JP2017171964A - Magnesium alloy sinter billet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesium alloy sinter billet capable of increasing strength and ductility of manufactured forging material when warm forging is conducted for example at 300 to 450°C and a manufacturing method therefor.SOLUTION: A magnesium alloy sinter billets 21 and 41 has a constitution having an inner part 50, a surface part 38 arranged on an outer periphery of the inner part 50 and to which a magnesium alloy powder 2 is sintered and true density ratio of the surface layer 38 of 100%. A manufacturing method of the magnesium alloy sinter billets 21 and 41 includes a cold dust process S2 for cold dust molding the magnesium alloy powder 2 at a temperature of 5 to 35°C to mold a cold dust molded body 4, a warm compression molding process S3 for warm compression molding the cold dust molded body 4 at a temperature of 300 to 450°C to mold a warm compression molded body 7 and a surface extrusion process S4 for surface extrusion molding the warm compression molded body 7 to mold a surface extrusion molded body 19, 39.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnesium alloy sintered billet as a material for forging, extrusion, or rolling and a method for producing the same.

  In recent years, against the background of global warming, weight reduction and toughening of aircraft parts, etc., in addition to vehicles, particularly automobile wheels and important safety parts, are expected. For example, steel wheels and aluminum alloys have been used as automobile wheels. In contrast, forged wheels for automobiles made of magnesium alloy, which have a smaller specific gravity and superior specific strength (strength per unit weight) compared to those made of aluminum alloy, have been put to practical use in the general market, and will become popular in the future. Is expected.

  A material billet having a sound internal quality and a sufficient size for a finished product is required as a material for forging or extrusion or rolling. Regarding powder metallurgy of aluminum alloys, various methods have been put into practical use and have been popular for a long time. However, regarding magnesium alloy powder, sintering molding has not yet been put into practical use due to the risk of ignition and explosion and the undeveloped manufacturing method due to the excessively active characteristics.

  As a method for forming a magnesium alloy powder, a rapidly solidified magnesium alloy non-equilibrium (supersaturated solid solution) fine crystal grain ribbon material is pulverized and powdered, and then sintered at a temperature just below the solidus line in vacuum. A method for producing a reforming material and extruding it into a high-strength complex shape in the atmosphere has been reported (see, for example, Patent Document 1). In addition, a plate-like or massive magnesium alloy material is subjected to plastic working at a predetermined reduction ratio to introduce strain without causing dynamic recrystallization, and then the powder produced by crushing the material is compressed. A method of extruding a compacted powder billet has been reported (for example, see Patent Document 2).

JP 2002-256307 A JP 2009-35749 A

  The above patent document relates to a billet of magnesium alloy for extrusion. That is, there is no idea at all about forging using the material billet. For example, when warm forging is performed at 300 to 450 ° C., the bonding between powders is insufficient and it can be formed into a predetermined shape. Even if they are not formed or can be formed, there is a concern that internal defects may occur or a sound forged structure may not be obtained.

  The present invention is based on the new knowledge of the present inventors, and the strength of the forged material produced when warm forging is performed at, for example, 300 to 450 ° C. using a technique different from the above-described prior art. And it aims at providing the magnesium alloy sintered billet which can increase ductility, and its manufacturing method.

  In order to achieve this object, the present invention includes a magnesium alloy sintered billet comprising an inner layer portion and a surface layer portion provided on the outer periphery of the inner layer portion, the magnesium alloy powder being sintered, and the true density ratio of the surface layer portion is 100%. Moreover, the manufacturing method of a magnesium alloy sintered billet includes a cold compacting step of forming a cold compacted body by cold compacting a magnesium alloy powder at a temperature of 5 to 35 ° C, and a cold pressure. A warm compression step of forming a warm compression molded body by performing warm compression molding of the powder molded body at a temperature of 300 to 450 ° C., and surface extrusion molding the warm compression molded body to form a surface extrusion molded body And a surface layer extrusion step.

  In the present invention, a magnesium alloy sintered billet having a large diameter and a high height can be formed by forming a high-density surface layer portion by press working with a low extrusion ratio. Furthermore, by using the billet, a forged material having high formability capable of dealing with a complex shape of an ultrafine structure and having a high strength in which 0.2% proof stress (0.2% YS) exceeds 260 MPa is manufactured. be able to.

It is a flowchart which shows the manufacturing process for producing the magnesium alloy sintered billet in Embodiment 1 of this invention. It is a schematic diagram which shows a cold compacting apparatus roughly same as the above. It is a perspective view of a cold compacting body same as the above. It is a schematic diagram which shows a warm compression apparatus roughly same as the above. It is a perspective view of a warm compression molding object same as the above. It is a schematic diagram which shows schematically an upright type surface layer extrusion apparatus same as the above. It is a schematic diagram which shows schematically an upright type surface layer extrusion apparatus same as the above. It is a side view of a surface layer extrusion molding same as the above. It is a side view of a material billet as above. It is a side view of a forging material same as the above. It is a schematic diagram which shows roughly the elongate billet type extrusion apparatus in Embodiment 2 of this invention. It is a schematic diagram which shows a long billet type extrusion apparatus roughly same as the above. It is a side view of a surface layer extrusion molding same as the above. It is a side view of a material billet as above. It is a figure which shows the A direction of the test piece of the tension test in an Example. It is a figure which shows the B direction of the test piece of a tensile test same as the above. 2 is a fracture surface of a tensile test piece of Example 1. FIG. 2 is a fracture surface of a tensile test piece of Comparative Example 1. 1 is a diameter longitudinal sectional view of a forged material of Example 1. FIG. 3 is a diameter longitudinal sectional view of a forged material of Comparative Example 1. FIG. It is a SS curve (stress-strain curve) of Example 1 and Comparative Example 1. It is a SS curve (stress-strain curve) of Example 2. It is a figure of the surface layer extrusion molding of Examples 3-5. It is sectional drawing of the raw material billet of Example 3. FIG. It is sectional drawing of the raw material billet of Example 4. FIG. It is sectional drawing of the raw material billet of Example 5. FIG. It is a diameter longitudinal cross-sectional view of the forging material of Example 3. It is a diameter longitudinal cross-sectional view of the forging material of Example 4. FIG. 6 is a diameter longitudinal sectional view of a forged material of Example 5. It is a SS curve (stress-strain curve) of Example 3. It is a SS curve (stress-strain curve) of Example 4. 10 is an SS curve (stress-strain curve) of Example 5. 6 is a surface layer extrusion-molded body of Example 6. It is a perspective view of a material billet same as the above. It is sectional drawing of a material billet same as the above. It is a top view of a forging material same as the above. It is a side view of a forging material same as the above. It is a diameter longitudinal cross-sectional view of a forging material same as the above. The above is an SS curve (stress-strain curve).

  A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a flowchart schematically showing a manufacturing process for producing a magnesium alloy sintered billet (material billet) 21 according to Embodiment 1 of the present invention.

  The manufacturing process will be described in detail. First, magnesium alloy powder is prepared in S1. Magnesium alloy powder has risks of ignition and explosion. Therefore, the magnesium alloy powder used in the present invention is preferably a magnesium alloy powder in which 1 to 3 wt% of Ca is added to improve flame retardancy. The magnesium alloy powder may contain Ca, Al or Mn.

  S2 is a cold compacting (cold forming) step. FIG. 2 shows a schematic diagram of the cold compacting device 1. The magnesium alloy powder 2 prepared in S1 is loaded into the cold compacting device 1. A cold compacted body 4 shown in FIG. 3 is obtained by compressing the magnesium alloy powder 2 by applying a pressure of, for example, 600 MPa from above with the upper punch 3. It is preferable that the true density ratio (ratio with respect to 100% of true density) of the cold compacting body 4 is 85% or more. The true density can be measured by the Archimedes method. The temperature of the cold compacting step S2 is preferably room temperature, specifically 5 to 35 ° C.

  FIG. 4 shows a schematic diagram of the warm compression device 5. The cold compacting body 4 formed in the cold compacting step S <b> 2 is loaded into the warm compressing device 5. The cold compact 4 is heated to 300 to 450 ° C. below the recrystallization temperature by a heating means (not shown). By heating within the temperature range, the structure of the magnesium alloy powder 2 is maintained without increasing the particle size by recrystallization or growing the alloy compound. The heated cold compact 4 is compressed by applying a pressure of 600 MPa, for example, from above with the upper punch 6 to obtain a warm compact 7 shown in FIG. The warm compression is preferably performed in an inert atmosphere such as argon gas.

  If the warm compression (warm forming) step S3 is performed directly without going through the cold compacting step S2, the powder grain boundary (powder interface) remains, and the true density ratio is about 96 to 97%. Insufficient coupling. On the other hand, by performing the cold compaction step S2 and then the warm compression step S3, the bonding (sintering) between the powders becomes dense, and a true density ratio of 98% or more can be realized. . By performing the cold compaction step S2 and the warm compression step S3, when the magnesium alloy sintered billet 21 of the present invention is warm forged, a forged material having high tensile strength and proof stress and high elongation can be obtained. it can.

  S4 is a surface layer extrusion process. The surface layer extrusion of the present invention is preferably a low extrusion ratio warm extrusion. 6 and 7 are schematic views of the upsetting surface layer extrusion apparatus 10. A die 12 having a through hole 14 whose bottom is closed by a bottom member 15 is provided inside the upright surface layer extrusion apparatus 10, and the warm compression molded body 7 is loaded on the upper surface 13 of the die 12. . The warm compression molded body 7 is heated to, for example, 400 ° C. by a heating means (not shown), and pressure is applied from above by the upper punch 11. The warm compression molded body 7 is filled in the through hole 14 and reaches the upper surface 16 of the bottom member 15. At this time, a part of the warm compression molded body 7 remains between the upper surface 13 of the die 12 and the lower surface 18 of the upper punch 11 to form the upper end portion 17 of the surface extrusion molded body. The surface extrusion is preferably performed in an inert atmosphere such as argon gas.

FIG. 8 shows a surface layer extrusion molded body 19 formed by the upsetting surface layer extrusion apparatus 10, and has an upper end portion 17 and a reduced material billet portion 20. φ _A is the diameter (solidified diameter) of the upper surface of the upper end portion 17 and is equivalent to the diameter of the warm compression molded body 7 before surface layer extrusion. φ _B is the diameter of the material billet portion 20.

FIG. 9 shows a material billet 21 of S5 formed by cutting the upper end portion 17 of the surface layer extrusion molding 19. φ _B is the diameter of the material billet 21, and H _B is the height of the material billet 21.

FIG. 10 shows a disk-shaped forged material 22 formed by forging using a material billet 21. φ _C is the diameter of the forging material 22 and _HC is its height.

  The surface layer extrusion ratio, which is the ratio of the cross-sectional area of the warm compression molded body 7 before surface layer extrusion to the cross-sectional area of the material billet part 20 after surface layer extrusion, is preferably 2-9. By using warm surface layer extrusion with a low extrusion ratio, only the surface layer portion 38 (see FIG. 12 and the like) is sufficiently sintered and densified (true density ratio is 100%), and forging can be performed. A forging material billet 21 having a large diameter and a high height can be formed. When the surface layer extrusion ratio is less than 2, the surface layer portion 38 having a sufficient thickness cannot be formed. When the surface layer extrusion ratio exceeds 9, a large press is required, the equipment cost increases, and the productivity decreases. The warm surface layer extrusion temperature is also set to the recrystallization temperature or lower so that the structure of the magnesium alloy powder 2 is maintained and does not grow.

  Since the material billet 21 of the present invention is a dense sintered bonded structure with a surface layer portion 38 having a true density ratio of 100%, it is heated to 300 to 450 ° C. in the atmosphere without using an inert gas shield. Warm forging can be performed in the atmosphere. In addition, because it is a surface layer extruded billet 21 that maintains the ultrafine structure of the magnesium alloy powder 2, a forged material that has high strength and high corrosion resistance and has a complex shape with an ultrafine structure is formed by warm forging. can do. The crystal grain size of the magnesium alloy powder 2 is about 1 to 2 μm. The material billet 21 of the present invention has the same effect not only for forging but also for extrusion and rolling.

  A second embodiment of the present invention will be described with reference to FIGS.

  The manufacturing process for producing the magnesium alloy sintered billet (material billet) 41 of the second embodiment is the same as that of the first embodiment shown in FIG. The difference from the first embodiment is that long billet type surface layer extrusion is employed in the surface layer extrusion step of S4. The specific contents of the other steps are exactly the same as in the first embodiment.

  11 and 12 are schematic views of a long billet type surface layer extrusion device 30 used in the surface layer extrusion step of S4. The long billet surface layer extrusion apparatus 30 has a die 32 having a through hole 34 formed in the center, and the warm compression molded body 7 is loaded on the upper surface 33 of the die 32. The warm compression molded body 7 is heated to, for example, 400 ° C., and pressure is applied from above by the upper punch 31. The warm compression molded body 7 is filled in the through hole 34, is reduced in diameter, and passes through the through hole 34. At this time, a part of the warm compression molded body 7 remains between the upper surface 33 of the die 32 and the lower surface 34 of the upper punch 31 to form the upper end portion 35 of the surface layer extrusion molded body. The surface extrusion is preferably performed in an inert atmosphere such as argon gas.

  In the vicinity of the surface layer of the material billet portion 37, only the surface layer portion 38 is plastically flow-deformed, and inter-powder bonding (sintering) is promoted. If the bonding between powders is insufficient, the surface is broken in a large deformation forging process, and cannot be molded into a predetermined shape in a healthy surface state. Further, the inside of the forged material is also affected by insufficient bonding between powders, occurrence of internal defects, and failure to form a sound forged structure.

FIG. 13 shows a surface layer extruded product 39 formed by a long billet type surface layer extrusion apparatus 30, which has an upper end portion 35, a reduced diameter billet portion 37 and a lower end portion 36. phi _D is the upper surface of the upper end portion 35 diameter (solidified diameter), it is equivalent to the diameter of the warm compacts 7 before the surface layer extrusion. φ _E is the diameter of the material billet part 37.

FIG. 14 is a material billet 41 of S5 formed by cutting the upper end portion 35 and the lower end portion 36 of the surface layer extrusion-molded body 39. φ _E is the diameter of the material billet 41, and H _E is the height of the material billet 41.

  The surface layer extrusion ratio, which is the ratio of the cross-sectional area of the warm compression molded body 7 before surface layer extrusion to the cross-sectional area of the material billet part 37 after surface layer extrusion, is preferably 2-9. By adopting a warm surface layer extrusion with a low extrusion ratio, only the surface layer part is densified (true density ratio is 100%), and a forging material billet 41 with a large diameter and high height that can be forged. Can be molded. The warm surface layer extrusion temperature is also set to the recrystallization temperature or lower so that the structure of the magnesium alloy powder 2 is maintained and does not grow.

  The material billet 41 of the present invention is a dense sintered bonded structure whose surface layer portion has a true density ratio of 100%. Therefore, the billet 41 is heated in the atmosphere to 300 to 450 ° C. without using an inert gas shield. Warm forging is possible. In addition, the billet 41 is a surface extruded material billet 41 that maintains the ultrafine structure of the magnesium alloy powder 2, so that forgings with high strength, high corrosion resistance, and complex shapes of ultrafine structures are formed by warm forging. can do. The particle size of the magnesium alloy powder 2 is about 1-2 μm. The material billet 41 of the present invention has the same effect not only in forging but also in extrusion and rolling.

  Hereinafter, although an example is given with a comparative example and the effect of the present invention is explained concretely, the present invention is not limited to this example.

<Example 1 and Comparative Example 1>
Based on FIGS. 18-24 and Table 1, the effect which performs warm compression process S3 after cold compacting process S2 in Embodiment 1 is demonstrated.

  In both Example 1 and Comparative Example 1, as the magnesium alloy powder 2, a magnesium alloy in which Ca was added to improve flame retardancy was used. The crystal grain size of the powder is 1 to 2 μm, and the alloy compound has an ultrafine structure. Further, this powder contains 2.0 wt% Ca, 6.0 wt% Al, and 0.3 wt% Mn, and is easily compressed into a green compact by pressing and compressing.

In Example 1, first, the cold compacting step S2 was performed on the magnesium alloy powder 2 at a pressure of 600 MPa. Next, the cold compacting body 4 was heated to 380 ° C. in an argon gas atmosphere, and the warm compression step S3 was performed at a pressure of 600 MPa. The true density ratio of the cold compact 4 was 92.5%, and the true density ratio of the warm compact 7 was 98.8%. The true density was measured by the Archimedes method. The solidified body diameter φ _A of the warm compression molded body 7 was 43 mm. Next, the warm compression molded body 7 was heated to 380 ° C. in an argon gas atmosphere using the upsetting surface layer extrusion apparatus 10, and the diameter was reduced to 30 mm in diameter φ _B. The surface layer extrusion ratio is 2.05. The upper end portion 17 of the obtained surface layer extruded product 19 was cut to produce a magnesium alloy sintered billet (material billet) 21 having a diameter φ _B of 30 mm and a height H _B of 40 mm. The billet 21 was forged into a disk shape having a diameter φ _C of 51 mm and a height H _C of 8 mm in an argon gas atmosphere at 400 ° C.

  In Comparative Example 1, the cold compacting step S2 was not performed, and the magnesium alloy powder 2 was heated to 380 ° C. in an argon gas atmosphere and subjected to warm compression at a pressure of 600 MPa. The true density ratio of the warm compression molded product that was directly warm-compressed was 96.6%, which was less than 98%. Other manufacturing conditions were the same as in Example 1.

  A tensile test was performed on the forged materials of Example 1 and Comparative Example 1. The test was performed in the direction A shown in FIG. 15 and the direction B shown in FIG. 16 with respect to the thickness direction T of the test piece.

  17 is a fracture surface of the tensile test piece of Example 1, and FIG. 18 is a fracture surface of the tensile test piece of Comparative Example 1. It is observed that the residual of the powder grain boundary remains strongly on the fracture surface of Comparative Example 1. It can be seen that Comparative Example 1 lacks powder-to-powder bonding and has a lower degree of sintering than Example 1.

  19 and 20 are longitudinal longitudinal sectional views of the forged material 22 of Example 1 and the forged material 22 'of Comparative Example 1, respectively, and a macro structure is observed.

  FIG. 21 shows SS curves (stress-strain curves) of Example 1 and Comparative Example 1. Table 1 shows 0.2% yield strength (0.2% YS), maximum tensile strength (UTS), and elongation (Elongation). The measurement results are shown. In Example 1, 0.2% proof stress, maximum tensile strength, and elongation were all larger than those in Comparative Example 1.

<Example 2>
Based on FIG. 22 and Table 2, another example in upset surface layer extrusion of Embodiment 1 will be described.

Example 2 differs from Example 1 in that the heating temperature in the warm compression step S3 is 400 ° C., the heating temperature in the surface layer extrusion step S4 is 400 ° C., and the diameter φ _B after surface layer extrusion is 21 mm. . The true density ratio of the warm compression molded body 7 was 98%. The surface layer extrusion ratio was 4.2. The upper end portion 17 of the obtained surface layer extruded product 19 was cut to produce a magnesium alloy sintered billet (material billet) 21 having a diameter φ _B of 21 mm and a height H _B of 49 mm. The billet 21 was forged into a disk shape having a diameter φ _C of 51 mm and a height H _C of 5 mm in an argon gas atmosphere at 400 ° C.

  The same tensile test as in Example 1 was performed on the forged material 22 of Example 2.

  FIG. 22 is an SS curve (stress-strain curve) of Example 2, and Table 2 shows measurement results of 0.2% proof stress (0.2% YS), maximum tensile strength (UTS), and elongation (Elongation). Show. The 0.2% yield strength (0.2% YS) exceeded 260 MPa, and the elongation exceeded 11%.

<Examples 3 to 5>
Based on FIGS. 23 to 32 and Table 3, examples in the long billet type surface layer extrusion of Embodiment 2 will be described.

  In Examples 3 to 5, similarly to Example 2, the heating temperature in the warm compression step S3 was set to 400 ° C, and the heating temperature in the surface layer extrusion step S4 was set to 400 ° C. In the surface layer extrusion step S4, a long billet surface layer extrusion apparatus 30 was used and heated to 400 ° C. in an argon gas atmosphere to prepare a surface layer extrusion molded body 39.

Solidified diameter phi _D of the front surface layer extrusion of Example 3 is 50 mm, the surface layer extrusion ratio was 5.7. The true density ratio of the cold compact 4 was 92.1%, and the true density ratio of the warm compact 7 was 99.9%. The solidified body diameter φ _D before surface layer extrusion of Example 4 was 43 mm, and the surface layer extrusion ratio was 4.2. The true density ratio of the cold compact 4 was 91.6%, and the true density ratio of the warm compact 7 was 99.0%. The solidified body diameter φ _D before surface layer extrusion of Example 5 was 37 mm, and the surface layer extrusion ratio was 3.1. The true density ratio of the cold compact 4 was 89.0%, and the true density ratio of the warm compact 7 was 99.1%. The diameter φ _E after the surface layer extrusion is all 21 mm.

23, to cut the upper portion 35 and lower portion 36 of the resulting surface layer extrudate 39, making 21mm diameter phi _E, the height H _E is magnesium alloy sintered billet 49 mm (material billet) 41 did. The billet 41 was forged into a disk shape having a diameter φ _C of 51 mm and a height H _C of 5 mm in an argon gas atmosphere at 400 ° C.

  24 to 26 are cross-sectional views of the material billet 41 of Examples 3 to 5, respectively, and a macro structure is observed. The surface layer portion 38 from the boundary line 51 to the outer peripheral surface is subjected to surface layer extrusion deformation, and the powder shape is deformed and powdered (sintered). As the surface layer extrusion ratio increases, the radius of the circular boundary line 51 decreases, the area of the surface layer portion 38 increases, and the area of the inner layer portion 50 decreases. The ratio of the width (thickness) in the diameter direction of the surface layer portion 38 to the diameter of the material billet 41 is about 0.44 in Example 3, about 0.38 in Example 4, and about 0.22 in Example 5. .

  27 to 29 are diameter longitudinal sectional views of the forged material 22 of Examples 3 to 5, respectively, and a macro structure is observed.

  A tensile test similar to that of Example 1 was performed on the forged material 22 of Examples 3 to 5.

  30 to 32 are SS curves (stress-strain curves) of Examples 3 to 5, respectively. Table 3 shows 0.2% proof stress (0.2% YS), maximum tensile strength (UTS), and elongation. The measurement result of (Elongation) is shown. The 0.2% yield strength (0.2% YS) exceeded 260 MPa, and the elongation was high.

<Example 6>

  Based on FIGS. 33 to 39 and Table 4, another example in the long billet type surface layer extrusion of Embodiment 2 will be described.

In Example 6, compared to Examples 3 to 5, the heating temperature in the warm compression step S3 was 380 ° C., the heating temperature in the surface layer extrusion step S4 was 380 ° C., and the diameter φ _B after surface layer extrusion was 15 mm. It is different. The true density ratio of the cold compact 4 was 91.8%, and the true density ratio of the warm compact 7 was 99.1%. The surface layer extrusion ratio is 8.2. The resulting cutting the upper portion 35 and lower portion 36 of the surface layer extrudate 39, the diameter phi _E 15 mm, a height H _E was prepared magnesium alloy sintered billet (material billet) 41 50 mm. FIG. 33 shows a surface layer extruded product 39 actually formed, and FIG. 34 shows a material billet 41. The billet 41 was forged into a disk shape having a diameter φ _C of 51 mm and a height H _C of 7 mm in an argon gas atmosphere at 400 ° C.

  FIG. 35 is a cross-sectional photograph of the material billet 41. The surface layer portion 38 has large deformation of the powder and good binding properties, whereas the central portion 52 of the inner layer portion 51 has a confirmed powder shape and insufficient binding properties. It turns out that it is.

  FIG. 36 is a top view of the forging material 22, and FIG. 37 is a side view of the forging material 22. FIG. 38 is a diameter longitudinal cross-sectional view of the forging material 22, and a macro structure is observed.

  The same tensile test as in Example 1 was performed on the forged material 22 of Example 6.

  39 is an SS curve (stress-strain curve) of Example 6. Table 4 shows the measurement results of 0.2% proof stress (0.2% YS), maximum tensile strength (UTS), and elongation (Elongation). Show. The 0.2% yield strength (0.2% YS) exceeded 260 MPa, and the elongation was high.

  Although the present invention has been described based on the embodiments and examples, the present invention can be variously modified. For example, the conditions such as the pressing pressure in the cold compaction step S2 and the warm compression step S3, the heating temperature in the warm compression step S3 and the surface layer extrusion step S4, the material and particle size of the magnesium alloy powder 2 to be used, It can be appropriately changed according to the size of the molded body to be manufactured. As the magnesium alloy powder 2, in addition to the magnesium alloy powder 2 used in the examples, various magnesium alloy powders 2 can be used as long as the forming process used in the present invention such as cold compacting is possible. it can.

2 Magnesium alloy powder 4 Cold compacted compact 7 Warm compacted compact
19, 39 Surface extrusion molding
21, 41 Magnesium alloy sintered billet (material billet)
38 Surface layer
50 Inner layer S2 Cold compaction process S3 Warm compression process S4 Surface extrusion process

Claims (6)

The inner layer,
Provided on the outer periphery of the inner layer part, and a surface layer part obtained by sintering the magnesium alloy powder,
A magnesium alloy sintered billet characterized in that the true density ratio of the surface layer portion is 100%.   The magnesium alloy sintered billet according to claim 1, wherein the magnesium alloy powder is a magnesium alloy powder to which Ca is added in an amount of 1 to 3 wt%. Cold compacting step of forming a cold compacted body by cold compacting the magnesium alloy powder at a temperature of 5 to 35 ° C;
A warm compression step of warm compression molding the cold compacted body at a temperature of 300 to 450 ° C. to form a warm compression molded body,
A method of manufacturing a magnesium alloy sintered billet comprising a surface layer extrusion step of forming a surface layer extrusion molding by surface extrusion molding the warm compression molding.   4. The magnesium alloy sintered billet according to claim 3, wherein a true density ratio of the cold compacted body is 85% or more, and a true density ratio of the warm compacted body is 98% or more. Production method.   5. The magnesium alloy sintered billet according to claim 3, wherein in the surface layer extrusion step, only the surface layer portion is plastically flow-deformed to promote sintering, and the true density of the surface layer portion is 100%. Manufacturing method. In the said surface layer extrusion process, surface layer extrusion ratio shall be 2-9, The manufacturing method of the magnesium alloy sintered billet of any one of Claims 3-5 characterized by the above-mentioned.