Titanium alloy based on SLM technology and component design method thereof

Abstract

The invention discloses a titanium alloy based on an SLM technology and a component design method thereof, and belongs to the technical field of titanium alloy materials. A sedimentary titanium alloy is prepared by adopting an SLM technology, and the sedimentary titanium alloy is subjected to heat treatment to prepare an air-cooled titanium alloy or a quenched titanium alloy. By controlling technological parameters of the SLM technology and utilizing the rapid melting characteristic of the technology, precise control over phase composition and mechanical properties of the titanium alloy is achieved, and by means of the synergistic effect of Cu and Sn, the plasticity of the titanium alloy is improved while the strength of the titanium alloy is improved. A new thought is provided for developing the titanium alloy with high strength, high toughness and low cost, and application of the multi-component titanium alloy in the field of additive manufacturing is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium alloy materials, in particular to a titanium alloy based on SLM technology and a component design method thereof. BACKGROUND

[0002] Titanium and its alloys have been widely used in aerospace, biomedical, chemical industry and marine engineering due to their excellent specific strength, corrosion resistance and biocompatibility. However, the strength of pure titanium is relatively low, which cannot meet the requirements of high load or wear-resistant working conditions. Traditional high-strength titanium alloys (such as TC4, i.e. Ti-6Al-4V) usually rely on expensive alloying elements (such as V, Nb, etc.) or complex heat treatment processes, resulting in high cost and limiting their large-scale application. Therefore, developing new titanium alloys with low cost and high performance has become one of the current research hotspots.

[0003] In recent years, in-situ alloying of titanium alloys through SLM technology (selective laser melting technology) has become a research hotspot. By precisely controlling the laser energy and powder mixing ratio, uniform alloying of elements in the molten pool is achieved. Copper (Cu) and tin (Sn) are common alloying elements that are often added to titanium alloys to increase their mechanical properties. Chinese patent CN 112359249 A discloses a nano-crystalline Ti6Al4V-Cu alloy and its additive manufacturing preparation method, which improves the mechanical properties of titanium alloys. Chinese patent CN 105154701 B discloses a method for preparing high-temperature titanium alloys using selective laser melting rapid prototyping technology, which involves adding Sn to the titanium alloy to prepare a titanium alloy with a chemical composition of Ti5.5Al3.5Sn3Zr0.7Mo0.3Si0.4Nb0.4Ta.

[0004] However, excessive addition of Cu can cause brittle fracture of the alloy, and both strength and plasticity decrease significantly. Excessive addition of Cu-Sn alloy can also cause composition segregation and uneven microstructure, unstable molten pool, metallurgical defects (unfused, cracks, pores, inclusions, etc.), decreased density, thermal cracks and residual stress concentration, etc., resulting in significant decrease in mechanical properties of the alloy. SUMMARY

[0005] To solve the adverse effects caused by improper addition of Cu and Sn in titanium alloys, an innovative strategy is proposed: controlling the total amount of added Cu and Sn alloying elements, introducing low-cost Cu-Sn alloy powder into pure titanium or TC4 through SLM technology, and realizing in-situ alloying to prepare titanium alloys.

[0006] In a first aspect, the present application provides a titanium alloy based on SLM technology, the titanium alloy being one of a Ti-Cu-Sn titanium alloy or a TC4-Cu-Sn titanium alloy, the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn titanium alloy being 1:1.5-4.5:0.6-1.8, and the molar ratio of TC4, Cu and Sn in the TC4-Cu-Sn titanium alloy being 1:1-3:0.8-2.4.

[0007] Copper (Cu) and tin (Sn) are common beta stabilizing elements and neutral elements in titanium alloys, and have a unique strengthening effect in titanium alloys. The addition of copper (Cu) to titanium alloys can significantly improve the strength of titanium alloys through solid solution strengthening and aging precipitation. Cu has a high solid solubility in titanium (about 17 wt% in beta-Ti), which can significantly improve the beta phase stability; it is easy to form Ti2Cu intermetallic compounds (orthorhombic structure) with high hardness and high thermal stability, which is an effective strengthening phase; Cu element can reduce the surface tension of titanium alloy melt and improve the fluidity of the molten pool. Tin (Sn) has a large solid solubility in both alpha-Ti and beta-Ti, with a solid solubility of about 14-15 wt% in alpha-Ti (hexagonal close-packed structure, <882℃), and a higher solid solubility in beta-Ti (body-centered cubic structure, >882℃), which can reach more than 25 wt%, and the solid solution strengthening effect is significant; it can improve the lattice constant ratio c / a of alpha-Ti, thereby promoting the conical slip of titanium alloy and improving its plasticity; it can form ordered phases such as Ti3Sn; and it can further regulate phase change dynamics and precipitation behavior in cooperation with Cu.

[0008] In a second aspect, the present application provides a component design method of a titanium alloy based on SLM technology, which uses SLM technology to design the components of the titanium alloy described above to obtain a deposited Ti-Cu-Sn alloy or a deposited TC4-Cu-Sn alloy.

[0009] Preferably, the process parameters of the SLM technology are as follows: laser power is 170-180 W, scanning speed is 1300-1500 mm / s, spot diameter is 0.08-0.12 mm, powder thickness is 0.02-0.04 mm, and the atmosphere is Ar gas.

[0010] Preferably, the yield strength of the deposited Ti-Cu-Sn alloy is >785 MPa, the tensile strength is >891 MPa, and the elongation is >7.8%; the yield strength of the deposited TC4-Cu-Sn alloy is >1041 MPa, the tensile strength is >1252 MPa, and the elongation is >9.0%.

[0011] Preferably, the surface microstructure of the as-deposited Ti-Cu-Sn alloy is in the form of fine lath-shaped alpha phase in cross-basket distribution; the surface transverse microstructure of the as-deposited TC4-Cu-Sn alloy is in the form of fine needle-shaped alpha prime lamella or lamella cluster in cross-basket distribution, and the longitudinal microstructure is in the form of columnar crystal growing vertically and fine needle-shaped alpha prime phase or lath-shaped alpha prime phase in cross-basket distribution filling in the columnar crystal.

[0012] Preferably, the width of the lath-shaped alpha phase is 0.1-0.3 μm; the width of the columnar crystal is 80-150 μm, and the width of the lath-shaped alpha prime phase is 0.1-0.3 μm.

[0013] Preferably, the as-deposited Ti-Cu-Sn alloy is heat treated by air cooling annealing after being kept at 700-800 ℃ for 0.5-2 h to obtain the air-cooled Ti-Cu-Sn alloy; the as-deposited TC4-Cu-Sn alloy is heat treated by air cooling annealing after being kept at 700-800 ℃ for 0.5-2 h to obtain the air-cooled TC4-Cu-Sn alloy, or by quenching after being kept at 750-850 ℃ for 1-3 h to obtain the quenched TC4-Cu-Sn alloy.

[0014] Preferably, the yield strength of the air-cooled Ti-Cu-Sn alloy is >517 MPa, the tensile strength is >627 MPa, and the elongation is >13.7%; the yield strength of the air-cooled TC4-Cu-Sn alloy is >1050 MPa, the tensile strength is >1102 MPa, and the elongation is >3.22%; the yield strength of the quenched TC4-Cu-Sn alloy is >680 MPa, the tensile strength is >1029 MPa, and the elongation is >16.4%.

[0015] Preferably, the surface microstructure of the air-cooled Ti-Cu-Sn alloy is in the form of coarsening and merging of the lath-shaped alpha phase and precipitation of intermetallic compound Ti2Cu, and the width of the coarsened lath-shaped alpha phase is 15-30 μm; the surface microstructure of the air-cooled TC4-Cu-Sn alloy is in the form of alpha + beta lath bundle in cross-basket distribution converted from the needle-shaped alpha prime phase and lath-shaped alpha prime phase, and the width of the alpha + beta lath bundle is 0.5-1.4 μm.

[0016] Advantages (1) The synergistic effect of Cu and Sn can improve the strength of the titanium alloy while improving the plasticity by optimizing the microstructure (such as refining the grain or forming a ductile phase), avoiding the composition segregation caused by the mixing of single elements; (2) By reasonably controlling the adding amount of Cu and Sn, the composition segregation, uneven structure, unstable molten pool, metallurgical defects (unfused, cracks, holes, inclusions, etc.), density reduction, hot cracks and residual stress concentration, etc. which lead to the adverse effects of the mechanical properties of titanium alloy are avoided; (3) By controlling the process parameters of SLM technology, the rapid melting characteristics of the technology are utilized to realize the precise control of the phase composition and mechanical properties of titanium alloy; (4) The present application provides a new idea for developing high-strength, high-toughness and low-cost titanium alloy, and promotes the application of multi-component titanium alloy in the field of additive manufacturing.

[0017] The technical solutions of the present application will be further described in detail below by means of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a working principle diagram of a laser selective melting equipment; Figure 2 is a schematic diagram of a tensile specimen specification; Figure 3 is a stress-strain curve of the deposited Ti-Cu-Sn alloy prepared in examples 1~3; Figure 4 is a stress-strain curve of the air-cooled Ti-Cu-Sn alloy prepared in examples 4~6; Figure 5 is an SEM image of the deposited Ti-Cu-Sn alloy prepared in example 1 (a: 5μm; b: 1μm); Figure 6 is an SEM image of the air-cooled Ti-Cu-Sn alloy prepared in example 4 (a: 100μm; b: 40μm); Figure 7 is an EDS image and an SEM image of the precipitated Ti2Cu phase of the air-cooled Ti-Cu-Sn alloy prepared in example 4 (a: EDS image, 4μm; b: SEM image, 4μm); Figure 8 is a stress-strain curve of the deposited, air-cooled and quenched TC4-1Cu-0.8Sn alloy prepared in examples 7~9; Figure 9 is a stress-strain curve of the deposited, air-cooled and quenched TC4-2Cu-1.6Sn alloy prepared in examples 10~12; Figure 10 is a stress-strain curve of the deposited, air-cooled and quenched TC4-3Cu-2.4Sn alloy prepared in examples 13~15; Figure 11is a tensile strength and elongation comparison chart of the as-deposited TC4-Cu-Sn alloy prepared in Example 7, 10, 13 and the reported TC4, TC4-xCu, TC4-316L, Ti-Cu alloys; Figure 12 is a cross-section electron microscope scanning chart of the as-deposited TC4-1Cu-0.8Sn alloy; Figure 13 is a longitudinal-section electron microscope scanning chart of the as-deposited TC4-1Cu-0.8Sn alloy; Figure 14 is a cross-section electron microscope scanning chart of the air-cooled TC4-1Cu-0.8Sn alloy; Figure 15 is a longitudinal-section electron microscope scanning chart of the air-cooled TC4-1Cu-0.8Sn alloy. DETAILED DESCRIPTION

[0019] The application will be further described below, and it should be noted that the embodiment takes the technical solution as the premise, and gives a detailed implementation mode and specific operation process, but the application is not limited to the embodiment.

[0020] The S210 model laser selective melting (SLM) equipment produced by BLT company is adopted to design the composition of the titanium alloy sample, and the working principle of the equipment is shown in Figure 1 .

[0021] Example 1 The embodiment provides a composition design method of a Ti-Cu-Sn alloy based on SLM technology, the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:1.5:0.6, and the process parameters of the SLM technology are as follows: the laser power is 175 W, the scanning speed is 1400 mm / s, the spot diameter is 0.1 mm, the powder thickness is 0.03 mm, and the atmosphere is Ar gas, so that the as-deposited Ti-1.5Cu-0.6Sn alloy is obtained.

[0022] Example 2 The embodiment provides a composition design method of a Ti-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 1 is that the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:3:1.2, so that the as-deposited Ti-3Cu-1.2Sn alloy is obtained.

[0023] Example 3 The embodiment provides a component design method of a Ti-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 1 is that the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:4.5:1.8, so that the as-deposited Ti-4.5Cu-1.8Sn alloy is obtained.

[0024] Embodiment 4 The embodiment provides a component design method of a Ti-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 1 is that the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:4.5:1.8, so that the as-deposited Ti-4.5Cu-1.8Sn alloy is obtained.

[0025] It has been reported that annealing treatment of the titanium alloy below the eutectoid temperature of 740 DEG C promotes the precipitation and growth of the Ti2Cu phase in the structure, and can effectively coordinate the matching relationship between the strength and the plasticity of the alloy. The heat treatment mode adopted in the Ti-xCu-ySn alloy in the application is 740 DEG C for 1h and air cooling annealing, and the 1h holding time is sufficient to realize the full solid solution and composition homogenization of Cu and Sn elements, and meanwhile, the grain coarsening or excessive precipitation of brittle phases (such as Ti2Cu and Ti3Sn) caused by long-time high temperature is avoided. Subsequently, the cooling mode of air cooling can inhibit the coarse precipitated phase while ensuring a certain cooling rate, and the residual stress possibly introduced by water cooling is avoided, which is beneficial to balance the strength and plasticity of the material and obtain a relatively balanced structure state.

[0026] Embodiment 5 The embodiment provides a component design method of a Ti-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 1 is that the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:4.5:1.8, so that the as-deposited Ti-4.5Cu-1.8Sn alloy is obtained.

[0027] Embodiment 6 The embodiment provides a component design method of a Ti-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 1 is that the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:4.5:1.8, so that the as-deposited Ti-4.5Cu-1.8Sn alloy is obtained.

[0028] Comparative Example 1 The embodiment provides a component design method of a Ti-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 1 is that the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:4.5:1.8, so that the as-deposited Ti-4.5Cu-1.8Sn alloy is obtained.

[0029] Comparative Example 2 The embodiment provides a component design method of a Ti-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 1 is that the molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn alloy is 1:6.5:6.5, so that the deposition state Ti-6.5Cu-6.5Sn alloy is obtained.

[0030] Embodiment 7 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and the molar ratio of TC4, Cu and Sn in the TC4-Cu-Sn alloy is 1:1:0.8, and the process parameters of the SLM technology are as follows: the laser power is 175 W, the scanning speed is 1400 mm / s, the spot diameter is 0.1 mm, the powder thickness is 0.03 mm, and the atmosphere is Ar gas, so that the deposition state TC4-Cu-0.8Sn alloy is obtained.

[0031] Embodiment 8 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and the deposition state TC4-Cu-0.8Sn alloy obtained in the embodiment 7 is subjected to air cooling annealing after being kept at 740 DEG C for 1 h, so that the air cooling state TC4-Cu-0.8Sn alloy is obtained.

[0032] Embodiment 9 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and the deposition state TC4-Cu-0.8Sn alloy obtained in the embodiment 7 is subjected to quenching after being kept at 800 DEG C for 2 h, so that the quenching state TC4-Cu-0.8Sn alloy is obtained.

[0033] Embodiment 10 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and the difference from the embodiment 7 is that the molar ratio of TC4, Cu and Sn in the TC4-Cu-Sn alloy is 1:2:1.6, so that the deposition state TC4-2Cu-1.6Sn alloy is obtained.

[0034] Embodiment 11 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and the deposition state TC4-2Cu-1.6Sn alloy obtained in the embodiment 10 is subjected to air cooling annealing after being kept at 740 DEG C for 1 h, so that the air cooling state TC4-2Cu-1.6Sn alloy is obtained.

[0035] Embodiment 12 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and quenching of the as-deposited TC4-2Cu-1.6Sn alloy obtained in the embodiment 10 after 2h of heat preservation at 800 DEG C, to obtain a quenched TC4-2Cu-1.6Sn alloy.

[0036] Embodiment 13 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and the difference between the embodiment and the embodiment 7 is that the molar ratio of TC4, Cu and Sn in the TC4-Cu-Sn alloy is 1:3:1.8, to obtain an as-deposited TC4-3Cu-2.4Sn alloy.

[0037] Embodiment 14 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and air cooling annealing of the as-deposited TC4-3Cu-2.4Sn alloy obtained in the embodiment 13 after 1h of heat preservation at 740 DEG C, to obtain an air-cooled TC4-3Cu-2.4Sn alloy.

[0038] Embodiment 15 The embodiment provides a component design method of a TC4-Cu-Sn alloy based on SLM technology, and quenching of the as-deposited TC4-3Cu-2.4Sn alloy obtained in the embodiment 13 after 2h of heat preservation at 800 DEG C, to obtain a quenched TC4-3Cu-2.4Sn alloy.

[0039] Detection method In order to analyze the microstructure and mechanical properties of the titanium alloys, 9 titanium alloy samples with a size of 25mm*15mm*14mm are prepared for each of the 17 titanium alloys obtained in the embodiments 1-15 and the comparative examples 1-2.

[0040] One of the titanium alloy samples in the embodiments 1-15 and the comparative examples 1-2 is made into a tensile sample, and the tensile sample has a specification as shown in Figure 2 The tensile sample is placed in a tensile machine for tensile test, to obtain the mechanical property data of the titanium alloy sample (as shown in Tables 1-5), and the stress-strain curve of the titanium alloy is drawn as shown in Figures 3-4 , 8-10.

[0041] One of the titanium alloy samples prepared in Examples 1, 4, 7 and 10 was taken, cut, inlaid, ground, polished, and then corroded with Kroll reagent (HF:HNO3:H2O = 1:2.5:100 by volume) for 15-20 seconds, and the microstructure of the titanium alloy sample was observed with a Thermo Scientific Apreo 2 scanning electron microscope (SEM) with an electron beam energy of 20 KV, a working distance of 20 mm, and a magnification range of 80x to 80000x. Figures 5-6 In addition, the selected area of the titanium alloy sample in Example 4 was subjected to preliminary component determination with an energy dispersive spectrometer (EDS) equipped with the scanning electron microscope, and the results are shown in Table 2. Figure 7

[0042] Result analysis The mechanical property data of the as-deposited titanium alloy samples in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1, and the stress-strain curves are shown in Figure 3

[0043] Table 1 Mechanical properties of as-deposited titanium alloys in Examples 1-3 and Comparative Examples 1-2

[0044] As can be seen from Table 1 and Figure 3 , compared with the as-deposited Ti-1.5Cu-0.6Sn alloy in Example 1, the yield strength of the as-deposited Ti-3Cu-1.2Sn alloy in Example 2 is increased by 14%, the tensile strength is increased by 21%, and the elongation is decreased by 41%. Compared with the as-deposited Ti-3Cu-1.2Sn alloy in Example 2, the yield strength of the as-deposited Ti-4.5Cu-1.8Sn alloy in Example 3 is increased by 10%, the tensile strength is increased by 6%, and the elongation is decreased by 33%. In summary, the yield strength and the tensile strength of the three as-deposited Ti-Cu-Sn alloys with different component ratios are gradually increased, and the elongation is gradually decreased, indicating that the strength is gradually increased and the plasticity is gradually decreased.

[0045] It has been reported that the yield strength and the tensile strength of pure Ti prepared by SLM technology are 550 MPa and 650 MPa, respectively, and the elongation is 30%. The yield strength of the Ti-Cu-Sn alloy prepared by SLM technology in the present application is >830.4±45.2 MPa, the tensile strength is >913.8±22.0 MPa, and the elongation can reach more than 20%, indicating that the alloy has high strength and good plasticity.​​

[0046] Copper added to titanium alloy can play a role of solid solution strengthening and second phase precipitation strengthening, but at the same time, the alloy plasticity and toughness are reduced, as shown in Table 1, with the addition of Cu and Sn continues to increase, the yield strength, tensile strength, elongation of titanium alloy are significantly reduced. Thus, if the copper content is too high, the alloy will produce brittle fracture, and the strength and plasticity will decrease significantly. Therefore, the Cu / Ti molar ratio is preferably controlled below 7.

[0047] Sn added to titanium alloy mainly plays a role of solid solution strengthening, and can also improve its plasticity. Since in situ alloying of titanium alloy by SLM technology, if the proportion of Cu-Sn alloy powder added is too high, a series of adverse effects will be brought, such as composition segregation and uneven structure, unstable molten pool and metallurgical defects (unfused, cracks, pores, inclusions, etc.), density reduction, hot cracking and residual stress concentration, etc., which will lead to a significant decrease in the mechanical properties of the alloy. As shown in Table 1, compared with the mechanical properties of titanium alloys of Examples 1-3, the yield strength, tensile strength, and elongation of the titanium alloy prepared in Comparative Example 2 are all decreased. Therefore, it is also necessary to control the total amount of added alloying elements of copper and tin, and the (Cu+Sn) / Ti molar ratio is preferably not more than 12.

[0048] The mechanical property data of the air-cooled titanium alloy samples of Examples 4-6 are shown in Table 2, and the stress-strain curves are shown in Figure 4 .

[0049] Table 2 Mechanical properties of air-cooled alloys of Examples 4-6

[0050] From Table 2 and Figure 4 , it can be seen that compared with the air-cooled Ti-1.5Cu-0.6Sn alloy obtained in Example 1, the yield strength of the air-cooled Ti-3Cu-1.2Sn alloy obtained in Example 2 is increased by 29%, the tensile strength is increased by 23%, and the elongation is decreased by 26%. Compared with the air-cooled Ti-3Cu-1.2Sn alloy obtained in Example 2, the yield strength of the air-cooled Ti-4.5Cu-1.8Sn alloy obtained in Example 3 is decreased by 9%, the tensile strength is decreased by 8%, and the elongation is decreased by 37%. It is shown that the excessive addition of Cu and Sn in titanium alloy will cause the strength and plasticity of the alloy to decrease after heat treatment, and therefore, reasonable control of the addition amount of Cu and Sn can avoid the decrease of the mechanical properties of the titanium alloy.

[0051] Figure 5SEM image of the as-deposited Ti-1.5Cu-0.6Sn alloy prepared in Example 1 is shown, which can be seen that the microstructure mainly presents fine α-lath structure (width of 0.1-0.3 μm) in a cross-basket distribution. This typical rapid solidification structure is derived from the extremely high cooling rate (10 3 ~10 6 K / s) specific to SLM technology, which promotes the non-equilibrium phase transition of high-temperature β phase to form sub-micron α-lath, with a small amount of β phase or martensite (α' phase) possibly remaining. Cu and Sn as β-stabilizing elements mainly exist in the form of supersaturated solid solution in the α-Ti matrix during rapid solidification, and the formation of precipitated phase is limited due to the significant inhibition of atomic diffusion by the ultra-fast cooling rate, so that the metastable microstructure is formed mainly by solid solution strengthening.

[0052] Figure 6 SEM image of the air-cooled Ti-Cu-Sn alloy prepared in Example 4 is shown, Figure 7 EDS image of the precipitated Ti2Cu phase of the air-cooled Ti-Cu-Sn alloy prepared in Example 4 is shown. As can be seen from the figure, after the Ti-1.5Cu-0.6Sn alloy prepared by SLM technology is heat treated at 740 °C for 1 h and air-cooled, the microstructure changes significantly, mainly presenting the merging and coarsening of α-lath structure ( Figure 6 ) and the precipitation of Ti2Cu intermetallic compound ( Figure 7 ). During the heat treatment process, the high temperature promotes the coarsening of the α-lath structure and reduces the grain boundary density, resulting in the weakening of the fine-grain strengthening effect, thereby reducing the strength of the material (in Tables 1-2, the yield strength of the Ti-1.5Cu-0.6Sn alloy decreases from 830.4 ± 45.2 MPa to 534.5 ± 17.1 MPa). At the same time, the supersaturated solid solution of Cu element precipitates in the form of Ti2Cu phase with an orthorhombic structure, which is uniformly distributed in the α matrix and the grain boundaries in the form of fine particles or needles, and the precipitation strengthening partially compensates for the strength loss due to the weakening of solid solution strengthening. In addition, the coarsening of the α-lath structure and the release of residual stress significantly improve the plasticity of the material (in Tables 1-2, the elongation of the Ti-1.5Cu-0.6Sn alloy increases from 21.6 ± 0.7% to 28.2 ± 3.7%), but with the increase of Cu-Sn content, the excessive precipitation of Ti2Cu phase may cause the increase of brittleness, which is manifested by the further decrease of the elongation of the Ti-4.5Cu-1.8Sn alloy to 15.3 ± 1.6%. This structure-property correlation shows that the changes in mechanical properties after heat treatment are the result of the combined action of α phase coarsening, solid solution weakening, precipitation strengthening and residual stress relaxation.

[0053] Figure 8The stress-strain curves of the as-deposited, air-cooled and quenched TC4-1Cu-0.8Sn alloys prepared in Examples 7-9 are shown in Table 3, and the corresponding mechanical property data of the three titanium alloys are shown in Table 3. From Figure 8 As can be seen from Table 3, after the two kinds of heat treatment, the yield strength and tensile strength of the as-deposited TC4-1Cu-0.8Sn alloy are decreased, and the elongation is increased. Among them, the yield strength of the air-cooled TC4-1Cu-0.8Sn alloy is decreased by 8.4%, the tensile strength is decreased by 12.8%, and the elongation is increased by 17.3%; the yield strength of the quenched TC4-1Cu-0.8Sn alloy is decreased by 25.2%, the tensile strength is decreased by 18.8%, and the elongation is increased by 28.1%.

[0054] Table 3 Mechanical property data table of TC4-1Cu-0.8Sn alloys in different states

[0055] Figure 9 The stress-strain curves of the as-deposited, air-cooled and quenched TC4-2Cu-1.6Sn alloys prepared in Examples 10-12 are shown in Table 4, and the corresponding mechanical property data of the three titanium alloys are shown in Table 4. From Figure 9 As can be seen from Table 4, after the two kinds of heat treatment, the yield strength and tensile strength of the as-deposited TC4-2Cu-1.6Sn alloy are decreased, and the elongation is increased. Among them, the yield strength of the air-cooled TC4-2Cu-1.6Sn alloy is decreased by 6.0%, the tensile strength is decreased by 11.9%, and the elongation is increased by 9.5%; the yield strength of the quenched TC4-2Cu-1.6Sn alloy is decreased by 22.9%, the tensile strength is decreased by 9.4%, and the elongation is increased by 55.0%.

[0056] Table 4 Mechanical property data table of TC4-2Cu-1.6Sn alloys in different states

[0057] Figure 10 The stress-strain curves of the as-deposited, air-cooled and quenched TC4-3Cu-2.4Sn alloys prepared in Examples 13-15 are shown in Table 5, and the corresponding mechanical property data of the three titanium alloys are shown in Table 5. From Figure 9As shown in Table 4, both the yield strength and tensile strength of the deposited TC4-3Cu-2.4Sn alloy decreased after heat treatment using the two methods. Specifically, the yield strength of the air-cooled TC4-3Cu-2.4Sn alloy decreased by 0.4%, the tensile strength decreased by 12.5%, and the elongation decreased by 58.3%; while the yield strength of the quenched TC4-3Cu-2.4Sn alloy decreased by 33.8%, the tensile strength decreased by 16.6%, and the elongation increased by 73.4%.

[0058] Table 5. Mechanical property data of TC4-3Cu-2.4Sn alloys in different states.

[0059] The tensile strength and elongation of the deposited TC4-Cu-Sn alloys prepared in Examples 7, 10, and 13 were compared with those of previously reported TC4, TC4-xCu, TC4-316L, and Ti-Cu alloys, respectively. The results are as follows: Figure 11 And as shown in Table 6. From Figure 11 As shown in Table 6, compared with the TC4-xCu alloy containing pure copper, the ultimate tensile strength of the TC4-Cu-Sn alloy decreased, but the elongation was significantly improved. Compared with the TC4 alloy (tensile strength 1126.5±71.72 MPa; elongation 8.68±0.94%), the TC4-xCu-ySn alloy showed significant improvements in both tensile strength and elongation, especially the TC4-1Cu-0.8Sn alloy, whose ultimate tensile strength increased by 21.90% and elongation by 69.59%.

[0060] Table 6 Comparison of Mechanical Properties of Different Titanium Alloys

[0061] Figure 12 , Figure 13 The images show scanning electron microscope (SEM) images of the cross-section and longitudinal section of the deposited TC4-1Cu-0.8Sn alloy, respectively. Figure 12 It can be seen that the cross-section of the deposited TC4-1Cu-0.8Sn alloy contains a large number of fine needle-like α′ lamellae / lamellae bundles, approximately 0.1~0.3 μm wide, distributed in a cross-bass network pattern. This microstructure is due to the ultra-high cooling rate of the SLM (>10). 6 K / s) inhibited the β→α+β equilibrium transition, thereby forming the metastable α′ phase (HCP structure). Figure 13It can be seen that the longitudinal section of the as-deposited TC4-1Cu-0.8Sn alloy has coarse columnar crystals (width about 80-150 μm) penetrating the picture, which grow along the vertical direction (building direction). The columnar crystals are filled with fine needle-like or lath-like α' phase (light color area), the width of the lath-like α' phase is about 0.1-0.3 μm, and the lath-like α' phase is distributed in a cross-basket net shape (middle dense light color strip). Figure 13 The α' lath grows along a specific habit plane in the columnar crystal, and the direction is related to the local gradient of heat flow, forming a sub-grain level texture. The reason for forming such an organization is that when SLM is solidified layer by layer, the maximum thermal gradient direction is the driving direction (Z axis) of the epitaxial growth of β grains.

[0062] Figure 14 、 Figure 15 are the electron microscope scanning images of the transverse section and the longitudinal section of the air-cooled TC4-1Cu-0.8Sn alloy, respectively. It can be seen that the transverse section of the air-cooled TC4-1Cu-0.8Sn alloy has a large number of fine lath-like α+β phase (light color area) distributed in a cross-basket net shape (middle dense light color strip). Figure 14 and Figure 15 It can be seen that the transverse section of the air-cooled TC4-1Cu-0.8Sn alloy has a large number of fine lath-like α+β phase (light color area) distributed in a cross-basket net shape (middle dense light color strip).

[0063] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application rather than limiting them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements also cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. Titanium alloy based on SLM technology, characterized in that, The titanium alloy is one of a Ti-Cu-Sn titanium alloy or a TC4-Cu-Sn titanium alloy, a molar ratio of Ti, Cu and Sn in the Ti-Cu-Sn titanium alloy is 1:1.5-4.5:0.6-1.8, and a molar ratio of TC4, Cu and Sn in the TC4-Cu-Sn titanium alloy is 1:1-3:0.8-2.

4.

2. A composition design method for a titanium alloy based on SLM technology, characterized by, The titanium alloy in claim 1 is designed in composition by using an SLM technology to obtain a deposited Ti-Cu-Sn alloy or a deposited TC4-Cu-Sn alloy.

3. The method of claim 2, wherein, Process parameters of the SLM technology are as follows: a laser power is 170-180 W, a scanning speed is 1300-1500 mm / s, a spot diameter is 0.08-0.12 mm, a powder thickness is 0.02-0.04 mm, and an atmosphere is Ar gas.

4. The method of claim 2, wherein, The deposited Ti-Cu-Sn alloy has a yield strength of >785 MPa, a tensile strength of >891 MPa and an elongation of >7.8%, and the deposited TC4-Cu-Sn alloy has a yield strength of >1041 MPa, a tensile strength of >1252 MPa and an elongation of >9.0%.

5. The method of claim 2, wherein, Surface micro-morphology of the deposited Ti-Cu-Sn alloy is in a fine and dense lath-shaped alpha phase in a cross-basket net distribution, and surface transverse micro-morphology of the deposited TC4-Cu-Sn alloy is in a fine needle-shaped alpha' sheet or sheet bundle in a cross-basket net distribution, and longitudinal micro-morphology is in columnar crystals growing in a vertical direction and filled with fine needle-shaped alpha' phase or lath-shaped alpha' phase in a cross-basket net distribution.

6. The method of claim 5, wherein, The lath-shaped alpha' phase has a width of 0.1-0.3 μm, the columnar crystal has a width of 80-150 μm, and the lath-shaped alpha' phase has a width of 0.1-0.3 μm.

7. The method of claim 2, wherein, The deposited Ti-Cu-Sn alloy is heat-treated by being annealed after being kept at 700-800 ℃ for 0.5-2 h and then air-cooled to obtain an air-cooled Ti-Cu-Sn alloy. The deposited TC4-Cu-Sn alloy is heat-treated by being annealed after being kept at 700-800 ℃ for 0.5-2 h and then air-cooled to obtain an air-cooled TC4-Cu-Sn alloy, or quenched after being kept at 750-850 ℃ for 1-3 h to obtain a quenched TC4-Cu-Sn alloy.

8. The method of claim 7, wherein, The air-cooled Ti-Cu-Sn alloy has a yield strength of >517 MPa, a tensile strength of >627 MPa and an elongation of >13.7%, the air-cooled TC4-Cu-Sn alloy has a yield strength of >1050 MPa, a tensile strength of >1102 MPa and an elongation of >3.22%, and the quenched TC4-Cu-Sn alloy has a yield strength of >680 MPa, a tensile strength of >1029 MPa and an elongation of >16.4%.

9. The method of claim 7, wherein, The surface micro-morphology of the air-cooled Ti-Cu-Sn alloy is the combination and coarsening of the lath-shaped alpha phase and the precipitation of intermetallic compound Ti2Cu, and the width of the coarsened lath-shaped alpha phase is 15-30 μm; the surface micro-morphology of the air-cooled TC4-Cu-Sn alloy is the transformation of the needle-shaped alpha' phase and the lath-shaped alpha' phase into the cross-basket-shaped distributed alpha+beta lath bundle, and the width of the alpha+beta lath bundle is 0.5-1.4 μm.

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