Numerical and Experimental Analysis of Magnetic Pulse Welding for Joining Similar and Dissimilar Materials

Magnetic pulse welding, a high speed joining process using electromagnetic forces, because of clean and multi-material operation has a wide range of possibilities for further development and application. Unlike conventional joining processes, the weld interface does not melt keeping the material properties intact without generation of hazardous emissions in form of heat, fume, and spatters. The present investigation deals with the feasibility study of the magnetic pulse welding technology for joining of similar and dissimilar materials through numerical modelling and simulation work followed by experimental validation of the obtained results. A finite element model was developed and validated with results available in literature. The model developed in this study helped predict accurate values of weld validation criteria for a wide range of process parameters and for different combinations of similar and dissimilar materials with varying geometry

Comprehensive Weldability Criterion for Magnetic Pulse Welding of Dissimilar Materials

Despite its exceptional ability to join dissimilar materials and environmental friendliness, several challenges must be addressed in magnetic pulse welding (MPW). The conventional weldability criterion (i.e., minimum impact velocity) is analytically calculated as a function of material properties without considering the geometry of electromagnetic coil, electrical and physical parameters, making the minimum impact velocity a necessary but not sufficient condition for a sound MPW joint. A new weldability criterion, namely effective impact velocity, is proposed, which overcomes the conventional weldability criterion’s limitations. The effective impact velocity can be inversely modelled to identify shop-floor relevant process parameters and it eliminates the need to fabricate several coils in the process and product proving stages. The proposed approach is demonstrated by a case study on tubular welding of Aluminium and SS304. The weld’s soundness produced with computed process parameters was corroborated by experimental observations on lap shear tests, hardness measurements, optical and scanning electron microscopy, and surface energy dispersive spectroscopy mapping. This investigation is expected to pave the way for developing the process window for MPW of several material combinations, with high cost and time savings. © 2022 by the authors

A resource-efficient process design for heavy fabrication: A case of single-pass-per-layer narrow gap welding

The welding process, omnipresent in the heavy fabrication industry, is a potential source of hazardous emissions. The article is motivated by the need to improve the sustainability of the heavy fabrication processes. Single-pass-per-layer narrow gap welding (NGW) is a potential alternative for reducing carbon footprint in high-thickness joints conventionally fabricated using the multi-pass multi-layers, sometimes even 100 or more layers, which is time-, material-, and energy- consuming. A newly developed mathematical model allows process design based on resource-efficient bead-on-plate welds (i.e., one layer deposited on a substrate). The results of bead-on-plate experiments are firstly utilized to identify the process capabilities in terms of strength, process, and production measures and subsequently coupled with the NGW mathematical model to arrive at feasible process parameters for a given groove design. The proposed approach implemented for a candidate case reveals significant improvement in the utilization of process capabilities, i.e., increase in strength, melting efficiency, and deposition rate and reduction in energy and material consumption. This investigation brings out three fundamental design rules for single-pass-per-layer NGW, namely i) the corresponding width of the bead-on-plate weld should be >1.5 times the groove width, ii) an upper limit on the utilization of process capabilities exists beyond which the productivity goes down drastically, and iii) the upper limit can be realized only at critical layer thicknesses. The design approach can be implemented to achieve more productive, economical, and sustainable design for processes involving high energy and material consumption. © 2022 The Author(s

A review on multiplicity in multi-material additive manufacturing

Additive manufacturing (AM) has experienced exponential growth over the past two decades and now stands on the cusp of a transformative paradigm shift into the realm of multi-functional component manufacturing, known as multi-material AM (MMAM). While progress in MMAM has been more gradual compared to single-material AM, significant strides have been made in exploring the scientific and technological possibilities of this emerging field. Researchers have conducted feasibility studies and investigated various processes for multi-material deposition, encompassing polymeric, metallic, and bio-materials. To facilitate further advancements, this review paper addresses the pressing need for a consolidated document on MMAM that can serve as a comprehensive guide to the state of the art. Previous reviews have tended to focus on specific processes or materials, overlooking the overall picture of MMAM. Thus, this pioneering review endeavors to synthesize the collective knowledge and provide a holistic understanding of the multiplicity of materials and multiscale processes employed in MMAM. The review commences with an analysis of the implications of multiplicity, delving into its advantages, applications, challenges, and issues. Subsequently, it offers a detailed examination of MMAM with respect to processes, materials, capabilities, scales, and structural aspects. Seven standard AM processes and hybrid AM processes are thoroughly scrutinized in the context of their adaptation for MMAM, accompanied by specific examples, merits, and demerits. The scope of the review encompasses material combinations in polymers, composites, metals-ceramics, metal alloys, and biomaterials. Furthermore, it explores MMAM’s capabilities in fabricating bi-metallic structures and functionally/compositionally graded materials, providing insights into various scale and structural aspects. The review culminates by outlining future research directions in MMAM and offering an overall outlook on the vast potential of multiplicity in this field. By presenting a comprehensive and integrated perspective, this paper aims to catalyze further breakthroughs in MMAM, thus propelling the next generation of multi-functional component manufacturing to new heights by capitalizing on the unprecedented possibilities of MMAM

Generalised overlapping model for multi-material wire arc additive manufacturing (WAAM)

The single-material overlapping models are incompatible with multi-material wire arc additive manufacturing (WAAM). A newly developed generalised model considers dissimilar adjoining beads in multi-material WAAM. The geometric model of dissimilar overlapping beads coupled with an algorithm identifies the process conditions for the two materials to maintain the same bead heights. The model, implemented for stainless-steel and creep-resistant-steel pair, yields significant scientific and practical findings. Compared to a fixed overlapping distance in single-material, e.g. 0.66 or 0.738 times the bead width, the multi-material overlapping distance is a complex function of individual bead widths. The bi-metallic interface fusion is affected by the molten metal flow, bead dimensions, and heat input. Contrary to the prevailing notion of a flat-top surface in the intermediate layer ideal for multi-layer deposition, a slight hill ensures a defect-free interface. The repeatable and defect-free bi-metallic walls and matrix is expected to have a breakthrough in multi-material WAAM

Unveiling Liquation and Segregation Induced Failure Mechanism in Thick Dissimilar Aluminum Alloy Electron-Beam Welds

This study presents new findings on the underlying failure mechanism of thick dissimilar electron-beam (EB) welds through a study on the AA 2219-AA 5083 pair. Contrary to the prior studies on EB welding of thin Al alloys, where liquation in the grain boundaries (GBs) in the partially melted zone (PMZ) was not observed, the present investigation for thick EB welds reports both liquation and increased segregation of Cu in the PMZ. The work is thus directed towards understanding the unusual observation in the PMZ of thick EB weld through investigation of the microstructural variation across the various regions of the produced weld. The microstructural results are correlated with the mechanical properties of the weld, i.e., hardness variation and tensile response. Results of this investigation suggest that unlike the convention that EB welding produces sound dissimilar Al welds, the weld performance for thick EB Al welds is affected by the heat input, the associated cooling rates, and most importantly by the base material thickness. Extensive liquation and Cu segregation induced failure in the PMZ on the AA 2219 side of the dissimilar weld. The underlying failure mechanism is explained through a heat-transfer analysis. Beyond a certain plate thickness, the heat transfer changes from two to three-dimensional. As a result, retarded cooling promotes liquation and Cu segregation in thick EB welds. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Elucidation of the photophysical and biochemical properties of small molecules can facilitate their applications as prospective therapeutic imaging (theragnostic) agents. Herein, we demonstrate the luminescence behavior of a strategically designed potential therapeutic thiosemicarbazone derivative, (E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), accompanied by the illustration of its solvation and solvation dynamics using spectroscopic techniques and exploring its promising antitumor activities by adopting the necessary biochemical assays. Solvent-dependent photophysical properties, namely UV–vis absorption, fluorescence emission, and excitation profiles, concentration-dependent studies, and time-resolved fluorescence decays, serve as footprints to explain the existence of DAHTS monomers, its excited-state intramolecular proton transfer (ESIPT) product, and dimeric and aggregated forms. The emission intensity progressively intensifies with increasing polarity and proticity of the solvents up to MeOH, but in water, a sudden dip is seen. Solvent polarity and H-bonding modulate the fluorescence behavior of the primary emission peak and significantly influence the formation of the dimer and DAHTS aggregates. The designed luminophore (DAHTS) exhibits significant antiproliferative activity against the human lung cancer (A549) cell lines with inhibitory concentrations (IC50) of 16.88 and 11.92 μM for 24 and 48 h, respectively. DAHTS effectively reduces the cell viability and induces cytotoxicity with extensive morphological changes in A549 cells in the form of spikes when compared to the normal HEK cell lines. More importantly, it increases the p53 expression at the mRNA level that consolidates its potential therapeutic activity. The effect of DAHTS on apoptotic pathways against the A549 cell line has been investigated to determine its probable mechanism of cell death. Thus, the all-inclusive understanding of the photophysical properties and the necessary biochemical assays put forward important steps toward tailoring the thiosemicarbazone core structure for favorable cancer theragnostic applications in academic and pharmaceutical research