Method for predicting tensile yield strength of different orientations of magnesium alloy extruded bar

Abstract

The application discloses a method for predicting tensile yield strength of magnesium alloy extruded rods in different orientations, and mainly comprises the following steps: establishing a yield strength distribution equation model, testing yield strength in any two orientations, calculating the yield strength distribution equation in a yield space, further calculating the change of the yield strength along the loading direction, and predicting the yield strength. The yield strength distribution equation can be obtained through twice uniaxial tensile tests, and the yield strength of the magnesium alloy extruded rod in different orientations during uniaxial tension can be obtained through further calculation, so that the yield strength of the magnesium alloy extruded rod with strong basal plane texture can be accurately predicted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic deformation of magnesium alloy, and particularly relates to a method for predicting tensile yield strength of magnesium alloy extruded rods in different orientations. BACKGROUND

[0002] Magnesium alloy is the lightest metal structural material, and has excellent properties such as small density, high specific strength and specific stiffness, good thermal conductivity and strong anti-vibration and shock absorption capacity, and is widely used in rail transit and electronic information fields. However, the magnesium alloy has a close-packed hexagonal structure, and the axial ratio is 1.623. In the process of deformation, the basal slip is very easy to start, so that the magnesium alloy is prone to form basal texture. The formation of texture leads to strong mechanical property anisotropy of the magnesium alloy along different directions, which has an important influence on the processing and forming of the magnesium alloy.

[0003] The magnesium alloy extruded rod generally has basal filament texture, and the basal plane of the grain is parallel to the extrusion direction of the rod. When the magnesium alloy extruded rod is loaded in different directions, the deformation mechanisms are quite different. For example, when the magnesium alloy extruded rod is stretched along the extrusion direction, the main deformation mechanism is cylindrical slip, and when the magnesium alloy extruded rod is stretched along the transverse direction, the main deformation mechanisms are basal slip and tensile twinning. Because these deformation mechanisms have different critical shear stresses and different abilities to coordinate plastic deformation, the magnesium alloy extruded rod exhibits different yield behaviors and work hardening behaviors when loaded in different orientations, that is, the magnesium alloy extruded rod has strong anisotropy.

[0004] The anisotropy can lead to uneven plastic deformation of the magnesium alloy rod during processing, and is prone to cause cracking of the workpiece, which is not conducive to the plastic forming of the magnesium alloy, and is one of the key problems limiting the popularization and application of the magnesium alloy. Therefore, it is of great significance to study the anisotropy of the magnesium alloy rod and propose a method for predicting the yield strength of the magnesium alloy extruded rod in different orientations, so as to accurately predict the yield strength of the magnesium alloy rod in different orientations. SUMMARY

[0005] The present application discloses a method for predicting tensile yield strength of magnesium alloy extruded rods in different orientations, which can accurately predict the yield strength when the magnesium alloy extruded rod is uniaxially stretched in different orientations.

[0006] The technical scheme is as follows:

[0007] S1, a distribution equation model of the tensile yield strength of the magnesium alloy rod in different orientations in a yield coordinate space, that is, a yield strength distribution equation model, is established.

[0008] S2, test the uniaxial tensile properties of the magnesium alloy extruded bar along any two directions of the bar, and obtain two sets of tensile yield strength values;

[0009] S3, calculate the coordinates (x, y) of the oriented yield strength in the yield coordinate space according to the yield strength values and the included angle θ between the loading direction and the transverse direction of the bar;

[0010] S4, bring the coordinate values of the two yield strengths into the yield strength distribution equation model to obtain the distribution equation of the tensile yield strength of the magnesium alloy bar in different orientations in the yield coordinate space;

[0011] S5, calculate the yield strength σ T along any orientation according to the distribution equation of the tensile yield strength in different orientations in the yield coordinate space;

[0012] S6, calculate the included angle θ between the loading direction and the transverse direction of the bar according to the distribution equation of the tensile yield strength in different orientations in the yield coordinate space;

[0013] S7, draw a curve of the yield strength changing with the angle θ according to the corresponding relationship between the calculated yield strength along any orientation and the included angle between the loading direction and the transverse direction of the bar, and the tensile yield strength along any orientation of the magnesium alloy extruded bar can be predicted through the curve.

[0014] Further, S1 specifically is:

[0015] S1-1, test the uniaxial tensile properties of the magnesium alloy extruded bar along different orientations of the bar;

[0016] S1-2, obtain the tensile yield strength of the samples in different orientations according to the tensile stress-strain curve;

[0017] S1-3, calculate the coordinates of the tensile yield strength of each oriented sample in the yield coordinate space, and draw the tensile yield strength to the coordinate system;

[0018] S1-4, fit the distribution of the tensile yield strength in the yield strength coordinate space to obtain the yield strength distribution equation model.

[0019] Further, S2 specifically is to test the uniaxial tensile properties of the magnesium alloy extruded bar along any two orientations of the bar, obtain the tensile stress-strain curve, and obtain the tensile yield strength of the two orientations according to the tensile stress-strain curve.

[0020] Further, the yield strength distribution equation model in S3 is: y T = ax T +b, wherein (x T , y T) is the coordinate of yield strength in the yield coordinate space, the horizontal coordinate is the yield strength along the transverse direction of the bar, the vertical coordinate is the yield strength along the extrusion direction of the bar, and a and b are constants.

[0021] Further, in S5:

[0022]

[0023] Further, in S6:

[0024]

[0025] Advantages: Compared with the prior art, the advantages of the present application are: the yield strength distribution equation can be obtained through two uniaxial tensile experiments, and the yield strength along different orientations of the bar during uniaxial tensile is obtained through further calculation, so that the yield strength of the magnesium alloy extruded bar with strong basal plane texture can be accurately predicted; the relationship between the yield strength of the magnesium alloy extruded bar and the loading direction can be established, the variation law of the yield strength with the loading direction is obtained, and the anisotropy of the magnesium alloy bar is strengthened; through the prediction of the tensile yield strength of the magnesium alloy bar according to the present application, important guidance can be provided for the processing and forming of the magnesium alloy bar, and the application and promotion of the magnesium alloy bar have important significance. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 (a) is a schematic diagram of loading along different orientations of the bar (the angle between the loading direction (LD) and the transverse direction (TD) of the bar is θ); Figure 1 (b) is the 0002 pole figure of the AZ31 magnesium alloy extruded plate;

[0027] Figure 2 (a) is the true stress-strain curve when tensile along 0° and 90° with respect to the transverse direction of the AZ31 magnesium alloy bar; Figure 2 (b) is the distribution curve of the predicted yield strength in the yield coordinate space;

[0028] Figure 3 is the variation of the predicted yield strength and the experimentally tested yield strength with the loading direction. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be further described below in combination with the drawings and examples.

[0030] The yield strength of the AZ31 magnesium alloy extruded bar is predicted.

[0031] The uniaxial tensile properties of AZ31 magnesium alloy extruded rod along different orientations were tested, the tensile yield strengths of different orientation samples were obtained according to the tensile stress-strain curves, the coordinates of the tensile yield strengths of each orientation sample in the yield coordinate space were calculated, and the tensile yield strengths were plotted in the coordinate system, the distribution equation model of the yield strength in the yield coordinate space was obtained by fitting the distribution of the tensile yield strengths in the yield strength coordinate space: y T = ax T +b.

[0032] The tensile properties of AZ31 magnesium alloy extruded rod along the TD direction and the ED direction with strong basal plane texture were tested, as shown in Figure 1 , (a) is a schematic diagram of loading along different orientations of the rod, the angle between the loading direction (LD) and the transverse direction (TD) of the rod is θ; (b) is the 0002 pole figure of the AZ31 magnesium alloy extruded plate.

[0033] The true stress-strain curves were obtained, as shown in Figure 2 , (a) is the true stress-strain curve when tensile along the 0° and 90° directions relative to the transverse direction of the AZ31 magnesium alloy rod.

[0034] The yield strengths when tensile along the TD direction and the ED direction are 53.3 MPa and 188.1 MPa, respectively.

[0035] According to the orientation relationship between the loading direction and the transverse direction of the rod, the coordinate values of the TD direction and the ED direction yield strength in the yield coordinate space were calculated as (53.3, 0) and (0, 188.1), respectively.

[0036] The calculated coordinate values were brought into the yield strength distribution equation model y T = ax T +b, the values of the constants a and b in the equation were-3.53 and 188.1, respectively, and the distribution equation of the yield strength in the yield coordinate space was y T =-3.53x T +188.1.

[0037] According to the coordinate space distribution equation, the yield strength when loaded along any orientation was calculated:

[0038] As shown in Figure 2 , (b) is the distribution curve of the predicted yield strength in the yield coordinate space.

[0039] According to the coordinate space distribution equation, the angle between the loading direction and the transverse direction of the rod was calculated:

[0040]

[0041] For any x value, the corresponding yield strength σT and the angle θ between the loading direction and the transverse direction of the bar, so according to σ T and the corresponding relationship between θ, the yield strength with the change of loading direction is drawn, as shown in Figure 3

[0042] According to the yield strength curve with the change of θ angle, the yield strength of AZ31 magnesium alloy extruded bar can be predicted, as shown in Figure 3 The yield strength measured by experiment is very close to the predicted value, which verifies the accuracy of the method.​

Claims

1. A method for predicting the tensile yield strength of magnesium alloy extruded bars with different orientations, characterized in that, Includes the following steps: S1. Establish a distribution equation model of the tensile yield strength of magnesium alloy bars with different orientations in the yield coordinate space, i.e., the yield strength distribution equation model. S2. Test the uniaxial tensile properties of the magnesium alloy extruded bar along any two directions to obtain two sets of tensile yield strength values. S3. Calculate the coordinates (x, y) of the orientation yield strength in the yield coordinate space based on the yield strength value and the angle θ between the loading direction and the transverse direction of the bar. S4. Substitute the coordinate values ​​of the two yield strengths into the yield strength distribution equation model to obtain the distribution equation of the tensile yield strength of the magnesium alloy bar in different orientations in the yield coordinate space. S5. Calculate the yield strength under arbitrary orientation loading based on the distribution equation of tensile yield strength in yield coordinate space for different orientations. ; S6. Calculate the angle θ between the loading direction and the transverse direction of the bar based on the distribution equation of tensile yield strength in different orientations in the yield coordinate space; S7. Based on the calculated yield strength under arbitrary orientation loading and the corresponding relationship between the loading direction and the transverse direction of the bar, plot the curve of yield strength versus angle θ. The tensile yield strength under arbitrary orientation of magnesium alloy extruded bar can be predicted by this curve. The yield strength distribution equation model in S4 is as follows: In the formula (x T y T () represents the coordinates of the yield strength in the yield coordinate space, where the horizontal axis is the yield strength along the transverse direction of the bar and the vertical axis is the yield strength along the extrusion direction of the bar, and a and b are constants. In S5: ； In S6: 。 2. The method for predicting the tensile yield strength of magnesium alloy extruded bars with different orientations according to claim 1, characterized in that, S1 specifically refers to: S1-1. Test the uniaxial tensile properties of magnesium alloy extruded bars along different orientations. S1-2. Obtain the tensile yield strength of samples with different orientations based on the tensile stress-strain curve; S1-3. Calculate the coordinates of the tensile yield strength of each orientation sample in the yield coordinate space, and plot the tensile yield strength on the coordinate system. S1-4. Fit the distribution of tensile yield strength in the yield strength coordinate space to obtain the yield strength distribution equation model.

3. The method for predicting the tensile yield strength of magnesium alloy extruded bars with different orientations according to claim 1, characterized in that: S2 specifically involves testing the uniaxial tensile properties of a magnesium alloy extruded bar with a strong basal texture along any two orientations to obtain tensile stress-strain curves, and then obtaining the tensile yield strength of the two orientations based on the tensile stress-strain curves.

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