A 1100mpa grade high strength cast titanium alloy

Abstract

The application discloses a 1100MPa high-strength cast titanium alloy, which contains, in percentage by weight, Al: 6.5-7.0%, Sn: 2.0-3.0%, Mo: 1.5-2.5%, Cr: 1.5-2.5%, Zr: 4.0-4.5%, Nb: 1.0-2.0%, Gd: 0.2-0.4%, Si: 0.1-0.3%, and the balance of Ti and inevitable impurities. The application adds Zr element in the titanium alloy, so that the crystal lattice of the titanium alloy is distorted, the difficulty of dislocation slip is increased, the crystal lattice distortion serves as a nucleation point in the alloy solidification and crystallization process, the grain size is refined, and the comprehensive mechanical properties of the alloy are improved. Meanwhile, a small amount of Gd is introduced into the alloy, so that the quality consistency of different structural features of a large complex titanium alloy casting is improved. The alloy has a tensile strength of 1100MPa and good casting performance, can be used for integrated forming of complex components in aerospace and the like, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to a 1100MPa-grade high-strength cast titanium alloy, and particularly to a 1100MPa-grade high-strength cast titanium alloy applied in the field of light alloy materials technology. Background Technology

[0002] With the continuous improvement of China's industrial manufacturing capabilities, aerospace vehicles have put forward higher requirements for indicators such as flight speed and flight distance. High-strength titanium alloys have advantages such as low density, high specific strength and good corrosion resistance. They can replace some high-strength steel components, achieving dual weight reduction in aircraft materials and structures, and are widely used in aerospace and other fields.

[0003] Since the 1970s, high-strength β-titanium alloys with strengths ranging from 1000MPa to 1400MPa have been developed abroad and applied to aircraft load-bearing components, resulting in weight reductions of over 20% in aircraft structures. However, existing high-strength titanium alloys are all forged titanium alloys, mainly used for titanium alloy profiles and plates. Currently, cast titanium alloys all use the alloy composition of forged titanium alloys without optimizing the composition for the specific characteristics of the casting process. This leads to problems such as cracking during the casting process of high-strength titanium alloys, making them unsuitable for integrated casting forming processes. Existing cast titanium alloys that have achieved engineering applications all have strengths below 1000MPa. Developing 1100MPa-grade high-strength cast titanium alloys has high practical value for lightweight design and integrated forming of structural components in aerospace and other fields.

[0004] Application content

[0005] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is to overcome the problem of easy cracking in the casting process of existing high-strength titanium alloys, and to provide a 1100MPa grade high-strength cast titanium alloy.

[0006] To address the aforementioned problems, this invention provides a 1100MPa-grade high-strength cast titanium alloy, which, by weight percentage, contains Al: 6.5%-7.0%, Sn: 2.0-3.0%, Mo: 1.5-2.5%, Cr: 1.5-2.5%, Zr: 4.0-4.5%, Nb: 1.0-2.0%, Gd: 0.2-0.4%, Si: 0.1-0.3%, with the balance being Ti and unavoidable impurities.

[0007] In the above-mentioned 1100MPa grade high-strength cast titanium alloy, the room temperature tensile strength of the titanium alloy is not less than 1100MPa and the elongation is not less than 6%, and the tensile strength at 350℃ is not less than 580MPa and the elongation is not less than 8%. The alloy fluidity is comparable to that of ZTA15 alloy, which meets the application requirements of cast titanium alloy under high strength conditions.

[0008] As a further improvement to this application, the composition consists of the following components in weight percentage: Al: 6%, Sn: 2.5%, Mo: 1.5%, Cr: 2.0%, Zr: 4.0%, Nb: 1.5%, Gd: 0.2%, Si: 0.2%, with the balance being Ti and unavoidable impurities.

[0009] As a further improvement to this application, the composition consists of the following components in weight percentage: Al: 7.0%, Sn: 2.0%, Mo: 1.5%, Cr: 2.0%, Zr: 4.5%, Nb: 1%, Gd: 0.3%, Si: 0.3%, with the balance being Ti and unavoidable impurities.

[0010] As a further improvement to this application, the composition consists of the following components in weight percentage: Al: 6.5%, Sn: 2.2%, Mo: 2.5%, Cr: 2.0%, Zr: 4.2%, Nb: 2%, Gd: 0.4%, Si: 0.1%, with the balance being Ti and unavoidable impurities.

[0011] As another improvement of this application, a method for preparing a 1100MPa high-strength cast titanium alloy specifically includes the following steps:

[0012] Step 1: Prepare alloy raw materials according to the above-mentioned composition range requirements;

[0013] Step 2: After thoroughly mixing the prepared raw materials, clean them and press them into electrodes;

[0014] Step 3: Melt twice in a vacuum consumable electrode arc furnace to obtain a secondary high-strength titanium alloy ingot;

[0015] Step 4: After peeling and cleaning the high-strength titanium alloy secondary ingot, it is melted in a vacuum consumable electrode arc solidification furnace and poured into the mold cavity. After cooling, it forms a high-strength titanium alloy casting and attached sample.

[0016] Step 5: The high-strength titanium alloy casting and the attached casting sample are subjected to hot isostatic pressing and heat treatment to obtain the 1100MPa grade high-strength titanium alloy casting and the attached casting sample.

[0017] As a further improvement to this application, the hot isostatic pressing step in step five is as follows:

[0018] A. Place the high-strength titanium alloy casting and the attached casting sample into a sealed pressure-resistant container, evacuate the container, and then introduce argon gas with a pressure of 100-140MPa.

[0019] B. Heating the sealed pressure vessel at a temperature of 910-1000℃.

[0020] C. After heat preservation for 2-2.5 hours, wait for the sealed pressure vessel to air cool to below 300℃, and then take out the high-strength titanium alloy casting and attached sample from the sealed pressure vessel.

[0021] As a further improvement to this application, the heat treatment in step five is a thermal hydrogen treatment, which includes the following steps:

[0022] A1. After the high-strength titanium alloy castings and attached samples that have undergone hot isostatic pressing are cleaned and dried, they are placed in a hydrogenation furnace and then vacuumed.

[0023] A2. Turn on the temperature control system to heat the inside of the hydrogenation furnace until the internal temperature of the hydrogenation furnace reaches 700-750℃, then close the vacuum valve.

[0024] A3. Fill the hydrogenation furnace with hydrogen gas at a pressure of 0.7-5 bar. Keep the temperature until the hydrogen gas pressure in the hydrogenation furnace stabilizes. This step is recorded as step 1.

[0025] A4. Continue to fill the hydrogenation furnace with hydrogen and keep it warm until the hydrogen pressure in the hydrogenation furnace is stable. At this time, the hydrogen filling step number is +1.

[0026] A5. Repeat A4 until the hydrogen content in the hydrogenation furnace is 2.5%-4.5%;

[0027] A6. After the final step of hydrogen charging and heat preservation, air cool to room temperature and remove the high-strength titanium alloy casting and attached sample from the hydrogenation furnace.

[0028] As a further improvement to this application, the alloy raw materials in step one, namely Ti, Al, Sn, Mo, Cr, Zr, Nb, Gd, and Si, are respectively selected from grade 0 sponge titanium, pure aluminum, high-purity tin, Al-80Mo, pure chromium, sponge zirconium, Al-75Nb, Al-30Gd, and Al-10Si.

[0029] In summary, the beneficial effects of the present invention are as follows:

[0030] 1. This invention improves the strength of titanium alloys by adding 6.5-7.0% Al, 2.0-3.0% Sn, 1.5-2.5% Mo, 1.5-2.5% Cr, 4.0-4.5% Zr, 1.0-2.0% Nb, 0.2-0.4% Gd, and 0.1-0.3% Si by mass percentage, while also giving the alloys good plasticity and casting properties.

[0031] 2. The high-strength titanium alloy of the present invention contains 6.5-7.0% by mass of Al element. Al atoms exist in the titanium alloy in a substitutional manner. The higher Al content increases the solubility of β-stabilizing elements in the α phase, thereby playing a strengthening role, while ensuring the thermal stability of the high-strength titanium alloy during the casting process.

[0032] 3. The high-strength titanium alloy of this invention contains 4.0%-4.5% Zr by mass. Zr atoms distort the lattice of the titanium alloy, increasing the lattice constants a and c of the α phase, thus increasing the difficulty of dislocation slip. Simultaneously, the lattice distortion acts as nucleation points during the alloy's solidification process, refining the grain size. In summary, the addition of Zr significantly improves the overall mechanical properties of the titanium alloy. Furthermore, excessive Zr content reduces the alloy's casting performance; a Zr content of 4.0%-4.5% ensures the alloy's fluidity and filling properties, among other casting characteristics.

[0033] 4. The high-strength titanium alloy of the present invention contains 0.2-0.4% Gd by mass, which can improve the creep resistance, thermal stability and fatigue performance of the alloy. At the same time, it helps to ensure the uniformity of microstructure and performance of thick and variable cross-section parts, and improve the quality consistency of different structural features of large and complex titanium alloy castings.

[0034] 5. The high-strength titanium alloy of the present invention can obtain high mechanical properties through hot isostatic pressing and simple heat treatment, with a room temperature tensile strength of not less than 1100 MPa and an elongation of not less than 6%, and a tensile strength of not less than 580 MPa and an elongation of not less than 8% at 350°C.

[0035] 6. Compared with traditional high-strength titanium alloys, the high-strength titanium alloy of the present invention has better casting properties such as fluidity and filling properties. Its casting properties are similar to those of ZTA15, which meets the requirements of complex structure castings for titanium alloy filling performance. Attached Figure Description

[0036] Figure 1 This is a flowchart of the preparation method of this application. Detailed Implementation

[0037] The following describes in detail six embodiments of this application with reference to the accompanying drawings.

[0038] Implementation method 1:

[0039] According to the nominal composition (mass percentage) of the alloy: Ti: balance, Al: 6.5%, Sn: 2.5%, Mo: 1.5%, Cr: 2.0%, Zr: 4.0%, Nb: 1.5%, Gd: 0.2%, Si: 0.2%, the following materials were weighed: Grade 0 sponge titanium, pure aluminum, high-purity tin, Al-80Mo, pure chromium, sponge zirconium, Al-75Nb, Al-30Gd, and Al-10Si.

[0040] After cleaning the raw materials, the electrodes were pressed and then smelted twice in a vacuum consumable arc furnace to obtain a secondary titanium alloy ingot. The secondary titanium alloy ingot was peeled and cleaned, then smelted in a vacuum consumable arc furnace and poured into the mold cavity. After cooling, a high-strength titanium alloy casting and an attached casting sample were formed. The attached casting sample was subjected to hot isostatic pressing and stress-relief annealing heat treatment to obtain a 1100MPa grade high-strength titanium alloy casting and an attached casting sample. The mechanical properties of the attached casting sample were tested.

[0041] The second implementation method:

[0042] According to the nominal composition (mass percentage) of the alloy: Ti: balance, Al: 7.0%, Sn: 2.0%, Mo: 1.5%, Cr: 2.0%, Zr: 4.5%, Nb: 1%, Gd: 0.3%, Si: 0.3%, the following materials were weighed: Grade 0 sponge titanium, pure aluminum, high-purity tin, Al-80Mo, pure chromium, sponge zirconium, Al-75Nb, Al-30Gd, and Al-10Si.

[0043] After cleaning the raw materials, the electrodes were pressed and then smelted twice in a vacuum consumable arc furnace to obtain a secondary titanium alloy ingot. The secondary titanium alloy ingot was peeled and cleaned, then smelted in a vacuum consumable arc furnace and poured into the mold cavity. After cooling, a high-strength titanium alloy casting and an attached casting sample were formed. The attached casting sample was subjected to hot isostatic pressing and stress-relief annealing heat treatment to obtain a 1100MPa grade high-strength titanium alloy casting and an attached casting sample. The mechanical properties of the attached casting sample were tested.

[0044] The third implementation method:

[0045] According to the nominal composition (mass percentage) of the alloy: Ti: balance, Al: 6.5%, Sn: 2.2%, Mo: 2.5%, Cr: 2.0%, Zr: 4.2%, Nb: 2%, Gd: 0.4%, Si: 0.1%, the following materials were weighed: Grade 0 sponge titanium, pure aluminum, high-purity tin, Al-80Mo, pure chromium, sponge zirconium, Al-75Nb, Al-30Gd, and Al-10Si.

[0046] After cleaning the raw materials, the electrodes were pressed and then smelted twice in a vacuum consumable arc furnace to obtain a secondary titanium alloy ingot. The secondary titanium alloy ingot was peeled and cleaned, then smelted in a vacuum consumable arc furnace and poured into the mold cavity. After cooling, a high-strength titanium alloy casting and an attached casting sample were formed. The attached casting sample was subjected to hot isostatic pressing and stress-relief annealing heat treatment to obtain a 1100MPa grade high-strength titanium alloy casting and an attached casting sample. The mechanical properties of the attached casting sample were tested.

[0047]

[0048] Based on the above experimental data, it can be seen that the higher the Al content, the higher the strength of the titanium alloy, while the ductility is lower and the stability is stronger in high-temperature environments.

[0049] Furthermore, when the Gd content is controlled in the range of 0.2-0.3%, the tensile strength of the titanium alloy increases with the increase of Gd content. When it is in the range of 0.3-0.4%, the tensile strength of the titanium alloy decreases with the increase of Gd content. Therefore, in order to maximize the tensile strength of the titanium alloy, the amount of Gd added can be controlled at around 0.3%.

[0050] Furthermore, when the Zr content is in the range of 4-4.2%, the tensile strength of the titanium alloy decreases with increasing Zr content, while in the range of 4.2-4.5%, the tensile strength of the titanium alloy increases with increasing Zr content. Therefore, it can be seen that the tensile strength of the titanium alloy is at its lowest point when the Zr content is around 4.2%. Thus, when actually adding Zr, it is sufficient to control the content to around 4% or 4.5%.

[0051] The fourth implementation method:

[0052] The raw materials were prepared according to the proportions in the second embodiment to obtain high-strength titanium alloy castings and attached casting samples.

[0053] During the hot isostatic pressing process, A. the high-strength titanium alloy casting and the attached casting sample are sent into a sealed pressure-resistant container, and after evacuation, argon gas with a pressure of 100MPa is introduced.

[0054] B. Heating the sealed pressure vessel at a temperature controlled at 910℃.

[0055] C. After heat preservation for 2 hours, wait for the sealed pressure vessel to air cool to below 300℃, and then take out the high-strength titanium alloy casting and attached sample from the sealed pressure vessel.

[0056] After heat treatment, A1, the high-strength titanium alloy castings and attached samples that have undergone hot isostatic pressing are cleaned and dried and then placed in a hydrogenation furnace and vacuumed.

[0057] A2. Turn on the temperature control system to heat the inside of the hydrogenation furnace until the internal temperature of the hydrogenation furnace reaches 700℃, then close the vacuum valve.

[0058] A3. Fill the hydrogenation furnace with hydrogen gas at a pressure of 3 bar. Keep the temperature until the hydrogen gas pressure in the hydrogenation furnace stabilizes. At this point, the hydrogen filling step is recorded as step 1.

[0059] A4. Continue to fill the hydrogenation furnace with hydrogen and keep it warm until the hydrogen pressure in the hydrogenation furnace is stable. At this time, the hydrogen filling step number is +1.

[0060] A5. Repeat A4 until the hydrogen content in the hydrogenation furnace is 3%;

[0061] A6. After the final step of hydrogen charging and heat preservation, air cool to room temperature and remove the high-strength titanium alloy casting and attached sample from the hydrogenation furnace.

[0062] The mechanical properties of the cast specimens were tested.

[0063] Fifth implementation method:

[0064] The raw materials were prepared according to the proportions in the second embodiment to obtain high-strength titanium alloy castings and attached casting samples.

[0065] During the hot isostatic pressing process, A. the high-strength titanium alloy casting and the attached casting sample are sent into a sealed pressure-resistant container, and after evacuation, argon gas with a pressure of 120MPa is introduced.

[0066] B. Heating the sealed pressure vessel at a temperature controlled at 1000℃.

[0067] C. After heat preservation for 2 hours, wait for the sealed pressure vessel to air cool to below 300℃, and then take out the high-strength titanium alloy casting and attached sample from the sealed pressure vessel.

[0068] After heat treatment, A1, the high-strength titanium alloy castings and attached samples that have undergone hot isostatic pressing are cleaned and dried and then placed in a hydrogenation furnace and vacuumed.

[0069] A2. Turn on the temperature control system to heat the inside of the hydrogenation furnace until the internal temperature of the hydrogenation furnace reaches 750°C, then close the vacuum valve.

[0070] A3. Fill the hydrogenation furnace with hydrogen gas at a pressure of 5 bar. Keep the temperature until the hydrogen gas pressure in the hydrogenation furnace stabilizes. At this point, the hydrogen filling step is recorded as step 1.

[0071] A4. Continue to fill the hydrogenation furnace with hydrogen and keep it warm until the hydrogen pressure in the hydrogenation furnace is stable. At this time, the hydrogen filling step number is +1.

[0072] A5. Repeat A4 until the hydrogen content in the hydrogenation furnace is 2.5%;

[0073] A6. After the final step of hydrogen charging and heat preservation, air cool to room temperature and remove the high-strength titanium alloy casting and attached sample from the hydrogenation furnace.

[0074] The mechanical properties of the cast specimens were tested.

[0075] The sixth implementation method:

[0076] The raw materials were prepared according to the proportions in the second embodiment to obtain high-strength titanium alloy castings and attached casting samples.

[0077] During the hot isostatic pressing process, A. the high-strength titanium alloy casting and the attached casting sample are sent into a sealed pressure-resistant container, and after evacuation, argon gas with a pressure of 100MPa is introduced.

[0078] B. Heating the sealed pressure vessel at a temperature controlled at 1000℃.

[0079] C. After heat preservation for 2 hours, wait for the sealed pressure vessel to air cool to below 300℃, and then take out the high-strength titanium alloy casting and attached sample from the sealed pressure vessel.

[0080] After heat treatment, A1, the high-strength titanium alloy castings and attached samples that have undergone hot isostatic pressing are cleaned and dried and then placed in a hydrogenation furnace and vacuumed.

[0081] A2. Turn on the temperature control system to heat the inside of the hydrogenation furnace until the internal temperature of the hydrogenation furnace reaches 700℃, then close the vacuum valve.

[0082] A3. Fill the hydrogenation furnace with hydrogen gas at a pressure of 3 bar. Keep the temperature until the hydrogen gas pressure in the hydrogenation furnace stabilizes. At this point, the hydrogen filling step is recorded as step 1.

[0083] A4. Continue to fill the hydrogenation furnace with hydrogen and keep it warm until the hydrogen pressure in the hydrogenation furnace is stable. At this time, the hydrogen filling step number is +1.

[0084] A5. Repeat A4 until the hydrogen content in the hydrogenation furnace is 2.5%;

[0085] A6. After the final step of hydrogen charging and heat preservation, air cool to room temperature and remove the high-strength titanium alloy casting and attached sample from the hydrogenation furnace.

[0086] The mechanical properties of the cast specimens were tested.

[0087]

[0088] According to the above test data, when the hydrogen content is 5% and the temperature in the hydrogenation furnace is maintained at around 750°C during the heat treatment process, the tensile strength of the titanium alloy is relatively high. During the hot isostatic pressing process, the higher the argon gas pressure and the higher the heating temperature is maintained at 1000°C, the higher the tensile strength of the titanium alloy.

[0089] In light of current practical needs, the above-described embodiments adopted in this application are not limited to these. Any changes made within the scope of knowledge possessed by those skilled in the art without departing from the concept of this application still fall within the protection scope of this invention.

Claims

1. A high-strength cast titanium alloy with a strength of 1100 MPa, characterized in that, By weight percentage, the alloy contains Al: 6.5%-7.0%, Sn: 2.0-3.0%, Mo: 1.5-2.5%, Cr: 1.5-2.5%, Zr: 4.0-4.5%, Nb: 1.0-2.0%, Gd: 0.2-0.4%, Si: 0.1-0.3%, with the balance being Ti and unavoidable impurities; The preparation method of this alloy includes the following steps: Step 1: Prepare alloy raw materials according to the above-mentioned composition range requirements; Step 2: After thoroughly mixing the prepared raw materials, clean them and press them into electrodes; Step 3: Melt twice in a vacuum consumable electrode arc furnace to obtain a secondary high-strength titanium alloy ingot; Step 4: After peeling and cleaning the high-strength titanium alloy secondary ingot, it is melted in a vacuum consumable electrode arc solidification furnace and poured into the mold cavity. After cooling, it forms a high-strength titanium alloy casting and attached sample. Step 5: The high-strength titanium alloy casting and the attached casting sample are subjected to hot isostatic pressing and heat treatment to obtain the 1100MPa grade high-strength titanium alloy casting and the attached casting sample. The heat treatment in step five is a thermal hydrogen treatment, which includes the following steps: A1. After the high-strength titanium alloy castings and attached samples that have undergone hot isostatic pressing are cleaned and dried, they are placed in a hydrogenation furnace and then vacuumed. A2. Turn on the temperature control system to heat the inside of the hydrogenation furnace until the internal temperature of the hydrogenation furnace reaches 700-750℃, then close the vacuum valve. A3. Fill the hydrogenation furnace with hydrogen gas at a pressure of 0.7-5 bar. Keep the temperature until the hydrogen gas pressure in the hydrogenation furnace stabilizes. This step is recorded as step 1. A4. Continue to fill the hydrogenation furnace with hydrogen and keep it warm until the hydrogen pressure in the hydrogenation furnace is stable. At this time, the hydrogen filling step number is +1. A5. Repeat A4 until the hydrogen content in the hydrogenation furnace is 2.5%-4.5%; A6. After the final step of hydrogen charging and heat preservation, air cool to room temperature and remove the high-strength titanium alloy casting and attached sample from the hydrogenation furnace.

2. The 1100MPa grade high-strength cast titanium alloy according to claim 1, characterized in that, Composed of the following components by mass percentage Composition: Al: 6%, Sn: 2.5%, Mo: 1.5%, Cr: 2.0%, Zr: 4.0%, Nb: 1.5%, Gd: 0.2%, Si: 0.2%, balance Ti and unavoidable impurities.

3. The 1100MPa grade high-strength cast titanium alloy according to claim 1, characterized in that, Composed of the following components by mass percentage composition: Al: 7.0%, Sn: 2.0%, Mo: 1.5%, Cr: 2.0%, Zr: 4.5%, Nb: 1%, Gd: 0.3%, Si: 0.3%, balance Ti and unavoidable impurities.

4. The 1100MPa grade high-strength cast titanium alloy according to claim 1, characterized in that, Composed of the following components by mass percentage composition: Al: 6.5%, Sn: 2.2%, Mo: 2.5%, Cr: 2.0%, Zr: 4.2%, Nb: 2%, Gd: 0.4%, Si: 0.1%, balance Ti and unavoidable impurities.

5. The method for preparing a 1100MPa grade high-strength cast titanium alloy according to claim 1, characterized in that, The hot isostatic pressing step in step five is as follows: A. Place the high-strength titanium alloy casting and the attached casting sample into a sealed pressure-resistant container, evacuate the container, and then introduce argon gas with a pressure of 100-140MPa. B. Heating the sealed pressure vessel at a temperature of 910-1000℃. C. After heat preservation for 2-2.5 hours, wait for the sealed pressure vessel to air cool to below 300℃, and then take out the high-strength titanium alloy casting and attached sample from the sealed pressure vessel.

6. The method for preparing a 1100MPa grade high-strength cast titanium alloy according to claim 1, characterized in that, In step one, the alloy raw materials, namely Ti, Al, Sn, Mo, Cr, Zr, Nb, Gd, and Si, are respectively selected from grade 0 sponge titanium, pure aluminum, high-purity tin, Al-80Mo, pure chromium, sponge zirconium, Al-75Nb, Al-30Gd, and Al-10Si.

Images