A shape memory alloy-fused armature structure and a method for manufacturing the same

Abstract

The application discloses a kind of armature structures and preparation methods of fusing shape memory alloy, belong to electromagnetic orbit launching technical field.The armature structure includes at least one group of shape memory alloy elements and armature body, armature body includes two oppositely arranged side arm parts and the arc curved part connecting two side arm parts, at least one recess is opened on side arm part, shape memory alloy element is set in recess and is transitionally cooperated with armature body.Shape memory alloy element has shrinkage state under normal temperature and outer expansion state of phase change recovery under electric heating excitation, can occur reverse phase change from martensite to austenite under the thermal effect excitation of electromagnetic launch current, generates radial pre-tightening force to maintain the contact pressure between armature and track, effectively inhibits the transition arc phenomenon caused by the drop of contact pressure, improves the stability and reliability of launch.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic orbital launch technology, specifically to an armature structure incorporating shape memory alloy and its preparation method. Background Technology

[0002] Electromagnetic orbital launch technology is a novel launch technology that uses electromagnetic force to accelerate projectiles or other payloads to hypersonic speeds. It holds significant application potential in aerospace launches, hypersonic collision tests, pulsed power devices, and military defense. The core components of an electromagnetic orbital launch system include a power system, a track, and an armature. The armature, as the key carrier for current transfer from the track to the launch system, directly determines launch efficiency and system lifespan through its electrical contact performance with the track. In recent years, as electromagnetic launch technology has developed towards higher initial velocities and larger launch masses, more stringent requirements have been placed on the design of the armature structure. During electromagnetic orbital launch, the armature and track are driven by pulsed high currents, with current amplitudes typically reaching hundreds of kiloamperes or even megaamperes, current rise rates on the order of megaamperes per millisecond, and current densities on the order of gigaamperes per square meter. Under such extreme electrical and mechanical conditions, the armature must simultaneously meet multiple performance indicators, including high current-carrying capacity, good mechanical strength, and reliable sliding electrical contact performance.

[0003] Currently, the solid armatures commonly used in electromagnetic rail launches are mostly C-shaped, saddle-shaped, or U-shaped structures. They rely on the elastic deformation of the armature tail fins to provide initial contact pressure, ensuring a tight fit between the armature tail fins and the inner wall of the rail, thus achieving effective current conduction. However, during electromagnetic launch, as the armature accelerates, the armature-rail interface experiences extremely high contact pressure and intense friction. The armature tail fins gradually thin due to wear, leading to a decrease or even loss of contact pressure, which in turn causes phenomena such as loss of armature-rail contact and transition arcing. Transition arcing not only causes severe ablation of the armature and rail but also drastically reduces energy transmission efficiency, seriously affecting launch stability and device reliability. Existing armature structures mainly rely on the elastic deformation of the material itself to maintain contact pressure, lacking the ability to actively adjust contact pressure and failing to maintain a stable electrical contact state throughout the launch process. Furthermore, in the initial stage of launch, the contact area between the armature and rail is limited, resulting in high contact resistance and a tendency for overheating in localized areas, further exacerbating armature damage. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an armature structure incorporating shape memory alloys and its preparation method.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A first aspect of the present invention provides an armature structure incorporating a shape memory alloy, comprising: an armature body, the armature body including a first side arm and a second side arm disposed opposite to each other, and an arcuate curved portion connecting one end of the first side arm and the second side arm, the other end of the first side arm and the second side arm being an open end; at least one groove extending longitudinally therein and at least one set of shape memory alloy elements are provided on the side arm of the armature body, the shape memory alloy elements are disposed in the groove, and the shape memory alloy elements and the groove are in a transition fit; wherein, the shape memory alloy elements have a contracted state at room temperature and an expanded state that undergoes phase transition recovery under electrothermal excitation, the shape memory alloy elements in the contracted state together with the armature body to form an assembly profile adapted to the cross section of the guide rail, so as to facilitate assembly between the guide rails, and in the expanded state, a radially outward preload is applied to the side arm of the armature body.

[0007] Preferably, the groove has a rectangular cross-sectional shape, the outer contour of the shape memory alloy element is adapted to the cross-sectional shape of the groove, and the transition fit has a tolerance grade of H7 / k6 to H7 / m6.

[0008] Preferably, the shape memory alloy element is a shape memory alloy strip, and the side arm is provided with a strip-shaped groove and an arc-shaped groove; the strip-shaped groove includes four side strip-shaped grooves located on the upper and lower parts of the outer side surface of the first side arm and the upper and lower parts of the outer side surface of the second side arm respectively; the arc-shaped groove includes at least one arc-shaped groove located on the inner side surface of the arc-shaped curved portion.

[0009] Preferably, the inner side of the arc-shaped curved portion is provided with three arc-shaped grooves, namely the upper-middle arc-shaped groove located at the top, the middle arc-shaped groove located in the middle, and the lower-middle arc-shaped groove located at the bottom.

[0010] Preferably, the material of the shape memory alloy element is a Cu-Zn-Al type shape memory alloy, which includes, by mass fraction: 18%-37% Zn, 2%-8% Al, and the remainder Cu.

[0011] Preferably, the shape memory alloy element has a width of 3-10 mm, a thickness of 1-3 mm, and a length that matches the extension length of the groove.

[0012] Preferably, the curvature of the arc-shaped shape memory alloy strip disposed in the arc-shaped groove matches the curvature of the inner surface of the arc-shaped curved portion, and the ratio of the depth of the arc-shaped groove to the thickness of the arc-shaped shape memory alloy strip is 1.05-1.2.

[0013] Preferably, the armature body is made of high-strength aluminum alloy.

[0014] A second aspect of the present invention provides a method for preparing an armature structure incorporating a shape memory alloy as described in the first aspect, comprising the following steps: wire cutting a shape memory alloy material to obtain a shape memory alloy element of a predetermined size; subjecting the shape memory alloy element to shape memory heat treatment, the shape memory heat treatment including solution treatment and aging treatment, so that the shape memory alloy element acquires a shape memory effect; pre-deforming the shape memory alloy element after shape memory heat treatment below the martensitic phase transformation end temperature Mf of the shape memory alloy element, so that it is deformed to a predetermined shape in a contracted state and held therein; and inserting the pre-deformed shape memory alloy element into a groove of the armature body in a transition fit manner.

[0015] Preferably, the solution treatment temperature is 800-900℃, the holding time is 10-30 minutes, and after the holding time is completed, the solution is quenched in water or oil to room temperature.

[0016] Preferably, the aging treatment temperature is 180-220℃, the holding time is 10-30 minutes, and after the holding time is completed, the temperature is cooled to room temperature.

[0017] Preferably, the pre-deformation is carried out at a temperature lower than the martensitic transformation end temperature Mf of the shape memory alloy element, and the pre-deformation temperature is not higher than (Mf-10)℃.

[0018] In summary, this application has the following beneficial effects:

[0019] (1) By setting shape memory alloy elements on the side arm of the armature body, the shape memory alloy can undergo reverse phase transformation from martensite to austenite and restore its memory shape under electrothermal excitation. Under the thermal effect excitation of the electromagnetic launch current, a radially outward preload force is generated to actively compensate for the wear of the armature tail fin during the launch process. This ensures that the armature and the track maintain sufficient contact pressure throughout the launch process, thereby effectively suppressing the transition arc phenomenon caused by the decrease in contact pressure and improving the stability and reliability of the launch.

[0020] (2) By using Cu-Zn-Al type shape memory alloy as the material of shape memory alloy element, the alloy system has a high shape memory strain recovery rate (the recoverable strain can reach 4%-6%), a low phase transformation temperature hysteresis (about 10-20℃) and good fatigue resistance. At the same time, it has a moderate electrical conductivity (the electrical conductivity is about 10-15MS / m). It can be effectively heated to above the phase transformation temperature through its own resistance heating effect while withstanding electromagnetic emission pulse current, so as to realize the shape recovery function.

[0021] (3) By using a transition fit method to install the shape memory alloy element in the slot of the armature body, the shape memory alloy element can be reliably prevented from coming out of the slot under the high acceleration condition of electromagnetic emission, while ensuring that the restoring force generated by the shape memory alloy element during the phase change process can be effectively transmitted to the armature body.

[0022] (4) By using the preparation method provided by the present invention, the process of wire cutting, shape memory heat treatment and martensitic pre-deformation can be used to obtain shape memory alloy elements with stable shape memory effect, ensuring that they can reliably realize phase change driving function under electromagnetic emission conditions. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall armature structure of the fused shape memory alloy provided in an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the armature body structure provided in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the shape memory alloy strip and the armature body slot provided in an embodiment of the present invention.

[0026] Figure 4(a) is a schematic diagram of the morphological changes of the side shape memory alloy strip under different phase states provided in the embodiment of the present invention.

[0027] Figure 4(b) is a schematic diagram of the morphological changes of the arc-shaped shape memory alloy strip under different phase states provided in the embodiment of the present invention.

[0028] Figure 5 This is a flowchart of the preparation method of shape memory alloy strips provided in the embodiments of the present invention.

[0029] Figure 6(a) is a schematic diagram of the shaping mold for the heat treatment process of the side shape memory alloy strip in an embodiment of the present invention.

[0030] Figure 6(b) is a schematic diagram of the shaping mold for the heat treatment process of the arc-shaped memory alloy strip according to an embodiment of the present invention.

[0031] Figure 7(a) is a schematic diagram of the forming mold for pre-deforming the side shape memory alloy strip to the shrinkage state according to an embodiment of the present invention.

[0032] Figure 7(b) is a schematic diagram of the forming mold for pre-deforming the arc-shaped shape memory alloy strip to the contracted state according to an embodiment of the present invention.

[0033] Figure 8 This is a schematic diagram of the working state of the armature structure assembled on the track according to an embodiment of the present invention.

[0034] In the diagram, 1-arc-shaped bend, 2-top left shape memory alloy strip, 3-bottom left shape memory alloy strip, 4-top right shape memory alloy strip, 5-bottom right shape memory alloy strip, 6-top middle arc-shaped shape memory alloy strip, 7-middle arc-shaped shape memory alloy strip, 8-bottom middle arc-shaped shape memory alloy strip, 9-top left strip groove, 10-bottom left strip groove, 11-top right strip groove, 12-bottom right strip groove, 13-top middle arc groove, 14-middle arc groove, 15-bottom middle arc groove. Detailed Implementation

[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0036] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0037] In some embodiments of this application, an armature structure incorporating shape memory alloy is provided, comprising: an armature body, the armature body including a first side arm and a second side arm disposed opposite to each other, and an arc-shaped curved portion 1 connecting one end of the first side arm and the second side arm, the other end of the first side arm and the second side arm being an open end; at least one groove extending longitudinally and at least one shape memory alloy element are provided on the side arm of the armature body, the shape memory alloy element being disposed in the groove, and the shape memory alloy element and the groove being in a transition fit; wherein, the shape memory alloy element has a contracted state at room temperature and an expanded state undergoing phase transition recovery under electrothermal excitation, the shape memory alloy element in the contracted state and the armature body together forming an assembly profile adapted to the cross section of the guide rail, so as to facilitate assembly between the guide rails, and in the expanded state, a radially outward preload is applied to the side arm of the armature body.

[0038] In the specific implementation process, refer to Figure 1 and Figure 2The armature body is the main load-bearing component of the armature structure. Its first and second side arms are arranged parallel to each other, with one end being a free-opening end and the other end connected by an arc-shaped bend 1, forming a C-shaped or U-shaped cross-sectional profile for insertion between the two parallel guide rails of the electromagnetic rail launcher. At least one longitudinally extending groove is formed on the side arm of the armature body to accommodate a shape memory alloy element. The shape memory alloy element is installed in the groove, forming a transition fit with it. This transition fit ensures that the shape memory alloy element is reliably fixed in the groove without loosening under the high acceleration conditions of electromagnetic launch, and also applies sufficient contact pressure radially to the groove wall during phase change recovery, thereby transmitting the shape recovery force to the side arm of the armature body.

[0039] In this invention, the shape memory alloy element has two morphological states: one is the contracted state at room temperature, in which the shape memory alloy element is in a thermoelastic martensite state or a stress-relieved martensite state, and its shape corresponds to the contracted form after pre-deformation, which together with the armature body constitutes a contour dimension that is easy to assemble; the other is the outward expansion state under electrothermal excitation. When a pulsed large current passes through the armature and track during electromagnetic emission, the Joule heating effect raises the temperature of the shape memory alloy element to above the austenite phase transformation end temperature Af, triggering the reverse phase transformation from martensite to austenite. The shape memory alloy element recovers to the outward expansion shape remembered by the shape memory heat treatment, thereby applying a radially outward expansion force, i.e., a preload force, to the side arm of the armature body. It should be noted that the heating mechanism of shape memory alloy elements includes two pathways: First, due to the inherent resistivity of the shape memory alloy material, when a large pulsed current flows directly through the shape memory alloy element, it is heated by Joule heating generated by its own resistance; second, the armature body also heats up under the action of the pulsed current due to the resistance effect and the contact resistance at the armature-rail interface, and some of the heat is transferred to the shape memory alloy element through thermal conduction. Under the condition of electromagnetic emission pulsed current, the Joule heating of the element itself is the main heating mechanism, which can rapidly heat the shape memory alloy element to the phase transition temperature within a millisecond timescale. As shown in Figures 4(a) and 4(b), the morphological differences of the shape memory alloy element in the contracted and expanded states are illustrated.

[0040] By integrating shape memory alloy elements on the side arm of the armature body, the Joule heating of the current triggers the phase change of the shape memory alloy, causing it to recover from the contracted state to the expanded state, and actively generating radial preload. This dynamically maintains the contact pressure between the armature and the track throughout the entire electromagnetic launch process, effectively overcoming the technical defect of traditional armatures where contact pressure decays due to tail fin wear, and significantly improving the stability and reliability of electromagnetic launch.

[0041] In some preferred embodiments of this application, the cross-sectional shape of the groove is rectangular, and the outer contour of the shape memory alloy element is adapted to the cross-sectional shape of the groove.

[0042] In the specific implementation process, refer to Figure 3 The groove adopts a rectangular cross-section design, and the outer contour of the shape memory alloy element is also a rectangular cross-section corresponding to the rectangular cross-section, allowing the shape memory alloy element to be tightly embedded in the groove. A transition fit is used between the shape memory alloy element and the groove. The recommended tolerance grade for this transition fit is H7 / k6~m6, where H7 represents the tolerance zone of the groove, and k6~m6 represent the tolerance zone of the shape memory alloy element. The H7 / k6 fit has a smaller interference tendency, facilitating loading; the H7 / m6 fit has a larger interference tendency, providing stronger radial restraint force, suitable for conditions with higher launch acceleration. In specific implementations, an appropriate fit grade can be selected based on the armature's expected launch acceleration and the structural load-bearing capacity.

[0043] In some preferred embodiments of this application, the shape memory alloy element is a shape memory alloy strip, and the side arm is provided with a strip-shaped groove and an arc-shaped groove; the strip-shaped groove includes four side strip-shaped grooves located on the upper and lower parts of the outer side surface of the first side arm and the upper and lower parts of the outer side surface of the second side arm respectively; the arc-shaped groove includes at least one arc-shaped groove located on the inner side surface of the arc-shaped curved portion.

[0044] In the specific implementation process, refer to Figures 1 to 3 The armature structure has seven shape memory alloy strips on its side arms. On the outer surface of the first side arm, there are two side strip grooves: an upper left strip groove 9 and a lower left strip groove 10, corresponding to upper left shape memory alloy strip 2 and lower left shape memory alloy strip 3, respectively. On the outer surface of the second side arm, there are two side strip grooves: an upper right strip groove 11 and a lower right strip groove 12, corresponding to upper right shape memory alloy strip 4 and lower right shape memory alloy strip 5, respectively. The four side shape memory alloy strips extend longitudinally along the side arm, their length matching the longitudinal length of the side arm. In addition, three arc-shaped grooves are provided on the inner surface of the arc-shaped bend: an upper arc-shaped groove 13, a middle arc-shaped groove 14, and a lower arc-shaped groove 15. The corresponding shape memory alloy strips are an upper arc-shaped shape memory alloy strip 6, a middle arc-shaped shape memory alloy strip 7, and a lower arc-shaped shape memory alloy strip 8. The bending shape of the three arc-shaped shape memory alloy strips is adapted to the contour of the inner surface of the arc-shaped bend. Under the joint excitation of the electromagnetic emission pulse current, the seven shape memory alloy strips undergo phase change synchronously and generate radially outward expansion force, so that the side arm and the arc-shaped bend of the armature body are uniformly compensated by preload force.

[0045] By adopting the above technical solution, shape memory alloy strips are set in the upper and lower parts of the side arm, and arc-shaped shape memory alloy strips are set in the arc-shaped bending part, multi-dimensional preload compensation in the radial and longitudinal directions of the armature structure is realized, making the contact pressure distribution between the armature and the track more uniform and avoiding arc ablation caused by insufficient contact pressure in local areas.

[0046] In some preferred embodiments of this application, the material of the shape memory alloy element is a Cu-Zn-Al type shape memory alloy, which includes, by mass fraction: 18%-37% Zn, 2%-8% Al, and the balance Cu.

[0047] In practical implementation, the martensitic transformation completion temperature (Mf) of Cu-Zn-Al shape memory alloys can be controlled by adjusting the content of Zn and Al, with the control range of Mf being -100℃ to 100℃. In electromagnetic orbital launch applications, considering that the armature is in a room temperature environment before launch, the shape memory alloy element needs to be in the martensitic state at room temperature. Therefore, an alloy composition with Mf higher than room temperature should be selected. In a preferred embodiment, the alloy composition, by mass fraction, is: 24%-30% Zn, 5%-7% Al, and the balance Cu. In this case, Mf is 30-60℃, and Al is 50-80℃.

[0048] The electrical conductivity of Cu-Zn-Al shape memory alloys is 10⁻¹² MS / m, approximately 17%-21% of that of pure copper (58 MS / m). Under electromagnetic emission pulse current conditions of hundreds of kiloamperes, the Joule heat power density can reach 10⁻¹². 9 -10 11 W / m 3 The temperature of Cu-Zn-Al shape memory alloys can be raised from room temperature to above Af within milliseconds. Furthermore, Cu-Zn-Al shape memory alloys possess advantages such as recoverable strain of 4%-6%, phase transformation temperature hysteresis of 10-15℃, mature manufacturing processes, and low cost, making them suitable as intelligent drive components in electromagnetic launch armatures. Those skilled in the art can also select other types of shape memory alloy materials according to actual needs, such as Cu-Al-Ni shape memory alloys, which have higher upper limits of operating temperature, but are relatively more difficult to process.

[0049] By adopting the above technical solution and selecting Cu-Zn-Al shape memory alloy, the shape memory effect, moderate electrical and thermal conductivity, good machinability and economy are taken into account, which can meet the requirements of electromagnetic launch armature under extreme working conditions.

[0050] In some preferred embodiments of this application, the shape memory alloy element has a width of 3-10 mm, a thickness of 1-3 mm, and a length that matches the extension length of the groove, i.e., the length of the shape memory alloy element is slightly less than the extension length of the groove.

[0051] In practical implementation, the geometric dimensions of the shape memory alloy element need to be comprehensively designed based on the structural dimensions of the armature body, the required preload force, and the operating parameters of electromagnetic emission. In a preferred embodiment, the width of the shape memory alloy strip within the side groove is 3-6 mm, the thickness is 2-3 mm, and the length matches the longitudinal length of the side arm, typically 50-80 mm. The width of the arc-shaped shape memory alloy strip is 3-6 mm, the thickness is 2-3 mm, and the length is measured along the arc path, typically 30-100 mm. The above dimensional ranges ensure that the shape memory alloy element, under electromagnetic emission pulse current excitation, heats up to above the phase transition temperature within a millisecond timescale and generates sufficient radial restoring force.

[0052] By adopting the above technical solution and reasonably limiting the geometric size range of the shape memory alloy element, it is ensured that it can reliably realize the phase change driving function under electromagnetic launch conditions, without affecting the overall structural performance of the armature.

[0053] In some preferred embodiments of this application, the curvature of the shape memory alloy strip disposed in the arc-shaped groove matches the curvature of the inner surface of the arc-shaped curved portion, and the ratio of the depth of the arc-shaped groove to the thickness of the shape memory alloy strip is 1.05-1.2.

[0054] In practical implementation, the curvature of the arc-shaped shape memory alloy strip is matched with the curvature of the inner surface of the arc-shaped bend, meaning the bending radius of the arc-shaped shape memory alloy strip is approximately the same as or slightly larger than the bending radius of the arc-shaped bend. This curvature matching design ensures that the arc-shaped shape memory alloy strip can fit tightly within the arc-shaped groove, and the restoring force generated during the phase transformation can be uniformly transmitted along the normal direction of the arc-shaped bend. The ratio of the depth of the arc-shaped groove to the thickness of the shape memory alloy strip is limited to the range of 1.05-1.2. This ratio is slightly greater than 1, providing the necessary space for the radial deformation of the shape memory alloy strip during the phase transformation process, while ensuring good positioning of the shape memory alloy strip within the groove.

[0055] By adopting the above technical solution, the curvature matching design of the arc-shaped shape memory alloy strip and the groove depth ratio limit ensure the reliable positioning and effective force transmission of the shape memory alloy strip in the arc-shaped area, and further improve the preload compensation effect of the armature in the arc-shaped bending area.

[0056] In some preferred embodiments of this application, the armature body is made of high-strength aluminum alloy.

[0057] In practical implementation, the selection of materials for the armature body needs to comprehensively consider factors such as conductivity, mechanical strength, density, and processing technology. High-strength aluminum alloys, such as 7-series aluminum alloys (e.g., 7075 aluminum alloy), have high specific strength and good machinability, with a conductivity of approximately 20-30 MS / m, which can meet the basic requirements for armature conductivity in electromagnetic launch. In a preferred embodiment, the armature body is made of 7075-T6 aluminum alloy, integrally formed by CNC milling, with strip-shaped grooves and arc-shaped grooves machined on the side arm portion and the curved portion, respectively.

[0058] By adopting the above technical solution and selecting high-strength aluminum alloy as the armature body material, a lightweight design of the armature can be achieved while ensuring structural strength and conductivity.

[0059] In some embodiments of this application, a method for preparing an armature structure incorporating a shape memory alloy is provided, comprising the following steps: wire cutting a shape memory alloy material to obtain a shape memory alloy element of a predetermined size; subjecting the shape memory alloy element to shape memory heat treatment, the shape memory heat treatment including solution treatment and aging treatment, so that the shape memory alloy element acquires a shape memory effect; pre-deforming the shape memory alloy element below the martensitic transformation end temperature Mf of the shape memory alloy element, so that it is deformed to a predetermined shape in a contracted state; and inserting the pre-deformed shape memory alloy element into a groove of the armature body in a transition fit manner.

[0060] In the specific implementation process, refer to Figure 5 The preparation method includes the following four main steps. The first step is wire cutting: Select a Cu-Zn-Al type shape memory alloy billet that meets the target composition, and use slow wire cutting or fast wire cutting technology to cut the billet into near-net-shape shape memory alloy elements in sheet or strip form. For side shape memory alloy strips, cut them into straight strips; for curved shape memory alloy strips, cut them into curved strips that match the curvature of the curved part. After wire cutting, the cross-sectional surface where the element mates with the groove is precision ground to ensure that the cross-sectional dimensional accuracy meets the transition fit tolerance requirements (H7 / k6~m6).

[0061] The second step is shape memory heat treatment: This step is the key process for imparting the shape memory effect to shape memory alloy components, and includes two sub-steps: solution treatment and aging treatment. Solution treatment heats the alloy to the β-phase region and holds it at that temperature for a sufficient time to allow the alloying elements to fully dissolve and form a uniform β-phase solid solution. During the solution treatment holding stage, as shown in Figures 6(a) and 6(b), the shape memory alloy component is placed into a shaping mold, which constrains it into a predetermined outward-expanding shape (a small-curvature arc for side shape memory alloy strips, and an outward-expanding arc with a curvature greater than the groove for arc-shaped shape memory alloy strips). Subsequently, it is rapidly quenched along with the shaping mold, preserving the high-temperature β-phase structure and outward-expanding shape to room temperature. Aging treatment promotes the ordered transformation at an appropriate temperature, obtaining a stable shape memory effect. After this step, the shape memory alloy component remains essentially consistent with its wire-cut state in terms of physical dimensions, but its austenite parent phase shape has been memorized as the outward-expanding shape constrained by the shaping mold cavity.

[0062] The third step is martensitic pre-deformation: Pre-deformation must be carried out when the shape memory alloy element is in a fully martensitic state, that is, the pre-deformation temperature must be lower than the martensitic phase transformation end temperature Mf, preferably not higher than (Mf-10)℃, to ensure that the alloy structure is 100% thermoelastic martensite. As shown in Figures 7(a) and 7(b), pre-deformation is carried out in a forming mold, and the cavity of the mold defines the longitudinal shape of the element in its contracted state. The element with outward expansion shape memory after shape memory heat treatment is placed into the forming mold, and pressure is applied to deform the element to fit the mold cavity, thereby deforming from the memory outward expansion arc shape to a contracted shape - for the side shape memory alloy strip, it is pressed from a small curvature arc shape into a straight strip shape; for the arc shape memory alloy strip, it is pressed from an outward expansion arc shape into an arc shape consistent with the curvature of the groove.

[0063] The fourth step is assembly: the pre-deformed shape memory alloy element is pressed into the groove of the armature body using a transition fit. During assembly, the shape memory alloy element is in a contracted state, its cross-sectional dimensions matching the groove to form a transition fit, and its longitudinal shape is a straight strip or a small-curvature arc for easy insertion. After assembly, the shape memory alloy element remains in a martensitic contracted state at room temperature, together with the armature body, forming a contour dimension that facilitates assembly to the guide rail. Figure 8 As shown, the armature structure is assembled on the track in operation. During electromagnetic launch, the Joule heating generated by the pulse current raises the temperature of the shape memory alloy element above the austenite phase transformation end temperature Af. The element attempts to recover to its memory outward expansion shape, but is constrained by the groove wall, which generates a radial restoring force, causing the armature arms to slightly open outward and maintain a tight fit with the guide rail, thus realizing the active preload compensation function.

[0064] In practical implementation, the solution treatment temperature for the β phase of Cu-Zn-Al shape memory alloys is typically within the range of 800-900℃. If the solution treatment temperature is too low (below 800℃), the alloying elements cannot be fully dissolved, and impurity phases such as α or γ phases may remain in the β phase structure, leading to instability in the shape memory effect. If the solution treatment temperature is too high (above 900℃), excessive grain growth may occur, reducing the mechanical properties of the alloy and the cyclic stability of the shape memory effect. The holding time should be 10-30 minutes. Too short a holding time will result in insufficient solution, while too long a time may lead to grain coarsening and the volatilization loss of Zn. Quenching after holding is a crucial step in ensuring that the high-temperature β phase structure is retained to room temperature. The choice of quenching medium depends on the cross-sectional size of the component: for thin, sheet-like components with small cross-sectional dimensions, the cooling rate is easier to ensure, and oil quenching can be used to reduce the risk of thermal stress cracking; for components with large cross-sectional dimensions, a faster cooling rate is required to fully suppress the decomposition of the high-temperature β phase, and water quenching is recommended. After quenching to room temperature, the alloy microstructure is mainly thermoelastic martensite, possessing the structural basis for shape memory effect. In a preferred embodiment, the solution treatment temperature is 850℃, the holding time is 15-20 min, and after the holding time, it is quenched in water to room temperature.

[0065] By adopting the above technical solution and precisely controlling the temperature and holding time of the solution treatment, the Cu-Zn-Al shape memory alloy is ensured to obtain a uniform β phase structure and a stable shape memory effect, providing reliable phase change driving performance for shape memory alloy components in the armature.

[0066] In practical implementation, aging treatment is an important auxiliary step in shape memory heat treatment. Its purpose is to promote the ordering transformation in the alloy microstructure after solution treatment, gradually transforming the disordered β phase into an ordered B2 or DO3 structure. Increased ordering helps stabilize the reversibility of the martensitic phase transformation, thereby enhancing the cycle stability and recovery accuracy of the shape memory effect. The aging treatment temperature is selected between 180-220℃. This temperature range effectively promotes the ordering transformation without causing excessive precipitation of precipitates or the formation of harmful second phases at grain boundaries. If the aging treatment temperature is too low (below 180℃), the ordering transformation rate is too slow, requiring excessively long holding times, which is uneconomical in actual production. If the aging treatment temperature is too high (above 220℃), it may induce the precipitation of α or γ phases, damaging the shape memory effect. The holding time is 10-30 minutes, after which the material is allowed to cool naturally to room temperature in air. In a preferred embodiment, the aging treatment temperature is 200℃, and the holding time is 15-20 minutes. It should be noted that if aging treatment is performed after pre-deformation, the aging temperature and time should be controlled to avoid excessive martensite stabilization, which could lead to difficulties in shape recovery.

[0067] By adopting the above technical solution and performing aging treatment at an appropriate temperature, the stability of the shape memory effect and cycle life of the shape memory alloy element are effectively improved, ensuring that it maintains reliable phase change driving performance during repeated use of electromagnetic emission.

[0068] In practical implementation, pre-deformation is a crucial step for shape memory alloy components to achieve a contracted state and must be performed in the martensitic state. This is because the physical mechanism of the shape memory effect is as follows: applying deformation in the martensitic state allows macroscopic strain to be accommodated through the reorientation (detwinning) of the martensite variants; subsequently, upon heating above Af, the martensite undergoes a reverse phase transformation to the parent austenite phase, restoring the shape to its memory state. If pre-deformation is performed in the austenitic state, it exhibits hyperelastic behavior rather than a shape memory effect, failing to achieve the desired contraction-recovery function. Therefore, the pre-deformation temperature must be lower than the martensitic phase transformation end temperature Mf, preferably not higher than (Mf-10)℃, to ensure that the alloy microstructure is 100% thermoelastic martensite. For Cu-Zn-Al alloys with Mf above room temperature (e.g., alloys with Ms≈60℃ and Mf≈30℃), pre-deformation can be performed directly at room temperature. By adopting the above technical solution, and by strictly controlling the pre-deformation temperature and pre-deformation amount, the shape memory alloy component is ensured to be in a stable shrinkage state in the assembled state, and can generate a sufficiently large shape recovery force and recovery displacement under electromagnetic emission current excitation, so as to achieve effective pre-tightening force compensation between the armature and the track.

[0069] In summary, the armature structure and its fabrication method based on fused shape memory alloy provided by this invention integrates Cu-Zn-Al shape memory alloy elements on the side arm and curved portion of the armature body. Utilizing the Joule heating effect of the electromagnetic launch pulse current to trigger the martensite-austenite inverse phase transformation of the shape memory alloy, the shape memory alloy elements recover from a room-temperature contraction state to an outward expansion state, generating a radially outward preload force. This actively compensates for armature wear during launch, thereby maintaining a stable and uniform contact pressure between the armature and the track throughout the launch process. This armature structure effectively overcomes the technical defects of traditional armatures, such as contact pressure attenuation and transition arcing caused by tail fin wear, significantly improving the stability and reliability of electromagnetic launch and extending the service life of the armature and track. Furthermore, the fabrication method provided by this invention is mature, simple to operate, and enables the mass production and reliable assembly of shape memory alloy elements, showing promising engineering application prospects.

[0070] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. An armature structure incorporating shape memory alloy, characterized in that, include: An armature body includes a first side arm and a second side arm disposed opposite to each other, and an arc-shaped curved portion (1) connecting one end of the first side arm and the second side arm. The other end of the first side arm and the second side arm is an open end. At least one groove extending longitudinally and at least one shape memory alloy element are provided on the side arm of the armature body. The shape memory alloy element is disposed in the groove, and the shape memory alloy element and the groove are in a transition fit. The shape memory alloy element has a contracted state at room temperature and an expanded state that undergoes phase change recovery under electrothermal excitation. In the contracted state, the shape memory alloy element and the armature body together form an assembly profile that is adapted to the cross section of the guide rail, which facilitates assembly between the guide rails. In the expanded state, a radially outward preload is applied to the side arm of the armature body.

2. The armature structure of the fused shape memory alloy according to claim 1, characterized in that, The groove has a rectangular cross-sectional shape, and the outer contour of the shape memory alloy element is adapted to the cross-sectional shape of the groove. The transition fit has a tolerance grade of H7 / k6 to H7 / m6.

3. The armature structure of the fused shape memory alloy according to claim 1, characterized in that, The shape memory alloy element is a shape memory alloy strip, and the side arm is provided with a strip groove and an arc groove; the strip groove includes four side strip grooves located on the upper and lower parts of the outer side surface of the first side arm and the upper and lower parts of the outer side surface of the second side arm respectively; the arc groove includes at least one arc groove located on the inner side surface of the arc-shaped curved part (1).

4. The armature structure of the fused shape memory alloy according to claim 3, characterized in that, The inner side of the arc-shaped curved portion is provided with three arc-shaped grooves, namely the upper middle arc-shaped groove (13) located in the upper part, the middle arc-shaped groove (14) located in the middle part, and the lower middle arc-shaped groove (15) located in the lower part.

5. The armature structure of the fused shape memory alloy according to claim 1, characterized in that, The material of the shape memory alloy element is a Cu-Zn-Al type shape memory alloy, which by mass fraction includes: 18%-37% Zn, 2%-8% Al, and the remainder Cu.

6. The armature structure of the fused shape memory alloy according to claim 1, characterized in that, The shape memory alloy element has a width of 3-10 mm, a thickness of 1-3 mm, and a length that matches the extension length of the groove.

7. The armature structure of the fused shape memory alloy according to claim 3, characterized in that, The curvature of the arc-shaped shape memory alloy strip disposed in the arc-shaped groove matches the curvature of the inner surface of the arc-shaped curved portion (1), and the ratio of the depth of the arc-shaped groove to the thickness of the arc-shaped shape memory alloy strip is 1.05-1.

2.

8. The armature structure of the fused shape memory alloy according to claim 1, characterized in that, The armature body is made of high-strength aluminum alloy.

9. A method for preparing an armature structure of a fused shape memory alloy as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Wire cutting is performed on shape memory alloy materials to obtain shape memory alloy components of a set size; The shape memory alloy element is subjected to shape memory heat treatment, which includes solution treatment and aging treatment, so that the shape memory alloy element acquires the shape memory effect; the shape memory alloy element after shape memory heat treatment is pre-deformed below the martensitic phase transformation end temperature Mf of the shape memory alloy element, so that it is deformed to a predetermined shape in a contracted state and held; the pre-deformed shape memory alloy element is installed into the groove of the armature body in a transition fit manner.

10. The preparation method according to claim 9, characterized in that, The solution treatment temperature is 800-900℃, the holding time is 10-30min, and after the holding time is completed, the solution is quenched in water or oil to room temperature; the aging treatment temperature is 180-220℃, the holding time is 10-30min, and after the holding time is completed, the solution is air-cooled to room temperature; the pre-deformation temperature is not higher than (Mf-10)℃.

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