A super-elastic small hysteresis cycle stable shape memory alloy and a preparation method thereof

Abstract

The application provides a high-super-elastic small-hysteresis cyclic-stable shape memory alloy and a preparation method thereof. The shape memory alloy is composed of TiNiFeHf; wherein, the content of Ni is 47-49 at.%, the content of Fe is 1-3 at.%, the content of Hf is 1-3 at.%, and the rest is Ti, based on the total atom number of the shape memory alloy; and the atomic percentage of Ni+Fe is greater than or equal to 50%. The application also provides a preparation method of the high-super-elastic small-hysteresis cyclic-stable shape memory alloy. The high-super-elastic small-hysteresis cyclic-stable shape memory alloy has a lower stress hysteresis and better cyclic stability.

Description

Technical Field

[0001] This invention relates to a highly elastic, low-hysteresis, cyclically stable shape memory alloy and its preparation method, belonging to the field of shape memory alloy technology. Background Technology

[0002] In certain engineering applications, metal components are required to undergo significant reversible deformation within their load-bearing capacity. Traditional metallic materials typically have an elastic strain limit of no more than 1%. Shape memory alloys, due to their ability to undergo reversible martensitic transformation, can exhibit hyperelastic recovery strain of approximately 8%, with TiNi-based alloys demonstrating the best performance among various memory alloys. However, the primary martensitic transformation characteristic of TiNi-based alloys results in significant stress hysteresis during hyperelastic deformation. Commercially available TiNi alloys typically exhibit a hyperelastic stress hysteresis of approximately 300-400 MPa, which is detrimental to energy storage and recovery, as well as precise control in certain engineering fields. Therefore, developing shape memory alloys with low stress hysteresis is a pressing technical challenge in this field. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a highly elastic, low-hysteresis, cyclically stable shape memory alloy and its preparation method.

[0004] To achieve the above objectives, the present invention provides a highly elastic, low-hysteresis, cyclically stable shape memory alloy, wherein the elemental composition of the shape memory alloy is: TiNiFeHf;

[0005] In this shape memory alloy, based on the total number of atoms, the Ni content is 47-49 at.%, the Fe content is 1-3 at.%, the Hf content is 1-3 at.%, and the remainder is Ti; and the atomic percentage of Ni+Fe is greater than or equal to 50%.

[0006] According to a specific embodiment of the present invention, preferably, the shape memory alloy has an elemental composition of Ni. 48 TiFe3Hf2.

[0007] The present invention also provides a method for preparing the above-mentioned shape memory alloy, wherein elemental titanium, nickel, iron, and hafnium with a purity of 99 wt.% or higher are selected according to the composition ratio of the shape memory alloy;

[0008] Elemental titanium, nickel, iron, and hafnium are placed in a vacuum with a degree higher than 10. -1 Shape memory alloys are smelted in a furnace protected by Pa or inert gas.

[0009] According to a specific embodiment of the present invention, preferably, the preparation method further includes: casting the shape memory alloy obtained by melting into an ingot.

[0010] According to a specific embodiment of the present invention, preferably, the preparation method further includes: hot forging, hot rolling, cold rolling, and cold drawing of the ingot to obtain wire.

[0011] According to a specific embodiment of the present invention, preferably, the preparation method further includes an annealing treatment of the filament.

[0012] According to a specific embodiment of the present invention, preferably, the diameter of the filament is less than 1 mm, more preferably 0.33 mm.

[0013] According to a specific embodiment of the present invention, preferably, the hot forging temperature is 800-900℃.

[0014] According to a specific embodiment of the present invention, preferably, the hot rolling temperature is 800-900℃, more preferably 800-850℃.

[0015] According to a specific embodiment of the present invention, preferably, the annealing temperature is 350-500℃ (preferably 400-500℃) and the time is 10-20min (preferably 10-15min).

[0016] The high-elasticity, low-hysteresis, and cyclically stable shape memory alloy provided by this invention has low stress hysteresis and good cyclic stability. Attached Figure Description

[0017] Figure 1 Nanocrystalline Ni 48 Tensile stress-strain curves of TiFe3Hf2 at different temperatures.

[0018] Figure 2 Nanocrystalline Ni 48 Stress-strain curve of TiFe3Hf2 under 8% strain at -100℃ for 30 cycles of loading and unloading. Detailed Implementation

[0019] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0020] Example 1

[0021] This embodiment provides a highly elastic, low-hysteresis, cyclically stable shape memory alloy, specifically Ni. 48 TiFe3Hf2 is actually prepared through the following steps:

[0022] According to Ni 48The composition of the TiFe3Hf2 alloy is selected from elemental titanium, nickel, iron, and hafnium with a purity of 99.99 wt.% or higher.

[0023] Elemental titanium, nickel, iron, and hafnium are placed in a vacuum with a degree higher than 10. -1 Ni is smelted in a furnace protected by Pa or inert gas to form Ni. 48 TiFe3Hf2 alloy was cast into ingots;

[0024] The ingot was hot-forged at 900℃ and hot-rolled to a diameter of 1 mm, then cold-drawn into an amorphous state, eventually becoming a fine wire with a diameter of about 0.3 mm. Subsequently, the sample was annealed at 400-500℃ to recrystallize it, yielding Ni. 48 TiFe3Hf2 alloy.

[0025] Ni obtained in Example 1 48 Stress-strain tests were performed on the TiFe3Hf2 alloy, including:

[0026] Figure 1 Nanocrystalline Ni 48 Tensile stress-strain curves of TiFe3Hf2 alloy at different temperatures. Figure 1 It can be seen that: Ni 48 The TiFe3Hf2 alloy exhibits superelasticity from -100℃ to 0℃, with a superelastic critical stress exceeding 1000MPa. It shows almost no hysteresis at 0℃, and a hysteresis (y) of approximately 60MPa at -50℃ and -100℃, significantly lower than the hysteresis of 300-400MPa observed in commonly used TiNi-based shape memory alloys. This low stress hysteresis has engineering significance for actuator applications, and after unloading with an 8% strain load, approximately 7.8% of the strain can be recovered.

[0027] Lower stress hysteresis means lower internal friction during loading and unloading cycles. To improve engineering applicability, the cyclic stability of the material should also be examined. Figure 2 Nanocrystalline Ni 48 Stress-strain curves of TiFe3Hf2 alloy under 8% strain loading and unloading cycles at -100℃. Figure 2 It can be seen that: Ni 48 The recoverable strain of TiFe3Hf2 alloy can reach 7.7%, and the critical stress drops to 990 MPa, a decrease of only 5.7%.

Claims

1. A highly elastic, low-hysteresis, cycle-stable shape memory alloy, wherein, The elemental composition of this shape memory alloy is: TiNiFeHf; In this shape memory alloy, based on the total number of atoms, the Ni content is 47-49 at.%, the Fe content is 1-3 at.%, the Hf content is 1-3 at.%, and the remainder is Ti; furthermore, the atomic percentage of Ni+Fe is greater than 50%. The hyperelastic, low-hysteresis, cyclically stable shape memory alloy is prepared through the following steps: Select elemental titanium, nickel, iron, and hafnium with a purity of 99 wt.% or higher according to the composition ratio of shape memory alloy; Elemental titanium, nickel, iron, and hafnium are placed in a vacuum with a degree higher than 10. -1 Shape memory alloys are smelted in a furnace protected by Pa or inert gas. The shape memory alloy obtained by melting is cast into ingots; The ingot is hot-forged at 900℃ and hot-rolled to a diameter of 1 mm, then cold-drawn into an amorphous state, eventually becoming a fine wire with a diameter of 0.3 mm; subsequently, the sample is annealed at 400-500℃ to recrystallize the sample, thus obtaining the hyperelastic, low-hysteresis, cyclically stable shape memory alloy.

2. The hyperelastic, low-hysteresis, cyclically stable shape memory alloy according to claim 1, wherein, The elemental composition of this shape memory alloy is Ni 48 TiFe3Hf2.

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