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Aluminum alloy (Al 5052) and magnesium alloy (AZ31B) plates were welded at different loading ratios (mass of explosive/mass of flyer plate, R = 0.7, 0.8, and 0.9) through explosive welding. The interface microstructure revealed a wavy interface for the attempted loading ratios, whereas, for a higher loading ratio (R = 0.9), cracks and pores were observed in the aluminum alloy (Al 5052). X-ray diffraction detected the presence of the Al12Mg17 compound at the interface for all the attempted conditions. The interface microhardness is directly proportional to the loading ratio. The maximum ram tensile strength (167 MPa) and shear strength (103 MPa) were obtained at a lower loading ratio (R = 0.7). Therefore, the satisfactory weld of the Al 5052/AZ31B composite plate was achieved at a lower loading ratio (R = 0.7). [ABSTRACT FROM AUTHOR]

The study presents the microstructural and strength characteristics of Al5052/SS316 explosive clads interlaced with different interlayer (aluminium 1100/SS 304/copper) by varying standoff distance (6 and 8 mm), loading ratio, R (mass of explosive/mass of flyer plate: 0.6 and 0.8) and preset angle between flyer and interlayer (6 and 8°), A. The interface microstructure shows the transformation of an uninterrupted melted layer formed in conventional cladding (no interlayer) into a thin or no reaction product clad, when an interlayer is introduced. Similarly, the kinetic energy utilization (1.26 –1.79 MJ/m2) and deformation work (0.76 –1.10 MJ/m2) during explosive cladding increase. The explosive clads having an interlayer exhibit higher mechanical strength than the interlayer less explosive clads and the highest strength (RTS: 263 MPa; Ss: 175 MPa) was witnessed for Al 5052/SS 304/SS316 explosive clads at higher parametric levels. [ABSTRACT FROM AUTHOR]

Hastelloy C-276 (UNS N10276) nickel-based alloy is widely employed in the fabrication of nuclear reactor components and corrosive resistant equipment. In this work Hastelloy C-276 sheets were butt welded by a pulsed Nd:YAG laser welding machine at different thermal energy conditions. The resulting variation in macrostructure, microstructure and mechanical properties are presented. The thermal energy supplied (beam power/weld speed) was altered by varying the operational parameters viz. weld speed (350 to 450 mm/min), laser beam energy (10 to 14 J) and laser beam pulse width (6 to 8 ms). The weld macrostructures were seen to be free from cracks and defects, exhibiting complete penetration and the crest (top width) of the weld increases with the thermal energy supplied. In the microanalysis, growth of dendrite grains from periphery to mid-section of the weld was observed. In addition, Mo rich compounds and carbides are witnessed in the weld zone (WZ) for higher thermal energy conditions. The tensile and yield strengths of the weld joints are inversely proportional to the thermal energy supplied. [ABSTRACT FROM AUTHOR]

This study attempts to develop statistical model for predicting the tensile strength of Nd:YAG laser butt welded UNS S32750 super duplex stainless steel (SDSS) joints. Experimental design based on the central composite face centred design is attempted by varying the process parameters viz. laser power, welding speed and pulse frequency. Weld microstructure exhibit a smooth interface free from defects. Tensile strengths of the resulting welds are determined, as per relevant standard, for each experimental condition. The determined strengths are utilized to develop predictive models by employing response surface methodology (RSM). Analysis of variance determines the factors viz. welding speed and laser power are more influential in dictating the tensile strengths of the weld joints. In addition, the percentage error between the experimental and the predicted models is less than 2%. [ABSTRACT FROM AUTHOR]

Aluminium composites are inevitable in the manufacture of aircraft structural elements owing to less weight, superior corrosion resistance and higher specific properties. These composites reduce the weight of the aircraft, improve the fuel efficiency and enhance the maintenance duration. This study proposes the development of dissimilar grade aluminium (aluminium 1100-aluminium 5052) composites with different reinforcement's viz., stainless steel wire-mesh, silicon carbide (SiC) powders and SiC powder interspersed wire-mesh, by explosive cladding technique. Wire-mesh enhances the friction and restricts the movement of flyer plate to craft a defect free clad, while SiC particles form a band on the interface. Highest strength is obtained when SiC powder interspersed wire mesh is employed as reinforcement. The dissimilar aluminium explosive clad with SiC particle reinforcement results in lower strength, which is higher than that of the weaker parent alloy and that of the conventional dissimilar aluminium explosive clads without any reinforcement. [ABSTRACT FROM AUTHOR]

Aluminium composites are inevitable in ship building, commercial and defence aircrafts construction due to their light weight, high strength to weight ratio, admirable properties and cost affordability. In this study, the microstructural characteristics of explosive cladded dissimilar grade aluminium (Al 1100-A1 5052) clad composites reinforced with silicon carbide (SiC) particles is presented.Microstructure taken at the interface by optical and scanning electron microscopes (SEM) revealed the formation of a silicon carbide layer between the dissimilar grade aluminium sheets. Though reaction layers were witnessed at few locations along the interface, the diffusion of atoms between the participant metals is not visible as confirmed by energy dispersive spectroscopy, elemental mapping, line analysis and X-ray diffraction (XRD). The variation in microhardness at various regions of the silicon carbide reinforced dissimilar aluminium explosive clad is reported. The increase in tensile strength of the SiC laced clad is also presented. [ABSTRACT FROM AUTHOR]

This study reports the effect of different heat input (126 J/mm to 330 J/mm) on the microstructure and mechanical properties of pulsed Nd: YAG laser welded super duplex stainless steel UNS S32750 (SDSS) butt weld joints. Macrostructure exhibit incomplete, complete and complete penetration with a crater at the top of the weld bead, for low, middle and higher heat input respectively. Experimental macrostructure is in agreement with the numerical simulation performed by SYSWELD - a 3D software package. Maximum temperature is obtained at the mid section of the weld for all attempted heat inputs. Micro-analysis display an enhancement in the ferrite concentration in the weld zone for an increase in the heat input. Sigma phase, a reaction compound, is observed for the highest heat input. Higher micro-hardness is witnessed at the interface for the mid range heat input. The results of tensile test show that the tensile strength tends to reach a peak and then decrease with the increasing heat input. [ABSTRACT FROM AUTHOR]

Super duplex stainless steel (SDSS), an advanced duplex stainless steel with higher alloying concentration, is employed widely in acidic atmospheres. In this study, we make an attempt to develop a process window for the pulsed mode Nd:YAG laser welding of SDSS, as reference maps, to identify the range of process parameters viz., laser power, welding speed, defocusing distance, and pulse frequency for obtaining a defect free full penetration welds. The eminence of the welds, based on the macrostructure, microstructure, and tensile strength, is reported. We obtain a complete penetration weld devoid of undercut, crating at the top and minimum heat affected zone (HAZ) with a overlapping factor of 80-90% and heat input at 100-200 J/mm. The experimental settings prevailing inside the preferred region of the process window exhibit a higher tensile strength as well. [ABSTRACT FROM AUTHOR]

Highlights • The weld morphology is determined numerically and experimentally. • Pores and coarse grains emerges at lower and higher heat input respectively. • Mechanical strength of the weld joints is reported. Abstract The digressions in microstructure and mechanical properties of 600 W pulsed Nd:YAG laser welded Monel 400 alloy sheets, subjected to varied pulse energies (8–12 J) are reported. The influence of pulse energy on the weld morphology is determined and correlated with the numerical simulation by employing finite element software ‘Visual weld 8.5′. The peak temperature, width of the weld and the size of the heat affected zone (HAZ) increase with the pulse energy, owing to the enhanced heat input (laser power/welding speed). Weld zone microstructure reveals the formation of fine dendritic grains. Maximum hardness and tensile strength were obtained for the pulse energy of 10 J and the tensile fracture shows a ductile fracture mode for all the attempted conditions. [ABSTRACT FROM AUTHOR]

The objective of this research is to perform an experimental study on the tribological behavior of Al-7075 alloy reinforced with boron carbide (B4C), graphite (Gr) and fly ash. The reinforcements added to aluminium alloy in three different compositions like B4C at 3wt%/Gr at 3wt%/fly ash at 6wt%, B4C at 3wt%/Gr at 4wt%/fly ash at 7wt% and B4C at 3wt%/Gr at 5wt%/fly ash at 8wt%. The composites were fabricated through stir casting process. Hardness and wear tests were conducted for all three different composites using Brinell hardness testing machine and pin on disc wear test apparatus respectively. The inverted microscope examination was also carried out to check the microstructural view of the specimens and it was observed that the reinforcement was uniformly distributed in the primary matrix without agglomeration. From the experimental results, it was found that B4C at 3wt%/Gr at 5wt%/fly ash at 8wt% composite specimen has shown better results than other two composition specimens and may suggest for automobile industries. [ABSTRACT FROM AUTHOR]

The influence of process parameters viz., plate thickness, laser power and welding speed in enhancing the tensile strength of laser welded austenitic 316 stainless steel is presented. The experiments based on Taguchi analogy were conducted in a Nd:YAG laser welding machine and the signal-to-noise ratio (SNR) was computed to determine the optimum parameters. The contribution of each selected parameter is determined by analysis of variance (ANOVA). Mathematical model based on regression analysis is developed to predict the tensile strength of the 316 stainless steel welded joints at any given conditions using statistical software. In addition, tensile strength of the post weld heat treated 316 stainless steel joints were correlated with the as welded joints. [ABSTRACT FROM AUTHOR]

In this study UNS S32750 super duplex stainless steel (SDSS) sheets were laser welded at different welding speeds, frequencies and focal positions using Nd:YAG pulsed laser welding machine. Whereas the weld bead profiles show complete penetration irrespective of welding speed, the microstructures of fusion zones differ. The aspect ratio of fusion zone is found to be higher at lower welding speeds. This is due to enhanced heat input which results in increase in average grain size and formation of columnar dendritic structure in the weld zones. The tensile strength and microhardness of the laser welded joints are higher than the base alloy. [ABSTRACT FROM AUTHOR]

This study reports the effect of heat input (21.3–41.3 J/mm) on the microstructure and mechanical properties of pulsed Nd: YAG laser butt welded UNS N10276 (Hastelloy C-276) and UNS N4400 (Monel 400) sheets. The different heat input was achieved by changing the experimental parameters viz., welding speed (350, 400, 450 mm/min), pulse energy (8, 10, 12 J) and pulse width (5, 6, 7 ms). Though the weld macrostructure exhibit full penetration, the morphology and top weld width differs for the attempted conditions. Weld zone microstructures at lower, medium and higher heat input conditions display unmixed islands, dendrite grains with a slender heat affected zones (HAZ) and Cr-carbide rich reaction compounds respectively. Highest micro-hardness is witnessed for a heat input of 30 J/mm. The tensile strength of the weld joints reaches a maximum and tends to decrease with the increasing heat input. [ABSTRACT FROM AUTHOR]

• Develop a numerical expression to predict the tensile strength of welded joint. • Fine dendritic grains and a narrow HAZ is witnessed in optimum condition. • Tensile strength of the dissimilar joints is reported. In this study, an empirical relationship is developed to predict the tensile strength of pulsed Nd: YAG laser welded Hastelloy C-276–Monel 400 alloy sheets by optimizing the process parameters viz., welding speed, pulse energy and pulse duration. Experiments were conducted based on a three factor, three level, central composite face centered design with full desirability. Analysis of Variance (ANOVA) results indicate that the welding speed holds the greatest influence on tensile strength, followed by pulse energy and pulse duration. Microstructural studies of the optimized condition reveal full penetration weld with finer dendritic grains and a narrow heat affected zone (HAZ). Tensile fracture surface of the optimized weld exhibits a ductile mode of fracture with high tensile strength. XRD analysis of weld zone exposed the formation of various Chromium-rich carbide and Nickel-rich oxides precipitates. [ABSTRACT FROM AUTHOR]