A heat treatment process for a dental Ti-Zr alloy additively manufactured piece

Abstract

The application belongs to the technical field of additive manufacturing titanium alloy, and particularly relates to a heat treatment method of additive manufacturing Ti-Zr alloy for dentistry. The Ti-Zr alloy is Ti-15Zr alloy after annealing treatment and additive manufacturing; the additive manufacturing comprises an SLM process, and SLM forming parameters are as follows: laser energy density is 100-110 J / mm 3 , laser power is 180-210 W, scanning speed is 800-1200 mm / s, scanning interval is 0.07-0.09 mm, and powder layer thickness is 0.02-0.04 mm. The annealing treatment temperature is 780-820 DEG C, the holding time is 25-35 min, and the product is obtained through water quenching. The ultimate tensile strength of the obtained product is 1265-1275 MPa, the yield strength is 1015-1020 MPa, and the elongation is 10.6-10.7%. The application has simple and controllable process, high efficiency, and excellent product performance, and is convenient for large-scale industrial application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of additive manufacturing of titanium alloys, and particularly relates to a heat treatment method for additive manufacturing of Ti-Zr alloy for dentistry. BACKGROUND

[0002] Ti-Zr alloy has good biocompatibility, wear resistance, corrosion resistance and mechanical properties, and has been used in the field of dental materials. Commercial Ti-Zr alloy is mainly prepared by casting and deformation processing, and the process is relatively complex, and the control of the microstructure and properties is difficult. Selective laser melting (SLM) technology can directly realize the near-net-shape forming of complex parts, and is the main solution for manufacturing complex titanium alloy parts. However, the extremely high cooling rate in the SLM process causes a large amount of needle-shaped alpha prime martensite to be generated in the titanium alloy, which seriously affects the plasticity of the titanium alloy. In addition, due to the input of local laser energy in the SLM forming process, the SLM formed parts often contain high residual thermal stress, which makes the parts prone to deformation and cracking, and the mechanical properties decrease. Therefore, for SLM formed parts, it is necessary to adjust the microstructure through appropriate heat treatment to improve the strength and toughness matching, and to eliminate the internal residual thermal stress.

[0003] According to the previous research work of the research group (such as the patent with application number 2023106306467), when the laser energy density is between 69-125 J / mm 3 , SLM can form Ti-Zr alloy with a density greater than 99%, and the specific parameter range is laser power of 250-350 W, scanning speed of 800-1200 mm / s, powder layer thickness of 0.02-0.04 mm, and scanning spacing of 0.06-0.1 mm. The tensile strength of the as-printed product is 963-1003 MPa, the yield strength is 897-921 MPa, and the elongation is 5.6-8.2%. The as-printed product has high strength but low ductility. For biomedical titanium alloy, the elongation generally requires to be greater than 10%, therefore the research group adopts an annealing process (temperature of 550-650℃, time of 1.5-2.5h) to process the above-mentioned printed parts. After annealing treatment, the tensile strength of the annealed product is 679-950 MPa, the yield strength is 629-890.9 MPa, and the elongation is 9.9-23.1%. In this technology, it is found that when the strength of the product reaches 950 MPa, the elongation is as low as 10.5%, and it is also found that the elongation of the product decreases significantly with the increase of the strength of the product.

[0004] The present application improves the ductility of the as-printed alloy through subsequent heat treatment to obtain an alloy with high comprehensive performance. SUMMARY

[0005] To date, there is very little research on the heat treatment of SLM-formed Ti-15Zr alloys. Based on our group's previous research, this invention, through optimization of the printing and heat treatment processes, has for the first time yielded a dental Ti-Zr alloy with a tensile strength greater than 1200 MPa and an elongation greater than or equal to 10.6%.

[0006] This invention achieves excellent performance in dental additive manufacturing parts by controlling the morphology of acicular α′ martensite and eliminating residual stress inside the additively manufactured parts.

[0007] This invention discloses a heat treatment process for dental Ti-Zr alloy additive manufacturing parts; the Ti-Zr alloy is a Ti-15Zr alloy that has undergone additive manufacturing and annealing; the additive manufacturing includes an SLM process, with the following SLM forming parameters: laser energy density of 100–110 J / mm². 3 The laser power is 180–210W, the scanning speed is 800–1200 mm / s, the scanning interval is 0.07–0.09 mm, and the powder layer thickness is 0.02–0.04 mm. The annealing treatment is carried out at a temperature of 780–820℃ for a holding time of 25–35 min, followed by water quenching to obtain the product.

[0008] In the Ti-Zr alloy of this invention, the Zr mass percentage content is 14.85–15.15 wt%, preferably 15 wt%.

[0009] As a preferred option, the SLM forming parameters are as follows: laser energy density of 10⁴ J / mm². 3 The laser power is 200W, the scanning speed is 1000mm / s, the scanning interval is 0.08mm, and the powder layer thickness is 0.03mm.

[0010] Preferably, the annealing treatment is performed at a temperature of 800°C and a holding time of 30 minutes, followed by water quenching to obtain the product.

[0011] This invention is based on 2023106306467. During further research and development, it was discovered that using lower printing power, combined with higher subsequent heat treatment temperature and reduced heat preservation time, can further improve the strength of the product and increase its elongation.

[0012] This invention discloses a heat treatment process for dental Ti-Zr alloy additive manufacturing parts. The Ti-Zr alloy exhibits a layered and acicular dual-phase structure, demonstrating excellent strength-ductility balance. Its ultimate tensile strength is 1265–1275 MPa, yield strength is 1015–1020 MPa, and elongation is 10.6–10.7%. Compared to patent 2023106306467, this invention achieves a strength as high as 1265–1275 MPa and an elongation of 10.6%–10.7% for the first time. This exceeds initial estimates.

[0013] Principles and advantages

[0014] This invention reduces the printing power to 180-210W and, with other appropriate printing parameters, obtains a preform composed of columnar primary β grains and fine acicular martensite phases distributed between the β grains. Then, through a higher heat treatment temperature and appropriate heat treatment time, a product is obtained consisting of acicular and layered structures, with some acicular structures exhibiting a high aspect ratio. The relatively fine acicular martensite is interspersed between the slender acicular structures, which is one of the reasons why the product obtained by this invention has extremely high ultimate tensile strength and high elongation. Furthermore, the fine acicular martensite phases in the printed state of this invention exhibit diverse orientations and different aspect ratios, while the structure of the product obtained after heat treatment is disordered and randomly arranged. This ensures that this invention does not suffer from significant anisotropy. Attached Figure Description

[0015] Figure 1 The image shows the microstructure of the printed Ti-Zr alloy obtained in Example 1.

[0016] Figure 2 The stress-strain curve of the printed Ti-Zr alloy obtained in Example 1 is shown.

[0017] Figure 3 The image shows the microstructure of the product obtained after heat treatment of the printed Ti-Zr alloy obtained in Example 1.

[0018] Figure 4 The stress-strain curve of the product obtained by heat treatment of the printed Ti-Zr alloy obtained in Example 1 is shown.

[0019] Figure 5 The images show the IPF diagram, grain size distribution diagram, and KAM diagram of the printed and quenched products obtained in Example 1.

[0020] from Figure 1 The microstructure of the printed Ti-Zr alloy product can be observed, from which... Figure 1 As shown in (a), the printed Ti-Zr alloy surface is dense, with no obvious pores or defects. Figure 1As shown in (b), the microstructure of the printed Ti-Zr alloy consists of columnar primary β grains and fine acicular martensite phases distributed between the β grains. Figure 1 The magnified images of (c) and 1(d) show that these fine needle-like martensite phases have diverse orientations and different aspect ratios, which is caused by the rapid cooling and thermal cycling characteristics during the SLM forming process.

[0021] from Figure 2 It can be seen that the printed Ti-Zr alloy obtained in Example 1 has high tensile strength, with an ultimate tensile strength of 983±20MPa, a yield strength of 909±12MPa, and an elongation of 6.9±1.3%.

[0022] from Figure 3 It can be seen that in the quenched state, the microstructure of the alloy consists of acicular and layered structures. Some of the acicular structures have a high aspect ratio. Relatively small acicular martensite is interspersed between the slender acicular structures. The structure is randomly oriented and arranged.

[0023] from Figure 4 It can be seen that in the quenched state, the alloy's maximum tensile strength is 1270 MPa, its maximum yield strength is 1019 MPa, and its elongation is 10.6%.

[0024] Figure 5 In the figure, (a), (c), and (e) are the IPF diagram, grain size distribution diagram, and KAM diagram of the printed state, respectively; (b), (d), and (f) are the IPF diagram, grain size distribution diagram, and KAM diagram of the water-quenched state, respectively. Figure 5 Combination Figure 4 , Figure 2 As can be seen from the figure, the grain size of the Ti-Zr alloy increases and the internal dislocation density decreases after heat treatment. Therefore, compared with the printed Ti-Zr alloy, the hardness and tensile strength of the heat-treated Ti-Zr alloy decrease, while the elongation increases. Detailed Implementation

[0025] Example 1

[0026] According to the design composition: Zr 15 wt% balance Ti, each component is prepared and powder is obtained by melting and gas atomization powdering process. Then, it is sieved to obtain powder with a particle size of 10-100μm, which is used as spare powder. The composition of the spare powder is basically the same as that of Ti-15Zr purchased on the market.

[0027] The spare powder is used for SLM printing to obtain the printed product;

[0028] The SLM forming parameters are as follows: laser energy density is 10⁴ J / mm². 3The laser power is 200W, the scanning speed is 1000mm / s, the scanning interval is 0.08mm, and the powder layer thickness is 0.03mm.

[0029] The microstructure of printed Ti-Zr alloy products is as follows: Figure 1 As shown. First, from Figure 1 As shown in (a), the printed Ti-Zr alloy surface is dense, with no obvious pores or defects. Figure 1 As shown in (b), the microstructure of the printed Ti-Zr alloy consists of columnar primary β grains and fine acicular martensite phases distributed between the β grains. Figure 1 The magnified images of (c) and 1(d) show that these fine needle-like martensite phases have diverse orientations and different aspect ratios, which is caused by the rapid cooling and thermal cycling characteristics during the SLM forming process.

[0030] The printed product was heated to 800℃ at a heating rate of 10℃ / min, held for 0.5h, and then water-quenched to obtain the quenched product. The alloy has an ultimate tensile strength of 1270MPa, a yield strength of 1019MPa, and an elongation of 10.6%. In the quenched state, the alloy microstructure consists of acicular and layered structures. Some of the acicular structures have a high aspect ratio, and relatively fine acicular martensite is interspersed between the slender acicular structures. The microstructure is randomly oriented and arranged.

[0031] Comparative Example 1

[0032] Ti-50at.%Zr binary alloy ingots were prepared using pure Zr and pure Ti. The ingots were repeatedly melted five times in a vacuum arc furnace under an argon atmosphere to ensure uniform chemical composition. The ingots were homogenized at 800℃ for 6 hours. Subsequently, they were solution treated at 620℃ for 1 hour and then water quenched. The resulting samples had a tensile strength of 830 MPa and an elongation of 6%.

[0033] Comparative Example 2

[0034] Pure Ti and pure Zr were melted four times in an electric arc furnace under an argon atmosphere to obtain a Ti-30 at.% Zr ingot. The ingot was mechanically cut into 5 mm thick sheets, which were then cold-rolled at room temperature until the thickness was reduced by 60%. The sheets were then vacuum-sealed in quartz tubes, annealed at 973 K for 0.5 h, and then water-quenched. The resulting sample had a tensile strength of 760 MPa, a yield strength of 400 MPa, and an elongation of 7.6%.

[0035] Comparative Example 3

[0036] Other conditions were the same as in Example 1, except that the printed product was heated to 1000℃ at a heating rate of 10℃ / min, held for 1 hour, and then water-quenched to obtain the quenched product. The alloy had an ultimate tensile strength of 831 MPa, a yield strength of 700 MPa, and an elongation of 13.2%.

[0037] Comparative Example 4

[0038] Other conditions were the same as in Example 1, except that the printed product was heated to 1000°C at a heating rate of 10°C / min, held at that temperature for 1 hour, and then air-cooled. This yielded an air-cooled annealed product. The ultimate tensile strength of the air-cooled annealed product was 731 MPa, the yield strength was 687 MPa, and the elongation was 12.9%.

[0039] Comparative Example 5

[0040] Other conditions were the same as in Example 1, except that the printed product was heated to 1000°C at a heating rate of 10°C / min and held at that temperature for 1 hour before being furnace cooled. This yielded a furnace-cooled annealed product. The furnace-cooled annealed product had an ultimate tensile strength of 680 MPa, a yield strength of 606 MPa, and an elongation of 14.5%.

[0041] Comparative Example 6

[0042] Other conditions were the same as in Example 1, except that the printed product was heated to 800°C at a heating rate of 10°C / min, held at that temperature for 1 hour, and then water-quenched. This yielded a quenched product. The quenched product had an ultimate tensile strength of 852 MPa, a yield strength of 762 MPa, and an elongation of 15.7%.

[0043] Comparative Example 7

[0044] Other conditions were the same as in Example 1, except that the printed product was heated to 800°C at a heating rate of 10°C / min, held at that temperature for 1 hour, and then air-cooled. This yielded an air-cooled annealed product. The ultimate tensile strength of the air-cooled annealed product was 786 MPa, the yield strength was 690 MPa, and the elongation was 15.5%.

[0045] Comparative Example 8

[0046] Other conditions were the same as in Example 1, except that the printed product was heated to 800°C at a heating rate of 10°C / min and held at that temperature for 1 hour before being furnace cooled. This yielded a furnace-cooled annealed product. The furnace-cooled annealed product had an ultimate tensile strength of 778 MPa, a yield strength of 705 MPa, and an elongation of 14.9%.

[0047] Comparative Example 9

[0048] Other conditions were the same as in Example 1, except that the printed product was heated to 750°C at a heating rate of 10°C / min, held at that temperature for 1 hour, and then water-quenched. This yielded a quenched product. The quenched product had an ultimate tensile strength of 793 MPa, a yield strength of 710 MPa, and an elongation of 9.1%.

[0049] Comparative Example 10

[0050] Other conditions were the same as in Example 1, except that the printed product was heated to 750°C at a heating rate of 10°C / min, held at that temperature for 1 hour, and then air-cooled. This yielded an air-cooled annealed product. The ultimate tensile strength of the air-cooled annealed product was 788 MPa, the yield strength was 709 MPa, and the elongation was 18.1%.

[0051] Comparative Example 11

[0052] Other conditions were the same as in Example 1, except that the printed product was heated to 750°C at a heating rate of 10°C / min, held at that temperature for 1 hour, and then cooled in the furnace. This yielded a furnace-cooled annealed product. The ultimate tensile strength of the furnace-cooled annealed product was 823 MPa, the yield strength was 750 MPa, and the elongation was 14.2%.

[0053] Comparative Example 12

[0054] Other conditions were the same as in Example 1, except that the printed product was heated to 800°C at a heating rate of 10°C / min, held at that temperature for 2 hours, and then water-quenched. This yielded a quenched product. The ultimate tensile strength of the quenched product was 966 MPa, the yield strength was 817 MPa, and the elongation was 9.53%.

[0055] Comparative Example 13

[0056] Other conditions were the same as in Example 1, except that the printed product was heated to 800°C at a heating rate of 10°C / min and held at that temperature for 0.5 hours before being furnace cooled. This yielded a furnace-cooled annealed product. The ultimate tensile strength of the furnace-cooled annealed product was 808 MPa, the yield strength was 727 MPa, and the elongation was 14%.

[0057] Comparative Example 14

[0058] Other conditions were the same as in Example 1, except that the printed product was heated to 800°C at a heating rate of 10°C / min and held for 2 hours before being furnace cooled. This yielded a furnace-cooled annealed product. The ultimate tensile strength of the furnace-cooled annealed product was 752 MPa, the yield strength was 662 MPa, and the elongation was 15.1%.

[0059] Comparative Example 15

[0060] Other conditions were the same as in Example 1, except that the printed product was heated to 1000℃ at a heating rate of 10℃ / min, held for 1 hour, and then water-quenched. It was then heated to 800℃ at a heating rate of 10℃ / min, held for 1 hour, and water-quenched again. This resulted in a product that had undergone two quenching and annealing processes. The resulting product had an ultimate tensile strength of 825 MPa, a yield strength of 708 MPa, and an elongation of 9.3%.

[0061] Comparative Example 16

[0062] Other conditions were the same as in Example 1, except that the printed product was heated to 1000℃ at a heating rate of 10℃ / min, held for 1 hour, and then water-quenched. It was then heated to 650℃ at a heating rate of 10℃ / min, held for 1 hour, and water-quenched again. This resulted in a product that had undergone two quenching and annealing processes. The resulting product had an ultimate tensile strength of 785 MPa, a yield strength of 701 MPa, and an elongation of 14%.

[0063] Comparative Example 17

[0064] Other conditions were the same as in Example 1, except that the printed product was heated to 1000℃ at a heating rate of 10℃ / min and held for 1 hour before water quenching, then heated to 550℃ at a heating rate of 10℃ / min and held for 1 hour before water quenching again. This resulted in a product that had undergone two quenching and annealing processes. The resulting product had an ultimate tensile strength of 813 MPa, a yield strength of 740 MPa, and an elongation of 9.6%.

Claims

1. A heat treatment process for dental Ti-Zr alloy additive manufacturing parts; characterized in that: The Ti-Zr alloy is an additively manufactured and annealed Ti-15Zr alloy; the additive manufacturing includes SLM (Surface Mount Technology) process, with the following SLM forming parameters: laser energy density of 104 J / mm². 3 The laser power was 200 W, the scanning speed was 1000 mm / s, the scanning interval was 0.08 mm, and the powder layer thickness was 0.03 mm; the annealing temperature was 800℃, the holding time was 30 min, and the product was obtained by water quenching. Ti-Zr alloys exhibit a dual-phase structure characterized by both layered and acicular structures. The fine needle-like martensite phases in the printed state exhibit diverse orientations and varying aspect ratios. The product obtained after heat treatment has a disordered and haphazardly arranged microstructure. The resulting product has an ultimate tensile strength of 1265~1275 MPa, a yield strength of 1015~1020 MPa, and an elongation of 10.6~10.7%.

2. The heat treatment process for a dental Ti-Zr alloy additive manufacturing part according to claim 1; characterized in that: In the Ti-Zr alloy, the Zr mass percentage content is 14.85~15.15 wt%.

3. The heat treatment process for a dental Ti-Zr alloy additive manufacturing part according to claim 1; characterized in that: In the Ti-Zr alloy, the Zr mass percentage is 15 wt%.

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