Magnesium wire, method for producing magnesium wire, and method for evaluating magnesium wire

Abstract

To obtain a magnesium wire that has high flexibility and is hardly broken when complex deformation occurs. A magnesium wire according to the present invention is a magnesium wire containing magnesium as a main component, and in crystal grains constituting the magnesium wire, the proportion of crystal grains having a kernel average misorientation (KAM) value of 0° or more and less than 1° is 70% or more.

Description

TECHNICAL FIELD

[0001] The present invention relates to a magnesium wire containing magnesium as a main component, a method for producing a magnesium wire, and a method for evaluating a magnesium wire.BACKGROUND ART

[0002] In recent years, in view of the biocompatibility and bioabsorbability of magnesium, high-purity magnesium and magnesium alloys with high biosafety are expected to be used in the medical field. In a medical implement made of magnesium, according to healing and fixation of body tissues or after the elapse of the period required for healing and fixation, magnesium is corroded and dissolved in a body fluid, allowing the medical implement to be absorbed in the body. Therefore, there is no need to perform another operation to remove the medical implement when a predetermined period has elapsed since the implant of the medical implement, greatly reducing the burden on the patient.

[0003] Patent Document 1 discloses a magnesium-based alloy wire containing magnesium as a main component and a method for producing the magnesium-based alloy wire.PRIOR ART DOCUMENTPATENT DOCUMENT

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-293069SUMMARY OF THE INVENTION[Technical Problem]

[0005] A magnesium wire containing magnesium as a main component is considered, for example, as a medical implement used to suture an incision or the like. However, the crystal structure of magnesium is a hexagonal close-packed lattice structure, and thus in general, magnesium is a material having poor ductility. Therefore, a technical problem is that a magnesium wire that is a thin wire is broken when complex deformation occurs.

[0006] An object of the present invention is to provide a magnesium wire having high flexibility, a method for producing a magnesium wire, and a method for evaluating a magnesium wire.SOLUTION TO PROBLEM

[0007] As a result of intensive study, the inventor of the present invention has found that the amount of residual strain in crystal grains constituting a magnesium wire greatly influences the flexibility of the magnesium wire, that is, the plastic deformability of the magnesium wire.

[0008] As a value related to "the amount of residual strain in crystal grains", a kernel average misorientation (KAM) value that is the average of the crystal orientation difference between adjacent measurement points is known. A high KAM value indicates a large amount of residual strain in crystal grains, and a low KAM value indicates a small amount of residual strain in crystal grains.

[0009] As a result of further study, the inventor of the present invention has found that when in crystal grains constituting a magnesium wire, the proportion of crystal grains having a KAM value of less than 1° is 70% or more, it is possible to obtain a magnesium wire that has high flexibility and is hardly broken when complex deformation occurs.

[0010] That is, a magnesium wire according to the present invention is a magnesium wire containing magnesium as a main component, wherein in crystal grains constituting the magnesium wire, a proportion of crystal grains having a kernel average misorientation (KAM) value of 0° or more and less than 1° is 70% or more.

[0011] Thus, it is possible to obtain a magnesium wire that has high flexibility and is hardly broken when complex deformation occurs.

[0012] A method for producing a magnesium wire according to the present invention is a magnesium wire production method for producing a magnesium wire thinned by repeatedly performing drawing or extrusion, wherein a magnesium wire in which a proportion of crystal grains having a KAM value of 0° or more and less than 1° is 70% or more is produced without performing annealing in any of a drawing process or an extrusion process.

[0013] Thus, it is possible to obtain a magnesium wire that has high flexibility and is hardly broken when complex deformation occurs, without performing annealing in any of a drawing process or an extrusion process.

[0014] A method for evaluating a magnesium wire according to the present invention is a magnesium wire evaluation method for evaluating flexibility of a magnesium wire containing magnesium as a main component, wherein the flexibility is evaluated based on a proportion of crystal grains having a KAM value of 0° or more and less than a predetermined value in crystal grains constituting the magnesium wire.

[0015] Thus, the flexibility of a magnesium wire can be accurately evaluated by a novel evaluation method, that is, based on the proportion of crystal grains having a KAM value of less than a predetermined value.ADVANTAGEOUS EFFECT OF THE INVENTION

[0016] According to the present invention, it is possible to obtain a magnesium wire that has high flexibility and is hardly broken when complex deformation occurs.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a diagram illustrating a sample used in an evaluation test of a magnesium wire in an embodiment of the present invention; FIG. 2 is a table showing (Sample N1) to (Sample N9); FIG. 3 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N1); FIG. 4 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N2); FIG. 5 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N3); FIG. 6 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N4); FIG. 7 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N5); FIG. 8 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N6); FIG. 9 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N7); FIG. 10 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N8); FIG. 11 shows a measurement result obtained by measuring the distribution of KAM values in crystals of (Sample N9); FIG. 12 is a view showing a flexibility evaluation result of (Sample N4); FIG. 13 is a view showing a flexibility evaluation result of (Sample N8); FIG. 14 is a view showing a stitch size evaluation result of (Sample N4); FIG. 15 is a view showing a stitch size evaluation result of (Sample N8); and FIG. 16 is a summary table of evaluation results of (Sample N1) to (Sample N9). DESCRIPTION OF THE EMBODIMENT

[0018] A magnesium wire according to an embodiment of the present invention will be described below with reference to the drawings.

[0019] In a sample of a magnesium wire used as a biodegradable medical implement, the inventor of the present invention has analyzed the amount of residual strain in crystal grains constituting the magnesium wire by an electron back-scatter diffraction (EBSD) method. Specifically, a kernel average misorientation (KAM) value that is a value related to "the amount of residual strain in crystal grains constituting the magnesium wire" has been measured. A KAM value is the average of the crystal orientation difference between adjacent measurement points. A KAM value can be obtained by using measurement points obtained by the EBSD method and measuring the crystal orientation difference between adjacent measurement points.

[0020] The equipment used to measure KAM values by the EBSD method is as follows. <<SEM>> Scanning electron microscope (SEM): JSM-IT300HR (LA), JEOL Ltd. <<EBSD data acquisition software (software for controlling SEM stage, calculating crystal orientation, etc.)>> OIM Data Collection, TSL Solutions Co., Ltd. <<EBSD data analysis software (software for analyzing acquired data in detail and creating maps, graphs, etc.)>> OIM Analysis, TSL Solutions Co., Ltd.

[0021] As a method for measuring KAM values, in a magnesium wire 1 that has a long length and a circular cross section as illustrated in FIG. 1, the distribution of KAM values is measured in part of a transverse section 10 of the magnesium wire 1 in the longitudinal direction. In the present embodiment, the distribution of KAM values is measured in part of the transverse section 10; however, the measured distribution of KAM values is considered substantially the same as the distribution of KAM values in the entire transverse section 10.

[0022] As (Sample N1) to (Sample N9), nine types of magnesium wires shown in FIG. 2 are used. In (Sample N1) to (Sample N3), (Sample N5) to (Sample N7), and (Sample N9), as illustrated in FIG. 1 (a), the distribution of KAM values is measured in a region 12a whose length corresponds to the length of the radius of the transverse section 10 (region 12a extending from a predetermined outer surface toward a center portion). In (Sample N4) and (Sample N8), as illustrated in FIG. 1 (b), the distribution of KAM values is measured in a region 12b whose length corresponds to the length of the diameter of the transverse section 10 (region 12b extending from a predetermined outer surface toward an outer surface on the side opposite to the predetermined outer surface through the center portion). Each of (Sample N4) and (Sample N8) is a drawn material with φ0.2 mm that is a thin wire having a very small diameter, and the area of the region 12a whose length corresponds to the length of the radius of the transverse section 10 is small, making it difficult to perform measurement. Thus, the distribution of KAM values is measured in the region 12b whose length corresponds to the length of the diameter of the transverse section 10.(Sample N1): "High-purity extruded material with φ3.0"

[0023] (Sample N1) is an extruded material with φ3.0 mm having a magnesium purity of 99.995% or more, and is not annealed after extrusion.(Sample N2): "High-purity drawn material with φ2.0"

[0024] (Sample N2) is a drawn material with φ2.0 mm having a magnesium purity of 99.995% or more. Specifically, (Sample N2) is obtained by using (Sample N1) that is an extruded material with φ3.0 mm and repeatedly drawing (Sample N1) without performing annealing during each stage until the material has φ2.0 mm, and is not annealed after final drawing.(Sample N3): "High-purity drawn material with φ1.0"

[0025] (Sample N3) is a drawn material with φ1.0 mm having a magnesium purity of 99.995% or more. Specifically, (Sample N3) is obtained by using an extruded material with φ2.0 mm that is not annealed after extrusion (not presented as a sample in the present embodiment) and repeatedly drawing the extruded material without performing annealing during each stage until the material has φ1.0 mm, and is not annealed after final drawing.(Sample N4): "High-purity drawn material with φ0.2"

[0026] (Sample N4) is a drawn material with φ0.2 mm having a magnesium purity of 99.995% or more. Specifically, (Sample N4) is obtained by using (Sample N3) that is a drawn material with φ1.0 mm and repeatedly drawing (Sample N3) without performing annealing during each stage until the material has φ0.2 mm, and is not annealed after final drawing.(Sample N5): "Low-purity drawn material with φ2.0 (annealed for 30 minutes)"

[0027] (Sample N5) is a drawn material with φ2.0 having a magnesium purity of 99.9669% or less. Specifically, (Sample N5) is obtained by using (Sample N9) that is a drawn material with φ2.0 mm and annealing (Sample N9) at 250°C for 30 minutes.(Sample N6): "Low-purity drawn material with φ2.0 (annealed for 60 minutes)"

[0028] (Sample N6) is a drawn material with φ2.0 having a magnesium purity of 99.9669% or less. Specifically, (Sample N6) is obtained by using (Sample N9) that is a drawn material with φ2.0 mm and annealing (Sample N9) at 250°C for 60 minutes.(Sample N7): "Low-purity drawn material with φ2.0 (annealed for 120 minutes)"

[0029] (Sample N7) is a drawn material with φ2.0 having a magnesium purity of 99.9669% or less. Specifically, (Sample N7) is obtained by using (Sample N9) that is a drawn material with φ2.0 mm and annealing (Sample N9) at 250°C for 120 minutes.(Sample N8): "Low-purity drawn material with φ0.2 (not annealed)"

[0030] (Sample N8) is a drawn material with φ0.2 mm having a magnesium purity of 99.9669% or less. Specifically, (Sample N8) is obtained by using a raw material having a magnesium purity of 99.9669% and repeatedly drawing the raw material while performing annealing during each stage until the material has φ0.2 mm, and is not annealed after final drawing.(Sample N9): "Low-purity drawn material with φ2.0 (not annealed)"

[0031] (Sample N9) is a drawn material with φ2.0 mm having a magnesium purity of 99.9669% or less. Specifically, (Sample N9) is obtained by using an ingot having a magnesium purity of 99.9% and wire drawing the ingot by extrusion, and then repeatedly drawing the ingot while performing annealing during each stage until the material has φ2.0 mm, and is not annealed after final drawing.

[0032] The distribution of KAM values of (Sample N1) to (Sample N9) will be described below. In FIGs. 3 to 11, the KAM maps on the left side show the distribution of KAM values in the region 12 of the samples, and the white color indicates crystals having a KAM value of 0° or more and less than 1°, the gray color indicates crystals having a KAM value of 1° or more and less than 2°, and the black color indicates crystals having a KAM value of 2° or more and less than 5°. In the KAM maps in FIGs. 3 to 11, a direction A1 indicates the radial direction in the region 12, and a direction A2 indicates the tangential direction of the outer surface in the region 12. That is, in FIGs. 3 to 11, the upper portion indicates a distribution in the vicinity of the center of the magnesium wire, and the lower portion indicates a distribution in the vicinity of the outer surface of the magnesium wire. The KAM maps of (Sample 1) to (Sample 9) include the results obtained by measuring regions having different areas; however, FIGs. 3 to 11 show the KAM maps in substantially the same size. On the right side of the KAM maps in FIGs. 3 to 11, the numerical values indicate the proportion of crystal grains having a KAM value of 0° or more and less than 1°, the proportion of crystal grains having a KAM value of 1° or more and less than 2°, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° in the KAM maps.

[0033] As shown in FIG. 3, the measurement of the distribution of KAM values of (Sample N1) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 99.7%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 0.1%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 0.1%.

[0034] As shown in FIG. 4, the measurement of the distribution of KAM values of (Sample N2) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 88.8%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 8%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 3.2%.

[0035] As shown in FIG. 5, the measurement of the distribution of KAM values of (Sample N3) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 89.3%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 7.8%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 2.9%.

[0036] As shown in FIG. 6, the measurement of the distribution of KAM values of (Sample N4) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 94.5%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 3.5%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 2.0%.

[0037] As shown in FIG. 7, the measurement of the distribution of KAM values of (Sample N5) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 98.3%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 0.9%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 0.8%.

[0038] As shown in FIG. 8, the measurement of the distribution of KAM values of (Sample N6) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 98.5%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 0.6%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 0.9%.

[0039] As shown in FIG. 9, the measurement of the distribution of KAM values of (Sample N7) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 98.3%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 0.9%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 0.7%.

[0040] As shown in FIG. 10, the measurement of the distribution of KAM values of (Sample N8) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 67.1%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 13.8%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 19.2%.

[0041] As shown in FIG. 11, the measurement of the distribution of KAM values of (Sample N9) shows that the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 22.7%, the proportion of crystal grains having a KAM value of 1° or more and less than 2° is 33.9%, and the proportion of crystal grains having a KAM value of 2° or more and less than 5° is 43.3%.(Flexibility evaluation test)

[0042] In the present embodiment, in (Sample N4) and (Sample N8), a flexibility (plastic deformability) evaluation test of the magnesium wire was performed. As an evaluation test, the magnesium wire of each of (Sample N4) and (Sample N8) was wound around a bobbin with <p35 mm and allowed to stand for 15 hours, and then removed from the bobbin, and the shape of the magnesium wire was examined.

[0043] Then, it was found that, as shown in FIG. 12, (Sample N4) was uniformly plastically deformed along the bobbin, and had a neat spiral shape with uniform winding. On the other hand, it was found that, as shown in FIG. 13, (Sample N8) did not have a neat spiral shape with uniform winding. In the present embodiment, the evaluation result was determined to be good when a magnesium wire had a neat spiral shape as in (Sample N4), and the evaluation result was determined to be poor when a magnesium wire did not have a neat spiral shape as in (Sample N8).

[0044] As described above, in the distribution of KAM values of (Sample N4), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 94.8%, and the amount of residual strain in crystals is extremely small, and it is therefore considered that the magnesium wire is a material that has flexibility and is easily plastically deformed. On the other hand, in the distribution of KAM values of (Sample N8), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 67.9%, and the amount of residual strain in crystals is relatively large, and it is therefore considered that the magnesium wire is a material that lacks flexibility and is hardly plastically deformed.

[0045] Thus, the flexibility evaluation results of (Sample N4) and (Sample N8) show that the flexibility of a magnesium wire is greatly influenced by the distribution of KAM values in crystals constituting the magnesium wire (the amount of residual strain in crystals constituting the magnesium wire).

[0046] Therefore, the inventor of the present invention has found that in the distribution of KAM values in magnesium crystals, when the proportion of crystal grains having a KAM value of 0° or more and less than 1° is high, the amount of residual strain in crystals is extremely small and the magnesium wire is a material that has flexibility and is easily plastically deformed, and when the proportion of crystal grains having a KAM value of 0° or more and less than 1° is low, the amount of residual strain in crystals is large and the magnesium wire is a material that lacks flexibility and is hardly plastically deformed.

[0047] Thus, according to the above finding, it is possible to estimate, based on the proportion of crystal grains having a KAM value of 0° or more and less than 1°, whether the flexibility of the magnesium wires of the samples other than (Sample N4) and (Sample N8) is good or poor.

[0048] That is, in the distribution of KAM values of (Sample N1) to (Sample N7), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is approximately 90%, or 90% or more, which is high, and in the distribution of KAM values of (Sample N8) and (Sample N9), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is less than 70%. As described above, as in (Sample N4) in which the flexibility is good, the flexibility of (Sample N1) to (Sample N3) and (Sample N5) to (Sample N7) is estimated to be also good. On the other hand, as in (Sample N8) in which the flexibility is poor, the flexibility of (Sample N9) is estimated to be also poor.(Stitch size evaluation test)

[0049] In the present embodiment, in (Sample N4) and (Sample N8), a stitch size evaluation test of the magnesium wire was performed. As an evaluation test, the magnesium wire of each of (Sample N4) and (Sample N8) was flat knitted, and an image of the flat knitted magnesium wire was captured by a camera, and the stitch size of the magnesium wire was examined.

[0050] Then, it was found that, as shown in FIG. 14, in (Sample N4), the size (length in the left-right direction in FIG. 14) of each stitch of the flat knitted magnesium wire was approximately 1 mm. On the other hand, it was found that, as shown in FIG. 15, in (Sample N8), the size (length in the left-right direction in FIG. 15) of each stitch of the flat knitted magnesium wire was approximately 3 mm. In the present embodiment, the evaluation result was determined to be good when a magnesium wire was knittable with small stitches as in (Sample N4), and the evaluation result was determined to be poor when a magnesium wire was not knittable with small stitches as in (Sample N8).

[0051] In the distribution of KAM values of (Sample N4), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 94.8%, and the magnesium wire is a material that has flexibility and is easily plastically deformed, and it is considered that the obtained evaluation result shows that the magnesium wire is knittable with small stitches. On the other hand, in the distribution of KAM values of (Sample N8), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 67.9%, and the magnesium wire is a material that lacks flexibility and is hardly plastically deformed, and it is considered that the obtained evaluation result shows that the magnesium wire is not knittable with small stitches.

[0052] Thus, the stitch size evaluation results of (Sample N4) and (Sample N8) show that the size of each stitch of a flat knitted magnesium wire is greatly influenced by the distribution of KAM values in crystals constituting the magnesium wire (the amount of residual strain in crystals constituting the magnesium wire).

[0053] Therefore, the inventor of the present invention has found that in the distribution of KAM values in magnesium crystals, when the proportion of crystal grains having a KAM value of 0° or more and less than 1° is high, the magnesium wire is a material that is knittable with small stitches, and when the proportion of crystal grains having a KAM value of 0° or more and less than 1° is low, the magnesium wire is a material that is not knittable with small stitches.

[0054] Thus, according to the above finding, it is possible to estimate, based on the proportion of crystal grains having a KAM value of 0° or more and less than 1°, whether the size of each stitch of the flat knitted magnesium wires of the samples other than (Sample N4) and (Sample N8) is good or poor.

[0055] That is, in the distribution of KAM values of (Sample N1) to (Sample N7), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is approximately 90%, or 90% or more, which is high, and in the distribution of KAM values of (Sample N8) and (Sample N9), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is less than 70%. As in (Sample N4) in which the stitch size evaluation result is good, the stitch size evaluation results of (Sample N 1) to (Sample N3) and (Sample N5) to (Sample N7) are estimated to be also good. On the other hand, as in (Sample N8) in which the stitch size evaluation result is poor, the stitch size evaluation result of (Sample N9) is estimated to be also poor.

[0056] FIG. 16 shows a summary of the distribution of KAM values and the flexibility evaluation results of (Sample N1) to (Sample N9).

[0057] Considering the results in FIG. 16, it is found that in the case of (Sample N2) obtained by using (Sample N1) that is an extruded material with φ3.0 mm and repeatedly drawing (Sample N1) without performing annealing during each stage, in (Sample N1) that is an extruded material before drawing, the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 99.7%, which is high, and in (Sample N2) that is a drawn material with φ2.0 mm after drawing, the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 88.8%, which is not greatly changed. Similarly, it is found that in the case of (Sample N4) obtained by using (Sample N3) that is a drawn material with <p1.0 mm and repeatedly drawing (Sample N3) without performing annealing during each stage, in (Sample N3) that is a drawn material before drawing, the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 89.3%, which is high, and in (Sample N4) that is a drawn material with φ0.2 mm after drawing, the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 94.8%, which is not greatly changed. According to the results of (Sample N2) to (Sample N4), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is increased by repeatedly performing drawing until the magnesium wire has a small diameter.

[0058] In (Sample N1), the magnesium purity is 99.995% or more, and the amount of impurities at the grain boundaries between the magnesium crystal grains is small. Magnesium crystal grains tend to be moved and aligned in the same direction in response to processing pressure. When the amount of impurities at the grain boundaries between the magnesium crystal grains is small, the crystal grains are presumably more easily moved, leading to a low KAM value (small orientation difference). On the other hand, in (Sample N8) and (Sample N9), the magnesium purity is 99.9669% or less, which is low; thus, the impurities at the grain boundaries between the magnesium crystal grains presumably hinder movement of the magnesium crystal grains, leading to a high KAM value (large orientation difference).

[0059] In this regard, as in (Sample N1) and (Sample N3), when the amount of impurities at the grain boundaries between the magnesium crystal grains is small, it is considered that magnesium constituting the grain boundaries is easily aligned (crystallized) at an atomic level, leading to a phenomenon in which the crystal grains do not become fine, as if the crystal grains are coalesced (fused). This presumably makes it possible to repeatedly draw a material having a magnesium purity of 99.995% or more, without performing annealing during each stage.

[0060] On the other hand, as in (Sample N8) and (Sample N9), when the amount of impurities at the grain boundaries between the magnesium crystal grains is large, it is considered that due to the influence of the impurities, magnesium at the grain boundaries is hardly aligned (crystallized) at an atomic level, and the grain boundaries are increased while drawing is repeatedly performed, leading to fine magnesium crystal grains. This presumably results in a high KAM value, causing work hardening. Thus, although in (Sample N9), the proportion of crystal grains having a KAM value of 0° or more and less than 1° is approximately 22%, which is low, in (Sample N5) to (Sample N7) obtained by annealing (Sample N9) at 250°C for 30 minutes, 60 minutes, and 120 minutes, respectively, the proportion of crystal grains having a KAM value of 0° or more and less than 1° is increased to approximately 98%, achieving high flexibility.

[0061] The magnesium wire according to the present embodiment is made of high-purity magnesium containing magnesium as a main component, or a magnesium alloy containing magnesium as a main component. When the magnesium wire according to the present embodiment is made of high-purity magnesium, the magnesium wire contains 99 mass% or more of Mg, with the balance being impurities. The impurities include unavoidable impurities. Examples of impurities include Al, Si, Mn, Fe, Zn, Zr, Cu, Ni, Cr, and Ca. When the magnesium wire is used as a medical magnesium wire, the magnesium wire preferably has a higher magnesium purity, and contains no impurities or contains an inevitable amount of impurities. In particular, the magnesium wire preferably contains no element component with low biosafety. When the magnesium wire according to the present embodiment is made of a magnesium alloy, the magnesium wire contains less than 99 mass% of Mg as a main component, and additionally contains, for example, various elements such as Al, Si, Mn, Fe, Zn, Zr, Cu, Ni, Cr, or Ca, or a compound thereof.

[0062] The magnesium wire according to the present embodiment is a thin wire, and is knitted in the form of sheet or string and used as a medical implement (e.g., an implement used to suture an incision or the like). At that time, in the case of a magnesium wire in which the proportion of crystal grains having a KAM value of less than 1° is high, when deformation of the magnesium wire into a certain shape is attempted, the magnesium wire is smoothly deformed into the shape, and thus the magnesium wire knitted in the form of sheet or string has a predetermined shape and is very easy to use. On the other hand, in the case of a magnesium wire in which the proportion of crystal grains having a KAM value of 0° or more and less than 1° is low, when deformation of the magnesium wire into a certain shape is attempted, the magnesium wire after deformation has a distorted shape, and thus the magnesium wire knitted in the form of sheet or string does not have a predetermined shape and is difficult to use.

[0063] As described above, the magnesium wire according to the present embodiment is a magnesium wire containing magnesium as a main component, and in crystal grains constituting the magnesium wire, the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 70% or more.

[0064] Thus, it is possible to obtain a magnesium wire that has high flexibility and is hardly broken when complex deformation occurs.

[0065] The method for producing a magnesium wire according to the present embodiment is a magnesium wire production method for producing a magnesium wire thinned by repeatedly performing drawing or extrusion, and a magnesium wire in which the proportion of crystal grains having a KAM value of 0° or more and less than 1° is 70% or more is produced without performing annealing in any of a drawing process or an extrusion process.

[0066] Thus, it is possible to obtain a magnesium wire that has high flexibility and is hardly broken when complex deformation occurs, without performing annealing in any of a drawing process or an extrusion process.

[0067] The method for evaluating a magnesium wire according to the present embodiment is a magnesium wire evaluation method for evaluating flexibility of a magnesium wire containing magnesium as a main component, and the flexibility is evaluated based on the proportion of crystal grains having a KAM value of 0° or more and less than 1° in crystal grains constituting the magnesium wire.

[0068] Thus, the flexibility of a magnesium wire can be accurately evaluated by a novel evaluation method, that is, based on the proportion of crystal grains having a KAM value of less than a predetermined value.

[0069] The embodiment of the present invention has been described; however, the configuration of the present embodiment is not limited to the configuration described above, and various modifications can be made.

[0070] For example, in the embodiment described above, the magnesium wires having a diameter of φ3.0, φ2.0, φ1.0, and φ0.2 are used as samples of the magnesium wire; however, the diameter of the magnesium wire is not limited thereto. The magnesium wire according to the present invention may have any diameter.

[0071] In the embodiment described above, the flexibility and the stitch size of the magnesium wire are evaluated based on the proportion of crystal grains having a KAM value of 0° or more and less than 1° in crystal grains constituting the magnesium wire; however, the present invention is not limited thereto. The flexibility and the stitch size of the magnesium wire may be evaluated based on the proportion of crystal grains having a KAM value of 0° or more and less than a predetermined value in crystal grains constituting the magnesium wire. The predetermined value can be set to any value. Thus, for example, the flexibility and the stitch size of the magnesium wire may be evaluated based on the proportion of crystal grains having a KAM value of 0° or more and less than 2° in crystal grains constituting the magnesium wire.

[0072] In the embodiment described above, the magnesium wire is an extruded material, a drawn material, or a material obtained by annealing a drawn material; however, the present invention is not limited thereto. The present invention is applicable to a magnesium wire thinned by repeatedly performing drawing or extrusion.

[0073] Other configurations can also be variously modified without departing from the gist of the present invention.INDUSTRIAL APPLICABILITY

[0074] The present invention can be used as a magnesium wire containing magnesium as a main component, a method for producing a magnesium wire, and a method for evaluating a magnesium wire.[Reference Signs List]

[0075] 1 Magnesium wire

Claims

1. A magnesium wire containing magnesium as a main component, wherein in crystal grains constituting the magnesium wire, a proportion of crystal grains having a kernel average misorientation (KAM) value of 0° or more and less than 1° is 70% or more.

2. A method for producing a magnesium wire thinned by repeatedly performing drawing or extrusion, wherein a magnesium wire in which a proportion of crystal grains having a KAM value of 0° or more and less than 1° is 70% or more is produced without performing annealing in any of a drawing process or an extrusion process.

3. An evaluation method for evaluating a magnesium wire, the evaluation method evaluating flexibility of a magnesium wire containing magnesium as a main component, wherein the flexibility is evaluated based on a proportion of crystal grains having a KAM value of 0° or more and less than a predetermined value in crystal grains constituting the magnesium wire.

Images