Method for measuring alloy phase interface strength

Abstract

The present invention discloses a method for measuring the strength of alloy phase interfaces, including: heat treating an alloy to obtain an alloy sample containing a phase interface structure; treating the surface of the alloy sample to display the microstructure of the alloy; dividing the treated surface of the alloy sample into a plurality of regions and marking them; performing a grain orientation test on the treated surface of the alloy sample to obtain a grain orientation distribution diagram of the sample surface; selecting the same orientation grain interior according to the sample surface marking and the grain orientation distribution diagram, and processing the same size micrometer scale sample containing different phases and different types of phase interfaces; compressing and deforming the micrometer size sample to obtain a compressive stress-strain curve, and then obtaining the yield strength of each micrometer size sample; and calculating the strength of different phase interfaces using the sample strength mixing rule according to the yield strength of each micrometer size sample. The superposition effect of grain boundaries and different interface structures on mechanical behavior is eliminated, and the strength of different phase interfaces can be accurately measured.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials and relates to a method for measuring alloy phase interface strength. Background Art

[0002] Second phase strengthening is one of the most important strengthening methods for metal materials. The strengthening effect of the second phase on the alloy depends not only on the strength, size, shape and distribution of the second phase, but also on the interface strengthening between the second phase and the matrix. For example, in the field of titanium alloys, α phase strengthening is the main strengthening method. However, the α phase is lower in strength and easier to deform than the β phase matrix. The strengthening of the α phase on the β phase matrix mainly depends on the α / β interface strengthening. In order to meet the requirements of alloy strength and plasticity matching, the titanium alloy design field attempts to obtain a certain amount of primary α phase (α p ) and secondary lamellar α phase (α s ), the influence of different types of α / β interfaces on the mechanical behavior of alloys is exerted, making it the main way to regulate the mechanical properties of titanium alloys. For α-phase strengthened titanium alloys, mainly including α p / β(nascent α p Interface with β), α p / β+α s (Newborn α p With secondary α s phase-enhanced β phase interface) and α s / β(Secondary α s Therefore, accurate measurement of different types of interface strength is crucial for finding the optimal match of alloy mechanical behavior and guiding the design of high-strength and high-toughness alloys. However, the current problem is that traditional experimental methods cannot eliminate the superposition effect of grain boundaries and different interface structures on mechanical behavior, and it is difficult to accurately measure different interface structures (such as α in titanium alloys). p / β、α p / β+α s and α s / β and other interfaces) contribute to the material strength respectively. Summary of the invention

[0003] The purpose of the present invention is to provide a method for measuring the interface strength of alloy phases, which solves the problem in the prior art that it is difficult to accurately measure the interface strengths of different phases.

[0004] The technical solution adopted by the present invention is a method for measuring the alloy phase interface strength, comprising the following steps:

[0005] Step 1, heat treating the alloy to obtain an alloy sample containing a phase interface structure;

[0006] Step 2, treating the surface of the alloy sample to show the microstructure of the alloy;

[0007] Step 3, dividing the surface of the alloy sample processed in step 2 into several areas and marking them;

[0008] Step 4, testing and analyzing the surface of the alloy sample after the treatment in step 3 to obtain a grain orientation distribution map of the sample surface;

[0009] Step 5, according to the sample surface mark obtained in step 3 and the grain orientation distribution map obtained in step 4, select the interior of the grains with the same orientation, and process to obtain micrometer-scale samples of the same size with different phases and different types of phase interfaces;

[0010] Step 6, compressing and deforming the micron-sized samples to obtain a compressive stress-strain curve, and then obtaining the yield strength of each micron-sized sample;

[0011] Step 7: Based on the yield strength of each micron-sized sample, the strength of different phase interfaces is calculated using the sample strength mixing law.

[0012] The present invention is also characterized in that:

[0013] The method for treating the surface of the alloy sample in step 2 is electrolytic polishing and corrosion.

[0014] In step 4, the EBSD test and analysis method is used to test and analyze the surface of the alloy sample treated in step 3.

[0015] In step 5, a micron-sized sample is processed at the same location inside the grain using FIB technology.

[0016] The compression deformation in step 6 is completed by controlling the nanoindentation instrument.

[0017] The beneficial effects of the present invention are as follows: the method for measuring the strength of alloy phase interfaces of the present invention adopts micron-sized samples of the same size containing different phases and different phase interfaces in the same orientation of the grains by adopting micron-sized technology, and combines compression deformation test to establish a quantitative relationship between mechanical properties and several typical microstructures, and calculates the strength of different types of phase interfaces by the sample strength mixing rule. Compared with the existing method, the superposition effect of grain boundaries and different interface structures on mechanical behavior is eliminated, and the strength of different phase interfaces can be accurately measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1a is a microstructure diagram of a TC21 alloy sample after solution heat treatment at 900° C. / 1 h in an embodiment of the method for measuring alloy phase interface strength of the present invention;

[0019] Figure 1bIt is a microstructure diagram of the TC21 alloy sample of the embodiment of the method for measuring the alloy phase interface strength of the present invention after being subjected to 900°C / 1h solid solution treatment + 600°C / 1h aging heat treatment;

[0020] Figure 2 is a diagram of micrometer-scale samples containing different microstructures processed in an embodiment of the method for measuring alloy phase interface strength of the present invention;

[0021] Figure 3 is a compressive stress-strain curve diagram of an embodiment of the method for measuring alloy phase interface strength of the present invention;

[0022] Figure 4 This is a graph showing the mechanical properties test results of an embodiment of the method for measuring alloy phase interface strength of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] The method for measuring alloy phase interface strength comprises the following steps:

[0025] Step 1, heat treating the alloy to obtain an alloy sample containing a phase interface structure;

[0026] Step 2, electrolytically polishing and corroding the surface of the alloy sample treated in step 1 to reveal the microstructure of the alloy;

[0027] Step 3: using a hardness tester to divide the surface of the alloy sample processed in step 2 into several areas, and perform indentation marking;

[0028] Step 4: Using EBSD testing and analysis method to test and analyze the surface of the alloy sample treated in step 3 to obtain a grain orientation distribution map of the sample surface;

[0029] Step 5: According to the microstructure of the alloy sample surface, the sample surface mark obtained in step 3 and the grain orientation distribution map obtained in step 4, select the interior of the grains in the same orientation and use FIB technology to process to obtain the same-sized micron-scale samples containing different phases and different types of phase interfaces;

[0030] Step 6: Compress and deform the micron-sized sample by a nano-indentation instrument to obtain a compressive stress-strain curve, and then obtain the yield strength of each micron-sized sample;

[0031] Step 7: Based on the yield strength of each micron-sized sample, the strength of different phase interfaces is calculated using the sample strength mixing law.

[0032] Through the above manner, the method for measuring the strength of alloy phase interfaces of the present invention adopts micron-nano technology to process a series of micron-sized samples of the same size containing different phases and different phase interfaces inside the grains in the same direction, and combines compression deformation test to establish a quantitative relationship between mechanical properties and several typical microstructures. The strength of different types of phase interfaces is calculated by the sample strength mixing law. Compared with the existing method, the superposition effect of grain boundaries and different interface structures on mechanical behavior is eliminated, and the strength of different interfaces can be accurately measured.

[0033] Example

[0034] The following uses TC21 titanium alloy as an example to calculate the strength of different types of α / β phase interfaces. For other second phase strengthened metal materials, the same method can be used to achieve this.

[0035] Step 1: Heat treat the TC21 alloy to obtain α p / β、α s / β and α p / β+α s (where: α p It is the primary α phase in β titanium alloy. s (secondary α phase in β titanium alloy) Several typical α / β phase interface structures;

[0036] Step 2: Electrolytic polishing and corrosion are performed on the surface of the TC21 alloy sample treated in step 1. The microstructure of the alloy is as follows: Figure 1a ,b;

[0037] Step 3, marking the surface of the sample processed in step 2;

[0038] Step 4: Use EBSD technology to test the grain orientation distribution;

[0039] Step 5: According to the microstructure distribution map obtained in step 2, combined with the surface marking in step 3 and the sample grain orientation distribution map obtained in step 4, select the interior of the grain in the same orientation as β and use FIB technology to process the grains containing β phase, α phase and β phase respectively. p / β、α s / β and α p / β+α s The diameter of the phase interface structure is 2 microns. In order to calculate the volume of each phase, the α p / β、α p / β+α s The interface is placed in the middle of the sample, and the sample morphology is as follows Figure 2 As shown;

[0040] Step 6: Perform nanocompression deformation on the sample obtained in step 5 to obtain a compressive stress-strain curve, such as Figure 3The flow stress at 0.2% plastic deformation is taken as the yield strength, and the yield strength σ of the β phase sample is obtained. β =576MPa, including α p / β、α s / β and α p / β+α s The yield strengths of the samples at the interface are: and like Figure 4 shown.

[0041] Step 7: According to the β phase and α phase obtained in step 6 p / β、α s / β and α p / β+α s The yield strength of the sample, combined with the literature reports, the yield strength of the α phase with similar composition to TC21 alloy is about σ α =500MPa, and α can be calculated by the mixed law of sample strength. p / β、α s / β and α p / β+α s The strength of the three phase interfaces. The specific algorithm is as follows:

[0042] (1)α p Calculation of / β interface strength:

[0043] Contains α p The sample strength of the α / β interface organization is determined by p , β phase and α p / β interface consists of three items, according to the mixing law, including α p / β interface structure sample strength It can be expressed as:

[0044]

[0045] Where: is α p The strength of the phase, is α p Volume fraction; σ β is the strength of the β phase, σ β =576MPa; V β is the volume fraction of β phase; is α p / β phase interface provides strength. When processing the sample, α p The / β interface is approximately located in the middle of the sample, that is: Calculated: α p The strength of the / β interface is:

[0046] (2)α s Calculation of / β interface strength:

[0047] Contains α s The sample strength of the α / β interface organization is determined by s , β phase and α s / β interface consists of three items, according to the mixing law, including α s / β interface structure sample strength It can be expressed as:

[0048]

[0049] Where: is α s The strength of the phase, is α s Volume fraction of phase; σ β is the strength of the β phase, σ β =576MPa; V β is the volume fraction of β phase; is α s / β phase interface provides strength. If α is ignored s The strength difference between the β and β phases is approximately calculated at 576 MPa. Calculated: α s The strength of the / β interface is:

[0050] (3)α p / β+α s Calculation of interface strength:

[0051] Contains α p / β+α s The sample strength of the interface organization is determined by α p and β phase, α s / β and α p / β+α s The interface consists of four items, including α according to the mixing law p / β+α s Sample strength of interface structure It can be expressed as:

[0052]

[0053] Where: is α p The strength of the phase, is α p Volume fraction of phase; It contains α s / β interface structure sample strength, It contains α s / β volume fraction of interface structure; is α p / β+α s The strength provided by the phase interface. When processing the sample, α p / β+α s The interface is approximately located in the middle of the sample, that is: Calculated:

Claims

1. A method for measuring alloy phase interface strength, characterized in that: The following steps are involved: Step 1, heat treating the alloy to obtain an alloy sample containing a phase interface structure; Step 2, treating the surface of the alloy sample to display the microstructure of the alloy; Step 3, dividing the surface of the alloy sample processed in step 2 into several areas and marking them; Step 4, performing a grain orientation test on the surface of the alloy sample processed in step 3 to obtain a grain orientation distribution map on the surface of the sample; Step 5, according to the sample surface mark obtained in step 3 and the grain orientation distribution map obtained in step 4, select the same-sized micrometer-scale samples containing different phases and different types of phase interfaces inside the same orientation grains; Step 6, compressing and deforming the micron-sized samples to obtain a compressive stress-strain curve, and then obtaining the yield strength of each micron-sized sample; Step 7: Based on the yield strength of each micrometer-sized sample obtained in step 6, the strength of different phase interfaces is calculated using the sample strength mixing rule.

2. The method for measuring alloy phase interface strength according to claim 1, characterized in that: The method for treating the surface of the alloy sample in step 2 is electrolytic polishing and metallographic etching.

3. The method for measuring alloy phase interface strength according to claim 1, characterized in that: In step 4, the EBSD test analysis method is used to test the grain orientation of the surface of the alloy sample treated in step 3.

4. The method for measuring alloy phase interface strength according to claim 1, characterized in that: In step 5, a micron-sized sample is processed at the same location inside the grain using FIB technology.

5. The method for measuring alloy phase interface strength according to claim 1, characterized in that: The compression deformation in step 6 is completed by controlling the nanoindentation instrument.

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