A high oxygen-resistant, ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy and its preparation method

Abstract

This invention discloses a high-oxygen-resistant, ultra-high-strength, high-ductility Ti-Cr-Zr-Al-O titanium alloy and its preparation method. The ultra-high-strength, high-ductility titanium alloy is obtained by hot rolling and solution treatment of the Ti-Al-Zr-Cr-O titanium alloy. It comprises 4.7–6% Al, 4.0–5.0% Zr, 2.0–3.5% Cr, 0.3–0.9% O, with the balance being Ti and unavoidable impurity elements. This titanium alloy exhibits excellent room-temperature mechanical properties. Different strength-ductility ratios can be obtained by doping with different O contents. Compared with currently reported titanium alloys, its mechanical properties show a significant advantage in strength and ductility. More importantly, this research result will change the role of oxygen, which has always been considered a destructive factor in titanium and titanium alloys, and shows the possibility of effectively utilizing oxygen and reducing titanium production costs, possessing high application and promotion value.

Description

Technical Field

[0001] This invention relates to the field of high-performance alloy materials technology, specifically to a high oxygen tolerance, ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy and its preparation method. Background Technology

[0002] For both ecological and economic reasons, developing a new generation of ultra-high-strength titanium alloys with excellent ductility has been a long-standing goal in materials science. These alloys are beneficial for weight reduction and improved fuel efficiency, primarily due to their high specific strength and unparalleled corrosion resistance. Currently, titanium alloys are mainly produced through dense, incoherent α-cobalt alloys. s / β nanoprecipitates hinder dislocation movement for strengthening, but incoherent interfaces often lead to high stress concentrations, resulting in a strength-ductility inversion. Besides precipitation strengthening, solid solution strengthening is also an important strengthening mechanism in titanium alloys, especially since interstitial atoms can significantly harden them. However, interstitial oxygen (O) is considered a double-edged sword in titanium alloys; while it can strengthen, it also greatly reduces the alloy's ductility. Therefore, in actual production, high-purity raw materials and complex thermomechanical processing are usually required to prepare high-strength and ductile titanium alloys with ultra-low O content (typically less than 0.2 wt.%). In this case, the manufacturing cost of titanium alloys is relatively high, limiting their further widespread application.

[0003] Recent research has provided new insights into mitigating the O embrittlement effect in pure titanium. One approach is to disrupt the metastable mechanical recombination mechanism of interstitial O atoms through the strong repulsion of Al-O interactions, promoting cross-slip to maintain moderate ductility, but this measure reduces work hardening capacity. Another approach is to dilute the concentration of harmful solutes (e.g., interstitial O) at grain boundaries through grain refinement, which is beneficial for improving grain boundary cohesion and promoting dislocation activity in ultrafine-grained Ti, thereby improving ductility. However, due to limitations in Al content and grain boundary density, the concentration of doped O atoms remains relatively low, approximately 0.3 wt.%. Therefore, how to utilize the significant hardening capacity of O atoms to design high O tolerance and ultra-tough titanium alloys has become an international challenge in materials science. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides an ultra-high strength and plasticity Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance and a preparation method thereof. This titanium alloy has good corrosion resistance and high specific strength properties.

[0005] This invention is achieved through the following technical solution:

[0006] A high oxygen-resistant, ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy, comprising, by mass percentage, 4.7%–6% Al, 4.0%–5.0% Zr, 2.0%–3.5% Cr, 0.3%–0.9% O, with the balance being Ti and unavoidable impurity elements.

[0007] Preferably, the titanium alloy microstructure comprises equiaxed α p It is a layered structure composed of high-O nanomartensite α′ phase and orthogonal O′ nanodomains.

[0008] Preferably, the average lamellar thickness of the high-O nanomartensite α′ phase is 21-5 nm, and the average size of the orthogonal O′ nanodomains is 3±2 nm.

[0009] Preferably, the tensile strength R of the titanium alloy m The yield strength is 1467-1920 MPa, and the yield strength R is... p0.2 The strength ranges from 1143 to 1700 MPa, and the uniform elongation δ / % is 5.9 to 11.3.

[0010] A method for preparing an ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance includes the following steps:

[0011] Step 1: Mix titanium, aluminum, zirconium, chromium and titanium dioxide powders evenly and then melt them to obtain alloy ingots;

[0012] Step 2: Hot rolling the alloy ingot at 30–70°C below the α+β phase transformation point;

[0013] Step 4: The hot-rolled alloy ingot is solution treated at the α+β phase transformation point of 30-70℃ to obtain Ti-Al-Zr-Cr-O titanium alloy.

[0014] Preferably, in step 1, multiple vacuum melting processes are performed under an argon atmosphere, with an induced current of 350–400 A and a current frequency of 20–25 kHz during the melting process.

[0015] Preferably, in step 2, after holding at 30-70°C below the α+β phase transformation point for 5-10 minutes, hot rolling is performed, with each rolling pass holding time being 0.5-1 minutes and the total deformation being 80-86%.

[0016] Preferably, the solution treatment time in step 3 is 1-5 minutes, followed by quenching to room temperature.

[0017] Preferably, in step 2, the alloy ingot is homogenized and then hot-rolled.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] This invention provides an ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance. The addition of interstitial elements is transformed into a beneficial factor. By doping interstitial O, the shuffle mechanism in the martensitic phase transformation pathway is promoted. Specifically, a metastable O′ phase is initially formed, mediated by Zr-O atomic clusters, followed by further transformation during continuous cooling to trigger the formation of high-oxygen nanomartensite. This results in excellent mechanical properties for the titanium alloy. The alloy microstructure is a layered microstructure composed of ordered high-O nanomartensite and O′ nanodomains. The fully coherent α′ / β interface, with good strain compatibility, acts as both a barrier to dislocation sliding to provide strength and an effective dislocation source to provide high ductility. Furthermore, the stress-induced gradual O′→α′ phase transformation is also an important toughening mechanism for maintaining nonlocal plastic strain. The alloy of this invention exhibits excellent room-temperature mechanical properties. Different strength-ductility ratios can be obtained by doping with different O contents, as shown in Table 1. Its mechanical properties are compared with those of currently reported titanium alloys. Figure 4 As shown, it exhibits a significant advantage in strength and ductility. More importantly, this achievement will change the role of oxygen, which has long been considered a destructive factor in titanium and titanium alloys, and demonstrates the potential for effective utilization of oxygen and reduction of titanium production costs. Attached Figure Description

[0020] Figure 1 This describes the layered microstructure of the Ti-Cr-Zr-Al-O titanium alloy of the present invention.

[0021] Figure 2 This is a statistical diagram of the martensitic lamellar dimensions of the Ti-Al-Zr-Cr-xO titanium alloy of the present invention;

[0022] in, Figure 2 a is a martensitic lamellar diagram of a 0.3% O titanium alloy; Figure 2 b is a martensitic lamellar diagram of a 0.5% O titanium alloy; Figure 2 c is a martensitic lamellar diagram of a 0.7% O titanium alloy;

[0023] Figure 3 Tensile property curves of Ti-Cr-Zr-Al basic alloy and the Ti-Al-Zr-Cr-xO (x=0.3, 0.5 and 0.7wt.%) titanium alloy of the present invention;

[0024] Figure 4 This is a comparison chart of the properties of the Ti-Al-Zr-Cr-xO titanium alloy of the present invention with those of existing titanium alloys. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings. These descriptions are intended to explain the invention and not to limit it.

[0026] A high oxygen-resistant, ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy, comprising, by mass percentage, 4.7–6% Al, 4.0–5.0% Zr, 2.0–3.5% Cr, 0.3–0.9% O, with the balance being Ti and unavoidable impurity elements.

[0027] The preferred ultra-high strength ductile titanium alloy with high oxygen tolerance comprises, by mass percentage, 5.0–5.5% Al, 4.4–4.6% Zr, 2.6–3.0% Cr and 0.3–0.9% O, with the balance being Ti and unavoidable impurities.

[0028] The preparation method of the above-mentioned high oxygen tolerance, ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy includes the following steps:

[0029] Step 1: Mix high-purity titanium, high-purity aluminum, high-purity zirconium, high-purity chromium and titanium dioxide powder evenly according to the above percentage content, and then melt them to obtain alloy ingots.

[0030] Specifically, the mixed powder is melted using a cold crucible suspension melting method. Argon gas is introduced during the melting process, the induced current is 350-400A, and the current frequency is 20-25KHz. After the alloy is completely melted, it is held for 3-5 minutes and then cooled to obtain an ingot. To ensure uniform composition, the alloy is melted 5 times, and the ingot is loaded into the furnace with its head and tail reversed before each melting.

[0031] Step 2: After peeling and cutting the risers, the alloy ingot is homogenized.

[0032] Step 3: Hot rolling the homogenized alloy ingot in the two-phase region.

[0033] The rolling temperature in the two-phase region is 30-70℃ lower than the α+β phase transformation point. After holding at this temperature for 5-10 minutes, hot rolling is performed. The holding time for each rolling pass is 0.5-1 minutes, and the total deformation is 80-85%.

[0034] Step 4: The hot-rolled alloy ingot is solution treated in the α+β two-phase region to obtain Ti-Al-Zr-Cr-O titanium alloy.

[0035] The solution treatment method is as follows:

[0036] The temperature of the α+β two-phase region is 30–70°C below the phase transformation point, i.e., held at 30–70°C below the phase transformation point for 1–5 minutes, followed by quenching to room temperature to obtain a Ti-Al-Zr-Cr-O titanium alloy. During the quenching process of the two-phase region, the volume fraction of equiaxed α+β phases is 15–30%. pThe phase is retained from the quenching temperature to room temperature, while the pre-β grain transformation structure undergoes a diffusionless phase transformation, forming a layered structure composed of high O nanomartensite α′ phase and orthogonal O′ nanodomains.

[0037] This invention provides a high oxygen tolerance, ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy. By doping with O atoms, neutral Zr atoms combine with O atoms to form metastable O′ nanodomains mediated by Zr-O atom clusters. These nanodomains exhibit dual functions in the alloy: (1) These O′ nanodomains can serve as nucleation sites for α′ martensite, significantly refining the thickness of α′ martensite during quenching. (2) O′ nanodomains that are not fully transformed at room temperature are stress-induced to α′ martensite during subsequent plastic deformation, improving the alloy's work hardening and ductility.

[0038] Example 1

[0039] A method for preparing an ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance, comprising, by mass percentage, 5.2% Al, 4.5% Zr, 2.8% Cr and 0.7% O, with the balance being Ti and unavoidable impurity elements. The preparation method includes the following steps:

[0040] Step 1: According to the above percentage content, mix high-purity titanium, high-purity aluminum, high-purity zirconium, high-purity chromium and titanium dioxide powder evenly, and then put them into the furnace for 5 meltings.

[0041] The smelting process was carried out in a high-purity argon atmosphere, with a smelting current of 350A and a current frequency of 20KHz. The alloy was smelted 5 times, with the ingots being loaded into the furnace inverted before each smelting.

[0042] Step 2: After peeling and cutting the risers, the alloy ingot is homogenized.

[0043] Step 3: The homogenized alloy ingot is hot rolled in multiple passes at 40°C below the α+β phase transformation point. The holding time for each pass is 1 minute, and the total deformation is 84%.

[0044] Step 4: The hot-rolled alloy ingot is solution treated at 40°C below the α+β phase transformation point for 2 minutes, and then water-quenched to room temperature to obtain Ti-Al-Zr-Cr-O titanium alloy.

[0045] like Figure 1 As shown, after solid solution in the two-phase region, equiaxed α-phase particles appear in the microstructure. p The phase consists of nanoscale martensite α′ lamellae and nanoscale orthogonal O′ nanodomains. Clearly, a layered structure composed of high-O nanoscale martensite α′ lamellae and orthogonal O′ nanodomains was obtained. Furthermore, the average lamellar thickness of the nanomartensite reached a record-breaking 8 ± 3 nm. Figure 2c) The average size of the orthogonal O′ nanodomains is 3±2 nm. Therefore, this layered structure possesses extremely high strength and good plasticity. According to the requirements of GB / T228.1-2010 standard, the mechanical properties of the alloy were measured as follows: tensile strength R... m The yield strength is 1835 MPa, and the yield strength R is... p0.2 It has a strength of 1618 MPa and a uniform elongation δ / % of 10 ± 0.7. This alloy exhibits extremely excellent strength and ductility.

[0046] Example 2

[0047] A method for preparing an ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance, comprising, by mass percentage, 6% Al, 5.0% Zr, 3.5% Cr, 0.5% O, with the balance being Ti and unavoidable impurity elements, and the preparation method includes the following steps:

[0048] Step 1: According to the above percentage content, mix high-purity titanium, high-purity aluminum, high-purity zirconium, high-purity chromium and titanium dioxide powder evenly, and then put them into the furnace for 5 meltings.

[0049] The smelting process was carried out in a high-purity argon atmosphere, with a smelting current of 380A and a current frequency of 22KHz. The alloy was smelted three times, with the ingots being loaded into the furnace inverted before each smelting.

[0050] Step 2: After peeling and cutting the risers, the alloy ingot is homogenized.

[0051] Step 3: The homogenized alloy ingot is hot rolled in multiple passes at 60°C below the α+β phase transformation point. The holding time for each pass is 2 minutes, and the total deformation is 83%.

[0052] Step 4: The hot-rolled alloy ingot is solution treated at 60°C below the α+β phase transformation point for 3 minutes, and then water-quenched to room temperature to obtain Ti-Al-Zr-Cr-O titanium alloy.

[0053] In this embodiment, due to the reduced O content, the average lamellar thickness of the nanomartensite increased to 14±5 nm, and the average size of the orthogonal O′ nanodomains was 3±2 nm. Figure 2 As shown in b, the mechanical properties of the alloy were measured according to the requirements of GB / T228.1-2010 standard as follows: tensile strength R m The yield strength is 1673 MPa, and the yield strength R is 1673 MPa. p0.2 The strength is 1373 MPa, and the uniform elongation δ / % is 10.4 ± 0.5. This titanium alloy exhibits extremely excellent strength and ductility.

[0054] Example 3

[0055] A method for preparing an ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance, comprising, by mass percentage, 4.7% Al, 4.0% Zr, 2.3% Cr and 0.3% O, with the balance being Ti and unavoidable impurity elements. The preparation method includes the following steps:

[0056] Step 1: According to the above percentage content, mix high-purity titanium, high-purity aluminum, high-purity zirconium, high-purity chromium and titanium dioxide powder evenly, and then put them into the furnace for 4 meltings.

[0057] The smelting process was carried out in a high-purity argon atmosphere, with a smelting current of 400A and a current frequency of 25KHz. The alloy was smelted four times, with the ingots being loaded into the furnace inverted before each smelting.

[0058] Step 2: After peeling and cutting the risers, the alloy ingot is homogenized.

[0059] Step 3: The homogenized alloy ingot is hot rolled in multiple passes at 70°C below the α+β phase transformation point. The holding time for each pass is 3 minutes, and the total deformation is 80%.

[0060] Step 4: The hot-rolled alloy ingot is solution treated at 70°C below the α+β phase transformation point for 5 minutes, and then water-quenched to room temperature to obtain Ti-Al-Zr-Cr-O titanium alloy.

[0061] In this embodiment, as the O content decreases, the average lamellar thickness of the nanomartensite is 8±3 nm, and the average size of the orthogonal O′ nanodomains is 3±2 nm. For example... Figure 2 As shown in b, the mechanical properties of the titanium alloy were measured according to the requirements of GB / T228.1-2010 standard as follows: tensile strength R m The yield strength is 1467 MPa, and the yield strength R is... p0.2 With a strength of 1143 MPa and a uniform elongation δ / % of 11.3 ± 0.6, this alloy exhibits good strength and ductility.

[0062] Example 4

[0063] A method for preparing an ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance, comprising, by mass percentage, 5.0% Al, 4.5% Zr, 2.8% Cr and 0.9% O, with the balance being Ti and unavoidable impurity elements. The preparation method includes the following steps:

[0064] Step 1: According to the above percentage content, mix high-purity titanium, high-purity aluminum, high-purity zirconium, high-purity chromium and titanium dioxide powder evenly, and then put them into the furnace for 6 meltings.

[0065] The smelting process was carried out in a high-purity argon atmosphere, with a smelting current of 360A and a current frequency of 22KHz. The alloy was smelted four times, with the ingots being loaded into the furnace inverted before each smelting.

[0066] Step 2: After peeling and cutting the risers, the alloy ingot is homogenized.

[0067] Step 3: The homogenized alloy ingot is hot rolled in multiple passes at a temperature 30°C below the α+β phase transformation point. The holding time for each pass is 1 minute, and the total deformation is 84%.

[0068] Step 4: The hot-rolled alloy ingot is solution treated at 30°C below the α+β phase transformation point for 2 minutes, and then water-quenched to room temperature to obtain Ti-Al-Zr-Cr-O titanium alloy.

[0069] According to the requirements of GB / T228.1-2010 standard, the mechanical properties of titanium alloy were measured as follows: tensile strength R m The yield strength is 1920 MPa, and the yield strength R is... p0.2 The strength is 1700 MPa, and the uniform elongation δ / % is 5.9%. This alloy exhibits good strength and plasticity.

[0070] Example 5

[0071] A high oxygen-resistant, ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy, by mass percentage, comprises 5.5% Al, 4.5% Zr, 2.0% Cr, 0.6% O, with the balance being Ti and unavoidable impurity elements. The preparation method of this titanium alloy is the same as that in Example 1.

[0072] Table 1 below compares the mechanical properties of the Ti-Al-Zr-Cr basic alloy with the titanium alloys prepared in Examples 1-3.

[0073] Table 1

[0074]

[0075] Comparative Example 1

[0076] The main difference between this comparative example and Examples 1-5 is that it does not dope the gap O, as detailed below:

[0077] A Ti-Al-Zr-Cr titanium alloy, by weight percentage comprising 5.0–5.5% Al, 4.4–4.6% Zr and 2.6–3.0% Cr, with the balance being Ti and unavoidable impurities.

[0078] Based on the above composition, the alloy was prepared by cold crucible suspension melting and hot rolling. Specifically, high-purity titanium, high-purity aluminum, high-purity zirconium, and high-purity chromium were mixed uniformly according to the specified ratio and bulked into the furnace, followed by melting. The entire process was carried out in a high-purity argon atmosphere, with a melting current of 400A and a current frequency of 20kHz. To ensure uniform composition, the alloy underwent five melting processes, with the ingot head and tail reversed before each melting. After the riser was removed from the ingot, it was hot rolled in the two-phase region to obtain the Ti-Al-Zr-Cr titanium alloy; the hot rolling temperature was 40℃ below the phase transformation point, the holding time was 2 minutes, and the deformation was not less than 80%.

[0079] The Ti-Al-Zr-Cr titanium alloy was solution treated for 2 minutes at 40°C below its phase transformation point in the two-phase region, followed by quenching to room temperature. Because the titanium alloy was vacuum-melted without the addition of any oxygen atoms, the oxygen content was low, resulting in a significant decrease in the alloy's yield strength. According to the requirements of GB / T228.1-2010 standard, the mechanical properties of the alloy were measured as follows: tensile strength R... m The yield strength is 1136 MPa, and the yield strength R is 1136 MPa. p0.2 The strength is 985 MPa, and the uniform elongation δ / % is 12.4 ± 1.0. This alloy has a low yield strength.

[0080] Titanium alloys possess excellent corrosion resistance and high specific strength, making them highly attractive structural materials for a wide range of commercial applications. Furthermore, oxygen, an important interstitial impurity, can be intentionally or unintentionally incorporated into the alloy, providing powerful strengthening effects in various applications. However, titanium and its alloys are highly sensitive to oxygen, which significantly deteriorates the material's ductility and can even cause embrittlement. Therefore, this forces manufacturers to strictly control interstitial impurities during manufacturing, further increasing costs. This invention transforms the addition of interstitial elements into a beneficial factor by promoting the shuffle mechanism in the martensitic phase transformation pathway through interstitial O doping. Specifically, the metastable O′ phase is initially mediated by Zr-O atomic clusters, followed by continued transformation during continuous cooling to trigger the formation of oxygen-rich interstitial nanomartensite with a record-breaking average lamellar thickness of 8±3 nm. This results in ultra-high yield strength (~1.60 GPa), ultimate tensile strength (~1.83 GPa), and high uniform ductility (~10%), exceeding all previously reported bulk titanium alloys. This unusual combination of tensile strength and ductility is achieved by a hierarchical microstructure composed of ordered high-O nanomartensite and O′ nanodomains. The fully coherent α′ / β interface with good strain compatibility acts as both a barrier to dislocation sliding to provide strength and an effective dislocation source to provide high ductility. In addition, the stress-induced asymptotic O′→α′ phase transformation is also an important toughening mechanism to maintain nonlocal plastic strain.

[0081] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-oxygen-resistant, ultra-high-strength, high-ductility Ti-Cr-Zr-Al-O titanium alloy, characterized in that, By mass percentage, it comprises 4.7%–6% Al, 4.0%–5.0% Zr, 2.0%–3.5% Cr, 0.3%–0.9% O, with the balance being Ti and unavoidable impurity elements; the titanium alloy microstructure comprises equiaxed α p The structure consists of a layered structure composed of a high-O nano-martensite α′ phase and an orthogonal O′ nanodomain; the average lamellar thickness of the high-O nano-martensite α′ phase is 21–5 nm, and the average size of the orthogonal O′ nanodomain is 3 ± 2 nm. The preparation method of the ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance includes the following steps: Step 1: Mix titanium, aluminum, zirconium, chromium and titanium dioxide powders evenly and then melt them to obtain alloy ingots; Step 2: Hot rolling the alloy ingot at 30–70°C below the α+β phase transformation point; Step 3: The hot-rolled alloy ingot is solution treated at the α+β phase transformation point of 30-70℃ for 1-5 minutes, and then quenched to room temperature to obtain Ti-Al-Zr-Cr-O titanium alloy.

2. The ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance according to claim 1, characterized in that, The tensile strength R of the titanium alloy m The strength ranges from 1467 to 1920 MPa, and the yield strength R is... p0.2 The strength ranges from 1143 to 1700 MPa, and the uniform elongation δ ranges from 5.9 to 11.3%.

3. The ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance according to claim 1, characterized in that, In step 1, multiple vacuum melting processes are carried out under an argon atmosphere. During the melting process, the induced current is 350-400A and the current frequency is 20-25kHz.

4. The ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance according to claim 1, characterized in that, In step 2, after holding at 30–70°C below the α+β phase transformation point for 5–10 min, hot rolling is performed. The holding time for each rolling pass is 0.5–1 min, and the total deformation is 80–86%.

5. The ultra-high strength and ductility Ti-Cr-Zr-Al-O titanium alloy with high oxygen tolerance according to claim 1, characterized in that, In step 2, the alloy ingot is homogenized and then hot-rolled.

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