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Research on CuCrZr alloy in additive manufacturing field
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CuCrZr is a precipitation hardening copper alloy, compared with most copper-based alloys, it is also characterized by high strength, high wear resistance and high tempering resistance at high temperatures, and has good castability, cutting and machining, excellent mechanical properties and excellent thermal conductivity, and it is widely used in integrated circuit lead frames, high-speed rail contact wires, aerospace heat dissipation components, rocket engines and nuclear fusion reactors combustion chambers, and main candidate heat sinks for plasma components.
The production of traditional CuCrZr alloys is mainly prepared by casting method. With the industrial demand for functional parts with complex structures, it is difficult to prepare CuCrZr parts with complex structures by traditional manufacturing process. Additive manufacturing technology has the advantages of high degree of design freedom, low post-processing complexity, and large degree of freedom of production geometry, which has become the main technology of modern industrial manufacturing and has received wide attention. The following are the relevant studies of CuCrZr alloy materials in the field of additive manufacturing.
1、Fabrication of CuCrZr alloy using laser powder bed melting technology
In additive manufacturing technology, laser powder bed fusion (LPBF), or selective laser melting (SLM), is an effective method for constructing complex spatial structures in a single step for different parts of the whole, such as International Thermonuclear Experimental Reactor (ITER) components, medium pressure circuit breakers, and liquid rocket engine components.LPBF uses a laser beam to melt metal powders in a selected area. The LPBF process is therefore highly dependent on the availability of high-power lasers. However, pure copper and copper alloys tend to reflect near-infrared laser irradiation and significantly dissipate laser energy, making the LPBF process for copper alloys very challenging.
The experimenters used a short-wavelength laser (515 nm) in the LPBF process, and the relative density of the made samples was 98.07% and showed good mechanical properties, with an ultimate tensile strength (UTS) of 447±13 MPa, yield strength (YS) of 400±11 MPa, total elongation at break (EL) of 10±3%, and a Vickers hardness of 130±15 HV. electrical properties were poor at 30±1% IACS (International Annealed Copper Standard). In order to improve the sample properties, excellent mechanical properties (UTS=566±18MPa, YS=487±13MPa, EL=15±1%, Vickers hardness=161±15HV) were later obtained by direct aging treatment at 500°C sheshidu for 1h, while maintaining a good electrical conductivity (64±3% IACS).
Many researchers have studied SLM-formed CuCrZr alloys, including the effects of process parameters and heat treatment on the organization and properties.Ma et al. obtained nearly fully dense CuCrZr specimens by SLM forming by optimizing the process parameters and found that the elongation increased by 67.7% compared with that of a deformed copper alloy of comparable strength; Wallis et al. investigated the effects of heat treatment on the SLM-formed CuCrZr alloys on their organizational, thermal and mechanical properties, pointing out that higher ageing treatment temperatures are conducive to obtaining higher thermal conductivity. After direct age-hardening treatment, the room-temperature ultimate tensile strength was increased from 287 MPa to 466 MPa due to the formation of precipitated phases, but the elongation decreased; Guan et al. investigated the effects of process parameters and heat treatment on the properties of SLM-prepared CuCrZr alloys, and the optimized relative density could reach up to 97.65% and the strength of 267 MPa, and the conductivity increased with the increase of aging treatment temperature , but the change in strength shows an opposite trend. The evolution of the organization and mechanical properties of SLM-prepared CuCrZr under different scanning parameters has also been experimentally investigated, and CuCrZr specimens with high relative densities (99.5±0.3%) have been obtained by optimizing the scanning parameters and have a strength of 280±6 MPa and a ductility of up to 23.4±0.4% as compared to other SLM-prepared specimens.
2. Development of CuCrZr alloys by electron beam melting
Electron beam melting (EBM) technology has advantages when processing copper alloys, it avoids the problems associated with the high thermal conductivity and reflectivity of copper-based materials, and uses working in a high vacuum to prevent their oxidation.EBM additive manufacturing always keeps the substrate at a high temperature when forming the part, and this special heat treatment process is similar to an aging treatment, which successfully generates in situ CuCrZr alloys with a nano-Cr phase. alloy with nano-Cr phase. The specimens showed excellent comprehensive performance, in which the maximum elongation, ultimate tensile strength and electrical conductivity were 32.1%, 257.7 MPa and 70.6±1.4% IACS, respectively, which experimentally proved the feasibility of obtaining almost completely dense CuCrZr alloy parts (up to 99.8%) by EBM technology.
3、Electric arc additive manufacturing of CuCrZr alloy
Among the various AM technologies, arc additive manufacturing (WAAM) is a promising direct energy deposition technology, which uses an electric arc as a heat source to realize layer-by-layer deposition using metal wires as the raw material, which has the advantages of high deposition efficiency, cost-effectiveness, and low impact on the environment, and is particularly suitable for the manufacture of medium- and large-sized metal parts. Some experiments have successfully prepared CuCrZr alloys using WAAM technology and studied the effects of different heat treatment processes on the alloy organization, mechanical properties, electrical and thermal conductivity. The results showed that the specimens treated using solid solution annealing + age hardening (SAAH) had uniform distribution of Cr elements and no coarse Cr precipitates, with an ultimate tensile strength of 301±5 MPa, a maximum hardness of 119.5±2.4 HV, an electrical conductivity of 45.8±0.1 MS/m, a thermal conductivity of
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