JPH05306404A - Production of magnesium alloy member - Google Patents

Abstract

PURPOSE:To produce an Mg alloy member having excellent mechanical properties, especially high tensile strength and elongation, from Mg alloy cuttings contg. Al. CONSTITUTION:An Al-contg. Mg alloy member which has been heat-treated T6 2 is cut to cuttings, and the cuttings are hot-pressed in a die and then extruded. The turnings subjected to other treatment such as heat-treatment T5 7 may be incorporated and used. The effect of the heat treatment T6 and the effect of the microstructure due to extrusion are synergically exhibited.

Description

Detailed Description of the Invention

[0001]

The present invention relates to magnesium (hereinafter referred to as M
g. ) The present invention relates to a method for manufacturing an alloy member, and more particularly to a method for reusing, as an extruded material, Mg alloy chips and the like discharged during cutting of the member.

[0002]

2. Description of the Related Art Mg alloys are the lightest structural metals in practical use and have the characteristics of high specific strength (proof strength / specific gravity). Widely used for parts of machinery.
On the other hand, as a result of a large amount of Mg alloy members being used as parts in various fields in this way, a large amount of chips from cutting or grinding operations are discharged, and at the same time Mg alloy scraps and A large amount of used waste has also been released.

These chips and the like are often incinerated, buried in the soil and discarded, or collected and remelted, but this is not only a waste of resources and energy but also a danger. , Various means for effectively reusing this have been studied. For example, JP-A-55-38
According to the description of Japanese Patent No. 963, attempts have been made to manufacture a sintered part by utilizing hot pressing, and to perform hot pressing followed by extrusion molding, according to the description of Japanese Patent Laid-Open No. 182806/1990.

[0004]

As a result, in the above method, the shape of the part that can be formed is limited, and in the case of Mg alloy chips, it cannot be solidified sufficiently to withstand use as a machine part. was there.

On the other hand, when the above method is applied to a Mg alloy chip having a small amount of aluminum (hereinafter referred to as Al) content or no aluminum content, tensile strength and proof stress of a forged product level can be obtained. A considerable effect was recognized such as the elongation being much larger than that of the forged product. The extruded Mg alloy chips show such a greater elongation than the forged product because the chips themselves and the crystal grains are cut into small pieces through the cutting process. It was thought that this was due to miniaturization.

In addition, the above method is applied to M containing a large amount of Al.
When applied to g-alloy chips, tensile strength and proof stress were higher than those obtained by extrusion molding of cast products, and considerable effects were also recognized. However, the elongation did not show the remarkable effect as seen with the Mg alloy chips with a low Al content or no Al content, and remained at the same level as that of a cast product extruded. This is because Mg alloys with a high Al content
_{Since the amount of 17} Al ₁₂ (intermetallic compound) produced was large, it was considered that sufficient elongation could not be obtained as compared with a Mg alloy containing little or no Al.

Further, even if such an extruded material of chips is subjected to T6 heat treatment (solution treatment + aging treatment) in order to improve the mechanical properties, not only the elongation is not improved but also the yield strength is drastically reduced. There was a drawback that it did. This is because a large amount of strain energy is accumulated in the extruded material, so recrystallization is likely to occur during the solution treatment, and the crystal grains finely aligned in the extrusion direction are coarsened by recrystallization and finely dispersed. It was considered that Mg ₁₇ Al ₁₂ which had been used also coarsely precipitates on the crystal grain boundaries by the aging treatment, and eventually the grain refinement effect of cutting and extrusion molding and the effect of refining Mg ₁₇ Al ₁₂ were lost. .. In order to prevent recrystallization, it is naturally conceivable to lower the heating temperature, but in order to perform solution treatment while preventing recrystallization, it is necessary to carry out at a low temperature for a long period of time. There was something very severe.

By the way, many machine parts and the like require considerable elongation in addition to high mechanical strength. For example, a member called an impact bar is installed inside an automobile door to protect an occupant from a side impact. The total impact energy that can be absorbed by this impact bar corresponds to the area surrounded by the tensile strength-elongation curve shown in FIG. 3, and the higher the strength and the greater the elongation to break, the greater the energy that can be absorbed and the more effective it is. .. The material of this impact bar is preferably light and has high specific strength, and contains M containing Al.
Although g-alloy extruded materials are currently receiving attention, Mg alloys with a high Al content have a large amount of Mg ₁₇ as described above.
There is a drawback that the elongation is not sufficient because Al ₁₂ is generated.

[0009]

The method for producing a Mg alloy member according to the present invention was made in order to solve such conventional problems.
The alloy particles are compacted and then extruded. A Mg alloy particularly suitable for the present invention contains about 6-11% Al. If it is less than 6%, the effect of the T6 heat treatment is not sufficiently exerted, and if it is 11% or more, Mg ₁₇ Al ₁₂
This is because the production amount of is too large and becomes brittle.

Chips are suitable as the particles used in the present invention. Here, the cutting chips include not only cutting chips obtained by cutting or grinding, but also chips made into chips by a crusher or the like. In order to obtain the T6 heat treated chips, the material that has been T6 heat treated in advance is cut,
It is better to collect the chips. For example, the chips produced during the cutting process of the T6 heat-treated Mg alloy member can be suitably used, and if the waste has been already T6 heat-treated before use, it is not necessary to perform the T6 heat-treatment again. The chips can be cut as they are and the chips can be used. Although it may be heat-treated after cutting into chips, caution is required because of the danger of ignition.

As the condition of the T6 heat treatment in the present invention, the condition which is carried out in a normal Mg alloy wrought material may be adopted. In the conventional example in which T6 heat treatment is performed after extrusion, the solution temperature conditions were extremely severe if recrystallization was attempted to be avoided. As a result, the crystal grains and Mg ₁₇ Al ₁₂ are refined again, so that the temperature condition of the T6 heat treatment is greatly relaxed.

The powder compacting in the present invention is carried out in the temperature range of 20.
0 ° C to 450 ° C, applied pressure 78 MPa (8.0 Kgf / m
m ² ) or more is preferable, and under the conditions, it can be performed in the atmosphere. If the temperature is 200 ° C. or lower, the adhesion of the chips becomes poor, and if the temperature is 450 ° C. or higher, it is necessary to carry out under vacuum, for example, from the viewpoint of oxidation prevention. The chemical treatment temperature should not be exceeded. Since chips are chip-shaped, they tend to form a layer in the mold and are easily solidified by one-way pressing in the mold, but when using other particles such as powder, it is necessary to keep them under hydrostatic pressure. Pressurization is required. Further, cold pre-compression molding may be performed before the powder compacting.

The extrusion molding is similar to the above-mentioned powder compacting in the temperature range, and an extrusion ratio of 4 or more is selected. This is because if the particle diameter is less than this, the particles cannot be adhered sufficiently and cannot be used as a member.

In the present invention, the T6 heat-treated Al-containing Mg alloy particles and other Al-containing Mg alloy particles are appropriately mixed within the range in which the former characteristics are not lost, and the powder is compacted. It can also be extruded. As other Al-containing Mg alloy particles, Al-containing Mg alloy particles that have or have not been subjected to other heat treatment such as T5 heat treatment (aging treatment) can be used. For example, Al-containing M
Many of the g-alloy members are subjected to T5 heat treatment, and inevitably a large amount of T5 heat-treated chips are produced. Therefore, these may be mixed with T6-treated Al-containing Mg alloy particles.

[0015]

In the present invention, Al which has been previously heat-treated with T6 is used.
By using Mg-containing alloy particles, which are compacted and then extruded, both the effect of heat treatment and the effect of extrusion can be brought out, and an Mg alloy member with excellent mechanical properties can be produced. be able to.
That is, since the Mg alloy particles used are subjected to T6 heat treatment, mechanical properties such as tensile strength, proof stress, and elongation are originally excellent, and the crystal grains are refined by extrusion molding. In parallel with the miniaturization, the precipitated intermetallic compound Mg ₁₇ Al ₁₂ is also miniaturized and uniformly dispersed in the base material, so that it is considered that good mechanical properties, especially high elongation can be obtained. .. In particular, when chips are used as the Mg alloy particles, the crystal grains are cut into small pieces by a cutting process or the like, which is more effective.

According to the present invention, in addition to the T6 heat-treated chips, other heat-treated or non-heat-treated chips can be mixed and used, so that chips and scraps having various heat treatment history, It is possible to reutilize used waste. Further, scraps, used wastes, etc. can be cut as they are to collect chips and treat them according to the above-mentioned steps.
It can be said that it is suitable as a means for recycling alloy products.

[0017]

EXAMPLE A test piece was obtained according to the process shown in FIG. That is, (1) AZ80Mg alloy (ASTM standard, Al:
7.8 to 9.2%, Mn: 0.12 to 0.35%, Z
Prepare a die casting material of n: 0.2 to 0.8%, Mg: balance. (2) T6 heat treatment (400 ° C × 4Hr + 175 ° C ×
After 16 hours, (3) cutting and collecting chips. (4) The obtained chips are housed in a mold 11 heated by a heater 10 as shown in FIG. 2A, and hot-pressed by a punch 12 to obtain a molded body 13. Pressurization conditions are atmospheric, 350 ° C,
20 Kgf / mm ² . (5) Subsequently, as shown in FIG. 3B, the die for extruding 14 was replaced, and the extruded member 16 was pushed into the die 11 by the stem 15 to obtain the extruded member 16. This is Example 1. Extrusion conditions are atmospheric, 350
℃, extrusion ratio 8.

(6) Similarly, a die casting material of AZ80Mg alloy is prepared, and (7) T5 heat treatment (175 ° C. × 16).
After Hr), (8) cutting was performed to collect chips, and (9) T6-treated chips were mixed in a volume ratio of 1: 1. Next, the mixed chips were subjected to the moldings of (4) and (5) above, and this was designated as Example 2.

On the other hand, the same AZ80Mg alloy die casting material was used in all cases, and chips were collected without heat treatment, and the above (3)
After adding the moldings of (4) and (4), T6 heat treatment (same condition as the example) was performed as Comparative Example 1, no heat treatment at all was performed as Comparative Example 2, and T5 heat treatment (same condition as the Example). Comparative Example 3 was prepared by using the chips alone and adding the moldings of (3) and (4) above.

Table 1 shows the data of mechanical properties obtained by measuring in the extrusion direction in both Examples and Comparative Examples. As shown here, in Comparative Example 1 in which T6 heat treatment was added after extrusion molding, the tensile strength was slightly higher than in Comparative Example 2 in which no heat treatment was added, but the yield strength was greatly reduced and the elongation was also There is no improvement. this is,
It is considered that this is because recrystallization occurred during the solution heat treatment to coarsen the crystal grains and coarse Mg ₁₇ Al ₁₂ was precipitated during the aging heat treatment. On the other hand, in Example 1 in which the chips subjected to the T6 heat treatment in advance were used, not only the tensile strength was further improved but also the elongation was remarkably improved, and the impact bar and the like requiring high strength and large elongation were obtained. Suitable mechanical properties were obtained.

[0021]

[Table 1]

In Example 2 in which equal amounts of T6 heat treated chips and T5 heat treated chips were mixed, the degree of improvement in mechanical properties was lower than in Example 1, but T5 heat treatment was added in advance. The tensile strength and elongation were improved as compared with Comparative Example 3 using only chips.

[0023]

As described above, according to the present invention, both the effect of T6 heat treatment and the effect of extrusion molding can be brought out, and excellent mechanical properties, especially high tensile strength and elongation can be obtained from the Mg alloy particles. It is possible to manufacture a Mg alloy member having the same.

Further, in the present invention, since cutting chips can be used as particles, Mg which has not been an effective treatment means in the prior art.
There is also an effect that alloy chips, scraps, used wastes and the like can be recycled by a simple means.

[Brief description of drawings]

FIG. 1 is a flow chart showing steps of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a powder compacting step (a) and an extrusion step (b) of an example.

FIG. 3 is a tensile strength-elongation diagram for explaining absorbed energy until a member breaks.

[Explanation of symbols]

 13 Powder compact 16 Extruded compact

Claims (4)

[Claims] 1. A method for producing a magnesium alloy member, which comprises subjecting T6 heat-treated aluminum-containing magnesium alloy particles to powder compacting and then extrusion molding. 2. A method for producing a magnesium alloy member, which comprises mixing T6 heat-treated aluminum-containing magnesium alloy particles with other aluminum-containing magnesium alloy particles, compacting and then extruding. 3. The method for producing a magnesium alloy member according to claim 1 or 2, wherein the aluminum-containing magnesium alloy particles are chips. 4. The method for manufacturing a magnesium alloy member according to claim 3, wherein the chips are formed after the heat treatment.