Method for rapidly preparing Ni-Ti-Fe shape memory alloy

Abstract

The invention relates to the field of electric arc additive manufacturing, in particular to a method for preparing Ni-Ti-Fe shape memory alloy through electric arc additive manufacturing. A multi-wire electric arc additive manufacturing system is adopted, a pure Ti wire, a pure Ni wire and a pure Fe wire are fed into a molten pool, in-situ alloying is achieved, and the Ni-Ti-Fe shape memory alloy component with the high performance is prepared. A scanning electron microscope image shows that the prepared Ni-Ti-Fe shape memory alloy component is completely composed of fine isometric crystals. And compared with NiTi, the microhardness and the tensile property of the prepared Ni-Ti-Fe shape memory alloy component are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of Ni-Ti-Fe shape memory alloy preparation, specifically a method for in-situ preparation of Ni-Ti-Fe shape memory alloy using heterogeneous wire arc additive manufacturing. Background Technology

[0002] NiTi-based shape memory alloys (SMAs) are widely used in aerospace, biomedical, and robotics fields due to their excellent shape memory effect (SME), pseudoelasticity (PE), and mechanical properties. In NiTi alloys, replacing some Ni atoms with Fe effectively lowers the phase transformation temperature and separates the R-phase transformation and martensitic transformation temperature ranges, allowing Ni-Ti-Fe alloys to exhibit a two-stage martensitic transformation. Due to their excellent SME and low phase transformation temperature, Ni-Ti-Fe alloys are widely used in aerospace hydraulic pipe fittings, ensuring that no phase transformation occurs during use. Furthermore, among all TiNi-based shape memory alloys, Ti-Ni-Fe alloys possess an extremely low martensitic transformation temperature while maintaining good mechanical properties, making them widely used in applications such as couplings for jet fighters.

[0003] Ti 50 Ni 50-x Fe x Low-temperature shape memory alloys (0 < x ≤ 5) possess low phase transformation temperatures (the martensitic transformation initiation temperature decreases by 60°C for every 0.5 at.% Ni replacement by Fe) and excellent shape recovery properties, corrosion resistance, and wear resistance. They have been used in the aerospace field for hydraulic pipeline fittings and deformable wings operating at temperatures from -50°C to -30°C. Currently, Ti... 50 Ni 50- x Fe x Alloy preparation methods mainly rely on traditional processing techniques such as casting and powder sintering, but the Ti prepared by these methods... 50 Ni 50-x Fe x Alloys are prone to defects such as porosity and cracks, and also have disadvantages such as high cost, long production cycle and low material utilization, making it difficult to meet the needs of the rapid development of the aviation industry. Summary of the Invention

[0004] This invention provides a novel method for preparing Ni-Ti-Fe shape memory alloys. Using pure Ti, pure Ni, and pure Fe as raw materials, this invention employs a three-wire arc additive manufacturing technique to prepare the nickel-titanium shape memory alloy in situ. Under the action of the arc, multiple wire ends first form independent molten droplets, which are then dripped into the molten pool under gravity, achieving a multi-wire eutectic pool. Heterogeneous solutes diffuse into each other, undergoing a metallurgical reaction, and solidifying to form a metallic component.

[0005] This invention is achieved through the following technical solution:

[0006] A multi-wire electric arc additive manufacturing system was used to prepare high-performance NiTi shape memory alloy components by feeding pure Ti wire, Ni wire, and Fe wire into a molten pool for in-situ alloying. XRD phase analysis was used to verify its feasibility, and hardness and tensile tests were conducted to test its performance. Attached Figure Description

[0007] Figure 1 Microstructure of Ni-Ti-Fe component cross section

[0008] Figure 2 XRD results of Ni-Ti-Fe components

[0009] Figure 3 Microhardness comparison between NiTi and Ni-Ti-Fe

[0010] Figure 4 Stress-strain curves of NiTi and Ni-Ti-Fe Detailed Implementation

[0011] The implementation scheme of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0012] Preparation of Ti 50 Ni 50-x Fe x For an alloy of (0 < x ≤ 5), using TA1 alloy as the substrate, the diameters of pure Ti, Ni, and Fe welding wires are all 1.2 mm. The wire feed rate of each welding wire is calculated using the following formula, which utilizes the atomic fraction Ax and relative mass fraction Ex:

[0013]

[0014]

[0015] Where i represents welding wire No. 1, welding wire No. 2, and welding wire No. 3, E xi ρ is the mass fraction of the elements in the welding wire, WFS is the wire feed speed (in mm / min), d is the diameter of the welding wire used, and ρ is the density of the welding wire used (in g / cm³). 3 Mx (x = Ni, Ti, Fe) represents the relative atomic mass. The feed rate for pure Ti welding wire is 1500 mm / min, for Ni wire it is 910 mm / min, and for Fe wire it is 104 mm / min. The current during the preparation process is 120 A, and the gas flow rate is consistently 15 L / min.

[0016] After additive manufacturing, test specimens were prepared by wire cutting, followed by grinding and polishing. The polished specimens underwent microhardness testing from bottom to top, with a loading time of 15 seconds and a load of 0.2 kg. Keller's reagent was used for etching. The microstructure of the components was analyzed using a metallographic microscope and a scanning electron microscope.

[0017] Figure 1 The microstructure of the Ni-Ti-Fe component is shown. The grains inside the crystal are mostly columnar and small in size. Figure 2 The XRD results of the Ni-Ti-Fc component are shown, indicating that the internal phases of the prepared component are NiTi, NiTi2, and Ti. 50 Ni 48 Fe2. Figure 3 and Figure 4 The microhardness and tensile properties of Ni-Ti-Fe and NiTi were compared. The Ni-Ti-Fe prepared by arc additive manufacturing technology had an average microhardness of 303 MPa and an elongation of 5.5%, which were improved compared with NiTi.

[0018] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for rapidly preparing Ni-Ti-Fe shape memory alloys, comprising the following steps: (1) Using an electric arc additive manufacturing system, Fe element is fed into the molten pool to achieve in-situ alloying. In the molten pool, Ni, Ti and Fe undergo in-situ metallurgical reaction to form Ni-Ti-Fe shape memory alloy. (2) For the electric arc additive manufacturing system in step 1, a multi-wire feeding mechanism is adopted to simultaneously feed pure Ti, Ni and Fe wires into the molten pool to achieve in-situ alloying and prepare titanium-nickel alloy components containing Fe. (3) The micro strength and tensile properties of the titanium-nickel alloy components prepared in step 1 were significantly improved.

2. A method for rapidly preparing Ni-Ti-Fe shape memory alloys, characterized in that: Titanium-nickel alloy components were prepared using an electric arc additive manufacturing method, achieving low-cost and rapid manufacturing. Furthermore, the performance of NiTi-based shape memory alloys was significantly improved after the addition of Fe.

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