JPH04284963A - Light alloy-made member containing fiber reinforced part - Google Patents

Abstract

PURPOSE:To improve settling resistance to compressive stress in a light alloy- made member and to prevent the development of defect, such as crack in interface between fiber reinforced part and non-fibrous reinforced part. CONSTITUTION:Position 34 receiving the compressive stress in the light alloy- made member 36 is reinforced with the reinforcing fiber 10. In the case angle of the reinforcing fiber shown in the cross section along direction of the compressive stress to this direction is used to theta deg. and degree of orientation Y of the reinforcing fiber is made to be {(90-theta)/90}X100, the average aspect ratio Ra and the average degree of orientation Ya are made to be 100-2000, 10-85, respectively and also relation of Ya>-0.125XRa+50 is satisfied. Volume ratio of the reinforcing fiber is made to be >=5%.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light alloy member including a fiber-reinforced portion, and more particularly to a light alloy member in which a portion subjected to compressive stress is fiber-reinforced.

0002

BACKGROUND OF THE INVENTION For example, as described in Japanese Patent Publication No. 56-35981, for the purpose of improving the mechanical properties of a joint of a member made of light metal and having a joint with another member, It is already known to provide a fiber reinforced layer at the joint. According to such a member, mechanical properties such as rigidity and creep resistance of the joint can be improved compared to a case where the joint is not reinforced with fibers.

0003

[Problems to be Solved by the Invention] However, even when the joint is reinforced with fibers, if the joint is always subjected to compressive stress in a fixed direction, such as in a bolted joint, The parts may become sagging relatively early, making it impossible to maintain sufficient fastening force. Furthermore, if the joint is only partially reinforced with fibers, defects such as cracks may occur at the interface between the fiber-reinforced part and the non-fiber-reinforced part during long-term use of the component. .

The inventor of the present application has conducted various experimental studies in view of the above-mentioned problems in conventional light alloy members that include a fiber-reinforced portion and are subject to compressive stress in the fiber-reinforced portion.
In order to improve the fatigue resistance and avoid the occurrence of cracks, etc.
As stated in the above-mentioned publication, the aspect ratio and orientation state of the reinforcing fibers are more important than setting the fiber diameter and volume fraction of the reinforcing fibers within a predetermined range, and if these are not set within a predetermined range, I discovered that this is not the case.

The present invention is based on the knowledge obtained as a result of experimental research conducted by the inventor of the present invention, and is based on the knowledge obtained as a result of experimental research conducted by the inventor of the present invention. The object of the present invention is to provide an improved light alloy member that is free from defects such as cracks.

[0006]

[Means for Solving the Problems] According to the present invention, the above-mentioned object is to provide a fiber-reinforced light alloy member in a portion receiving compressive stress, and to increase the aspect ratio of the fiber length to the fiber diameter of the reinforcing fibers. Let the ratio R be the angle that the reinforcing fibers appearing in the cross section along the direction of the compressive stress make with respect to the direction of the compressive stress as θ (°), and the degree of orientation Y of the reinforcing fibers is (90-θ)/9.
When 0x100, the average aspect ratio Ra and average orientation degree Ya of the reinforcing fibers are respectively 100 to 2000,
10 to 85 and Ya>-0.125×Ra+5
0 and is achieved by a light alloy member characterized in that the volume fraction of the reinforcing fibers is 5% or more.

[0007]

[Operation] According to the above structure, the average aspect ratio Ra and average degree of orientation Ya of the reinforcing fibers are each 100 to 2.
000, 10 to 85 and Ya>-0.125×
It is set to satisfy Ra+50, and the volume percentage of the reinforcing fibers is set to 5% or more.

[0008] Therefore, the amount of reinforcing fibers effective for carrying compressive stress is oriented in a direction that effectively carries compressive stress. As can be seen, the resistance to settling of the light alloy member against compressive stress is significantly improved compared to the case where the average aspect ratio Ra and average degree of orientation Ya of the reinforcing fibers do not satisfy the above-mentioned conditions.

[0009] Furthermore, since the average degree of orientation Ya is set to 85 or less, mechanical properties suddenly change at the interface between the fiber-reinforced part and the non-fiber-reinforced part, causing cracks at this interface. The occurrence of defects is effectively avoided.

0010

[Supplementary explanation of means for solving the problem] According to the results of experimental research conducted by the inventor of the present application, when the average aspect ratio Ra of reinforcing fibers exceeds 2000, when forming a molded article of reinforcing fibers, Since the fibers are easily broken, it is difficult to form a good fiber molded article that satisfies each of the above conditions. Therefore, in the present invention, the average aspect ratio R of the reinforcing fibers is
a is set to 2000 or less as described above.

[0011] Furthermore, according to the results of experimental research conducted by the inventor of the present application, it is extremely difficult to form a fiber molded article when the volume fraction of reinforcing fibers is less than 5%; Even if it is possible to form a compact, the strength of the compact is low, resulting in cracks and defects in the compact during the casting stage. I can't. In addition, when the volume fraction of the reinforcing fibers is less than 5%, the average aspect ratio Ra of the reinforcing fibers is
Even if the average degree of orientation Ya satisfies the above-mentioned conditions, it is not possible to sufficiently improve the fatigue resistance of the portion of the light alloy member that is subjected to compressive stress. Therefore, in the present invention,
The volume percentage of reinforcing fibers is set to 5% or more.

[0012] Furthermore, in the so-called suction molding method, in which it is relatively easier to control the orientation of fibers, etc. than in the compression molding method, it is difficult to form a fiber molded product with a fiber volume percentage of more than 25%. Moreover, as long as the volume fraction of the reinforcing fibers is 5% or more, the resistance to sagging can be sufficiently improved, so the volume fraction of the reinforcing fibers may be 5 to 25%.

Furthermore, the average aspect ratio Ra and the average degree of orientation Ya
The above-mentioned inequality indicating the relationship between .

Generally, the strength properties of fiber-reinforced metal composite materials depend on the aspect ratio of the reinforcing fibers and the volume fraction of the reinforcing fibers. In addition, the compressive creep properties of a two-dimensional randomly oriented short fiber-reinforced composite material in the direction perpendicular to the fiber orientation plane are substantially the same as those of the matrix metal, but the creep properties in the direction parallel to the fiber orientation plane are substantially the same as those of the matrix metal. The properties are far superior to the creep properties of matrix metals. Therefore, it is considered that the creep property improves as the number of reinforcing fibers having a certain length (longer than the fiber diameter) in the direction along the compressive stress increases and the fiber length increases. That is, it is considered that the following equation holds true.

Creep property=K (fiber length)×(number of fibers oriented in the compression direction) (K
is a proportionality constant) Furthermore, the fiber diameter of short fibers commonly used as reinforcing fibers for composite materials is from several μm to several tens of μm,
There is almost no change during the fiber forming process. On the other hand, the fiber length is distributed over a certain range and decreases due to breakage during the molding process and the like. Therefore, assuming that the fiber diameter of the reinforcing fibers is substantially constant, it can be considered that (1) the aspect ratio of the reinforcing fibers depends only on the fiber length. Also(
2) The degree of fiber orientation can be considered as the probability of existence of reinforcing fibers that are oriented in the direction of compressive stress, so (number of fibers oriented in the compression direction) = (degree of orientation) ×
(fiber volume fraction).

Therefore, from (1) and (2), the above proportional expression can be rewritten as follows. Creep property = K' (aspect ratio) x (degree of orientation)
× (fiber volume ratio)
(K' is a proportionality constant) In this equation, since the fiber volume fraction has upper and lower limits in the production technology of fiber molded bodies, the lower limit of the creep property is defined by (aspect ratio) and (degree of orientation), and therefore, It can be seen that the above inequality is in sign with this proportional expression.

The invention will now be described in detail by way of example with reference to the accompanying drawings.

[0018]

[Examples] Example 1 Alumina-silica fibers ("Arsilon" manufactured by Isolite Industries Co., Ltd., 50% Al2 O3, balance SiO2) having a fiber diameter of 2 to 5 μm and a fiber length of 1 to 4 mm were prepared. Next, as shown in FIG. 2, the alumina-silica fibers 10 and an inorganic binder were added to water and stirred and mixed to form a dispersion 12. Next, a mold 20 having a cylindrical body 14 made of punched metal, a disc 16 closing one end of the cylindrical body, and a flange 18 fixed to the other end of the cylindrical body 14 in parallel with the disc 16 is placed in the dispersion liquid 12. Suction molding was performed by immersing the mold in the mold, reducing the pressure inside the mold, and suctioning the dispersion liquid. After the molding is completed, the molded body is dried and fired, and by further performing necessary machining, the molded body is made of alumina-silica fiber 10 and has an outer diameter of 5 as shown in FIG.
A cylindrical fiber molded body 22 having dimensions of 6 mm, inner diameter 32 mm, and height 36 mm was formed.

In this case, by changing the concentration of alumina-silica fiber in the dispersion, the volume percentage of alumina-silica fiber was set at three levels, 5%, 10%, and 25%, and for each volume percentage, the fiber By changing the classification conditions and molding conditions, the degree of fiber orientation and aspect ratio can be changed to various values, thereby creating a fiber molded body with the same volume fraction of fibers, degree of fiber orientation, and aspect ratio. Two groups were formed.

Next, as shown in FIG. 4, the molded body 22 is placed at a predetermined position in a mold cavity 26 of a mold 24 for casting a crankshaft pulley of a gasoline engine, and is passed through a gate 30 by a plunger 28. A of 973K (700℃) inside mold cavity 26
30A of molten metal of l alloy (JIS standard AC8A) was injected under pressure, and the molten metal was pressurized at a pressure of 700 kgf/cm2.
The pressurized state was maintained until the molten metal completely solidified.

After the molten metal has completely solidified, the pulley rough material is taken out from the mold 24 and a predetermined machining process is performed on the rough material to form a boss portion around the bolt insertion hole 32 as shown in FIG. 34 formed a crankshaft pulley 36 made of an Al alloy compositely reinforced with alumina-silica fibers 10.

Next, one pulley of each set is connected to a 6-cylinder 300
Assemble the crankshaft of a 0CC gasoline engine with bolts so that the initial surface pressure of the boss part is 15kgf/mm2, and run the engine at 6500 rpm for 30 minutes.
A durability test was conducted in which the device was operated for 0 hours. In this case, measure the axial force of the pulley fastening bolt before and after the test, and pass if the axial force retention rate (axial force after test/initial axial force x 100) is 95% or more, and fail if it is less than that. Rated as passing. The evaluation standard for the axial force retention rate was set at 95% because the axial force retention rate in the case of cast iron pulleys is 95%.

The results of these tests are shown in FIG. Figure 5
In , the diamond, circle, and square symbols indicate cases where the fiber volume percentage is 5%, 10%, and 25%, respectively, and the white symbols in particular indicate that the axial force retention rate is acceptable. Each black symbol indicates that the axial force retention rate is unacceptable.

Further, the average degree of orientation Ya of the fibers in FIG. 5 was determined as follows. Each pulley that was not subjected to the above-mentioned durability test was inserted into the bolt insertion hole 32 as shown in FIG.
The boss portion 3 is parallel to the axis 38 of the
4, the cut surfaces were polished and observed with an optical microscope, and among the fibers that appeared on the cut surface, 10 fibers with clearly recognized long axes were randomly extracted from each surface. The direction of compressive stress as shown in Figure 7 for the fibers,
That is, the angle θ between the straight line 40 parallel to the axis 38 and each fiber 10 is determined, and the degree of orientation Y is calculated for each fiber according to the above-mentioned formula.
was calculated, and the average value of the degrees of orientation for all 20 fibers was taken as the average degree of orientation Ya.

From FIG. 5, in order to ensure sufficient resistance to fatigue in the boss portion, (1) the average aspect ratio Ra of the fibers is 100 or more, (2) the average orientation degree Ya of the fibers is 10 or more. Being (3)
) It is understood that the average aspect ratio Ra and the average degree of orientation Ya need to satisfy the following relationship: Ya>-0.125×Ra+50.

As shown in FIG. 5, when the average aspect ratio exceeds 2000, a good fiber molded article could not be formed due to breakage of the fibers.

Example 2 Among the pulleys for which good results were obtained in the above-mentioned Example 1, the pulleys labeled A to I in FIG. 1.8ks to
(30 min), then immersed in silicone oil at 243K (-30°C) for 1.8ks for 1 cooling/heating cycle.
After 00 cycles, the durability test was conducted again under the same procedure and conditions as in Example 1.

As a result, the axial force retention rate was good for all pulleys A to I, but for the three pulleys A, D, and G, there was a difference between the fiber reinforced part and the non-fiber reinforced part. It was observed that cracks had formed at the interface between the two. Therefore, it can be seen that the average degree of orientation Ya must be 85 or less in order to prevent defects such as cracks from occurring between the fiber-reinforced portion and the non-fiber-reinforced portion.

Example 3 Alumina fibers (manufactured by ICI, 97% Al2O3, balance SiO2) with an average fiber diameter of 3 μm and an average fiber length of 900 μm were used, except that the volume percentage of the fibers was set at 10%. In the same manner as in Example 1 described above, two types of molded bodies were formed: a molded body J in which the average fiber orientation degree was 10, and a molded body K in which the average fiber orientation degree was 56. Next, Al at 973 (700°C) was used as a molten Al alloy.
A crankshaft pulley with a boss reinforced with alumina fiber was formed in the same manner and under the same conditions as in Example 1, except that molten alloy (JIS standard AC4C) was used, and the test was carried out on these pulleys. A durability test was conducted under the same procedure and conditions as in Example 1.

As a result, the retention rate of the axial force of the pulley formed using the molded body K that satisfies all of the above conditions (1) to (3) was 96%; ) The retention rate of the axial force of the pulley formed using the molded body J which did not satisfy the following was 88%.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to the above-mentioned embodiments, and various other embodiments may be made within the scope of the present invention. It will be clear to those skilled in the art that this is possible.

[0032]

Effects of the Invention As is clear from the above description, according to the present invention, reinforcing fibers in an amount effective to support compressive stress are oriented in a direction that effectively supports compressive stress.
Compared to the case where the average aspect ratio Ra and the average degree of orientation Ya of the reinforcing fibers do not satisfy the conditions of the present invention, the resistance to settling of the light alloy member against compressive stress can be significantly improved.

Furthermore, since the average degree of orientation Ya of the reinforcing fibers is set to 85 or less, defects such as cracks can be effectively avoided from occurring at the interface between the fiber-reinforced portion and the non-fiber-reinforced portion. Accordingly, the durability of the light alloy member can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a crankshaft pulley as one embodiment of a light alloy member according to the present invention.

FIG. 2 is an explanatory diagram showing the procedure of suction molding.

FIG. 3 is a perspective view showing the fiber molded body formed by suction molding shown in FIG. 2;

4 is a sectional view showing a casting process performed using the fiber molded body shown in FIG. 3. FIG.

[Figure 5] Average aspect ratio Ra of alumina-silica fibers
There is also a graph showing the results of durability tests conducted on crankshaft pulleys in which the average degree of orientation Ya was set to various values.

FIG. 6 is an explanatory diagram showing the procedure for determining the average degree of orientation Ya of fibers in the boss portion of the crankshaft pulley.

FIG. 7 is an explanatory diagram showing the angle θ that fibers make with respect to the direction of compressive stress.

[Explanation of symbols]

10...Alumina-silica fiber 20...Molding mold 22...Fiber molded body 24...Mold 26...Mold cavity 34…Boss part 36...Crankshaft pulley

Claims (1)

[Claims] The part receiving compressive stress is a light alloy member reinforced with fibers, the ratio of the fiber length to the fiber diameter of the reinforcing fibers is set as R, and the reinforcing fibers appearing in the cross section along the direction of the compressive stress are in the direction of the compressive stress. When the angle formed with respect to 85 and satisfies Ya>-0.125×Ra+50,
A light alloy member characterized in that the volume percentage of the reinforcing fibers is 5% or more.