A process method for effectively improving the damage tolerance of titanium alloy

Abstract

The present invention relates to the field of titanium alloy application technology, and specifically to a process method for effectively improving the damage tolerance of titanium alloys, comprising the following steps: step (1) preparing a TA15 titanium alloy deposition sample with fine columnar crystals by additive manufacturing; step (2) measuring the α→β phase transition temperature T of the TA15 titanium alloy deposition sample by using a thermal differential analysis method combined with a metallographic method; β ; Step (3) in (T β -30℃)~T β Within the temperature range, hot isostatic pressing is performed on the as-deposited TA15 titanium alloy sample; in step (iv), the as-deposited TA15 titanium alloy sample after hot isostatic pressing is subjected to a tensile test, an impact test, a fracture toughness test, and a crack growth rate test, and the test results are recorded and compared. The present invention improves the microstructure and eliminates porosity. Furthermore, experiments have shown that the present invention effectively improves the damage tolerance of the titanium alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy applications, and in particular to a process for effectively improving the damage tolerance of titanium alloys. Background Art

[0002] TAl5 titanium alloy is a high aluminum equivalent near-alloy with good high-temperature creep resistance, thermal stability and good welding performance. It combines the advantages of α-type and (α+β)-type titanium alloys. Due to its moderate room temperature and high temperature strength, good thermal stability and welding performance, and long-term working temperature up to 500°C, the alloy has been widely used in the aerospace industry. Laser additive manufacturing of TA15 titanium alloy components has the advantages of short cycle and high performance compared to traditional forgings. However, as key load-bearing components of aircraft, TAl5 components are required to have excellent comprehensive mechanical properties (impact toughness, fracture toughness, crack propagation rate) due to their harsh service environment.

[0003] The microstructure of TA15 titanium alloy plays a decisive role in damage tolerance. The as-deposited structure and defects of laser additively manufactured TA15 titanium alloy are significantly affected by process parameters. The structure generally consists of β columnar crystals extending through the molten pool and α acicular martensite within the β crystals. The α phases are staggered, with a high aspect ratio. The specimens also contain defects such as porosity, resulting in high strength but poor ductility and toughness. Hot isostatic pressing (HIP) of laser additively manufactured TA15 titanium alloy to improve its microstructure and eliminate porosity is an important means of effectively enhancing the comprehensive mechanical properties of additively manufactured TA15 titanium alloy. The HIP process parameters are crucial. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a process method for effectively improving the damage tolerance of titanium alloy.

[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0006] A process for effectively improving the damage tolerance of titanium alloy comprises the following steps:

[0007] Step (1) preparing a TA15 titanium alloy deposition sample having fine columnar crystals by additive manufacturing;

[0008] Step (2) Using differential thermal analysis combined with metallographic method to measure the α→β phase transition temperature T of the TA15 titanium alloy deposited sample β ;

[0009] Step (3) in (T β -30℃)~T β Within the temperature range, hot isostatic pressing treatment was performed on the deposited TA15 titanium alloy specimens;

[0010] Step (4) Performing a tensile test, an impact test, a fracture toughness test, and a crack growth rate test on the as-deposited sample of the TA15 titanium alloy after hot isostatic pressing, recording and comparing the test results.

[0011] Preferably, in step (1), the additive manufacturing method is selected as selective laser melting.

[0012] Preferably, the processing parameters of the selective laser melting process are: laser power 150W to 220W; spot diameter 80μm; single layer powder thickness 40μm to 60μm; scanning speed 1000mm / s to 1400mm / s.

[0013] Preferably, the TA15 titanium alloy deposited sample additively manufactured in step (1) has a deposited microstructure α-phase volume fraction of ≥99%, a staggered arrangement, a high aspect ratio, and a fine grain size.

[0014] Preferably, the heating temperature of the thermal differential analysis method in step (2) is: 1°C / min to 10°C / min.

[0015] Preferably, the quenching temperature of the continuously heated metallographic sample in step (ii) is determined based on the differential thermal analysis results T β , set the quenching temperature: T β -15℃、T β -5℃、T β ℃、T β +5℃、T β +15℃.

[0016] Preferably, the process parameters of the hot isostatic pressing treatment in step (iii) are: in an argon atmosphere environment; oxygen content is less than 100 ppm; pressure is 120 MPa to 150 MPa; hot isostatic pressing treatment heating rate is 5°C / min to 6°C / min; holding time is 1.8h to 2.1h; and cooling with the furnace.

[0017] Preferably, after the hot isostatic pressing treatment in step (iii), the β grains of the TA15 titanium alloy deposited sample are equiaxed, the α phase in the β grains is distributed in lamellar form, and the porosity defects are eliminated.

[0018] Preferably, the tensile test in step (iv) corresponds to the national standard GB / T 228.1-2010; the impact test corresponds to the national standard GB / T 229-2020; the fracture toughness test corresponds to the national standard GB / T 6398-2017; and the crack growth rate test corresponds to the national standard GB / T4161-2007.

[0019] The beneficial effects of the present invention are:

[0020] Compared with the prior art, the present invention compares the microstructure of the deposited TA15 titanium alloy sample after hot isostatic pressing with that of the untreated deposited TA15 titanium alloy sample through organization and testing. The original β grains of the deposited TA15 titanium alloy sample after hot isostatic pressing are equiaxed, and the α phase in the β grains is distributed in lamellar form, which improves the microstructure and eliminates porosity. Experiments have shown that the present invention effectively improves the damage tolerance of the titanium alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0022] Figure 1 Schematic diagram of the as-deposited microstructure of TA15 titanium alloy prepared by SLM in the present invention;

[0023] Figure 2 Schematic diagram of the microstructure of the deposited TA15 titanium alloy after hot isostatic pressing treatment of the present invention;

[0024] Figure 3 Schematic diagram of the scatter plot of Log(da / dN) and log(ΔK) and the linear fitting in the present invention;

[0025] Figure 4 Schematic diagram of the engineering stress-strain curve of the TA15 titanium alloy after hot isostatic pressing treatment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0027] like Figures 1 to 4 As shown, a process method for effectively improving the damage tolerance of titanium alloy includes the following steps:

[0028] Step (1) Prepare a TA15 titanium alloy deposition sample with fine columnar crystals by additive manufacturing.

[0029] Specifically, the additive manufacturing method uses a selective laser melting process. The corresponding processing parameters for the selective laser melting process are: laser power 150W to 220W; spot diameter 80μm; single-layer powder thickness 40μm to 60μm; scanning speed 1000mm / s to 1400mm / s. The deposited TA15 titanium alloy sample produced has an α-phase volume fraction of ≥99% with a staggered arrangement, a high aspect ratio, and fine grain size.

[0030] Step (2) Using differential thermal analysis combined with metallographic method to measure the α→β phase transition temperature T of the TA15 titanium alloy deposited sample β .

[0031] Specifically, the heating temperature of the differential thermal analysis method is: 1℃ / min~10℃ / min; the quenching temperature of the sample of the continuous heating metallographic method is based on the differential thermal analysis results T β , set the quenching temperature: T β -15℃、T β -5℃、T β ℃、T β +5℃、T β +15℃.

[0032] Step (3) in (T β -30℃)~T β The TA15 titanium alloy as-deposited samples were subjected to hot isostatic pressing (HIP) within a certain temperature range.

[0033] Specifically, the process parameters of the hot isostatic pressing treatment are: in an argon atmosphere environment; oxygen content is less than 100ppm; pressure is 120MPa~150MPa; hot isostatic pressing treatment heating rate is 5℃ / min~6℃ / min; holding time is 1.8h~2.1h; cooling with the furnace.

[0034] After hot isostatic pressing, the β grains of the TA15 titanium alloy deposited sample are equiaxed, the α phase within the β grains is distributed in lamellar form, and the porosity defects are eliminated.

[0035] Step (4) According to the national standards GB / T 228.1-2010, GB / T 229-2020, GB / T 6398-2017, and GB / T4161-2007, the TA15 titanium alloy deposited sample after hot isostatic pressing was subjected to a tensile test, an impact test, a fracture toughness test, and a crack growth rate test; the test results of the tensile test were: tensile strength 914 MPa, elongation 22%; the test results of the impact test were: impact absorbed energy 50.7 J; the test results of the fracture toughness test were: fracture toughness 123 KPa 0.5 The test results of the crack growth rate test are R=0.1, Log(da / dN)=-11.14+5.66Log(K). By comparison, the damage tolerance of the present invention is better than that of forgings made of the same material.

[0036] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and description merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for effectively improving the damage tolerance of titanium alloy, characterized by: The steps are as follows: Step (1) preparing a TA15 titanium alloy deposition sample having fine columnar crystals by additive manufacturing; Step (2) Using differential thermal analysis combined with metallographic method to measure the α→β phase transition temperature T of the TA15 titanium alloy deposited sample β ; Step (3) in (T β -30℃)~T β Within the temperature range, hot isostatic pressing treatment was performed on the deposited TA15 titanium alloy specimens; The process parameters of the hot isostatic pressing treatment in step (3) are: in an argon atmosphere; oxygen content is less than 100 ppm; pressure is 120 MPa to 150 MPa; hot isostatic pressing heating rate is 5°C / min to 6°C / min; holding time is 1.8h to 2.1h; cooling with the furnace; After the hot isostatic pressing treatment in step (3), the β grains of the TA15 titanium alloy deposited sample are equiaxed, the α phase in the β grains is distributed in a lamellar manner, and the porosity defects are eliminated; Step (4) performing a tensile test, an impact test, a fracture toughness test, and a crack growth rate test on the as-deposited TA15 titanium alloy sample after hot isostatic pressing, recording and comparing the test results; In step (1), the additive manufacturing method is selected as selective laser melting; the processing parameters of the selective laser melting process are: laser power 150W~220W; spot diameter 80μm; single layer powder thickness 40μm~60μm; scanning speed 1000mm / s~1400mm / s.

2. A process for effectively improving the damage tolerance of titanium alloy according to claim 1, characterized in that: The TA15 titanium alloy deposited sample manufactured by additive manufacturing in step (1) has a deposited microstructure α phase volume fraction of ≥99%, a staggered arrangement, a high aspect ratio, and a fine grain size.

3. The process for effectively improving the damage tolerance of titanium alloy according to claim 1, characterized in that: The heating temperature of the thermal differential analysis method in step (2) is: 1°C / min to 10°C / min.

4. The process for effectively improving the damage tolerance of titanium alloy according to claim 1, characterized in that: The quenching temperature of the metallographic sample in step (2) is determined based on the differential thermal analysis results T β , set the quenching temperature: T β -15℃、T β -5℃、T β ℃、T β +5℃、T β +15℃.

5. The process for effectively improving the damage tolerance of titanium alloy according to claim 1, characterized in that: The tensile test in step (4) corresponds to the national standard GB / T 228.1-2010; the impact test corresponds to the national standard GB / T 229-2020; the fracture toughness test corresponds to the national standard GB / T 6398-2017; and the crack growth rate test corresponds to the national standard GB / T 4161-2007.

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