A method for determining coarse precipitated phase of metal material

Abstract

A method for determining coarse precipitated phases of metal materials comprises the following steps: (1) electroplating: using a metal sample to be tested as a cathode and a plated metal as an anode, electroplating a metal coating on the surface of the metal sample to be tested; (2) microscopic observation: observing the surface of the metal sample to be tested after electroplating under an optical microscope, and counting the number N of unplated areas in n observation fields, wherein n≥3, and N is a positive integer; (3) calculation: calculating the number η of coarse precipitated phases of metal materials per unit area according to the observation result of step (2). The present invention adopts an electroplating method to count the number and distribution of coarse precipitated phases of metal materials. The method has the characteristics of simple operation, low cost, efficient process, and high precision, and effectively avoids the problems of high sample preparation requirements, high cost, cumbersome operation, and inability to achieve large-area precipitated phase determination in conventional precipitated phase testing methods.

Description

Technical Field

[0001] The invention relates to the field of alloy detection, and in particular to a method for determining a coarse precipitated phase of a metal material. Background Art

[0002] Metal materials need to be alloyed in order to achieve high strength, but the presence of excessive alloying elements and impurity elements often leads to the formation of coarse precipitates (0.5-10μm). Coarse precipitates are usually hard and brittle, with little deformation ability. During the processing or service of the alloy, stress concentration is easily generated in the precipitates, forming crack initiation points, which is very unfavorable to the mechanical properties of the alloy and will lead to a decrease in the strength and plasticity of the metal material. In addition, coarse precipitates will also have an adverse effect on the corrosion resistance and wear resistance of metal materials.

[0003] In order to ensure the application performance of metal materials, the number and proportion of precipitated phases must be measured before the alloy materials are used to ensure the service performance of the materials. The conventional testing methods for analyzing micron-level precipitated phases are scanning electron microscopy, transmission electron microscopy, backscattered electron diffraction, X-ray diffraction and other methods. However, such detection methods have high detection costs, high sample quality requirements, and require cumbersome sample preparation processes. The operation is complex, the detection preparation time is long, and large-area precipitate phase determination cannot be achieved. Therefore, finding a method for accurately and quickly determining the coarse precipitated phases of metal materials plays an extremely important role in the research and application of metal materials.

[0004] Patent CN 112415029 A entitled "A method for directly testing the volume fraction of precipitated phases in alloys" and patent CN 113777115 A entitled "A quantitative statistical method for precipitated phases in alloys" respectively disclose quantitative statistical methods for precipitated phases in alloys, with objective and accurate test results, small errors and good repeatability. However, such methods are based on projection electron microscopy analysis technology, which requires cumbersome sample preparation and cannot achieve the determination of coarse-sized precipitated phases. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for determining the coarse precipitated phase of a metal material. It should be noted that the coarse precipitated phase of the metal material described in the present invention is a precipitated phase with a size of ≥0.5 μm in the metal material, which specifically includes the following contents:

[0006] A method for determining a coarse precipitated phase of a metal material, the method comprising the following steps:

[0007] (1) Electroplating: Using the metal sample to be tested as the cathode and the plated metal as the anode, a layer of metal coating is electroplated on the surface of the metal sample to be tested;

[0008] (2) Microscope observation: observe the surface of the metal sample to be tested after electroplating under an optical microscope, and count the total number N of unplated areas in n observation fields, where n≥3 and N is a positive integer;

[0009] (3) Calculation: Based on the observation results of step (2), the number η of coarse precipitated phases of the metal material per unit area is calculated. The specific calculation method is: η = N / S, where S is the total area of ​​n fields of view of the optical microscope, in units of mm 2 .

[0010] Specifically, before the electroplating treatment in step (1), the metal material to be tested needs to be cut into a certain size to obtain a metal sample to be tested; then the surface of the metal sample to be tested is degreased and pickled; the surface of the metal sample to be tested has no adverse morphology.

[0011] Specifically, the size of the metal sample to be tested is: 6cm-8cm in length and 2cm-4cm in width.

[0012] Specifically, the degreasing method is electrolytic degreasing or alkaline solution immersion degreasing, the electrolytic degreasing reagent is one of sodium carbonate and sodium phosphate or a mixture of the two, the electrolyte temperature is 50°C-80°C, and the current density is 8A / dm 2 -15A / dm 2 The treatment time is 20s-60s; the alkali solution temperature for oil removal by immersion in alkali solution is 50℃-80℃, and the immersion time is 5-10min.

[0013] Specifically, the acid solution used in the pickling is a sulfuric acid solution or a nitric acid solution, the temperature of the acid solution is 20° C.-30° C., and the pickling time is 0.5 min-2 min.

[0014] Specifically, before the microscopic observation in step (2), the metal sample to be tested needs to be cleaned and dried after the electroplating treatment.

[0015] Specifically, the plated metal in step (1) has a color difference from the metal to be tested; the electroplating process parameters are: cathode current density 2A / dm 2 -8 A / dm 2 , electroplating time 5s-30s.

[0016] Specifically, in step (2), the observation magnification of the optical microscope is 200-1000 times.

[0017] Specifically, in step (2), the unplated area is a circular or nearly circular area.

[0018] Beneficial effects of the present invention:

[0019] (1) During the electroplating process, the potential difference between the surface coarse precipitated phase and the substrate reduces the overpotential of hydrogen precipitation, and hydrogen bubbles are formed around the precipitated phase and stay on the surface of the metal material, hindering the further deposition of the coating ions, resulting in a circular or nearly circular unplated area near the precipitated phase. Based on the influence of the precipitated phase on the electroplating surface quality, the electroplating method is used to count the number and distribution of coarse precipitated phases of the metal material. This method has the characteristics of simple operation, low cost, efficient process and high precision, and effectively avoids the problems of high sample preparation requirements, high cost, cumbersome operation and inability to achieve large-area precipitated phase determination in conventional precipitated phase testing methods;

[0020] (2) The method disclosed in the present invention is used to degrease and pickle the metal material to be tested, which can better remove impurities on the surface of the sample and eliminate the influence of impurities on electroplating, making the subsequent observation results more accurate; secondly, the electroplating parameters disclosed in the present invention can ensure that the surface of the sample is plated with a coating while the precipitated phase on the surface is fully exposed, which is beneficial to improving the accuracy and reliability of subsequent observation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an optical microscope photo of the precipitated phase after Ni electroplating on the surface of C19400 copper alloy in the embodiment;

[0022] Figure 2 This is an optical microscope photograph of the precipitated phase after Sn electroplating on the surface of C70250 copper alloy in the embodiment. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments shown below do not limit the invention content described in the claims. In addition, the entire contents of the structures represented by the following embodiments are not limited to those necessary as solutions to the invention described in the claims.

[0024] A method for determining a coarse precipitated phase of a metal material, wherein the coarse precipitated phase of the metal material is a precipitated phase with a size of ≥0.5 μm in the metal material, and the method comprises the following steps:

[0025] (1) Electroplating treatment: First, the metal material to be tested is cut into a metal sample to be tested with a length of 6 cm-8 cm and a width of 2 cm-4 cm, and the surface of the metal sample to be tested has no bad morphology; then the surface of the metal sample to be tested is degreased and pickled; the degreasing method is electrolytic degreasing or alkaline solution immersion degreasing, the electrolytic degreasing reagent is one of sodium carbonate and sodium phosphate or a mixture of the two, the electrolyte temperature is 50°C-80°C, preferably 65°C; the current density is 8A / dm 2 -15A / dm 2 , preferably 10A / dm 2; The treatment time is 20s-60s, preferably 30s; the alkali solution temperature for oil removal is 50℃-80℃, the immersion time is 5-10min, preferably 40℃ for 5min; the acid solution used in pickling is sulfuric acid solution or nitric acid solution, the temperature of the acid solution is 20℃-30℃, the pickling time is 0.5min-2min, preferably 25℃ for 1min; then the metal sample to be tested is used as the cathode and the plated metal is used as the anode to electroplate a metal coating on the surface of the metal sample to be tested; the plated metal and the metal to be tested should have obvious color differences, such as nickel electroplating on the surface of copper alloy, tin electroplating on the surface of copper alloy, copper electroplating on the surface of aluminum alloy, etc.; the electroplating process parameters are: cathode current density 2A / dm 2 -8A / dm 2 , electroplating time 5s-30s, specific cathode current density can be selected: 2A / dm 2 , 4A / dm 2 、6A / dm 2 , 7A / dm 2 , 8A / dm 2 The electroplating time can be selected as 5s, 8s, 10s, 15s, 20s, 25s, 28s, 30s, etc. Firstly, the method disclosed in the present invention is used to degrease and pickle the metal material to be tested, which can better remove impurities on the surface of the sample, eliminate the influence of impurities on electroplating, and make the subsequent observation results more accurate; secondly, the electroplating parameters disclosed in the present invention can ensure that the sample surface is plated with a coating while the precipitation phase on the surface is fully exposed, which is conducive to improving the accuracy and reliability of subsequent observation results.

[0026] (2) Microscope observation: the metal sample to be tested after electroplating is cleaned and dried; the surface of the metal sample to be tested after electroplating is observed under an optical microscope, and the total number N of unplated areas in n observation fields of view is counted, wherein n≥3, and N is a positive integer; the observation magnification of the optical microscope is 200-1000, and the specific magnification can be 200, 300, 400, 500, 800, 900, 1000, etc.; the unplated area is a circular or nearly circular area.

[0027] (3) Calculation: Based on the observation results of step (2), the number η of coarse precipitates per unit area of ​​the metal material is calculated as follows: η = N / S, where η is the number of coarse precipitates per unit area of ​​the metal material, expressed in units of pieces / mm 2 ; N is the total number of uncoated areas in n observation fields; S is the total area of ​​n fields of view of the optical microscope, in mm 2 .

[0028] Example 1

[0029] A method for determining a coarse precipitate phase of a metal material in this embodiment is to electroplate Ni on the surface of a copper alloy to determine the coarse precipitate phase, and the method is performed in the following steps:

[0030] (i) A C19400 copper alloy strip with a size of 6 cm × 2 cm was selected as the test sample for precipitation phase determination.

[0031] (ii) Before electroplating, the cut test samples are subjected to electrolytic degreasing and pickling to remove surface oil and impurities.

[0032] The electrolytic degreasing reagent is Na2CO3 30g / L, Na3PO4 30g / L, the temperature is 65℃, and the current density is 10A / dm 2 , treatment time 30s. The pickling reagent is 10% H2SO4 solution, soaking for 1min at 25℃.

[0033] (III) Electroplating treatment: a layer of metal Ni is electroplated on the surface of the test sample. A high-purity Ni sheet is used as the anode, and the electroplating solution is NiSO4·6H2O 96g / 800ml, NiCl2 8g / 800ml, H3BO3 32g / 800ml, C 12 H25SO4Na 0.5g / 800ml; voltage 5V, current density 4A / dm 2 , treated at 65℃ for 10s.

[0034] (iv) Post-electroplating treatment: After the electroplating is completed, the copper alloy is cleaned with pure water and air-dried with a hair dryer.

[0035] (V) Determination of precipitated phase: observe the electroplated test samples under an optical microscope at a magnification of 1000, and count the average number of samples of all circular and approximately circular unplated areas in 5 observation fields, which is 20.

[0036] The field of view of an optical microscope at 1000x magnification is 0.012369 mm 2 The statistical result of coarse precipitates (≥0.5 μm) in the test sample is η=1216.94 / mm 2 .

[0037] Example 2

[0038] A method for determining a coarse precipitate phase of a metal material in this embodiment is to electroplate Sn on the surface of a copper alloy to determine the coarse precipitate phase, and the method is performed in the following steps:

[0039] (i) C70250 copper alloy strip with a size of 6 cm × 3 cm was selected as the test sample for precipitation phase determination.

[0040] (ii) Before electroplating, the cut test samples are subjected to electrolytic degreasing and pickling to remove surface oil and impurities.

[0041] The electrolytic degreasing reagent is Na2CO3 30g / L, Na3PO4 30g / L, the temperature is 65℃, and the current density is 10A / dm 2 , treatment time 30s. The pickling reagent is 10% H2SO4 solution, soaking for 1min at 25℃.

[0042] (III) Electroplating treatment: electroplating a layer of metal Sn on the surface of the test sample. High-purity Sn sheet is used as the anode, and the electroplating solution is K2[Sn(OH)6]80g / 800ml, KOH 15g / 800ml, CH3COONa 16g / 800ml, H2O2 1ml / 800ml; voltage is 5V, and the current density is 2A / dm 2 , treated at 70℃ for 20s.

[0043] (iv) Post-electroplating treatment: After electroplating is completed, the copper alloy is cleaned with pure water and air-dried with a hair dryer.

[0044] (V) Determination of precipitated phase: The electroplated test samples were observed under an optical microscope at a magnification of 200, and the average number of samples of all circular and approximately circular unplated areas in three observation fields was counted as 36.

[0045] The field of view under an optical microscope at 200x magnification is 0.3072 mm 2 The statistical result of coarse precipitates (≥0.5μm) in the test sample is η=117.18 / mm 2 .

[0046] Example 3

[0047] A method for determining a coarse precipitate phase of a metal material in this embodiment is to electroplate Cu on the surface of an aluminum alloy to determine the coarse precipitate phase, and the method is performed in the following steps:

[0048] (i) A 2024 aluminum alloy strip with a size of 8 cm × 4 cm was selected as the test sample for precipitation phase determination.

[0049] (ii) Before electroplating, the cut test samples are subjected to electrolytic degreasing and pickling to remove surface oil and impurities.

[0050] The degreasing agent is NaOH 30g / L, the temperature is 40℃, and the treatment time is 5min. The pickling agent is 10% HNO4 solution, and the immersion time is 1min at 25℃.

[0051] (III) Electroplating treatment: a layer of metal Cu is electroplated on the surface of the test sample. The pure Cu sheet is used as the anode, the electroplating solution is CuSO4 120g / L, CuCl2 35g / L, ZrSO4 15g / L, H3BO3 5g / L; the voltage is 5V, and the current density is 4A / dm 2 , electroplating at 25℃ for 30s.

[0052] (iv) Post-electroplating treatment: After electroplating is completed, the copper alloy is cleaned with pure water and air-dried with a hair dryer.

[0053] (V) Determination of precipitated phase: The electroplated test samples were observed under an optical microscope at a magnification of 1000, and the average number of samples of all circular and approximately circular unplated areas in 8 observation fields was counted as 13.

[0054] The field of view of an optical microscope at 1000x magnification is 0.012369 mm 2 The statistical result of coarse precipitates (≥0.5μm) in the test sample is η=1051.01 / mm 2 .

[0055] It should be noted that, although the above embodiments take copper alloy and aluminum alloy as examples, the statistics of coarse precipitates of other metal materials can also be measured by the same method. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in this article, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining a coarse precipitated phase of a metal material, characterized in that: The following steps are involved: (1) Electroplating: The metal sample to be tested is used as the cathode and the plated metal is used as the anode. A metal coating is electroplated on the surface of the metal sample to be tested. The plated metal has a different color from the metal to be tested. The electroplating process parameters in the electroplating process are: cathode current density 2A / dm 2 -8 A / dm 2 , electroplating time 5s-30s, cleaning and drying the metal sample to be tested after electroplating; (2) Microscope observation: Observe the surface of the metal sample to be tested after electroplating under an optical microscope, and count the total number N of unplated areas in n observation fields, where n≥3, N is a positive integer, and the unplated area is a circular or nearly circular area; (3) Calculation: Based on the observation results of step (2), the number η of coarse precipitated phases of the metal material per unit area is calculated. The specific calculation method is: η = N / S, where S is the total area of ​​n fields of view of the optical microscope, in units of mm 2 ; Before the electroplating treatment in step (1), the metal material to be tested needs to be cut into a certain size to obtain a metal sample to be tested; then the surface of the metal sample to be tested is degreased and pickled; the surface of the metal sample to be tested has no adverse morphology.

2. The method for determining the coarse precipitated phase of a metal material according to claim 1, characterized in that: The size of the metal sample to be tested is: 6cm-8cm in length and 2cm-4cm in width.

3. The method for determining the coarse precipitated phase of a metal material according to claim 1, characterized in that: The degreasing method is electrolytic degreasing or alkaline solution immersion degreasing, the electrolytic degreasing reagent is one of sodium carbonate and sodium phosphate or a mixture of the two, the electrolyte temperature is 50°C-80°C, and the current density is 8A / dm 2 -15A / dm 2 The treatment time is 20s-60s; the alkali solution temperature for oil removal by immersion in alkali solution is 50℃-80℃, and the immersion time is 5-10min.

4. The method for determining the coarse precipitated phase of a metal material according to claim 3, characterized in that: The acid solution used in the pickling is a sulfuric acid solution or a nitric acid solution, the temperature of the acid solution is 20° C.-30° C., and the pickling time is 0.5 min-2 min.

5. The method for determining the coarse precipitated phase of a metal material according to claim 1, characterized in that: In the step (2), the observation magnification of the optical microscope is 200-1000 times.

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