friction stir welding (FSW) is an innovative solid-state joining process, which is suitable for joining dissimilar materials with strongly differing physical and chemical properties such as aluminum and steel. Where other joining methods such as fusion welding struggle to achieve appropriate joint strengths due to the excessive formation of brittle aluminum-rich intermetallic phases (IMP), FSW joints of aluminum and steel only show small layers of IMP, thus, sufficient tensile strengths in proximity to the maximum tensile strength of the weaker aluminum base material can be reached. With the aim to optimize the mechanical and microstructural properties of such dissimilar joints for widening the field for possible industrial applications, several hybrid friction stir welding methods have been developed which include an additional energy input, whereas the ultrasound enhancement (USE-FSW) is one of the most promising. The current work was carried out on AA6061/DC04 joints which were successfully friction stir welded with and without ultrasound support, in respect to the influence of varying the ultrasound transmission side. The functionality of the USE-FSW setup could be verified by multi point laser vibrometer measurements. Additionally, a higher proportion of transversal oscillation for the transmission of power ultrasound into aluminum could be detected using a scanning vibrometer. In comparison to the conventionally friction stir welded joints the ultrasound enhancement led to an avoidance of weld defects and an increase of the steel particle volume in the stir zone. The joint produced with power ultrasound transmission via aluminum resulted in a more uniform interface.

Powder thixoforging was used to produce amorphous Ni55Nb35Si10-reinforced Al matrix composites from recycled Al powders obtained from ball-milled Al520 end-milled billets. The amorphous reinforcing material was uniformly dispersed in the Al matrix and bonded adequately with it without undesired interfacial reactions. The compressive yield strength of composites with 45% reinforcement content increased 248% to 794 MPa over as-cast samples. The maximum elongation and hardness of samples were 15%, and 60.4 HRA, respectively. The relative density of the unreinforced thixoforged sample was 99.8%, indicating near-perfect compaction of Al powders. The maximum elongation, hardness, and compressive yield strength of thixoforged monolithic matrix alloys were, respectively, 40%, 56.9 HRA, and 747 MPa (a 228% increase in CYS over the cast alloy). In contrast, cold-forged samples showed only 82% increase in compressive yield strength over the as-cast alloy. Powder thixoforging introduced in this study—even without reinforcement—delivers better mechanical properties compared to cold forging most likely due to the refinement and modification of the microstructure during powder ball milling. [ABSTRACT FROM AUTHOR]

This study applies a new method of mixing colloidal nano-silica (CNS). Previous studies have used powdered nano-silica or colloidal nano-silica and applied a binder weight substitution method. In this study, we tried to use ordinary Portland cement (OPC) as a binder and replace CNS with weight of mixing water. CNS was replaced by 10%, 20%, 30%, 40%, and 50% of the mixing water weight. The flow value, setting time, compressive strength, hydration reactant (X-ray diffractometer; XRD), pore structure (mercury intrusion porosimetry; MIP), thermal analysis, and scanning electron microscopy (SEM) analysis were performed. Experimental results show that the new substitution method improves the mechanical and microstructural properties through two effects. One is that the weight substitution of the mixing water shows a homogeneous dispersion effect of the nano-silica particles. The other is the effect of decreasing the w/b ratio when the CNS is substituted because the CNS is more dense than the mixing water. Therefore, we confirmed the applicability of mixing water weight replacement method as a new method of mixing CNS.

Mechanical and microstructural properties of hybrid fibers reinforced high strength concretes (HFRHSCs) containing metakaolin (MK) and metakaolin + silica fume (MK + SF) subjected to elevated temperatures and freezing-thawing (F-T) cycles were investigated in this paper. In the concrete mixtures without and with hybrid fibers, MK and MK + SF were replaced with eight percentage of cement by weight. A total of sixteen concrete mixtures were produced at a water-to-binder ratio of 0.25. Ultrasound pulse velocity (U pv ), compressive strength (f c ), splitting tensile strength (f sts ) and flexural strength (f fs ) tests were performed to evaluate the properties of HFRHSCs subjected to ambient and elevated temperatures (300, 400 and 500 °C). The U pv and f c tests of HFRHSCs subjected to F-T cycles were also conducted. Moreover, the alterations in the matrix, interface zone and aggregate of concretes without hybrid fibers subjected to ambient temperature, elevated temperatures and F-T cycles were analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) spot and polarized light microscope (PLM). The results of tests have shown that the replacement levels of MK and MK + SF have important influences on the mechanical and microstructural properties of high strength concretes. Moreover, the mechanical results have shown that the concretes with hybrid fibers have higher f c , f sts and f fs than other concretes. The results have also shown that the U pv , f c , f sts and f fs values of concretes without and with hybrid fibers decrease, as the temperature increases. [ABSTRACT FROM AUTHOR]

Ultrasonic welding has been widely used to bond dissimilar conductive wires, battery cell terminals in relay applications. In this paper, dissimilar metals, Al/Cu were joined using ultrasonic welding for conductive applications. Welding trials were carried out by varying three control parameters: (1) vibrational amplitude (40, 60, and 80 µm), (2) clamping pressure (1, 1.2, and 1.4 bar), (3) weld time (0.1, 0.2, and 0.3 s). Experimental trails were designed based on L Taguchi method. Interpretation of tensile strength and microhardness results revealed that the satisfactory weldments were obtained for higher welding energies when compared to low welding energies. From the microstructural analysis, the bond formation of metals and failure modes were studied. SEM and XRD images revealed the four major intermetallic compounds at the interface of joint; AlCu, AlCu, AlCu, and AlCu with resistivity values of 11.415, 8.027, 10.612, and 14.243 Ω-cm respectively. The resistivity values of intermetallic compounds observed in the joint was almost 5-6 times higher than the Al. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical and microstructural properties of expanded extrudates prepared from blends of high amylose corn (Zea mays L. ssp. Mays) starch (HACS) and soy protein concentrate (SPC) were studied in relation to the physicochemical changes in starch. Effects of screw speed (230 and 330rpm) and SPC level (10%, 20%, 30% and 50%) on expansion and mechanical properties were determined. Compared with 230rpm, screw speed at 330rpm resulted in increased specific mechanical energy, expansion ratio, water absorption and water solubility indices and decreased bulk density and piece density. Varying screw speeds did not significantly affect the mechanical strength of extrudates or starch molecular weight distribution. Bulk and piece densities, and water absorption index (WAI) only slightly increased or exhibited no significant trends as SPC level increased to 20%. A substantial increase in bulk and piece densities and decrease in expansion ratio and WAI were observed as SPC level increased from 20% to 30%. The trends were either reversed or moderated as SPC increased to 50%. These results in combination with average crushing force and water solubility index data provided a significant insight into the interactions between HACS and SPC during extrusion processing. As compared to an earlier baseline study by our research group on normal corn starch – SPC extrudates, results from the current study indicated that the expansion of extrudate containing HACS alone was lower than that of extrudates containing normal corn starch. However, expansion of the HACS–SPC blends was not significantly impacted at 10–20% SPC levels, whereas the expansion of normal corn starch was significantly reduced. [Copyright &y& Elsevier]

The aim of this study was to investigate the mechanical behavior, and the microstructure of NiTiCu shape memory alloy wires joined with silver-coated copper ferrules via ultrasonic spot welding. Therefore, the electrical resistance was measured during tensile testing, and the joints were analyzed by scanning electron microscopy. Energy-dispersive X-ray spectroscopy has determined the compounds of the developed welding zones. Furthermore, the influence of the ultrasonic welding on the transition temperatures of the NiTiCu wires was examined via differential scanning calorimetry. Tensile tests have shown that the ultimate tensile strengths of the joints reached almost 100% of that of the base material. An additional heat treatment rebuilt the typical shape memory alloy behavior after the ultrasonic welding process detwinned the martensitic wires. In addition, the B19′ structure of the welding zone and the ultrasonic spot-welding process did not affect the transition temperatures of the shape memory alloy. [ABSTRACT FROM AUTHOR]

Reinforced Inconel625 coatings have been successfully deposited by means of cold gas spray (CGS). Alumina has been simultaneously sprayed achieving a homogeneous distribution along the deposit with good cohesion between particles. The aim of this study was to investigate whether ceramic reinforcement could improve the mechanical and tribological properties of Inconel625 cold-sprayed coatings, while keeping the oxidation and corrosion resistance capacity. Furthermore, alumina particles were found to improve the spraying feasibility, by avoiding WC nozzle clogging during the process. A proper optimization of the spraying conditions was carried out in order to obtain the lowest possible porosity and best embedment of the alumina. Then, the mechanical and tribological properties as well as corrosion and oxidation behavior were characterized. Alumina acts as a reinforcement, improving the effects of abrasive and sliding wear. Regarding the oxidation and corrosion behavior, the coatings exhibit reasonably good oxidation resistance at temperatures up to 900 °C. The electrochemical corrosion performance in NaCl solution showed potentially lower noble corrosion values and corrosion current densities than bulk Inconel. [ABSTRACT FROM AUTHOR]

• Refuse mudstone, GGBS and red mud were used as the precursors for geopolymer. • A combination of water glass and NaOH were used for a desired activator modulus. • The coupled influence of refuse mudstone and water glass contents was investigated. • UCS and BTS tests were conducted and analysed on geopolymer composites. • Failure mode and SEM were analysed and compared with mechanical results. In this study, refuse mudstone, ground granulated blast-furnace slag (GGBS) and red mud were used as the precursor materials for geopolymer. Water glass was used as the alkaline activator for polymer synthesis and standard sand was used as the aggregate in the polymer composites. A series of laboratory tests including unconfined compressive strength (UCS) tests, Brazil tensile strength (BTS) tests, scanning electron microscopy (SEM) tests were carried out for mechanical and microstructural analysis. The coupled influence of the content of refuse mudstone (P) and the content of alkaline activator (Q) was investigated. Results show that it is feasible to synthesize geopolymer using refuse mudstone, GGBS and red mud. The produced geopolymer composites could have the highest UCS of 23.48 MPa (P = 30% and Q = 25%) and the highest BTS of 2.98 MPa (P = 30% and Q = 10%). Due to the inactive crystal phases in refuse mudstone, the UCS of geopolymer composites was increased and the strain at the UCS (ε UCS) was increased. The influence of Q on the UCS and ε UCS was not evident and it was affected by P. Similarly, the influence of P and Q on the BTS of geopolymer composites was also found to be dependent on each other. Compared with cemented paste backfill composites, the relatively high strength and small permeability of geopolymer composites originated from its compact microstructure. The influence of P and Q on the geopolymer composites was also confirmed by failure mode analysis and SEM analysis at the micro-scale. [ABSTRACT FROM AUTHOR]