•Wire and arc additive manufacturing (WAAM) has been used to manufacture lattice structures.•The struts diameter of lattice structure was controlled by the size and number of droplets.•The droplet ...size was controlled by the current, voltage, and period within a pulse period.•The struts angle of lattice structure was controlled by the inter-layer lift and offset of the arc torch.•Demonstration of aluminium alloy lattice structure was fabricated using WAAM technology via the manufacturing strategy.
Wire and arc additive manufacturing (WAAM) has been used to manufacture ER2319 aluminum alloy lattice structure, whereas a relationship of the struts diameter of lattice structure with the size and number of droplets, struts angle with the inter-layer lift and offset of the arc torch was developed. The manufacturing strategy of lattice structure by WAAM was formulated, and the aluminum alloy lattice structure demonstration was prepared where compressive properties were measured. The results show that the size of the droplet can be controlled by adjusting the current, voltage, and period within a pulse period; and then the struts diameter can be controlled by adjusting the size and number of droplets. The struts with a diameter of no less than 2.50mm were manufactured by WAAM, and its relative error was less than 2.0%. The struts angle can be controlled by adjusting the inter-layer lift and offset of the arc torch. The angle of the strut was from 15° to 90°, and its relative error was below 4.0%. A 3-layer pyramid lattice structure demonstration of the aluminum alloy composed of struts with a diameter of 3 mm and an angle of 45° was fabricated by WAAM. The average compressive strength of ER2319 aluminum Alloy lattice structure was 58.53 MPa.
High-building multi-directional pipe joint is a complex structure. A novel technology, which is called wire and arc additive manufacture (WAAM), was used to manufacture a high-building 10-directional ...pipe joint in this paper. Because the intersecting areas of multi-directional pipe joint are space surfaces, the conventional planar slicing method of WAAM is hard to form space surface with high precision. According to the study of space surface slicing method and space path planning by WAAM, this paper used the outer cylinder surface of main pipe to slice other forming pipes of 10-directional pipe joint, and the intersecting surfaces could be divided into two kinds: smooth surface and curved surface with inflection point areas. Two different path filling schemes were proposed for different intersecting surfaces: The former was filled in rotating approaches, while the latter was filled in raster approaches. The dimensional errors of forming pipes were controlled about ± 1 mm, and the angle errors of intersecting pipes were less than ± 0.5°. Compared with the properties of the casting pipe joint, the tensile strength of 10-directional pipe joint increased by 12.4% and the impact toughness (20 °C) increased more than 100%. The microstructure mainly consisted of pearlite and ferrite, and average grain size was about 15 μm. Rare defects such as pores and cracks were found.
•Propose a new technology to improve the precision of large WAAM metal component.•The surface structure light 3D measurement technology is applied to obtain the offset of cross-section center.•The ...printing path is adjusted according to the offset cross-section center between layers.•Improving the forming accuracy of WAAM parts by controlling the offset cross-section center between layers in real time.
The marine propeller bracket is a complex core component of large ship power system. Wire Arc additive manufacturing is an effective method to manufacture propeller bracket, which consists of the hub, the support and cross arm. For obtaining high forming precision, offset filling method for printing hub and scanning filling method for printing support and cross arm are adopted. Central deviations of deposition layer are acquired by a 3D scanner and a program written by Matlab software. Adjusting print path in real time to improve forming precision of bracket. The cross section center offset of each deposition layer is within ±0.6mm while the dimensional errors of bracket are within ±0.8 mm. The microstructure of bracket is composed of ferrite, lath bainite and VC precipitates. The tensile strength of printed bracket is 796 MPa, the yield strength is 660 MPa and the impact toughness at −20°C is 53 J.
The propeller bracket is an essential structural component of the large ship, with large structural size, high precision and performance. Multi-arc collaborative additive manufacturing is an ...effective method for forming high precision and performance large-scale propeller bracket. This paper studies the high-precision and performance multi-arc collaborative additive manufacturing propeller bracket forming strategy and path planning method. In the multi-arc cooperative additive manufacturing of the bracket, the two arcs in the front are used to form the contour of the depositing layer, while the rear three arcs are used to fill the contour. Finally, the five arcs collaborated additive manufacturing bracket is formed. Based on the structural characteristics of the bracket, it is divided into four regions: the hub, support arm, cross arm and intersecting area. The hub is a rotating body of equal thickness and cross-section. The relative positions of the five arcs are fixed, and the path is calculated by adjusting the attitude angle of the device in real-time during the printing process. The intersecting area, support arm and cross arm are all curved bodies with variable thickness and cross-section. The contour torches are used to form the two sides of the contour separately, and then the filling torch is used to variable amplitude swing filling the contour. The five arcs collaborative additive manufacture propeller bracket with a length of 3.5 m is formed by the above forming strategy and path planning method. The forming accuracy of the bracket is ±0.6 mm. The microstructure is composed of pearlite and massive ferrite. The tensile strength is 774 MPa, and the yield strength is 642 MPa. The mechanical properties are higher than the castings one with the same composition, and the forming efficiency reaches 1800 cm3/h.
•Design a multi-arc WAAM system and path planning method to form the propeller bracket and analyze its accuracy and properties.
Influence of varying heat input (0.66-1.43 kJ/mm) and different preheat temperatures (150-350 °C) on microstructure and mechanical properties of the coarse-grained heat-affected zone (CGHAZ) of ...MAG-welded pearlitic rail steel has been investigated. Results show that at low heat inputs (0.66-1.00 kJ/mm), microstructures are mainly composed of martensite, whereas high heat inputs (1.29-1.43 kJ/mm) have coarsened the grains and formed cracks. 1.16 kJ/mm of heat input is found optimum which has produced a crack-free surface with the least martensite. Afterward, by using the optimum heat input of 1.16 kJ/mm samples are welded at different preheat temperatures ranging from 150 to 350 °C, which has reduced the martensite and increased the pearlite, successively. Preheat temperatures of 250 °C are found optimum, where grain size and
t
800
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300
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cooling rate are 38.1 ± 9.8 μm and 3.1 °C/s, respectively. Furthermore, hardness is 659 ± 7 HV, tensile strength is 1349 ± 16 MPa, and toughness is 6.4 ± 0.5 J, respectively. Finally, the confocal scanning laser microscopy analysis, at optimum heat input of 1.16 kJ/cm and 250 °C of preheat temperature, is also presented. The entire study concludes that preheating is inevitable in MAG welding of pearlitic rail steel. 1.16 kJ/mm of heat input with 250 °C of preheating temperature is suitable in MAG welding of pearlitic rail steel where microstructure is composed of pearlite, ferrite, and sorbite having no martensite and no cracks.
The curved-generatrix-shell pyramid lattice structure (CPLS) is an important thermal insulation and load-bearing component of hypersonic vehicles (Mach>5). Directed energy deposition-arc (DED-Arc) is ...an effective method for fabricating CPLSs. In this study, the characteristics of a CPLS and the unit cells of the CPLS were analyzed in detail. The CPLS consisted of row-lattice unit cells along the axis of the curved-generatrix shell and column-lattice unit cells along the circumference. The strut inclination angles and strut lengths of different rows of each unit cell were different, in contrast to the previously reported planar unit cells. Based on the characteristics of the CPLS and unit cell, the curved-generatrix shell surface slicing method was used to obtain high-accuracy curved-generatrix-surface unit-cell deposition path points, and the initial position correction, variable process parameter values, and secondary deposition were used to control the droplet deposition amount to achieve the same layer height compensation. This ensured high-precision forming of the lattice struts. In this study, the fabrication of a CPLS was the ultimate goal. Thus, an eight-axis collaborative DED-Arc system composed of a six-axis robot and a two-axis positioner was adopted. The flip and rotation angles of the positioner were regulated so that the deposition plane of the formed struts was always horizontal, avoiding the flow of liquid metal in the molten pool. Finally, a large-size aluminum-alloy CPLS consisting of 23 rows of unit cells and 33 columns of unit cells was successfully fabricated using DED-Arc on the aluminum-alloy curved-generatrix shell. The maximum error of the lattice strut forming angle was within ±0.4°, and the maximum error of the forming strut length was within ±0.26 mm.
In this study, vanadium carbide (VC) was initially introduced into the molten pool using the cold wire method to refine the deposit grains and enhance the mechanical properties of arc direct energy ...deposition (ADED) aluminum alloy. Next, the grain structure's evolutionary behaviors and the second phase in the VC-strengthening ER5A06 aluminum alloy deposits were investigated, and the grain refinement mechanism was determined. The findings demonstrated that the cubic Al10V phase was produced after introducing VC, and the grain structure in the middle stable region of the building wall was transformed from coarse columnar grains (with an average size of 42.3 μm) into equiaxed fine grains (with an average size of 16.4 μm). Both Al10V and VC were coherent to α-Al in terms of orientation: (020)α-Al//(444)Al10V, 101―α-Al//112―Al10V, and (111)α-Al//(111)VC and 011α-Al//011VC. Their interatomic and interplanar spacing misfits were lower than 5 %, facilitating the heterogeneous nucleation of α-Al during molten pool solidification. Moreover, under multiple thermal cycles of ADED, the pinning effect of VC and Al10V effectively restricted the grain growth, thus enabling the building wall to steadily maintain a uniform, equiaxed, and fine-grained structure. Due to grain refinement and homogenization, the horizontal and vertical ultimate tensile strengths of the straight wall were improved by 16.8 % and 50.2 % (351.6 and 348.1 MPa), respectively, thereby eliminating the mechanical anisotropy. This work can provide a theoretical foundation and a novel method for the fine microstructure regulation and reinforcement of ADED aluminum alloy components.
Wire and arc additive manufacturing (WAAM) has been developed to be a highly efficient technique for making large Ti-alloy products. However, the deposition of metal by this method causes coarse ...texture, which limits its application. To address this, the study utilizes a wire and pulsed arc additive manufacturing (WPAAM) process for making TA15 alloy. Compared with the WAAM method, this WPAAM method inducts several current/voltage-impulse cycles under different pulse frequencies, which makes grains tiny and improves tensile strength. The study then uses a VOF model to discuss the effect of impulse cycles on the solidification process. The findings suggested that the impulse cycles deform the molten pool and influence the vibration in the solid/liquid interface. This makes the coarse columnar grains tiny and forms diminutive α laths. This paper further discusses the correlation between the microstructure and the mechanical properties. The results show that the CBGs and the α laths play a joint contribution to yield strength in the WAAMed TA15 alloy. This study provides a reference for optimizing the microstructure of WAAM titanium alloys by adjusting pulse frequencies and provides a theoretical basis for strengthening WAAMed Ti-alloy.
Laser scanning confocal microscopy（LSCM） was used to study the inhibition of austenite grain growth by the inclusions and the effect of cerium on the trend of acicular ferrite（AF） and ferrite side ...plate（FSP） transformation temperature in coarse grain heat affected zone（CGHAZ） of Ce-alloyed weld metals. The results showed there were lots of tiny cerium oxides and sulfides inclusions in the CGHAZ of Ce-alloyed weld metals. When the concentration of Ce was 0.021%, the volume fraction of inclusions in weld metal CGHAZ was higher and the inclusion size was smaller, therefore austenite grain size was smaller with the increase of hightemperature residence time. Cerium tended to segregate at austenite grain boundaries, so FSP transformation temperature decreased and FSP transformation was suppressed. On the contrary, AF transformation temperature increased because AF transformation was promoted in CGHAZ of the Ce-alloyed weld metal, especially when the concentration of Ce was 0.021%.
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