Net-shaping method of a ti / ti stack material and applications thereof

Abstract

The application provides a net forming method of Ti / Ti laminated material, comprising the following steps: step S1, uniformly mixing flaky graphite powder and titanium alloy raw materials of different sizes, then smelting to obtain an ingot, forging and rolling the ingot into a rod, and then using a plasma rotating electrode atomization method to prepare the rod into TiC composite (alpha+beta) titanium alloy powder; step S2, drying industrial pure titanium, TiC composite (alpha+beta) titanium alloy and (alpha+beta) titanium alloy powder, preheating a substrate, and under an argon protective atmosphere, sequentially laser melting and depositing the industrial pure titanium layer, the TiC composite (alpha+beta) titanium alloy layer, the (alpha+beta) titanium alloy layer and the TiC composite (alpha+beta) titanium alloy layer on the substrate from bottom to top; step S3, repeating step S2 at least four times to obtain a formed piece, and annealing to obtain a laminated material. Through the construction of the industrial pure titanium / TiC composite (alpha+beta) titanium alloy / (alpha+beta) titanium alloy laminated structure, the final Ti / Ti laminated material has medium-high strength and high impact toughness.

Description

A net forming method for Ti / Ti laminated materials and its application Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology for titanium alloys, specifically a net forming method for Ti / Ti laminated materials and its application. Background Technology

[0002] Titanium alloys, due to their high specific strength and impact resistance, have been used to replace steel in protective armor, thereby achieving lightweighting and high mobility in equipment such as tanks and land vehicles. However, the gradual iteration of high-end ballistic protection equipment has placed higher demands on the impact resistance and other properties of titanium alloy armor.

[0003] Studies have shown that the impact resistance of laminated materials is far superior to that of single homogeneous materials, which can significantly improve the armor protection coefficient. Currently, Ti / Ti3Al, Ti / Al, and Ti / TiAl laminated materials under development are difficult to guarantee uniform high impact resistance because uncontrollable brittle α2-Ti3Al and B2 phases precipitate at the heterogeneous laminate interface. When Ti / Ti laminated materials are prepared using Ti alloys with relatively low alloying degree, the tendency for brittle phase formation at the laminate interface is extremely low, which can guarantee the stable high impact resistance of the corresponding laminated materials.

[0004] As additive manufacturing technology matures, it has significant advantages in preparing multilayer and functionally graded materials with freely designable regional compositions and complex shapes and structures. However, when preparing Ti / Ti multilayer materials, additive manufacturing technology still suffers from poor interfacial metallurgical bonding or columnar crystal penetration, which is not conducive to fully utilizing the impact resistance of the multilayer structure. Further in-depth research is needed on additive manufacturing processes or Ti / Ti multilayer structure design. Summary of the Invention

[0005] The purpose of this invention is to overcome and supplement the shortcomings of existing technologies by providing a net-shape forming method for Ti / Ti laminated materials and its application. This method involves introducing nano-TiC + micro-TiC composite (α+β) titanium alloy powder prepared by a melting and casting method to construct an industrially pure titanium / TiC composite (α+β) titanium alloy / (α+β) titanium alloy laminated structure. Furthermore, the thickness of the TiC composite (α+β) titanium alloy layer and the forming process of each layer are optimized to prepare the final Ti / Ti laminated material. This invention can suppress defects such as poor interfacial metallurgical bonding or columnar crystal penetration in conventional Ti / Ti laminated materials. The final laminated material possesses medium-to-high strength and high impact toughness, meeting the requirements of medium strength and high impact resistance in protective armor.

[0006] The technical solution adopted in this invention is:

[0007] A net forming method for a Ti / Ti laminate material, comprising the following steps:

[0008] Step S1. After uniformly mixing flake graphite powder of different sizes and titanium alloy raw materials, the mixture is melted to obtain an ingot. The ingot is then forged and rolled into a bar. The bar is then prepared into TiC composite (α+β) titanium alloy powder using a plasma rotating electrode atomization method.

[0009] Step S2. Dry industrial pure titanium, TiC composite (α+β) titanium alloy and (α+β) titanium alloy powder, and preheat the substrate to 400-600℃. Under an argon protective atmosphere, laser melt deposit industrial pure titanium layer, TiC composite (α+β) titanium alloy layer one, (α+β) titanium alloy layer and TiC composite (α+β) titanium alloy layer two sequentially on the substrate from bottom to top.

[0010] Step S3. Repeat step S2 at least four times to obtain a molded part, and anneal the molded part to obtain a laminated material.

[0011] Preferably, in the net forming method of the Ti / Ti laminated material, the volume ratio of flake graphite powder to titanium alloy raw material in step S1 is 2-8%: 92-98%.

[0012] Preferably, the net forming method of the Ti / Ti multilayer material includes: in step S1, the flake graphite powder includes nano-flake graphite powder and micron-flake graphite powder in a ratio of 1:1 to 3:1, the thickness of the nano-flake graphite powder is 40-50 nm, and the thickness of the micron-flake graphite powder is 1-5 μm.

[0013] Preferably, in the net forming method of the Ti / Ti laminated material, the matrix (α+β) titanium alloy of the TiC composite (α+β) titanium alloy and the (α+β) titanium alloy powder in step S2 have the same (α+β) titanium alloy grade.

[0014] Preferably, in the net forming method of the Ti / Ti laminated material, the particle size of the industrial pure titanium, TiC composite (α+β) titanium alloy and (α+β) titanium alloy powder in step S2 is 45-150 μm.

[0015] Preferably, in the net forming method of the Ti / Ti laminated material, in step S2, the thickness of the industrial pure titanium layer and the (α+β) titanium alloy layer is the same, which is 0.3-0.8 mm, and the thickness of the TiC composite (α+β) titanium alloy layer one and the TiC composite (α+β) titanium alloy layer two is the same, which is 1 / 3-1 / 2 of the thickness of the industrial pure titanium layer.

[0016] Preferably, in the net forming method of the Ti / Ti laminated material, the scanning directions during the deposition of the (α+β) titanium alloy layer, the TiC composite (α+β) titanium alloy one, and the TiC composite (α+β) titanium alloy two are perpendicular to each other.

[0017] Preferably, in the net forming method of the Ti / Ti laminated material, the annealing temperature in step S3 is 500-600℃ and the annealing time is 1-4h.

[0018] An application of a laminated material, wherein: the Ti / Ti laminated material is used in automotive protective armor.

[0019] Advantages of this invention:

[0020] (1) The net forming method of the laminated material of the present invention avoids the precipitation of unstable brittle phases at the interface of the laminated structure by selecting the Ti / Ti system; the combination of (α+β) titanium alloy and industrial pure titanium, with strong-plastic-strong-plastic alternation, can maximize the energy dissipation of steady-state deformation at the laminated interface and suppress interlayer crack nucleation; the introduction of the (α+β) titanium alloy reinforcing layer of TiC composite has the effect of crack nucleation and propagation shielding, and the randomly oriented TiC composite particles can increase the additional energy consumption for crack propagation, making crack propagation difficult, and secondary cracks are prevented from propagating. Nucleation is difficult to occur at the interface of the laminate and within the TiC composite (α+β) titanium alloy layer. The fine-grained (α+β) titanium alloy layer reinforced by TiC composite often has high strength and hardness, but its plasticity is not as good as that of the (α+β) titanium alloy itself. The relatively thin TiC composite (α+β) titanium alloy layer can not only ensure the above-mentioned crack nucleation and propagation shielding effect, but also achieve a balance between improving strength, impact toughness and plasticity loss. Ultimately, the overall laminate material has a good coordination and matching of strength, plasticity and high impact toughness.

[0021] (2) The net forming method of the laminated material of the present invention, the introduction of the TiC composite (α+β) titanium alloy layer in the laminated material can, on the one hand, greatly increase the heterogeneous nucleation sites at the interface between the TiC composite (α+β) titanium alloy layer and industrial pure titanium, (α+β) titanium alloy layer; on the other hand, TiC itself has high thermal conductivity, which helps the temperature conduction between the TiC composite (α+β) titanium alloy layer and each interface of the laminated material, reduces the temperature gradient of the entire laminated material along the additive manufacturing direction, and ultimately helps to suppress the growth of columnar crystals.

[0022] (3) The net forming method of the laminated material of the present invention uses the melting casting method to prepare TiC composite (α+β) titanium alloy powder. Compared with the TiC composite (α+β) titanium alloy mixed powder prepared by the external addition method, it can significantly reduce the tube blockage and unstable deposition layer thickness caused by the high surface energy of nano and micro TiC composites during laser additive manufacturing. At the same time, it can also reduce the defects of poor metallurgical bonding at the laminated interface caused by the agglomeration of nano and micro TiC composites. Ultimately, it helps to accurately control the layer thickness of the laminated material and achieve good metallurgical bonding at the interface.

[0023] (4) The net forming method of the laminated material of the present invention, by setting an industrial pure titanium / TiC composite (α+β) titanium alloy / (α+β) titanium alloy laminated structure, can suppress defects such as poor metallurgical bonding at the interface of conventional Ti / Ti laminated materials or columnar crystal penetration growth. The final laminated material has medium-high strength and high impact toughness. The laminated material is conducive to the rapid repair of damaged protective armor layers. Attached Figure Description

[0024] Figure 1a is a schematic diagram of the nano-TiC + micro-TiC composite TC4 titanium alloy powder prepared by the melting and casting method in Example 1, and Figure 1b is a schematic diagram of the nano-TiC + micro-TiC composite TC4 titanium alloy powder prepared by the external addition method in Comparative Example 3.

[0025] Figure 2 is a metallographic image of the TC4 titanium alloy nano-TiC + micro-TiC composite material produced by laser melting deposition casting in Example 1.

[0026] Figure 3 is a schematic diagram of the forming process of the industrial pure titanium / cast TiC composite TC4 titanium alloy / TC4 titanium alloy laminate material prepared by the present invention in Example 2.

[0027] Figure 4 shows the industrial pure titanium / cast TiC composite TC4 titanium alloy / TC4 titanium alloy laminate material prepared in Example 2 according to the present invention.

[0028] Figure 5 shows the dimensions of the room temperature tensile specimen used in this invention.

[0029] Figure 6 shows the metallographic image of the poor interfacial metallurgical bonding of the conventional laminated material of industrial pure titanium / TC4 titanium alloy prepared in Comparative Example 1.

[0030] Figure 7 shows the metallographic image of columnar crystal penetration at the interface of the conventional laminated material of industrial pure titanium / TC4 titanium alloy prepared in Comparative Example 2.

[0031] Figure 8 shows the metallographic image of the poor metallurgical bonding at the interface of the industrial pure titanium / added TiC composite TC4 titanium alloy / TC4 titanium alloy laminate prepared in Comparative Example 3.

[0032] In Figure 9, a is a schematic diagram of impact crack propagation in a homogeneous titanium alloy material, b is a schematic diagram of impact crack propagation in a conventional Ti / Ti laminated material, and c is a schematic diagram of impact crack propagation in the industrial pure titanium / cast TiC composite TC4 titanium alloy / TC4 titanium alloy laminated material prepared in this invention. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] Example 1

[0035] A method for net forming of a laminated material, comprising the following steps:

[0036] Step S1. Prepare a mixture of raw materials including sponge titanium, Al-V master alloy, 45nm thick flake graphite powder, and 2.5μm thick micron-sized flake graphite powder. The nominal composition of the titanium alloy matrix is ​​Ti-6Al-4V (TC4), the volume ratio of nano-flake graphite powder is 4%, and the volume ratio of micro-flake graphite powder is 2%. After mixing, electrode pressing, electrode welding, and two vacuum arc furnace melting processes, a 200kg ingot with a diameter of Φ296mm is obtained. The melting current is 5-10KA, the voltage is 25-35V, and the vacuum degree is less than 1Pa. The Φ296mm... The original ingot surface oxide scale and inclusions were removed by turning to obtain an ingot with a diameter of 280 mm. The ingot was then drawn into a bar with a diameter of 120 mm in a single heat treatment at 50-100℃ above the phase transformation point. Then, it was rolled into a bar with a diameter of 45 mm in a single heat treatment at 30-50℃ below the phase transformation point. Finally, it was turned and cut into a bar with a diameter of 40 mm × 400 mm. The bar was then used to prepare spherical metal powder by plasma rotating electrode atomization method, with a current of 1400 A and a rotation speed of 24000 r / min. TiC composite TC4 alloy powder with a diameter of 45-150 μm was selected by sieve (the schematic diagram of the alloy powder is shown in Figure 1(a)).

[0037] Step S2. Thoroughly dry the TiC composite TC4 alloy powder and place it in the powder feeding tank of the laser melting deposition equipment. Preheat the TC4 substrate to 500°C and start deposition when the oxygen partial pressure is less than 50ppm. The process parameters of laser melting deposition are: laser power P = 1000W, scanning speed Vs = 360mm / min, powder feeding rate Vp = 4g / min, scanning spacing h = 1.6mm, and single-layer lifting amount 0.3mm.

[0038] Step S3. Repeat step S2 20 times, cut the sample along the additive manufacturing direction and prepare a metallographic sample, as shown in Figure 2. The deposited sample does not have obvious metallurgical defects. The TiC composite TC4 alloy has a fine basket structure with a strip length of about 10 μm. Nano-TiC and micro-TiC particles are dispersed in the structure, indicating that the process is suitable for laser melting deposition of this composite powder.

[0039] Example 2

[0040] A method for net forming of a laminated material, comprising the following steps:

[0041] Step S1. The raw materials, including sponge titanium, Al-V master alloy, 45nm thick flake graphite powder, and 2.5μm thick micron-sized flake graphite powder, are proportioned as follows: the nominal composition of the titanium alloy matrix is ​​Ti-6Al-4V (TC4), the volume ratio of nano-flake graphite powder is 4%, and the volume ratio of micro-flake graphite powder is 2%. After mixing, electrode pressing, electrode welding, and two vacuum arc furnace melting processes, a 200kg ingot with a diameter of Φ296mm is obtained. The melting current is 5-10KA, the voltage is 25-35V, and the vacuum degree is less than 1Pa. The oxide scale and inclusions on the surface of the original Φ296mm ingot were removed by turning to obtain a Φ280mm ingot. The ingot was then drawn into a Φ120mm bar in a single heat treatment at 50-100℃ above the phase transformation point. Then, it was rolled into a Φ45mm bar in a single heat treatment at 30-50℃ below the phase transformation point. Finally, it was turned and cut into Φ40mm×400mm bars. The bars were then used to prepare spherical metal powder by plasma rotating electrode atomization, with a current of 1400A and a rotation speed of 24000r / min. TiC composite TC4 alloy powder with a diameter of 45-150μm was selected by sieving (the schematic diagram of the alloy powder is shown in Figure 1(a)).

[0042] Step S2. Thoroughly dry TiC composite TC4 alloy powder, 45-150μm industrial pure titanium TA2, and TC4 alloy powder and place them in the powder feeding tank of the laser melting deposition equipment. Use one powder feeding tank 1 for each type of powder. Preheat the TC4 substrate to 500℃ and start deposition when the oxygen partial pressure is less than 50ppm. The first layer is deposited as a TA2 pure titanium layer 2. The laser melting deposition process parameters are: laser power P = 900W, scanning speed Vs = 480mm / min, powder feeding rate Vp = 8g / min, scanning spacing h = 1.6mm, and single-layer lift 0.6mm. The second layer is deposited as a TiC composite (α+β) titanium alloy layer 3. The laser melting deposition process parameters are: laser power P = 1000W, scanning speed Vs = 360mm / min, powder feeding rate Vp = 4g / min, scanning spacing h = 1.6mm, and single-layer lift 0.3mm. The scanning strategies for TiC composite TC4 alloy and TA2 alloy are perpendicular to each other; the third layer, (α+β) titanium alloy layer 4, is deposited with the following laser melting deposition parameters: laser power P = 1200W, scanning speed Vs = 480mm / min, powder feed rate Vp = 9g / min, scanning spacing h = 1.6mm, and single-layer lift 0.6mm. The scanning strategies for TC4 alloy and TiC composite TC4 alloy are perpendicular to each other; the fourth layer, (α+β) titanium alloy layer 5, is deposited with the following laser melting deposition parameters: laser power P = 1000W, scanning speed Vs = 360mm / min, powder feed rate Vp = 4g / min, scanning spacing h = 1.6mm, and single-layer lift 0.3mm. The scanning strategies for TiC composite TC4 alloy and TC4 alloy are perpendicular to each other.

[0043] Step S3. Repeat step S2 fifteen times to obtain a molded part with dimensions of approximately 60mm × 60mm × 27mm; perform stress-relief annealing on the above Ti / Ti laminated material at 600℃ for 2 hours to obtain the final laminated material.

[0044] The sample prepared in Example 2 was cut along the additive manufacturing direction to prepare metallographic samples. As shown in Figure 4, 6 indicates that the TA2 alloy has a basketweave structure with continuous α grain boundaries; 7 and 9 indicate that the TiC composite TC4 alloy has a fine basketweave structure with a lath length of about 10 μm, and micron-sized and nano-sized TiC particles are dispersed in the structure; 8 indicates that the TC4 alloy has a basketweave structure with discontinuous α grain boundaries. The microstructure of the fusion zone of the TA2 and TC4 alloy layers and the TiC composite TC4 alloy layer is significantly refined, and there is no grain boundary α phase in the fusion zone. The metallurgical bonding of each layer interface is good, and there are no columnar crystals. Along the additive manufacturing direction, room temperature tensile test samples were cut to the size shown in Figure 5 and sanded to 3000# before testing. The tensile strength was 986 MPa and the elongation was 7.9%. Along the length direction, V-shaped impact test samples were cut to the size of 55 mm × 10 mm × 10 mm and tested. The impact energy was 74 J.

[0045] Comparative Example 1

[0046] Laser melting deposition of conventional TA2 / TC4 multilayer materials

[0047] Step S1. Thoroughly dry TA2 and TC4 alloy powders (45-150 μm) and place them in the powder feeding hopper of the laser melting deposition equipment. One powder feeding hopper is used for each type of powder. Preheat the TC4 substrate to 500°C and begin deposition when the oxygen partial pressure is less than 50 ppm. The first layer is deposited with TA2 alloy powder. The laser melting deposition process parameters are: laser power P = 900 W, scanning speed Vs = 480 mm / min, powder feeding rate Vp = 8 g / min, scanning distance h = 1.6 mm, and single-layer lift 0.6 mm. The second layer is deposited with TC4 alloy powder. The laser melting deposition process parameters are: laser power P = 1200 W, scanning speed Vs = 480 mm / min, powder feeding rate Vp = 9 g / min, scanning distance h = 1.6 mm, and single-layer lift 0.6 mm. The scanning strategies for TC4 alloy and TA2 alloy are perpendicular to each other.

[0048] Step S2. With the above 1-2 layer deposition as one cycle, perform 30 cycles of deposition, for a total of 60 layers, to obtain the final Ti / Ti stack material with a size of approximately 60mm×60mm×30mm. Perform stress-relief annealing on the above Ti / Ti stack material at 600℃ for 2 hours to obtain the final stack material.

[0049] The sample was cut along the additive manufacturing direction and a metallographic sample was prepared. As shown in Figure 6, 10 was prepared using the process in Example 2. The interface between the TA2 alloy and TC4 alloy laminate had a large number of pores and poor metallurgical bonding. Along the additive manufacturing direction, a room temperature tensile sample was cut to the size shown in Figure 5 and sanded to 3000# before testing. The tensile strength was 674 MPa and the elongation was 3.8%. Along the length direction, a V-shaped impact sample was cut to the size of 55 mm × 10 mm × 10 mm and tested. The impact energy was 45 J.

[0050] Comparative Example 2

[0051] Based on the experimental results in Comparative Example 1, in order to further reduce the porosity defects at the interlayer interface of TA2 and TC4 alloys and improve the interlayer metallurgical bonding quality, the laser energy input will be slightly increased in this comparative example.

[0052] Laser melting deposition of conventional TA2 / TC4 multilayer materials

[0053] Step S1. Thoroughly dry TA2 and TC4 alloy powders (45-150 μm) and place them in the powder feeding hopper of the laser melting deposition equipment. One powder feeding hopper is used for each type of powder. Preheat the TC4 substrate to 500°C and begin deposition when the oxygen partial pressure is less than 50 ppm. The first layer is deposited using TA2 alloy powder. The laser melting deposition process parameters are: laser power P = 1000 W, scanning speed Vs = 480 mm / min, powder feeding rate Vp = 8 g / min, scanning interval h = 1.6 mm, and single-layer lift 0.6 mm. The second layer is deposited using TC4 alloy powder. The laser melting deposition process parameters are: laser power P = 1300 W, scanning speed Vs = 480 mm / min, powder feeding rate Vp = 9 g / min, scanning interval h = 1.6 mm, and single-layer lift 0.6 mm. The scanning strategies for TC4 alloy and TA2 alloy are perpendicular to each other.

[0054] Step S2. With the above 1-2 layer deposition as one cycle, perform 30 cycles of deposition, for a total of 60 layers, to obtain the final Ti / Ti stack material with a size of approximately 60mm×60mm×30mm. The above Ti / Ti stack material is then subjected to stress-relief annealing at 600℃ for 2 hours.

[0055] The sample prepared in Comparative Example 2 was cut along the additive manufacturing direction to prepare a metallographic sample, as shown in Figure 7. The internal structure of the TA2 alloy is columnar crystal, and the internal structure of the TC4 alloy is also columnar crystal. The layer interface is penetrated by columnar crystals. Along the additive manufacturing direction, a room temperature tensile sample was cut to the size shown in Figure 5 and sanded to 3000# before testing. The tensile strength was 841 MPa and the elongation was 4.5%. Along the length direction, a V-shaped impact sample was cut to the size of 55 mm × 10 mm × 10 mm and tested. The impact energy was 52 J.

[0056] Comparative Example 3

[0057] Laser melting deposition of TA2 / additional nano-TiC + micro-TiC composite TC4 alloy / TC4 laminated material

[0058] Step S1. Thoroughly dry TiC powder with particle sizes of 20-100nm and 1-10μm and Ti-6Al-4V (TC4) alloy powder respectively. Then, mix nano-TiC powder, micro-TiC powder and TC4 alloy powder at a volume ratio of 2:1:47, and mix them uniformly for 8 hours using a planetary three-dimensional motion mixer to obtain the additive nano-TiC + micro-TiC composite TC4 alloy powder. Place 45-150μm TA2, additive nano-TiC + micro-TiC composite TC4 alloy and TC4 alloy powder in the powder feeding tank of a laser melting deposition equipment. Use one powder feeding tank for each type of powder. Preheat the TC4 substrate to 5°C. Deposition begins at 00℃ and an oxygen partial pressure less than 50ppm. The first layer is deposited as TA2 alloy powder, as shown in Figure 3, 2. The laser melting deposition process parameters are: laser power P = 900W, scanning speed Vs = 480mm / min, powder feed rate Vp = 8g / min, scanning interval h = 1.6mm, and single-layer lift 0.6mm. The second layer is deposited as TiC composite TC4 alloy powder, as shown in Figure 3, 3. The laser melting deposition process parameters are: laser power P = 1000W, scanning speed Vs = 360mm / min, powder feed rate Vp = 4g / min, scanning interval h = 1.6mm, and single-layer lift 0.3mm. The scanning strategies for TiC composite TC4 alloy and TA2 alloy are perpendicular to each other. The third layer is deposited with TC4 alloy powder, as shown in Figure 3(4). The laser melting deposition process parameters are: laser power P = 1200W, scanning speed Vs = 480mm / min, powder feed rate Vp = 9g / min, scanning spacing h = 1.6mm, and single-layer lift 0.6mm. The TC4 alloy scanning strategy is perpendicular to the TiC composite TC4 alloy scanning strategy. The fourth layer is deposited with TiC composite TC4 alloy powder, as shown in Figure 3(5). The laser melting deposition process parameters are: laser power P = 1000W, scanning speed Vs = 360mm / min, powder feed rate Vp = 4g / min, scanning spacing h = 1.6mm, and single-layer lift 0.3mm. The TiC composite TC4 alloy scanning strategy is perpendicular to the TC4 alloy scanning strategy.

[0059] Step S2. With the above 1-4 layers as one cycle, perform 15 cycles of deposition, for a total of 60 layers, to obtain the final Ti / Ti stack material with a size of approximately 60mm×60mm×27mm. The above Ti / Ti stack material is subjected to stress-relief annealing at 600℃ for 2 hours to obtain the final stack material.

[0060] The sample was cut along the additive manufacturing direction and a metallographic sample was prepared, as shown in Figure 8, 11. A large number of unmelted TiC agglomerated composite particles with a particle size of 100 μm were present in the TiC composite TC4 alloy layer, resulting in poor metallurgical bonding between the TA2 and TC4 alloy layers. Along the additive manufacturing direction, a room temperature tensile sample was cut to the size shown in Figure 5 and sanded to 3000# before testing. The tensile strength was 940 MPa and the elongation was 4.3%. Along the length direction, a V-shaped impact sample was cut to the size of 55 mm × 10 mm × 10 mm and tested. The impact energy was 59 J.

[0061] Comparative Example 4

[0062] Preparation of TC4 alloy / TC4 laminated material using TA2 / melting casting method for nano-TiC + micro-TiC composites

[0063] Step S1. Thoroughly dry the TiC composite TC4 alloy powder obtained in Example 1, as well as the 45-150μm TA2 and TC4 alloy powders, and place them in the powder feeding hopper of a laser melting deposition equipment. One powder feeding hopper is used for each type of powder. Preheat the TC4 substrate to 500℃ and begin deposition when the oxygen partial pressure is less than 50ppm. The first layer is deposited using TA2 alloy powder. The laser melting deposition process parameters are: laser power P = 900W, scanning speed Vs = 480mm / min, powder feeding rate Vp = 8g / min, scanning spacing h = 1.6mm, and single-layer lift 0.6mm. The second layer is deposited using TiC composite TC4 alloy powder, as shown in Figure 3. The laser melting deposition process parameters are: laser power P = 1200W, scanning speed Vs = 480mm / min, powder feeding rate Vp = 9g / min, scanning spacing h = 1.6mm, and single-layer lift 0.6mm. The scanning strategies for TiC composite TC4 alloy and TA2 alloy are perpendicular to each other; the third layer is deposited with TC4 alloy powder, as shown in 4 of Figure 3; the process parameters for laser melting deposition are: laser power P = 1200W, scanning speed Vs = 480mm / min, powder feed rate Vp = 9g / min, scanning spacing h = 1.6mm, single-layer lift 0.6mm, and the alloy scanning strategy is perpendicular to the TiC composite TC4 alloy scanning strategy; the fourth layer is deposited with TiC composite TC4 alloy powder, as shown in 3 of Figure 3, and the process parameters for laser melting deposition are: laser power P = 1200W, scanning speed Vs = 480mm / min, powder feed rate Vp = 9g / min, scanning spacing h = 1.6mm, single-layer lift 0.6mm, and the TiC composite TC4 alloy scanning strategy is perpendicular to the TC4 alloy scanning strategy.

[0064] Step S2. With the above 1-4 layers as one cycle, perform 12 cycles of deposition, for a total of 48 layers, to obtain a Ti / Ti stack material with a size of approximately 60mm×60mm×29mm. Perform stress-relief annealing on the above Ti / Ti stack material at 600℃ for 2 hours to obtain the final stack material.

[0065] The sample was cut along the additive manufacturing direction and a metallographic sample was prepared. The microstructure type was similar to that of Example 2. Along the additive manufacturing direction, a room temperature tensile sample was cut to the size shown in Figure 5 and sanded to 3000# before testing. The tensile strength was 1047 MPa and the elongation was 5.2%. Along the length direction, a V-shaped impact sample was cut to the size of 55 mm × 10 mm × 10 mm and tested. The impact energy was 65 J.

[0066] Comparative analysis of the microstructures of the samples from Examples 1-2 and Comparative Examples 1-4 shows that:

[0067] In Example 1, the nano-TiC + micro-TiC composite TC4 alloy powder prepared by the casting method can be formed into a workpiece with no obvious metallurgical defects, fine basket structure and dispersed TiC distribution through laser melting deposition technology. In Comparative Example 1, the laser melting deposition process of the conventional TA2 / TC4 laminate material has a narrow range, and low energy input often leads to poor metallurgical bonding at the laminate interface. In Comparative Example 2, high energy input often leads to the formation of columnar crystals and the phenomenon of columnar crystals penetrating the laminate interface, resulting in large anisotropy of the alloy, which is not conducive to improving the impact resistance of the working surface.

[0068] Example 2 and Comparative Example 4 demonstrate that a suitable laser melting deposition process can deposit TA2 / cast nano-TiC + micro-TiC composite TC4 alloy / TC4 laminated material with no obvious columnar crystals and good metallurgical bonding at the laminate interface. This indicates that the introduction of the TC4 alloy layer in the cast nano-TiC + micro-TiC composite material helps to improve the metallurgical bonding at the laminate interface, reduces the overall temperature gradient of the laminated material, and thus reduces the tendency for columnar crystal formation.

[0069] In Comparative Example 3, the nano-TiC + micro-TiC composite TC4 alloy powder prepared by the additive method did not exhibit obvious columnar crystals when forming TA2 / additive nano-TiC + micro-TiC composite TC4 alloy / TC4 laminated materials. However, the large-sized TiC composites after agglomeration often formed unmelted particles, resulting in poor metallurgical bonding at the laminated interface. This also indicates that the nano-TiC + micro-TiC composite introduced by the additive method is beneficial to reducing the tendency of columnar crystal formation in TA2 / nano-TiC + micro-TiC composite TC4 alloy / TC4 laminated materials.

[0070] The room temperature mechanical properties of the samples from Example 2 and Comparative Examples 1-4 were compared and tested, and the data are shown in Table 1.

[0071] Table 1

[0072]

[0073] As shown in Table 1, the conventional TA2 / TC4 laminated material has a narrow range of laser melting deposition process. Using the corresponding process in Example 2, the laminated material (Comparative Example 1) has poor interfacial metallurgical bonding, resulting in low strength, plasticity and impact resistance. After slightly increasing the laser energy input, the conventional TA2 / TC4 laminated material (Comparative Example 2) no longer has interfacial pores, which improves its strength, plasticity and impact resistance compared to Comparative Example 1. However, the prevalence of columnar crystals limits further improvement in its strength, plasticity and impact resistance.

[0074] When the same process was used to prepare TA2 / melt casting method nano-TiC + micro-TiC composite TC4 alloy / TC4 laminate material (Example 2) and TA2 / additive method nano-TiC + micro-TiC composite TC4 alloy / TC4 laminate material (Comparative Example 3), the poor metallurgical bonding at the laminate interface caused by the agglomeration of the additive TiC composite material resulted in lower strength, plasticity and impact toughness than the workpiece in Example 2. This also shows that the introduction of various nano-TiC + micro-TiC composite TC4 layers helps to improve the strength and impact toughness of conventional TA2 / TC4 laminate materials.

[0075] In Comparative Example 4, the TA2 / cast nano-TiC + micro-TiC composite TC4 alloy / TC4 laminate material did not exhibit significant metallurgical defects. However, the thickness of the nano-TiC + micro-TiC composite TC4 alloy layer was twice that of the nano-TiC + micro-TiC composite TC4 alloy layer in Example 2, consistent with the thickness of the TA2 and TC4 layers. The thicker composite layer helps strengthen the laminate material, resulting in higher strength than in Example 2, but lower plasticity and impact energy. Ultimately, the workpiece from Example 2 exhibited a higher strength-plasticity-high impact toughness balance.

[0076] Based on the above, and according to Figure 9, the impact crack propagation mechanism of an ideal defect-free homogeneous TC4 alloy, a conventional TA2 / TC4 laminate, and a TA2 / cast nano-TiC + micro-TiC composite TC4 alloy / TC4 laminate is analyzed. In Figure 9(a), the TC4 alloy exhibits high stress concentration at the V-notch under impact load, leading to rapid crack propagation and eventual fracture. In Figure 9(b), the conventional TA2 / TC4 laminate also shows high stress concentration at the V-notch under impact load, resulting in rapid crack propagation. The presence of the laminate interface and the TA2 plastic layer contributes to crack redirection and rapid dissipation of crack propagation energy (interlaminar effect). The multilayer structure can further hinder crack propagation; in Figure 9(c), the TA2 / cast nano-TiC + micro-TiC composite TC4 alloy / TC4 laminate material under impact load has a high concentration of V-notch stress and rapid crack propagation. When the crack extends to the TiC composite layer, the interlayer effect helps to redirect the primary crack and dissipate energy. At the same time, the dispersed hard TiC composite particles can further hinder crack propagation and secondary crack nucleation. The presence of the TA2 alloy layer also has the interlayer effect corresponding to that described in Figure 9(b). Under the same layer thickness, this laminate material has more layers, the interlayer effect is more significant, and ultimately has high impact toughness.

[0077] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A net forming method for a Ti / Ti laminate material, characterized in that: The process includes the following steps: Step S1. Mixing flake graphite powder of different sizes and titanium alloy raw materials uniformly and then melting them to obtain an ingot. The ingot is then forged and rolled into a rod. The rod is then prepared into TiC composite (α+β) titanium alloy powder using a plasma rotating electrode atomization method. Step S2. Drying industrial pure titanium, TiC composite (α+β) titanium alloy, and (α+β) titanium alloy powder, and preheating the substrate to 400-600℃, and then laser melting and depositing industrial pure titanium layer, TiC composite (α+β) titanium alloy layer one, (α+β) titanium alloy layer, and TiC composite (α+β) titanium alloy layer two on the substrate from bottom to top under an argon protective atmosphere. Step S3. Repeating step S2 at least four times to obtain a molded part, and then annealing the molded part to obtain the final laminated material.

2. The net forming method for Ti / Ti laminated materials as described in claim 1, characterized in that: In step S1, the volume ratio of flake graphite powder to titanium alloy raw material is 2-8%: 92-98%.

3. The net forming method for Ti / Ti laminated materials as described in claim 1, characterized in that: In step S1, the flake graphite powder includes nano-flake graphite powder and micron-flake graphite powder in a ratio of 1:1 to 3:

1. The thickness of the nano-flake graphite powder is 40-50 nm, and the thickness of the micron-flake graphite powder is 1-5 μm.

4. The net forming method for Ti / Ti laminated materials as described in claim 1, characterized in that: In step S2, the matrix (α+β) titanium alloy of the TiC composite (α+β) titanium alloy and the (α+β) titanium alloy powder have the same (α+β) titanium alloy grade.

5. The net forming method for Ti / Ti laminated materials as described in claim 1, characterized in that: In step S2, the particle size of industrial pure titanium, TiC composite (α+β) titanium alloy and (α+β) titanium alloy powder is 45-150μm.

6. The net forming method for Ti / Ti laminated materials as described in claim 1, characterized in that: In step S2, the thickness of the industrial pure titanium layer and the (α+β) titanium alloy layer is the same, both being 0.3-0.8 mm. The thickness of the TiC composite (α+β) titanium alloy layer one and the TiC composite (α+β) titanium alloy layer two is the same, being 1 / 3-1 / 2 of the thickness of the industrial pure titanium layer.

7. The net forming method for Ti / Ti laminated materials as described in claim 1, characterized in that: In step S2, the scanning directions of the (α+β) titanium alloy layer, TiC composite (α+β) titanium alloy one, and TiC composite (α+β) titanium alloy two are perpendicular to each other during deposition.

8. The net forming method for Ti / Ti laminated materials as described in claim 1, characterized in that: In step S3, the annealing temperature is 500-600℃ and the annealing time is 1-4h.

9. The application of the Ti / Ti multilayer material formed by the net forming method of the Ti / Ti multilayer material according to any one of claims 1-8, characterized in that: Ti / Ti laminated materials are used in automotive protective armor.

Images