Corrosion display method of TA22 titanium alloy grain structure

Abstract

The invention discloses a corrosion display method of a TA22 titanium alloy grain structure. The method comprises the following steps: 1, machining a TA22 titanium alloy sample to form a microscopic structure observation plane, and grinding and washing the microscopic structure observation plane; 2, mechanical polishing is conducted till the surface is flat and bright and free of scratches and dragging; 3, anodic oxidation coating treatment; 4, immersing into an etchant solution for etching; and 5, placing under a metallographic microscope, and observing the metallographic microstructure in a way of transparent field observation. According to the method, the TA22 titanium alloy is subjected to anodic oxidation film coating and then subjected to erosion film removal, and a method for judging the grain size by observing different bright and dark contrast in a metallographic structure in a polarized field after film coating is abandoned; according to the method, the grain boundary structure in the TA22 titanium alloy metallographic structure can be clearly, accurately and intuitively observed by directly adopting a transparent field under the metallographic microscope, a polarized light view field does not need to be switched, the equipment requirement on the metallographic microscope is greatly reduced, and the method is easy to operate and suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of metallographic microstructure observation of metal materials, and particularly relates to a corrosion display method for TA22 titanium alloy grain structure. Background Art

[0002] TA22, also known as Ti31 alloy, is a near-α-type titanium alloy independently developed in my country. Its nominal composition is Ti-3Al-1Mo-1Ni-1Zr. The alloy has high plasticity and toughness, medium-temperature thermal strength and high-temperature durability. It also has good fatigue resistance and wear resistance, which enables it to maintain stable performance during long-term use. In addition, TA22 titanium alloy can show good corrosion resistance in a variety of harsh environments. It can work stably in extreme environments such as high temperature, high pressure, strong acid, and strong alkali without corrosion and oxidation. This makes TA22 titanium alloy one of the important materials in the fields of chemical industry, marine engineering, etc.

[0003] Grain size refers to the size of the grains in the crystal, and is an important physical property parameter in titanium alloys. The grain size will directly affect the mechanical properties and processing properties of titanium alloys. The smaller the grain size, the higher the strength and plasticity of the material, while the thermal conductivity and toughness are also better; large grain size itself will increase the hardness and brittleness of the alloy, and the finished product is prone to cracks and deformation. Therefore, controlling the grain size of titanium alloys can effectively improve the mechanical properties and processing properties of the alloy. Grain size rating is an effective means to control the grain size of titanium alloys, which can ensure the mechanical properties and processing properties of the alloy, making the titanium alloy manufacturing process more optimized and controllable.

[0004] Currently, the grain boundary structure of this TA22 titanium alloy cannot be observed after being treated with conventional corrosive agents. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a corrosion display method for the grain structure of TA22 titanium alloy in view of the shortcomings of the above-mentioned prior art. The method first performs anodizing coating on the TA22 titanium alloy and then performs etching to remove the film, abandoning the method of using polarized field of view to observe different light and dark contrasts in the metallographic structure to judge the grain size after coating. The grain boundary structure in the metallographic structure of the TA22 titanium alloy can be clearly, accurately and intuitively observed by directly using open field observation under a metallographic microscope, without switching the polarized field of view, which greatly reduces the equipment requirements for the metallographic microscope and solves the problem that the grain boundary structure of the TA22 titanium alloy cannot be observed by conventional corrosive agents.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a corrosion display method for TA22 titanium alloy grain structure, characterized in that the method comprises the following steps:

[0007] Step 1: Mechanically process the TA22 titanium alloy sample into a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane;

[0008] Step 2: Place the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag;

[0009] Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing coating for 2s to 5s;

[0010] Step 4, immersing the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching;

[0011] Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

[0012] During the research process of the present invention, it was found that the TA22 titanium alloy was corroded by using a conventional corrosive solution within the national standard, such as a hydrofluoric acid and nitric acid aqueous solution (5% HF + 12% HNO3 + 83% H2O by volume, erosion, 5s), and its metallographic structure diagram is as follows Figure 1 As shown, although the metallographic microstructure is visible, its grain boundary structure cannot be shown, and the grain size cannot be clearly identified, which can easily lead to wrong conclusions; if conventional corrosion is performed followed by anodizing coating, it is necessary to use the polarized field of view of a metallographic microscope for observation, which has relatively high requirements for the equipment. If the metallographic microscope is not equipped with a polarizing filter, its clear grain structure cannot be observed. Based on this, the present invention adopts a sequence different from that of conventional titanium alloys, which is first corrosion and then coating. The TA22 titanium alloy after grinding and mechanical polishing is first anodized and coated, and then corrosive solution is used for etching. The TA22 titanium alloy that has been coated after anodization is subjected to a "film removal" treatment. The method of using a polarized field of view to observe different light and dark contrasts in the metallographic structure after coating to determine the grain size is abandoned, so that the microstructure observation plane can be directly placed under a metallographic microscope and observed by open field observation. The grain boundary structure in the observed metallographic structure of the TA22 titanium alloy is very clear, accurate and intuitive, without the need to switch the polarized field of view, which greatly reduces the equipment requirements for the metallographic microscope.

[0013] The above-mentioned corrosion display method of TA22 titanium alloy grain structure is characterized in that the specific process of grinding in step 1 is: using a particle size of 120 # , 800 # , 1200# and 2000 #The metallographic water sandpaper is used for grinding step by step. Each time the metallographic water sandpaper is changed for grinding, the grinding direction is turned 90° to ensure that the previous grinding marks are completely eliminated.

[0014] The above-mentioned method for displaying corrosion of the grain structure of TA22 titanium alloy is characterized in that the polishing agent for mechanical polishing in step 2 is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth.

[0015] The above-mentioned method for displaying corrosion of the grain structure of TA22 titanium alloy is characterized in that the solution for the anodizing coating treatment in step three is an H2SO4 aqueous solution with a mass concentration of 5%, the equipment is an adjustable constant current source, and the voltage of the anodizing coating treatment is 18V~25V, the current is 0.8A~1.0A, and the time is 1s~3s.

[0016] The above-mentioned method for displaying the corrosion of the grain structure of a TA22 titanium alloy is characterized in that the corrosion solution in step 4 is composed of a 5% by volume HF aqueous solution, and the etching time is 3s to 8s. The present invention directly anodizes the polished TA22 titanium alloy sample without corroding the TA22 titanium alloy sample, and then uses a 5% HF aqueous solution for "film removal". The 5% HF aqueous solution can not completely remove the anodized film, and the residual film is only attached to the grain boundary of the titanium alloy grain under the action of the 5% HF aqueous solution, thereby making the grain boundary clearly visible.

[0017] The above-mentioned method for displaying corrosion of TA22 titanium alloy grain structure is characterized in that the H2SO4 in the H2SO4 aqueous solution is an analytically pure reagent.

[0018] The above-mentioned method for displaying corrosion of TA22 titanium alloy grain structure is characterized in that the HF in the HF aqueous solution is an analytically pure reagent.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The present invention adopts a sequence different from the conventional titanium alloy corrosion followed by coating. The TA22 titanium alloy is first anodized and coated and then etched to remove the film. The method of using a polarized field of view to observe different light and dark contrasts in the metallographic structure after coating to determine the grain size is abandoned. The grain boundary structure in the metallographic structure of the TA22 titanium alloy can be clearly, accurately and intuitively observed by directly using a bright field observation under a metallographic microscope.

[0021] 2. Compared with conventional corrosion methods that can only observe the metallographic structure but not the grain boundary structure, the method of the present invention can clearly and specifically observe the grain boundary structure of TA22 titanium alloy under the bright field of the metallographic microscope, which is beneficial to ensure the mechanical properties and processing properties of TA22 titanium alloy through grain size rating.

[0022] 3. The method of the present invention is easy to operate and non-toxic, can clearly observe the grain structure of TA22 titanium alloy, and does not require any special equipment. It also does not require higher requirements such as polarizing microscope observation on the metallographic microscope, which greatly reduces the equipment requirements for the metallographic microscope and is suitable for promotion and application.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the metallographic structure diagram of TA22 titanium alloy after being corroded by conventional corrosion solution within the national standard.

[0025] Figure 2 This is a microstructure diagram (400×) of the TA22 titanium alloy grain structure in Example 1 of the present invention.

[0026] Figure 3 This is a microstructure diagram (400×) of the TA22 titanium alloy grain structure in Example 2 of the present invention.

[0027] Figure 4 This is a microstructure diagram (400×) of the TA22 titanium alloy grain structure in Example 3 of the present invention.

[0028] Figure 5 This is a microstructure diagram (400×) of the TA22 titanium alloy grain structure in Example 4 of the present invention.

[0029] Figure 6 This is a microstructure diagram (400×) of the TA22 titanium alloy grain structure in Example 5 of the present invention.

[0030] Figure 7 This is a microstructure diagram (400×) of the TA22 titanium alloy grain structure in Example 6 of the present invention. DETAILED DESCRIPTION

[0031] Example 1

[0032] This embodiment includes the following steps:

[0033] Step 1: Machine the TA22 titanium alloy sample to obtain a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane; the specific grinding process is: use 120# , 800 # , 1200# and 2000 # Grind step by step with metallographic water sandpaper. Each time you change the metallographic water sandpaper for grinding, turn the grinding direction 90° to ensure that the last grinding marks are completely eliminated.

[0034] Step 2: placing the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag; the polishing agent for the mechanical polishing is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth;

[0035] Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing treatment; the solution for the anodizing treatment is a H2SO4 aqueous solution with a mass concentration of 5%, and the H2SO4 in the H2SO4 aqueous solution is an analytically pure reagent, the equipment is an adjustable voltage-stabilized constant current source, and the voltage of the anodizing treatment is 18V, the current is 0.8A, and the time is 1s;

[0036] Step 4: immerse the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching; the corrosion solution is composed of a 5% by volume HF aqueous solution, and the HF in the HF aqueous solution is an analytical pure reagent, and the etching time is 3s;

[0037] Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

[0038] Figure 2 The microstructure of the TA22 titanium alloy grain structure in this embodiment (400×) is shown in FIG. Figure 2 It can be seen that the base color is light brown after removing the anodized coating, the grain boundaries of the TA22 titanium alloy are white, and the grain boundary details are clearly visible.

[0039] Example 2

[0040] This embodiment includes the following steps:

[0041] Step 1: Machine the TA22 titanium alloy sample to obtain a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane; the specific grinding process is: use 120 # , 800 # , 1200# and 2000 #Grind step by step with metallographic water sandpaper. Each time you change the metallographic water sandpaper for grinding, turn the grinding direction 90° to ensure that the last grinding marks are completely eliminated.

[0042] Step 2: placing the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag; the polishing agent for the mechanical polishing is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth;

[0043] Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing treatment; the solution for the anodizing treatment is a H2SO4 aqueous solution with a mass concentration of 5%, and the H2SO4 in the H2SO4 aqueous solution is an analytical pure reagent, the equipment is an adjustable voltage-stabilized constant current source, and the voltage of the anodizing treatment is 18V, the current is 0.8A, and the time is 2s;

[0044] Step 4: immerse the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching; the corrosion solution is composed of a 5% by volume HF aqueous solution, and the HF in the HF aqueous solution is an analytical pure reagent, and the etching time is 6 seconds;

[0045] Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

[0046] Figure 3 The microstructure of the TA22 titanium alloy grain structure in this embodiment (400×) is shown in FIG. Figure 3 It can be seen that the light yellow background color gradually fades, the grain boundaries of the TA22 titanium alloy appear black, and the grain boundary details are clearly visible.

[0047] Example 3

[0048] This embodiment includes the following steps:

[0049] Step 1: Machine the TA22 titanium alloy sample to obtain a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane; the specific grinding process is: use 120 # , 800 # , 1200# and 2000 # Grind step by step with metallographic water sandpaper. Each time you change the metallographic water sandpaper for grinding, turn the grinding direction 90° to ensure that the last grinding marks are completely eliminated.

[0050] Step 2: placing the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag; the polishing agent for the mechanical polishing is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth;

[0051] Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing treatment; the solution for the anodizing treatment is a H2SO4 aqueous solution with a mass concentration of 5%, and the H2SO4 in the H2SO4 aqueous solution is an analytical pure reagent, the equipment is an adjustable constant current source, and the voltage of the anodizing treatment is 20V, the current is 1.0A, and the time is 3s;

[0052] Step 4: immerse the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching; the corrosion solution is composed of a 5% by volume HF aqueous solution, and the HF in the HF aqueous solution is an analytical pure reagent, and the etching time is 3s;

[0053] Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

[0054] Figure 4 The microstructure of the TA22 titanium alloy grain structure in this embodiment (400×) is shown in FIG. Figure 4 It can be seen that the base color is grayish white after further removal of the anodized coating. The grain boundaries of the TA22 titanium alloy are lighter and black, and the grain boundary details are clearly visible.

[0055] Example 4

[0056] This embodiment includes the following steps:

[0057] Step 1: Machine the TA22 titanium alloy sample to obtain a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane; the specific grinding process is: use 120 # , 800 # , 1200# and 2000 # Grind step by step with metallographic water sandpaper. Each time you change the metallographic water sandpaper for grinding, turn the grinding direction 90° to ensure that the last grinding marks are completely eliminated.

[0058] Step 2: placing the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag; the polishing agent for the mechanical polishing is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth;

[0059] Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing treatment; the solution for the anodizing treatment is a H2SO4 aqueous solution with a mass concentration of 5%, and the H2SO4 in the H2SO4 aqueous solution is an analytical pure reagent, the equipment is an adjustable constant current source, and the voltage of the anodizing treatment is 20V, the current is 1.0A, and the time is 3s;

[0060] Step 4: immerse the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching; the corrosion solution is composed of a 5% by volume HF aqueous solution, and the HF in the HF aqueous solution is an analytical pure reagent, and the etching time is 5s;

[0061] Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

[0062] Figure 2 The microstructure of the TA22 titanium alloy grain structure in this embodiment (400×) is shown in FIG. Figure 2 It can be seen that the base color is grayish white after further removal of the anodized coating. The grain boundaries of the TA22 titanium alloy are darker and black, and the grain boundary details are clearly visible.

[0063] Example 5

[0064] This embodiment includes the following steps:

[0065] Step 1: Machine the TA22 titanium alloy sample to obtain a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane; the specific grinding process is: use 120 # , 800 # , 1200# and 2000 # Grind step by step with metallographic water sandpaper. Each time you change the metallographic water sandpaper for grinding, turn the grinding direction 90° to ensure that the last grinding marks are completely eliminated.

[0066] Step 2: placing the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag; the polishing agent for the mechanical polishing is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth;

[0067] Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing treatment; the solution for the anodizing treatment is a H2SO4 aqueous solution with a mass concentration of 5%, and the H2SO4 in the H2SO4 aqueous solution is an analytical pure reagent, the equipment is an adjustable constant current source, and the voltage of the anodizing treatment is 20V, the current is 1.0A, and the time is 3s;

[0068] Step 4: immerse the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching; the corrosion solution is composed of a 5% by volume HF aqueous solution, and the HF in the HF aqueous solution is an analytically pure reagent, and the etching time is 7 seconds;

[0069] Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

[0070] Figure 6 The microstructure of the TA22 titanium alloy grain structure in this embodiment (400×) is shown in FIG. Figure 6 It can be seen that the base color is grayish white after further removal of the anodized coating. The grain boundaries of the TA22 titanium alloy are lighter and coarser, black, and the grain boundary details are clearly visible.

[0071] Example 6

[0072] This embodiment includes the following steps:

[0073] Step 1: Machine the TA22 titanium alloy sample to obtain a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane; the specific grinding process is: use 120 # , 800 # , 1200# and 2000 # Grind step by step with metallographic water sandpaper. Each time you change the metallographic water sandpaper for grinding, turn the grinding direction 90° to ensure that the last grinding marks are completely eliminated.

[0074] Step 2: placing the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag; the polishing agent for the mechanical polishing is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth;

[0075] Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing treatment; the solution for the anodizing treatment is a H2SO4 aqueous solution with a mass concentration of 5%, and the H2SO4 in the H2SO4 aqueous solution is an analytically pure reagent, the equipment is an adjustable voltage-stabilized constant current source, and the voltage of the anodizing treatment is 25V, the current is 1.0A, and the time is 2s;

[0076] Step 4: immerse the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching; the corrosion solution is composed of a 5% by volume HF aqueous solution, and the HF in the HF aqueous solution is an analytically pure reagent, and the etching time is 8s;

[0077] Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

[0078] Figure 7 The microstructure of the TA22 titanium alloy grain structure in this embodiment (400×) is shown in FIG. Figure 7 It can be seen that the base color is dark brown and grayish white, the grain boundaries of TA22 titanium alloy are lighter and coarser, black, and the grain boundary details are clearly visible.

[0079] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A corrosion display method for TA22 titanium alloy grain structure, characterized in that: The method comprises the following steps: Step 1: Mechanically process the TA22 titanium alloy sample into a microstructure observation plane, then grind the microstructure observation plane on a metallographic pre-grinder, and wash away the sand on the microstructure observation plane; Step 2: Place the microstructure observation plane washed away from the sand in step 1 on a polishing machine for mechanical polishing until the surface of the microstructure observation plane is smooth and bright without scratches and drag; Step 3, subjecting the microstructure observation plane after mechanical polishing in step 2 to anodizing coating for 2s to 5s; Step 4, immersing the microstructure observation plane after the anodized coating treatment in step 3 into a corrosion solution for etching; Step 5: Place the microstructure observation plane after etching in step 4 under a metallographic microscope, and observe the metallographic microstructure using open field observation.

2. The corrosion display method of TA22 titanium alloy grain structure according to claim 1 is characterized in that: The specific process of grinding in step 1 is: using a particle size of 120 # , 800 # , 1200# and 2000 # The metallographic water sandpaper is used for grinding step by step. Each time the metallographic water sandpaper is changed for grinding, the grinding direction is turned 90° to ensure that the previous grinding marks are completely eliminated.

3. The corrosion display method of TA22 titanium alloy grain structure according to claim 1 is characterized in that: The polishing agent for mechanical polishing in step 2 is a SiO2 suspension with a particle size of 0.5 μm, and the polishing cloth is a damping polishing cloth.

4. The corrosion display method of TA22 titanium alloy grain structure according to claim 1, characterized in that: The solution for the anodizing coating treatment in step three is a H2SO4 aqueous solution with a mass concentration of 5%, the equipment is an adjustable constant current source, and the voltage of the anodizing coating treatment is 18V~25V, the current is 0.8A~1.0A, and the time is 1s~3s.

5. The corrosion display method of TA22 titanium alloy grain structure according to claim 1, characterized in that: The etching solution in step 4 is composed of 5% by volume HF aqueous solution, and the etching time is 3s to 8s.

6. A corrosion display method for TA22 titanium alloy grain structure according to claim 4, characterized in that: The H2SO4 in the H2SO4 aqueous solution is an analytically pure reagent.

7. The corrosion display method of TA22 titanium alloy grain structure according to claim 5, characterized in that: The HF in the HF aqueous solution is an analytically pure reagent.

Images