Wire and arc additive manufacturing (WAAM) is a cost-effective technique; however, it confronts with excessive heat input resulted from high productivity. Herein, a novel programmable heat input WAAM ...(PHI-WAAM) is proposed to efficiently manufacture Al–Mg alloys with low heat input. In this method, the total current was dynamically distributed to the cathode wire current, and current of workpiece controlled by an insulated gate bipolar transistor (IGBT). The results indicated that the direct arc and current of workpiece appeared and vanished when the IGBT was switched between turn-on and turn-off states, respectively. In addition, periodic changes were observed in the deflection angles of the droplet trajectory and arc axis. Owing to the decreased current of workpiece, the heat input of the workpiece was reduced by 62.7%, and was precisely diminished via a programmable modified driven signal of the IGBT. The bridging transfer enhanced by an electromagnetic force and spray transfer occurred in the cathode and anode wires, respectively. The productivity was improved by 162.1% using the PHI-WAAM owing to the high melting rates of two wires. The average grain size was decreased from 69 µm in control group to 38 µm in PHI-WAAM. It was attributed to the reduced heat input of the workpiece and enhanced stirring effect. The ultimate tensile strength and yield strength were increased by 7.8% and 11.1%, respectively. The PHI-WAAM can fabricate metal parts with controlled low heat input, low cost, high flexibility, and high productivity.
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Dual phase duplex stainless steel comprised with ferrite and austenite shows its strength and corrosion resistance in many aggressive environments based on outstanding performance over the last 20 ...years establishment is a great attention for researchers, manufacturers and end users. The current worldwide rapid growth, demand, and consumption of duplex- stainless steels, particularly in petrochemical, marine, power plant and other engineering applications, where the multiphase steels are being utilized that require welding for fabrication of components. On the other hand, largest production and applications sectors are captured by austenitic stainless steels globally, but the Ni price volatility breaching the backbone of producers and end users. In such conditions for the cost flexibility, joining of dissimilar metals also reflects the overall industrial need. Joining of duplex alloys is a challenging, due to number of embrittling precipitates and metallurgical changes. On the other hand inappropriate welding conditions, imbalance phase ratio of austenite/ferrite leads to solidification cracking, corrosion susceptibility, and lower ductility. As the demand for higher productivity is increasing worldwide in many domains like oil pipeline, shipbuilding sectors etc., where the thick sections are used, which endorses the requirement of higher heat input, optimization of interpass temperature, cooling rate, proper selection of consumables, defect free joints for fast and rapid productivity. However, many advanced techniques like plasma, laser, PCGTAW, A-TIG and hybrid welding processes are developing to fulfill the requirements for higher productivity without distortion. But high ferritization is another issue with those processes. Moreover, suitability and standardization of duplex alloys for high current and large heat input are still in doubt. Even, no comprehensive accounts of the dissimilar welding operation on the effect of processes and welding conditions are found in the literature. This review paper systematically highlights the effect of welding processes and conditions on microstructure, mechanical properties and corrosion resistance of duplex stainless steels and its various combinations on the basis of structure–property co-relationship.
A wire and arc additive manufacture (WAAM) system, based on cold metal transfer (CMT) technology, was used to manufacture AlMg alloys. An aluminum‑magnesium ER5356 wire was employed as the filler ...metal to build AlMg components with different heat input by adjusting wire feed speed (WFS) and travel speed (TS). The macroscopic morphology and microstructure of AlMg thick walled samples were characterized using optical micro-graphs (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS). Vickers hardness and tensile properties were performed and mechanical properties were investigated. From microstructural studies, grain size variations in the range of 42.9–88.7 μm in inner-layer region (NLR) and 37.7–77.6 μm in inter-layer region (TLR) were observed when the WFS was 7.0 m/min, and TS was 0.9 m/min, whereas larger grains in significant amount were observed in similar regions under other WFS/TS combinations. The main phases of samples were identified to be α-phase (Al) and β-phase (Al3Mg2). The mechanical properties of the AlMg samples were relatively stable during different WFS/TS conditions; average micro-hardness showed a stability characteristic with the values ranging between 70-77Hv. The ultimate tensile strength (UTS), yield strength (YS) and elongation (%E) were found to be 255 ± 5 MPa, 128 ± 10 MPa and 23.2% ± 3% in identified location1 (taken from front to the back of the thick walled samples) and location2 (taken from root to the top of thick walled samples), respectively. For all samples, the fractographs exhibited typical dimple fracture characteristics. From the present work, it is evident that parts manufactured by WAAM-CMT have a better performance than the 5356 conventional casting alloys.
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•AlMg alloy is fabricated by WAAM, its mechanical properties are better than casting ones.•Small equiaxed grains and refine grain size were achieved in the TLR.•Dimple fracture characteristics are exhibited in the fracture surfaces.
•This work focused on the synthesis of newly created amines by varying the alkyl chain length with/without hydroxyl group in the structure.•The effect of chemical structure of newly synthesized ...tertiary amines; 4-(dimethylamino)-2-butanol (DMAB), 4-(dipropylamino)-2-butanol (DPAB), 4-(dibutylamino)-2-butanol (DBAB), 4-((2-hydroxyethyl)(methyl)amino)-2-butanol (HEMAB) and 4-((2-hydroxyethyl)(ethyl)amino)-2-butanol (HEEAB) were evaluated based on CO2 equilibrium solubility and cyclic capacity, as well as rates and heats of CO2 absorption and regeneration.•The results showed that these three amines had the highest CO2 absorption capacity (0.88, 0.44 and 0.68mol CO2/mol amine at 313K temperature and 15kPa CO2 partial pressure), and cyclic capacity (0.52, 0.26 and 0.40 at 313–353K temperature range, 15kPa CO2 partial pressure).•They also had fast CO2 absorption rate (0.082, 0.111 and 0.142mol CO2/min) and CO2 regeneration rate (0.512, 0.452 and 0.295mol CO2/min) while maintaining low heat of CO2 absorption (−34.17, −56.21 and −69.79kJ/mol CO2) and heat input of CO2 regeneration (39.73, 60.48 and 72.44kJ/mol CO2).•Based on these results, DMAB, HEMAB, and HEEAB can be considered to be promising amine components for blending for the next generation post-combustion CO2 capture processes.
This work focused on the synthesis of new tertiary amines by varying the alkyl chain length with/without hydroxyl group in the structure. The effect of chemical structure of newly synthesized tertiary amines; 4-(dimethylamino)-2-butanol (DMAB), 4-(dipropylamino)-2-butanol (DPAB), 4-(dibutylamino)-2-butanol (DBAB), 4-((2-hydroxyethyl)(methyl)amino)-2-butanol (HEMAB) and 4-((2-hydroxyethyl)(ethyl)amino)-2-butanol (HEEAB) were evaluated based on CO2 equilibrium solubility and cyclic capacity, as well as rates and heats of CO2 absorption and regeneration. The results showed that three amines (i.e. DMAB, HEMAB and HEEAB) had the highest CO2 absorption capacity (0.88, 0.44 and 0.68mol CO2/mol amine at 313K temperature and 15kPa CO2 partial pressure), and cyclic capacity (0.52, 0.26 and 0.40 at 313–353K temperature range, 15kPa CO2 partial pressure). These amines also had fast CO2 absorption rate (0.082, 0.111 and 0.142mol CO2/min) and CO2 regeneration rate (0.512, 0.452 and 0.295mol CO2/min) while maintaining low heat of CO2 absorption (−34.17, −56.21 and −69.79kJ/mol CO2) and heat input of CO2 regeneration (39.73, 60.48 and 72.44kJ/mol CO2). Based on these results, DMAB, HEMAB, and HEEAB can be considered to be promising amine components for blending for a post combustion CO2 capture process.
The microstructural characteristics and mechanical properties, including micro-hardness, tensile properties, three-point bending properties and Charpy impact toughness at different test temperatures ...of 8mm thick S960 high strength steel plates were investigated following their joining by multi-pass ultra-narrow gap laser welding (NGLW) and gas metal arc welding (GMAW) techniques. It was found that the microstructure in the fusion zone (FZ) for the ultra-NGLW joint was predominantly martensite mixed with some tempered martensite, while the FZ for the GMAW joint was mainly consisted of ferrite with some martensite. The strength of the ultra-NGLW specimens was comparable to that of the base material (BM), with all welded specimens failed in the BM in the tensile tests. The tensile strength of the GMAW specimens was reduced approximately by 100MPa when compared with the base material by a broad and soft heat affected zone (HAZ) with failure located in the soft HAZ. Both the ultra-NGLW and GMAW specimens performed well in three-point bending tests. The GMAW joints exhibited better impact toughness than the ultra-NGLW joints.
•Narrow gap laser welding (NGLW) was carried out on the new S960 high strength steel.•The microstructures of NGLW and GMAW of S960 high strength steel were characterised.•The NGLW joints displayed better tensile properties than the GMAW joints.•The GMAW joints exhibited better impact toughness than the ultra-NGLW joints.
A study of microstructure and volumetric dilution of Cold Metal Transfer (CMT) clad of Nickel based super alloy, Inconel 617M on type 316L stainless steel (SS) substrate was carried out. Overlay ...coatings were deposited at three different current inputs (80, 90 and 100 A) to synergetic CMT welding set while the wire feed rate and pulse frequency were pre-programmed. The ability of CMT to produce very low dilution and low heat input with the minimal heat affected zone (HAZ), when compared to conventional Tungsten Inert Gas welding (TIG) process was successfully demonstrated. Detailed microstructural evaluation of the cross sections revealed porosity and crack free Inconel 617M overlay with complete fusion, making a metallurgical bonding at the interface. Transverse micro Vickers hardness evaluation from clad to substrate showed the absence of significant HAZ for overlay produced by CMT. Calculation of percentage volumetric dilution, based on elemental Energy Dispersive Spectroscopy (EDS) of Fe-K counts, revealed that the cladding deposited at 100 A current exhibited low dilution value of 6.3% at 100 μm away from the interface while clad produced by TIG show significantly higher dilution value of ~50% at 100 μm from interface. Electron Backscattered Diffraction (EBSD) studies revealed morphology similar to epitaxial growth, with same crystallographic orientation of grains across the interface for CMT overlaid coatings.
•Cold Metal Transfer (CMT) is renowned to be a low heat input welding process.•CMT can produce porosity and defect free overlays of IN 617M over SS 316L.•CMT can produce low dilution (~6%) overlays of IN 617M over SS 316L.•CMT is advantageous over conventional weld overlay process in many aspects.
This article has investigated a 60 mm Ca‐treated Q550 steel used for high‐heat input welding. The results have shown that the Ca‐type inclusions account for 70% of the inclusions in the steel which ...are mainly CaAlMg type, Ca–Al type, and a small amount of CaS type while the non‐Ca‐type inclusions are mainly FeCO. After undergoing the welding thermal cycle, the number of Ca‐containing inclusions above 2 μm in size is decreased while the number of non‐Ca‐containing inclusions below 1 μm (mainly FeO) is increased significantly. However, the total area of inclusions is decreased. It has been found out that the CaAlSO‐type inclusions undergo “diffusion” of O element to the surroundings during the thermal cycle, forming a ring‐shaped oxygen‐rich zone and carbon‐rich zone which promotes the nucleation of acicular ferrite. In contrast, the CaAlMgSO‐type inclusions undergo “decomposition” during the thermal cycle which forms a group of inclusions with different sizes and types, promoting nucleation of multioriented acicular ferrite.
During the welding thermal cycle heating process, Ca–Al–Mg–O inclusions decompose into different size grades of inclusions. The decomposed multidimensional inclusions can promote ferritic nucle. Ca–Al–O‐type inclusions experience element diffusion during thermal cycle cooling. Regions enriched with O and C elements, within a certain size range, form around these inclusions, promoting AF generation.
•Three sets of the same heat input are obtained with different parameter combinations during the WAAM of aluminum-silicon alloy, the conclusions are as follows:•The change of geometric parameter of ...the deposited layer is caused by the change of arc force.•The refinement of microstructure is easily obtained by using the smaller current and voltage.•The better ultimate tensile strength is obtained by using the smaller current and voltage.
Heat input is a critical parameter in wire arc additive manufacturing (WAAM). A large number of studies have been carried out on the heat input of WAAM. However, the current research only focuses on the influence of different heat input values on the structure and performance of components, and the influence of equivalent heat input on the structure and performance of components is totally overlooked. In this paper, a new understanding of heat input is gained through analysis of the forming, microstructure and properties of WAAM components. Through the design of energy parameters (welding current, welding voltage, and traverse speed), three sets of the same heat input are obtained with different parameter combinations during the WAAM of aluminum-silicon alloy as the research object. The wire feeding speeds of Samples A, B, and C are 4, 6, and 8 (unit: m/min), respectively. The traverse speeds of Samples A, B, and C are 6, 11, and 16 (unit: mm/s), respectively. The results showed that the forming morphologies, microstructure and mechanical properties of thin-walled parts obtained under different parameters are significantly different with the same heat input. Under the interaction of wire feeding speed and traveling speed, the forming height of the sample decreases and the width increases, and the grain size increases with the increase of the two parameters. Sample A has the best mechanical properties, with an average tensile strength of 208.85 MPa and an average hardness of 71.66 HV. Compared with those of Sample C, the microhardness and tensile strength increased by 18.4 HV and 17.5 MPa, respectively.
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•The laser joining of CFRTP laminates and aluminum alloy 6061 are performed.•The laser generated heat is transferred to the contact interface area.•The surface resin melts and the irregular bubbles ...are produced at the interface.•The Al and carbon elements are diffused to each other in the interface area.
Laser joining technology with the advantages of high efficiency and good processing flexibility has the good application prospects in the connection of the Carbon Fibre Reinforced Thermoplastics Plastics (CFRTP) and aluminum alloy. Laser joining of CFRTP and 6061 aluminum alloy is investigated with various laser processing parameters. The microstructure characteristics and energy dispersive spectroscopy (EDS) results are analyzed. Besides, the fracture morphologies of the laser connection joints are studied. The results indicate that there is a partial unconnected area between the resin and the 6061 aluminum alloy due to the existence of the air bubbles, while most of the interface area is tightly connected where the mechanical anchoring effect exists.
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