| Abstract Scope |
Introduction:
There are a lot of breakthroughs on high-entropy alloy including properties and theory since it is developed. However, one of the biggest challenges is that it is hard to fabricate big size bulk materials due to composition segregation in casting. In recent years, additive manufacturing (AM) is getting increasing attention, as it does not require molds to manufacture complex metal parts. For the additive manufacturing (AM) of metallic components, the common heat sources include laser, electron beam and arc. Compared with the AM methods of laser and electron beam, the wire arc additive manufacturing (WAAM) uses metallic wire filler material (i.e. the material to be deposited). WAAM method which has the advantages of high deposition efficiency, high material utilization rate, large manufacturing parts size, low equipment cost, etc.
In this study, a new combined cable wire was designed, and for the first time used cold metal transfer (CMT) wire arc additive manufacturing (WAAM) technology for additive manufacturing of Al-Co-Cr-Fe-Ni non-equiatomic high-entropy alloys.
Experimental Procedures:
Considering the composition of the HEA to be developed, the CCW was designed accordingly. The CCW used in this research has a diameter of 1.8 mm (as shown in Figure 1b), which is used as the filler material (i.e material to be deposited). The CCW is composed of 2 nickel wires, 2 aluminum wires, 1 iron wire, 1 cobalt wire, 1 304 stainless steel wire, a total of 7 thin metal wires with a diameter of 0.6 mm each, with 1 central wire and 6 peripheral wires. The purity of each elemental wire material used to make the combined cable wire was > 99.5%. In this research work, iron wire was used as the central wire, and the remaining elemental wires as the peripheral wires. Further the wires of the same material were placed in opposite positions to ensure the uniformity of composition (wt.%) upon deposition.
the CMT-WAAM system was used, and a six-axis robot was used to drive the movement of the welding torch for AM (as shown in Fig.1a). High-purity argon gas (99.99% purity) was used as the protective gas during deposition, with glass flow rate of 25 L/min. The Distance from the end of the welding torch to the working surface distance was kept at 18 mm. The x direction is the travel direction (TD), and the Z direction is the building direction (BD). The process parameters are shown in Table 1. Single pass and multi-layer method is used to add materials, and three thin HEA walls with different torch travel speed of 8 mm/s, 10 mm/s and 12 mm/s are produced, as shown in Fig. 2. Each sample deposited consisted of 20 layers.
Results and Discussion:
Microstructural observations of the new developed HEA reveal: (i) BCC and FCC phases, (ii) Good bonding between layers and (iii) defect-free microstructure. The developed alloy exhibit high compression strength (~2.8 GPa) coupled with high elongation (~42%) values. The effect of welding torch travel speed on the microstructure and mechanical properties were investigated and was compared with cast specimen, we found by varying the travel speed appropriately, the heat input can be reduced, and faster cooling rates can be achieved, which give rise to fine grained HEAs, which in turn improves the mechanical properties. A comparative behavior of the mechanical properties with that of the Al-Co-Cr-Fe-Ni HEAs prepared using traditional casting is conducted, and the superiority of using CCW in WAAM process for HEA development is established.
Conclusion:
In this study, an innovative combined cable wire (CCW) of non-equiatomic Al-Co-Cr-Fe-Ni HEA has been developed using WAAM process. The CCW used in this research work is feasible and can be used to fabricate HEAs by WAAM method. The successful fabrication of the HEA by WAAM using CCW process indicate that large parts can be printed and simultaneously overcome the shortcoming of the powder based AM processes. The results of the present work provides a new direction in the development of HEAs by AM technologies.
Keywords: Arc additive manufacturing; High-entropy alloy; Microstructure; Mechanical properties |