Ti-Ni-Cu-Pd Shape Memory Alloy and Its Preparation Method

Abstract

The present invention discloses a Ti-Ni-Cu-Pd shape memory alloy and a preparation method thereof. The chemical formula of the shape memory alloy is (Ti 50 Ni 47 Cu3)‑x(Ti 50 Ni 30 Pd 20 ), according to atomic percentage, it includes the following components: 50at% Ti, 30-47at% Ni, 0-3at% Cu, 0-20at% Pd. 50 Ni 47 Cu3)‑0.35(Ti 50 Ni 30 Pd 20 ) alloy has a narrow thermal hysteresis, which reduces the thermal hysteresis of shape memory alloys.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloys, relates to a Ti-Ni-Cu-Pd shape memory alloy, and also relates to a preparation method of the shape memory alloy. Background Art

[0002] Shape memory alloys (SMAs) are metal materials that exhibit a shape memory effect. This effect occurs when a shape memory alloy is shaped at high temperature, cooled to a low temperature, and deformed, leaving a residual deformation. When the alloy is then heated above a certain temperature, the residual deformation disappears, and the material returns to its original shape at high temperature, as if it has memorized the high-temperature state. This phenomenon is based on the alloy's martensitic transformation, during which latent heat is released, accompanied by changes in isothermal entropy and adiabatic temperature. This property makes it suitable for applications in actuators, sensors, and other areas.

[0003] However, due to the changes in the alloy's crystal structure and unit cell volume before and after the martensitic transformation, shape memory alloys exhibit significant thermal hysteresis, a measure of the temperature difference between heating and cooling. This thermal hysteresis in shape memory alloys results in low energy conversion efficiency and poor temperature control accuracy, limiting their application in fields such as actuators and sensors. Therefore, while shape memory alloys are widely used as smart materials, this type of material still faces a difficult-to-overcome challenge: the significant thermal hysteresis of the temperature-induced martensitic transformation. Summary of the Invention

[0004] The purpose of the present invention is to provide a Ti-Ni-Cu-Pd shape memory alloy, which solves the problem of large thermal hysteresis of shape memory alloys in the prior art.

[0005] The technical solution adopted by the present invention is that Ti-Ni-Cu-Pd shape memory alloy, the chemical formula of the shape memory alloy is (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ), comprising the following components in atomic percentage:

[0006] 50at% Ti, 30~47at% Ni, 0~3at% Cu, 0~20at% Pd.

[0007] The present invention is also characterized in that:

[0008] In terms of atomic percentage, it includes: 50 at % Ti, 41.05 at % Ni, 1.95 at % Cu, and 7 at % Pd.

[0009] Another object of the present invention is to provide a method for preparing the Ti-Ni-Cu-Pd shape memory alloy.

[0010] Another technical solution adopted by the present invention is a method for preparing a Ti-Ni-Cu-Pd shape memory alloy, comprising the following steps:

[0011] Step 1, weighing Ti, Ni, Cu, and Pd raw materials according to atomic percentage, the percentage of the raw materials is: 50at% Ti, 30-47at% Ni, 0-3at% Cu, 0-20at% Pd, and placing the above raw materials into a vacuum arc melting furnace;

[0012] Step 2: introducing argon gas into the furnace chamber of the vacuum arc melting furnace to start the arc. After the arc is stable, the arc current is set, and the alloy ingot is obtained through melting.

[0013] Step 3: Turn off the arc gun, turn the ingot over, and repeat step 2;

[0014] Step 4: After the sample obtained in step 3 is cooled, a shape memory alloy (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ).

[0015] The x of the shape memory alloy is 0, 0.2, 0.3, 0.35, 0.4, 0.5, 0.6 or 1.

[0016] The arc current during step 2 melting is 250-350A.

[0017] The beneficial effects of the present invention are as follows: the Ti-Ni-Cu-Pd shape memory alloy of the present invention is selected by selecting Cu-doped and Pd-doped TiNi shape memory alloys, and selecting Ti that undergoes B2-B19′ martensitic transformation. 50 Ni 47 Cu3 system is used as the left end of the design phase diagram, and Ti 50 Ni 30 Pd 20 The system is taken as the right end of the design phase diagram, and (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ) shape memory alloy, find the triple point alloy according to the designed phase diagram. The test results show that at the triple point composition (Ti 50 Ni 47Cu3)-0.35(Ti 50 Ni 30 Pd 20 ) alloy has a narrow thermal hysteresis, which reduces the thermal hysteresis of shape memory alloys.

[0018] The preparation method of the Ti-Ni-Cu-Pd shape memory alloy of the present invention has simple process and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a DSC test curve diagram of the Ti-Ni-Cu-Pd shape memory alloy of the present invention;

[0020] Figure 2 The present invention (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ) Resistance-temperature test curve of shape memory alloy;

[0021] Figure 3 The present invention (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ) DMA test curve of shape memory alloy;

[0022] Figure 4 The present invention (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ) Thermal hysteresis-composition curve of shape memory alloy;

[0023] Figure 5 The present invention (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ) Pseudo-binary phase diagram of shape memory alloys. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Ti-Ni-Cu-Pd shape memory alloy, the chemical formula of shape memory alloy is (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd20 ), comprising the following components in atomic percentage:

[0026] 50at% Ti, 30~47at% Ni, 0~3at% Cu, 0~20at% Pd.

[0027] Furthermore, according to atomic percentage, it includes: 50 at % Ti, 41.05 at % Ni, 1.95 at % Cu, and 7 at % Pd.

[0028] The preparation method of Ti-Ni-Cu-Pd shape memory alloy comprises the following steps:

[0029] Step 1, weighing Ti, Ni, Cu, and Pd raw materials according to atomic percentage, the percentage of the raw materials is: 50at% Ti, 30-47at% Ni, 0-3at% Cu, 0-20at% Pd, and placing the above raw materials into a vacuum arc melting furnace;

[0030] Step 2: Under a 0.05 MPa argon atmosphere, place the smelting sample at the bottom of the arc gun, adjust the distance between the arc gun and the smelting sample to within 2 mm, strike the arc, and after the arc stabilizes, adjust the arc current to 250-350 A and start smelting. Maintain the raw material in a molten state for 60-74 seconds, then adjust the position of the arc gun to smelt and obtain an ingot.

[0031] Step 3: Turn off the arc gun and use a mechanical rod to turn the ingot over in the melting furnace, and repeat step 2 several times;

[0032] Step 4: Turn off the arc gun and the power of the melting furnace, and wait for the sample obtained in step 3 to cool down to obtain the shape memory alloy (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ), x of the shape memory alloy is 0, 0.2, 0.3, 0.35, 0.4, 0.5, 0.6 or 1.

[0033] In the above manner, the Ti-Ni-Cu-Pd shape memory alloy of the present invention is selected by selecting Cu-doped and Pd-doped TiNi shape memory alloys, and selecting Ti that undergoes B2-B19′ martensitic transformation. 50 Ni 47 Cu3 system is used as the left end of the design phase diagram, and Ti 50 Ni 30 Pd 20 The system is taken as the right end of the design phase diagram, and (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni30 Pd 20 ) shape memory alloy, find the triple point alloy according to the designed phase diagram. The test results show that at the triple point composition (Ti 50 Ni 47 Cu3)-0.35(Ti 50 Ni 30 Pd 20 ) alloy has a narrow thermal hysteresis, which reduces the thermal hysteresis of shape memory alloys. The present invention is based on a quasi-isotropic phase boundary principle starting from the triple point, that is, there is a quasi-isotropic phase boundary starting from the triple point in the composition-temperature phase diagram of the alloy. When approaching the phase boundary point, the phase change resistance that the system needs to overcome to transform from one structure to another is very small, and the alloy with the triple point composition will show a minimum value of thermal hysteresis. In a general martensitic phase transformation, the incompatibility between martensite and the parent phase will cause lattice defects to be generated during the phase transformation, resulting in a stress transition layer between the two phases and a hysteresis energy barrier. It can be seen from the phase diagram obtained by design in the present invention that the triple point composition is approximately at x=0.35, where the phase transformation transitions from a first-order discontinuous phase transformation to a continuous phase transformation,

[0034] At the triple point, the system undergoes a two-step transition from B2 to B19 and then to B19'. Compared with the one-step transition, the lattice compatibility of the system is improved, and the stress transition layer is basically eliminated, so there is a smaller thermal hysteresis.

[0035] x=0,Ti 50 Ni 47 Cu3 shape memory alloy;

[0036] Weigh 8.9519g Ti, 10.3528g Ni, and 0.7117g Cu as raw materials, and place the above raw materials in a smelting furnace; under a 0.05MPa argon environment, adjust the smelting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the smelting sample, and start the arc. After the arc is stable, adjust the arc current to 250A and start smelting. First, keep the raw materials in a molten state for 60s, then adjust the position of the arc gun to smelt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the smelting furnace, and repeat the above smelting process many times; then turn off the arc gun and the smelting furnace power supply, and cool the obtained sample to obtain Ti 50 Ni 47 Cu3 shape memory alloy.

[0037] Example 2

[0038] x=0.2,(Ti 50 Ni 47 Cu3)-0.2(Ti 50 Ni 30 Pd 20 ) shape memory alloys;

[0039] Weigh 8.9399g Ti, 9.4076g Ni, 0.5694g Cu, and 1.3531g Pd of raw materials, and place the above raw materials in a melting furnace; under a 0.05MPa argon environment, adjust the melting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the melting sample, and start the arc. After the arc is stable, adjust the arc current to 320A and start melting. First, keep the raw materials in a molten state for 72s, then adjust the position of the arc gun to melt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the melting furnace, and repeat the above melting process several times; then turn off the arc gun and the power supply of the melting furnace, and cool the obtained sample to obtain (Ti 50 Ni 47 Cu3)-0.2(Ti 50 Ni 30 Pd 20 )Shape memory alloy.

[0040] Example 3

[0041] x=0.3,(Ti 50 Ni 47 Cu3)-0.3(Ti 50 Ni 30 Pd 20 ) shape memory alloys;

[0042] Weigh 8.5372g Ti, 8.9349g Ni, 0.4982g Cu, and 2.0297g Pd of raw materials, and place the above raw materials in a melting furnace; under a 0.05MPa argon environment, adjust the melting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the melting sample, and start the arc. After the arc is stable, adjust the arc current to 310A and start melting. First, keep the raw materials in a molten state for 70s, then adjust the position of the arc gun to melt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the melting furnace, and repeat the above melting process several times; then turn off the arc gun and the power supply of the melting furnace, and cool the obtained sample to obtain (Ti 50 Ni 47 Cu3)-0.3(Ti 50 Ni 30 Pd 20 )Shape memory alloy.

[0043] Example 4

[0044] x=0.35,(Ti 50 Ni 47 Cu3)-0.35(Ti 50 Ni 30 Pd 20 ) shape memory alloys;

[0045] Weigh 8.4708g Ti, 8.6985g Ni, 0.4626g Cu, and 2.3680g Pd of raw materials, and place the above raw materials in a melting furnace; under a 0.05MPa argon environment, adjust the melting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the melting sample, and start the arc. After the arc is stable, adjust the arc current to 270A and start melting. First, keep the raw materials in a molten state for 67s, then adjust the position of the arc gun to melt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the melting furnace, and repeat the above melting process several times; then turn off the arc gun and the power supply of the melting furnace, and cool the obtained sample to obtain (Ti 50 Ni 47 Cu3)-0.35(Ti 50 Ni 30 Pd 20 )Shape memory alloy.

[0046] Example 5

[0047] x=0.4,(Ti 50 Ni 47 Cu3)-0.4(Ti 50 Ni 30 Pd 20 ) shape memory alloys;

[0048] Weigh 8.4045g Ti, 8.4623g Ni, 0.4270g Cu, and 2.7063g Pd of raw materials, and place the above raw materials in a melting furnace; under a 0.05MPa argon environment, adjust the melting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the melting sample, and start the arc. After the arc is stable, adjust the arc current to 270A and start melting. First, keep the raw materials in a molten state for 65s, then adjust the position of the arc gun to melt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the melting furnace, and repeat the above melting process several times; then turn off the arc gun and the melting furnace power supply, and cool the obtained sample to obtain (Ti 50 Ni 47 Cu3)-0.4(Ti 50 Ni 30 Pd 20 )Shape memory alloy.

[0049] Example 6

[0050] x=0.5,(Ti 50 Ni 47 Cu3)-0.5(Ti 50 Ni 30 Pd 20 ) shape memory alloys;

[0051] Weigh 8.2716g Ti, 7.9896g Ni, 0.3559g Cu, and 3.3828g Pd of raw materials, and place the above raw materials in a melting furnace; under a 0.05MPa argon environment, adjust the melting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the melting sample, and start the arc. After the arc is stable, adjust the arc current to 300A and start melting. First, keep the raw materials in a molten state for 60s, then adjust the position of the arc gun to melt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the melting furnace, and repeat the above melting process several times; then turn off the arc gun and the power supply of the melting furnace, and cool the obtained sample to obtain (Ti 50 Ni 47 Cu3)-0.5(Ti 50 Ni 30 Pd 20 )Shape memory alloy.

[0052] Example 7

[0053] x=0.6,(Ti 50 Ni 47 Cu3)-0.6(Ti 50 Ni 30 Pd 20 ) shape memory alloys;

[0054] Weigh the raw materials Ti8.1389g, Ni7.5169g, Cu0.2847g, and Pd4.0594g, and place the above raw materials in a melting furnace; under a 0.05MPa argon environment, adjust the melting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the melting sample, and start the arc. After the arc is stable, adjust the arc current to 320A and start melting. First, keep the raw materials in a molten state for 60s, then adjust the position of the arc gun to melt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the melting furnace, and repeat the above melting process several times; then turn off the arc gun and the melting furnace power supply, and cool the obtained sample to obtain (Ti 50 Ni 47 Cu3)-0.6(Ti 50 Ni 30 Pd 20 )Shape memory alloy.

[0055] Example 8

[0056] x=1,Ti 50 Ni 30 Pd 20 shape memory alloys;

[0057] Weigh 7.6079g Ti, 5.6264g Ni, and 6.7657g Pd as raw materials, and place the above raw materials in a melting furnace; under a 0.05MPa argon environment, adjust the melting sample to the bottom of the arc gun, adjust the arc gun to a distance of 2mm from the melting sample, and start the arc. After the arc is stable, adjust the arc current to 350A and start melting. First, keep the raw materials in a molten state for 74s, then adjust the position of the arc gun to melt and obtain an ingot; turn off the arc gun, use a mechanical rod to turn the ingot over in the melting furnace, and repeat the above melting process many times; then turn off the arc gun and the power supply of the melting furnace, and cool the obtained sample to obtain Ti 50 Ni 30 Pd 20 Shape memory alloy.

[0058] The eight shape memory alloy base ingots obtained in Examples 1-8 were hot rolled at 1273K, rolled into 1 mm thin sheets, and then cut into sizes suitable for different tests. The cut samples were mechanically polished to remove the oxide layer. After that, they were placed in a vacuum quartz glass tube and solution treated at 1273K for 1 hour before being quenched in ice. Any existing oxide layer was removed by mechanical polishing before testing.

[0059] DSC test was performed with a heating and cooling rate of 10 K / min -1 , test results see Figure 1 It can be seen that when x = 0.3 and 0.35, i.e., Example 3-4, two peaks appear during the cooling and heating processes, respectively. The smaller peak corresponds to the second phase transition from B19 to B19′; and when x = 0.35, the exothermic peak and the endothermic peak occur at almost the same temperature point. It can be seen that the shape memory alloy composition obtained in Example 3-4 has a very small thermal hysteresis.

[0060] The resistance variation with temperature was tested using a four-probe resistance test system with a heating and cooling rate of 2K / min. -1 ,See Figure 2 When x = 0.3, 0.35, and 0.4, a two-step transformation from B2 to B19 to B19′ occurs; at the same time, when x = 0.35 and 0.4, the area between the heating and cooling curves is very small, and an alloy with extremely small thermal hysteresis appears in this composition area.

[0061] The DMA test was carried out in a single cantilever beam mode. The six test frequencies selected were 0.2, 0.4, 1, 4, 10, and 20 Hz, and the heating and cooling rates were 2 K / min. -1 ,See Figure 3The upper half of the figure shows the change in internal friction, and the lower half shows the change in storage modulus. At x = 0.3, 0.35, and 0.4, another larger internal friction peak appears after the martensitic phase transformation internal friction peak. Its damping value is almost independent of the heating and cooling rates and has almost no hysteresis.

[0062] The variation of alloy thermal hysteresis with composition is obtained by taking values from DSC and resistance temperature curves. Figure 4 ab, it can be seen that when x = 0.35, the thermal hysteresis reaches its minimum.

[0063] Through the above test, it can be determined that (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 Phase transformation behavior of the alloy system (x=0、0.2、0.3、0.35、0.4、0.5、0.6、1) is constructed. 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ) Pseudo binary phase diagram of shape memory alloy, see Figure 5 The triple point composition of this alloy is approximately at 0.35. From the above test, it can be verified that the alloy at this triple point composition has narrow thermal hysteresis performance, that is, (Ti 50 Ni 47 Cu3)-0.35(Ti 50 Ni 30 Pd 20 )Shape memory alloys have better narrow thermal hysteresis performance.

Claims

1. Ti-Ni-Cu-Pd shape memory alloy, characterized in that The shape memory alloy comprises, in atomic percentage, 50 at % Ti, 41.05 at % Ni, 1.95 at % Cu, and 7 at % Pd; The preparation method of the Ti-Ni-Cu-Pd shape memory alloy comprises the following steps: Step 1, weighing Ti, Ni, Cu, and Pd raw materials according to the above atomic percentages, and placing the raw materials into a vacuum arc melting furnace; Step 2: introducing argon gas into the furnace chamber of the vacuum arc melting furnace to strike an arc. After the arc is stable, the arc current is set to 250-350A, and alloy ingots are obtained through melting. Step 3: Turn off the arc gun, turn the ingot over, and repeat step 2; Step 4: After the sample obtained in step 3 is cooled, the shape memory alloy Ti is obtained. 50 Ni 41.05 Cu 1.95 Pd7; The content of each component of the Ti-Ni-Cu-Pd shape memory alloy is obtained through the composition-temperature phase diagram of the alloy, specifically: By selecting Cu-doped and Pd-doped TiNi shape memory alloys, the TiNi alloy undergoing B2-B19′ martensitic transformation is selected. 50 Ni 47 Cu3 system is used as the left end of the design phase diagram, and Ti 50 Ni 30 Pd 20 The system is designed as the right end of the phase diagram, and the system is prepared (Ti 50 Ni 47 Cu3)-x(Ti 50 Ni 30 Pd 20 ) shape memory alloy, and construct a phase diagram through testing to obtain the content of each component of the alloy at the triple point, which is the content of each component in the Ti-Ni-Cu-Pd shape memory alloy.

Images