A MnNiTi-based dual-phase alloy, its preparation method and application

Abstract

This invention belongs to the field of alloy technology and discloses a MnNiTi-based dual-phase alloy, its preparation method, and its applications. The chemical formula of this MnNiTi-based dual-phase alloy is Mn. 50 Ni 50‑x Ti x Where 5≤x≤35. This MnNiTi-based dual-phase alloy, through its specific elemental ratios, solves the problem in existing technologies where the atoms in MnNiTi-based alloys are not easily ordered, resulting in a large phase transformation span and a large hysteresis. The unique microstructure of the MnNiTi-based dual-phase alloy, combined with the intrinsic mechanical properties of the main phase, synergistically enhances the alloy's compressive strength and toughness. Therefore, the alloy can withstand greater stress, promoting a more complete phase transformation and exhibiting a stress-induced large phase transformation heat effect that exceeds the temperature-induced phase transformation heat effect.

Description

Technical Field

[0001] This invention belongs to the field of alloy technology, and specifically relates to a MnNiTi-based dual-phase alloy, its preparation method, and its application. Background Technology

[0002] Shape memory alloys based on martensitic phase transformation are key materials in fields such as intelligent drives, solid-state phase change refrigeration, thermal management, and energy conversion. These applications rely on the abrupt changes in material properties during phase transformation, including changes in length and volume, entropy change, electrical resistance, thermal conductivity, and so on. To realize these materials in practical applications, on the one hand, the changes in these physical quantities during phase transformation must be sufficiently significant. In particular, for solid-state materials based on the thermal effect (i.e., elasto-thermal effect) generated by stress-induced shape memory alloy phase transformation, a sufficiently large phase transformation entropy change is needed to improve cooling capacity and efficiency; however, current shape memory alloy materials used as refrigerants inherently exhibit relatively small elasto-thermal effects. On the other hand, existing materials are brittle and prone to fracture failure, failing to meet practical application requirements. Therefore, obtaining materials with high spacing strength and large phase transformation thermal effects is crucial for achieving solid-state phase change refrigeration and efficient energy conversion.

[0003] In 2015, Liu Enke, Wei Zhiyang, and others discovered high-toughness all-transition Heusler alloys based on dd covalent hybridization, represented by NiMnTi and NiCoMnTi. These alloys exhibit large elastothermal and compressive-thermal effects. However, the Mn-rich MnNiTi system, due to the weak dd covalent hybridization between its transition elements, makes atomic ordering difficult and is extremely sensitive to relative annealing conditions. This results in MnNiTi-based alloys often having large phase transformation spans and significant hysteresis, and their phase transformation thermal effects cannot be fully realized. Their elastothermal effect has not been reported, and their strength needs further improvement. Summary of the Invention

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a MnNiTi-based dual-phase alloy, its preparation method, and its applications. The MnNiTi-based dual-phase alloy of this invention solves the problem in the prior art where the atoms in MnNiTi-based alloys are not easily ordered, resulting in a large phase transformation span and significant hysteresis. The unique microstructure of the MnNiTi-based dual-phase alloy of this invention, combined with the intrinsic mechanical properties of the main phase, synergistically enhances the alloy's compressive strength and toughness. Therefore, the alloy can withstand greater stress, promoting a more complete phase transformation and exhibiting a stress-induced large phase transformation heat effect exceeding the temperature-induced phase transformation heat effect. Simultaneously, it also possesses advantages such as high hardness, corrosion resistance, and good machinability, showing excellent application prospects in shape memory alloys, intelligent drives, solid-state phase change refrigeration, thermal management, and phase change thermal storage.

[0005] A first aspect of the present invention provides a MnNiTi-based dual-phase alloy.

[0006] Specifically, a MnNiTi-based dual-phase alloy with the chemical formula Mn 50 Ni 50-x Ti x , where 5≤x≤35.

[0007] Preferably, the value of x is in the range of 11≤x≤15, and more preferably 11≤x≤13.

[0008] Preferably, the main phase in the MnNiTi-based dual-phase alloy is a B2-ordered Heusler phase (body-centered cubic structure), and the second phase is a ductile γ phase (face-centered cubic structure), which are dispersed in the interior of the grains and at the grain boundaries.

[0009] Preferably, the chemical formula of the MnNiTi-based dual-phase alloy is Mn 50 Ni 37.5 Ti 12.5 or Mn 50 Ni 38.5 Ti 11.5 .

[0010] Preferably, the phase transformation temperature range of the MnNiTi-based dual-phase alloy is 50-500K. More preferably, the phase transformation temperature range is made closer to room temperature by adjusting the composition, wherein 11≤x≤13.

[0011] A second aspect of the present invention provides a method for preparing a MnNiTi-based dual-phase alloy.

[0012] Specifically, a method for preparing a MnNiTi-based dual-phase alloy includes the following steps:

[0013] According to the proportions of the elements in the chemical formula, Mn, Ni, and Ti are weighed, and then an alloy is prepared by means of electric arc melting, induction melting, rapid melt quenching, solid-state reaction, atomization, spray casting, suction casting, rolling, or directional solidification. After annealing, the alloy is quenched in an ice-water mixture to obtain the MnNiTi-based dual-phase alloy.

[0014] Preferably, the mass purity of Mn, Ni, and Ti all exceeds 99.95%. Mn, Ni, and Ti are all in elemental form.

[0015] Preferably, the alloy is formed as at least one of polycrystalline bulk, strip, rod or powder.

[0016] Preferably, the annealing temperature is 500-1200℃, and more preferably 600-1000℃.

[0017] Preferably, the annealing time is 0.1 to 144 hours, and more preferably 72 to 100 hours.

[0018] After annealing, it needs to be rapidly quenched in an ice-water mixture to form a two-phase coexistence structure.

[0019] A third aspect of the present invention provides an application of a MnNiTi-based dual-phase alloy.

[0020] Applications of the aforementioned MnNiTi-based dual-phase alloys in the fields of intelligent drive or energy conversion.

[0021] Preferably, the energy conversion includes solid-state phase change refrigeration or thermal management.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The MnNiTi-based dual-phase alloy of the present invention is composed of specific proportions of each element, which solves the problem that the atoms of the MnNiTi-based alloy are not easy to order, resulting in a large phase transformation span and large hysteresis in the prior art. The unique microstructure of the MnNiTi-based dual-phase alloy of the present invention, together with the intrinsic mechanical properties of the main phase, synergistically improves the compressive strength and toughness of the alloy. Therefore, the alloy can withstand greater stress to promote a more complete phase transformation, exhibiting a huge stress-induced phase transformation heat effect that exceeds the temperature-induced phase transformation heat effect.

[0024] (2) The MnNiTi-based dual-phase alloy of the present invention maintains the phase transformation entropy change while significantly reducing the phase transformation span and hysteresis. This alloy maintains a larger entropy change than other previously discovered Heusler alloys while significantly improving the heat effect release efficiency. This alloy has great application prospects in the fields of solid-state refrigeration and phase change energy storage.

[0025] (3) The MnNiTi-based dual-phase alloy of the present invention exhibits a significant phase transformation effect, and its phase transformation temperature can be controlled by changing the value of x in the alloy. Preferably, the MnNiTi-based dual-phase alloy undergoes a temperature-induced phase transformation from a B2-ordered Heusler phase to a 5-layer modulated martensite near room temperature, with a maximum entropy change value reaching 65.8 J kg. -1 K -1 Based on this entropy change, the theoretical temperature change is estimated to be 39.9 K.

[0026] (4) The MnNiTi-based dual-phase alloy of the present invention has the characteristics of high strength, high toughness, and easy processing. In particular, its excellent toughness and compressive strength provide mechanical support for the full release of the elasto-thermal effect of the MnNiTi-based dual-phase alloy of the present invention. Preferably, the MnNiTi-based dual-phase alloy has a strength exceeding 1.7 GPa and a toughness exceeding 450 J / cm². -3 The compression rate exceeds 32%.

[0027] (5) Such good mechanical properties enable the alloy to withstand large stress, which induces a full phase transformation from the B2 ordered Heusler phase to the unmodulated square L10 martensite. Since the L10 martensite has lower energy than the 5M martensite, it releases additional heat and produces a huge elasto-thermal effect. The measured adiabatic temperature change can reach 57.2-64.5K, exceeding the value of 39.9K corresponding to the entropy change of the phase transformation induced by the temperature. Attached Figure Description

[0028] Figure 1 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Room temperature XRD pattern of the dual-phase alloy;

[0029] Figure 2 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Schematic diagram of the structure of austenite and γ-phase crystals in a dual-phase alloy;

[0030] Figure 3 Mn is from Example 1 50 Ni 37.5 Ti 12.5 SEM image of a dual-phase alloy;

[0031] Figure 4 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Magnetization-temperature curves of a two-phase alloy;

[0032] Figure 5 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Heat flow-temperature curves of dual-phase alloys;

[0033] Figure 6 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Stress-strain curves of a two-phase alloy under small strain;

[0034] Figure 7 yes Figure 6 The corresponding DIC strain contour plot;

[0035] Figure 8 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Stress-strain curves of a dual-phase alloy under large strain;

[0036] Figure 9 yes Figure 8 The corresponding temperature-time curve;

[0037] Figure 10 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Temperature-time curve of another sample of the dual-phase alloy;

[0038] Figure 11 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Comparison of room temperature XRD patterns of dual-phase alloys before and after compression;

[0039] Figure 12 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Stress-strain curves for compressive strength testing of duplex alloys;

[0040] Figure 13 Mn in Comparative Example 1 49 Ni 48 XRD pattern of Ti3 alloy;

[0041] Figure 14 Mn in Comparative Example 1 49 Ni 48 Ti3 alloy, Comparative Example 2 Mn 50 Ni 48 Stress-strain curves from compressive strength tests of Ti2 alloy;

[0042] Figure 15 Mn in Comparative Example 1 49 Ni 48 Ti3 alloy, Comparative Example 2 Mn 50 Ni 48 Temperature-time curve of compressive strength test of Ti2 alloy;

[0043] Figure 16 Mn is from Example 2 50 Ni 38.5 Ti 11.5 Magnetization-temperature profiles of dual-phase alloys;

[0044] Figure 17 Mn is from Example 2 50 Ni 38.5 Ti 11.5 Comparison of room temperature XRD patterns of dual-phase alloys before and after compression. Detailed Implementation

[0045] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0046] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0047] The dual-phase alloys required for preparation in this invention are all polycrystalline samples. The raw materials for the alloys are metallic elements (Mn, Ni, Ti) in stoichiometric proportions, and the mass purity of the transition metals used all exceeds 99.95%.

[0048] Example 1

[0049] This embodiment prepares a MnNiTi-based dual-phase alloy that combines high strength and significant thermal effect. The preparation method is as follows:

[0050] Step 1: According to the stoichiometric ratio of Mn 50 Ni 37.5 Ti 12.5 Weigh out 25g of Mn, Ni, and Ti, each with a purity exceeding 99.95%. For volatile elements, such as Mn, add 0.5% of the total Mn mass during batching to balance losses during the smelting process and ensure sample composition. All oxide scale on the surfaces of raw materials must be removed before batching. Taking Mn as an example, arc melting is required before batching to improve the purity of the raw materials. The specific procedures are as follows:

[0051] (1) Place an appropriate amount of metal Mn, about 50g, into the electric arc furnace;

[0052] (2) Use a high current of over 200A to melt 3 times, and turn the Mn ingot over after each melting;

[0053] (3) After the oxide scale on the surface of the smelted Mn ingot is cleaned, it is crushed. The interior shows a silvery-white metallic luster and there are no oxide impurities of other colors, indicating that the purification of Mn has been completed.

[0054] Step Two: Melting is carried out using a water-cooled copper crucible electric arc furnace. The prepared raw materials are placed in the center of the bottom of the copper crucible. Volatile Mn can be placed at the bottom to reduce volatilization during the first melting process. Before melting, the furnace is evacuated. The evacuation process is divided into two stages: First, a mechanical pump is used for rough evacuation, during which the gas is purged three times. After purging, once the vacuum level drops below 8 Pa, the molecular pump is turned on to evacuate the gas pressure to 10 Pa. -3 A high vacuum below Pa was then introduced into the furnace, and finally, high-purity Ar gas (99.999% purity) was backfilled to 0.05 MPa.

[0055] During smelting, place the arc head 3 cm away from the raw material and use a small current to ignite the arc. After successful ignition, gradually increase the current while raising the arc head. The current should not be increased rapidly; the rate of increase should be controlled at 30 A / s. -1 To prevent uneven heating of the raw materials and splashing, electromagnetic stirring can be turned on after the raw materials are melted during the smelting process to ensure uniform smelting. To make the raw materials melt evenly, the ingot should be smelted repeatedly 6 times. After the smelting is completed, the current is slowly adjusted to zero and the arc head is raised. Finally, the power is turned off and the smelting is completed.

[0056] Step 3: Remove the oxides from the surface of the arc-melted ingot, and cut the ingot into 1mm thick slices using wire electrical discharge machining (EDM) for property testing; 4×4×8mm 3 The cube was used for elasto-thermal testing, and the wire-cut ablation marks on the surface of the ingot were polished clean and then ultrasonically cleaned with anhydrous ethanol.

[0057] Step 4: Place the cleaned ingot into a quartz tube and evacuate the tube to a vacuum level of 4×10⁻⁶. -4 Below Pa, the quartz tube was vacuum sealed and then annealed in a tube furnace at 915℃ for 4 days. Upon removal, the quartz tube was broken and quenched in an ice-water mixture to ensure a sufficiently fast cooling rate, yielding a MnNiTi-based dual-phase alloy with the chemical formula Mn. 50 Ni 37.5 Ti 12.5 (can be called Mn) 50 Ni 37.5 Ti 12.5 (Duplex alloys).

[0058] The measured Mn 50 Ni 37.5 Ti 12.5 The microstructure, physical properties, and elastothermal effect of polycrystalline samples were studied, and the test results were collected and analyzed.

[0059] At room temperature, the MnNiTi-based dual-phase alloy exhibits a coexistence of B2-structured austenite and a manganese-rich γ-phase. The room temperature XRD curve of the MnNiTi-based dual-phase alloy is shown below. Figure 1 ( Figure 1 The vertical axis "Intensity" represents intensity, and the horizontal axis represents diffraction angle. The corresponding crystal structures of B2 austenite and the γ phase are shown below. Figure 2 As shown. Figure 3 SEM images of MnNiTi-based dual-phase alloys, from Figure 3 The γ phase can be seen dispersedly distributed in the austenite.

[0060] Figure 4 Mn is from Example 1 50 Ni 37.5 Ti12.5 Magnetization-temperature curves of dual-phase alloys; from Figure 4 It can be seen that the corresponding phase transition temperature is lower than room temperature. Figure 4 The "M(emu g" in -1 "T(K)" represents the magnetization intensity per unit mass, "T(K)" represents the temperature, and M represents the temperature. f M represents the temperature at which the martensitic phase transformation begins. s A represents the temperature at which the martensitic phase transformation ends. f A represents the temperature at which the austenitic phase transformation ends. s This indicates the temperature at which the austenitic phase transformation ends; "H = 500 Oe" indicates that the applied magnetic field strength is 500 Oe. Figure 5 ( Figure 5 In this context, "DSC" stands for Differential Scanning Calorimetry, "exothermic" indicates exothermic, "Heating" indicates heating, and "Cooling" indicates cooling. f M represents the temperature at which the martensitic phase transformation ends. s M represents the temperature at which the martensitic phase transformation begins. p A represents the peak temperature of the martensitic phase transformation. f A represents the temperature at which the austenitic phase transformation ends. s A represents the temperature at which the austenitic phase transformation begins. p (Indicates the peak temperature of the austenite phase transformation) is Mn in Example 1 50 Ni 37.5 Ti 12.5 The heat flow-temperature curve of the dual-phase alloy, and the Mn obtained by integration. 50 Ni 37.5 Ti 12.5 The entropy change of the martensitic phase transformation in the dual-phase alloy is 65.8 J kg. -1 K -1 Based on this entropy change, the theoretical temperature change is estimated to be 39.9 K.

[0061] Figure 6 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Stress-strain curves of a two-phase alloy under small strain. Figure 6 ( Figure 6 In this context, "Strain" represents strain, "Stress" represents pressure, and "Strain rate" represents strain rate. The corresponding DIC (Digital Image Correlation) strain contour plot is shown below. Figure 7 ( Figure 7 The "e" yy As shown in the figure (representing strain in the vertical direction), Mn 50 Ni 37.5 Ti 12.5The martensitic phase transformation of the dual-phase alloy during compression exhibits multi-point nucleation phase transformation characteristics.

[0062] Figure 8 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Stress-strain curves of dual-phase alloys under large strain. Figure 8 ( Figure 8 In this context, "Strain" represents strain, "Stress" represents pressure, and "Strain rate" represents strain rate. The corresponding temperature-time curve is shown below. Figure 9 ( Figure 9 In the figure, "Time" represents time and "T(°C)" represents temperature. Mn 50 Ni 37.5 Ti 12.5 The dual-phase alloy exhibited a large temperature change (ΔT) of up to 57.2 K at a strain of 13%. ad (Indicates temperature change).

[0063] Figure 10 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Temperature-time curve of another sample of the dual-phase alloy (multiple samples can be obtained as needed, following the method of Example 1); the maximum temperature change at a single point of this sample reaches 64.5 K. This is due to the Mn prepared in Example 1... 50 Ni 37.5 Ti 12.5 Dual-phase alloys are non-oriented polycrystalline, and the local grain size and microstructure cannot be completely consistent, resulting in different degrees of phase transformation completion under stress. In addition, the distribution of internal forces under stress depends on the sample squareness, especially the parallelism of the upper and lower surfaces, which is difficult to be strictly parallel. These differences will lead to certain differences in local temperature changes.

[0064] Figure 11 Mn is from Example 1 50 Ni 37.5 Ti 12.5 Comparison of room temperature XRD patterns of the dual-phase alloy before and after compression; most of the Mn after compression... 50 Ni 37.5 Ti 12.5 The dual-phase alloy transforms from B2 austenite to L10 martensite, with a small amount of 5M martensite.

[0065] Figure 12 ( Figure 12 In this context, "Strain" represents strain, "Stress" represents pressure, and "Strain rate" represents strain rate. This refers to Mn in Example 1. 50 Ni37.5 Ti 12.5 Stress-strain curves of dual-phase alloy compressive strength test; Mn 50 Ni 37.5 Ti 12.5 The dual-phase alloy, when loaded to fracture at room temperature, exhibits a compressibility of 32.2 ± 0.6% and a compressive strength of 1.76 ± 0.05 GPa. Mn was obtained through stress-strain integration. 50 Ni 37.5 Ti 12.5 The toughness of the dual-phase alloy is 452.5 ± 23.5 J / cm. -3 .

[0066] Comparative Examples 1-2

[0067] Comparative Examples 1-2 are prepared using essentially the same process as Example 1, the difference being their composition and heat treatment conditions:

[0068] Step 1: According to the stoichiometric ratio of Mn 49 Ni 48 Ti3 (corresponding to the sample prepared in Example 1) and Mn 50 Ni 48 Ti2 (corresponding to the sample prepared in Example 2), weigh 25g of metal elements Mn, Ni and Ti with a purity of over 99.95%. The subsequent melting method and sample preparation before annealing are the same as steps one to three in Example 1, and will not be repeated here.

[0069] Step 4: While maintaining a high-purity argon atmosphere in the melting chamber, transfer the uniformly melted ingot into a special copper crucible and re-ignite the arc for melting. After it has fully melted, press the suction casting button to quickly draw the molten sample from the suction casting crucible into a copper mold with a diameter of 7mm that is cooled by circulating water, where it will rapidly solidify.

[0070] The surface of the obtained samples was polished and cleaned to characterize their microstructure, physical properties, and elastothermal effect. The test results were collected and analyzed.

[0071] The alloy samples prepared in Comparative Examples 1-2 were homogeneous single-phase, such as Figure 13 The image shows the XRD pattern of the sample from Comparative Example 1. Figure 14 The stress-strain curves of two samples with different compositions, Comparative Examples 1-2, are shown. Their compressive strengths are 1.03 GPa and 0.97 GPa, respectively. The mechanical properties of the single-phase alloy are significantly lower than those of the two-phase alloy in Example 1 of this invention.

[0072] Furthermore, due to limitations in their strength, the measured adiabatic temperature changes under stress in Comparative Examples 1 and 2 were 26.7 K and 21.2 K, respectively, significantly lower than those in Example 1. Figure 15("Temperature" refers to temperature, and "Time" refers to time.)

[0073] Example 2

[0074] The difference between Example 2 and Example 1 is that the chemical formula of the MnNiTi-based dual-phase alloy is Mn 50 Ni 38.5 Ti 11.5 The process is exactly the same as in Example 1, and will not be repeated here.

[0075] The Mn obtained in Example 2 50 Ni 38.5 Ti 11.5 The microstructure and physical properties of polycrystalline samples were studied, and the test results were collected and analyzed.

[0076] Figure 16 Mn is from Example 2 50 Ni 38.5 Ti 11.5 Magnetization-temperature profiles of dual-phase alloys; Figure 17 Mn is from Example 2 50 Ni 38.5 Ti 11.5 Comparison of room temperature XRD patterns of dual-phase alloys before and after compression.

[0077] Among them, from Figure 16 It can be seen that the resulting phase transition temperature is higher than room temperature, and the Mn in Example 2 50 Ni 38.5 Ti 11.5 Dual-phase alloys are in the martensitic state at room temperature. Figure 17 Mn before and after compression 50 Ni 38.5 Ti 11.5 Comparison of room temperature XRD curves of dual-phase alloys, Mn before compression 50 Ni 38.5 Ti 11.5 The dual-phase alloy is mainly composed of 5M martensite, and the compressed Mn 50 Ni 38.5 Ti 11.5 The dual-phase alloy is mainly L10 martensite.

[0078] In Example 1, Mn 50 Ni 37.5 Ti 12.5 The dual-phase alloy is able to achieve a huge temperature change of 57.2K thanks to its excellent high toughness, which supports the phase transformation from B2 austenite to L10 martensite.

[0079] Example 3

[0080] Example 3 is an extension of the process in Example 1. Based on the first two steps of Example 1, directional solidification is performed. Considering that the volatilization of Mn increases during directional solidification, resulting in a decrease in phase transformation temperature, the composition of the directional solidification alloy is adjusted to Mn. 50.4 Ni 37.5 Ti 12.1 The first two steps of the process are exactly the same as in Example 1 (only the amount of raw materials is adjusted), and will not be described again here.

[0081] Step 3: Remove the oxides from the surface of the arc-melted ingot and ultrasonically clean it with anhydrous ethanol. Then, cast the ingot into a 7mm rod-shaped alloy.

[0082] Step 4: The suction-cast rod-shaped alloy is used as the raw material for directional solidification. It is placed into an Al2O3 crucible with an inner diameter of 7.2 mm. After the whole assembly is fixed, it is placed into the directional solidification furnace. The cavity is evacuated to a low vacuum of less than 10 Pa using a mechanical pump, and then high-purity Ar gas is introduced for purging three times. After evacuating to less than 8 Pa again using a mechanical pump, the molecular pump is turned on to evacuate to a high vacuum of 7 × 10 Pa. -4 Below Pa, then backflushing with high-purity Ar gas to 0.05 MPa to begin smelting;

[0083] Step 5: Set the melting temperature on the temperature control system to 150K higher than the sample melting point, and hold for 5 minutes to ensure the sample is completely melted. At the melting temperature, set a fixed stretching rate and pull the sample down into the liquid metal Ga-In-Sn alloy at a uniform speed. Then, perform steps 3 and 4 in Example 1.

[0084] Example 4

[0085] Example 4 is an extension of the process of Example 1. Based on the first two steps of the process of Example 1, hot rolling deformation is performed. The first two steps of the process are exactly the same as those of Example 1, and will not be repeated here.

[0086] Step 3: Remove the oxides from the surface of the arc-melted ingot, cut the sample into 20×10×3mm3 plates using wire EDM, and clean the EDM burn marks with sandpaper before hot rolling deformation.

[0087] Step 4: Place the sheet material obtained in Step 3 into a 1073K heating furnace and heat for 2 minutes before rolling and deformation.

[0088] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims and their equivalents, this invention also intends to include these modifications and variations. The above-described embodiments are merely preferred embodiments for fully illustrating the invention, and their scope of protection is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on this invention are all within the scope of protection of this invention, which is defined by the claims.

Claims

1. A MnNiTi-based dual-phase alloy, characterized in that, The chemical formula of the MnNiTi-based dual-phase alloy is Mn 50 Ni 37.5 Ti 12.5 or Mn 50 Ni 38.5 Ti 11.5 ; The main phase in the MnNiTi-based dual-phase alloy is a B2-ordered Heusler phase, and the second phase is a tough γ phase, which is dispersed in the interior of the grains and at the grain boundaries. The MnNiTi-based dual-phase alloy is prepared by a method including the following steps: According to the element ratio in the chemical formula, Mn, Ni and Ti are weighed, and then an alloy is prepared by electric arc melting, induction melting, melt rapid quenching, solid-state reaction, atomization, spray casting, suction casting, rolling or directional solidification. After annealing, the alloy is quenched in an ice-water mixture to obtain the MnNiTi-based dual-phase alloy. The annealing temperature is 600-1000℃, and the annealing time is 72-100h.

2. The MnNiTi-based dual-phase alloy according to claim 1, characterized in that, The phase transformation temperature range of the MnNiTi-based dual-phase alloy is 50-500K.

3. The MnNiTi-based dual-phase alloy according to claim 1, characterized in that, The mass purity of Mn, Ni, and Ti all exceeds 99.95%.

4. The MnNiTi-based dual-phase alloy according to claim 1, characterized in that, The alloy is formed as at least one of polycrystalline bulk, strip, rod or powder.

5. The application of the MnNiTi-based dual-phase alloy according to any one of claims 1-4 in the field of intelligent drive or energy conversion.

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