JPH02298228A - Beta-type silicon nitride whisker reinforced magnesium composite - Google Patents

Abstract

PURPOSE:To obtain the fiber reinforced-type Mg series composite usable at a relatively high temp. by using an Mg alloy contg. Nd, Nd series metal or furthermore Mn, Y, Sm, Ce, etc., as a matrix and incorporating a formed body of beta-type silicon nitride whiskers as a reinforcing material. CONSTITUTION:As reinforcing fiber, a formed body 8 of beta-type silicon nitride whiskers having high strength, excellent high temp. stability and a low thermal expansion coefficient is arranged in a cavity 2 in a movable die I of a vertical die casting machine and a fixed die 3 having a sleeve 5 charged with the molten metal 10 of an Mg alloy as a matrix is assembled via a placed core 7. The molten metal 10 of the Mg alloy is fed into the cavity 2 of the movable die 1 by the pressurization of a plunger 6, which is cooled and solidified to manufacture the beta-type silicon nitride whisker reinforced-type Mg composite usable even at >=200 deg.C. As the Mg alloy, the one furthermore contg. <5% Mn, <1.5% Y, <5% Sm and <8% Ce in addition to Nd may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fiber-reinforced metal composite material, and more particularly to a composite material having β-type silicon nitride whiskers as reinforcing fibers and a magnesium alloy as a matrix, that is, β Regarding type silicon nitride whisker reinforced magnesium composite materials.

Examples of magnesium alloys that form the matrix of fiber-reinforced metal composite materials include MDCIA (equivalent to AZ91A according to ASTM standards), MC7 (ZK6 according to ASTM standards), etc.
1A), JIS standard alloys such as MC8 (equivalent to EZ33A according to ASTM standards), or AM60A, AS4
ΔSTM standard alloys such as 1A and QE22A were used.

However, in the case of a combination of these magnesium alloys and β-type silicon nitride whiskers, the heat resistance is still low even when cast into a composite material using, for example, a molten metal forging machine (a casting machine with high casting pressure). It cannot be used at relatively high temperatures above ℃.

The problem to be solved by β-type silicon nitride whiskers has the highest strength among the various reinforcing fibers used in the production of fiber-reinforced metal composite materials, excellent high-temperature stability, and low coefficient of thermal expansion. The present inventors have conducted extensive studies on composite materials with magnesium alloys that take advantage of the characteristics of such β-type silicon nitride whiskers. and relatively high temperatures requiring low thermal expansion, e.g.
The object of the present invention is to provide a β-type silicon nitride whisker-reinforced magnesium composite material (hereinafter sometimes simply referred to as composite material) that can withstand use at temperatures of 00°C or higher, and to find out what kind of chemical composition the magnesium alloy has. The present invention was achieved by conducting experiments to find out which material was most suitable as a matrix.

According to the present invention, the above-mentioned object for the purpose of
A β-type silicon nitride whisker-reinforced magnesium composite material comprising 5 to 75% by volume of β-type silicon nitride whiskers and 5 to 25% by volume of β-type silicon nitride whiskers; (2) the above magnesium alloy further containing 3% or less of Mn; (1) The β-type silicon nitride whisker-reinforced magnesium composite material described in (1) above, (3) the magnesium alloy further containing 1.5% or less of Y.
and (2) the β-type silicon nitride whisker-reinforced magnesium composite material as described in (4) the magnesium alloy as described in (1), (2) and (3) above, wherein the magnesium alloy further contains 5% or less Sm. β-type silicon nitride whisker reinforced magnesium composite material, (5) Magnesium alloy further contains 8% or less CE or CE
The β-type silicon nitride whisker-reinforced magnesium composite material according to (1) to (4) above, which contains a ce-based metal, (6) contains 3 to 10% of a ce-based metal, and the remainder is substantially MO. A β-type silicon nitride whisker-reinforced magnesium composite material comprising 95 to 75% by volume of a magnesium alloy and 5 to 25% by volume of β-type silicon nitride whiskers, (7) the magnesium alloy further containing 3% or less of Mn; A β-type silicon nitride whisker-reinforced magnesium composite material according to (6) above.

achieved by. However, the β-type silicon nitride whisker-reinforced magnesium composite materials described in (1) to (7) above may partially contain 5% or less of Pr, Gd, or SC as a magnesium alloy. Further, the β-type silicon nitride whisker-reinforced magnesium composite material described in (6) and (7) may contain 5% or less of Y or Sm.

These alloying elements are rare earth elements or elements with properties similar to rare earth elements, and depending on the content, they are not necessarily harmful and may even be beneficial in some cases.

In addition, in this specification, Nd, Y, Sm, Ce, Pr,
(3d and SC each have atomic number 60.39.62
．． 58, 59, 64, and 21 - B group elements, and the elements other than Y and SO are rare earth elements. Further, the Nd-based metal refers to didymium with a Nd metal content of 70% or more, and the Ce-based metal refers to didymium with a Ce content of 50% or more.

Table 1 shows Deidiumium and Mitsushmetal. Example of Didymium and Mitsushmetal Composition According to the present invention, β-type silicon nitride whiskers, which have high strength, excellent high temperature stability, and low coefficient of thermal expansion, are used as reinforcing fibers, and the Nd content is 1% as the matrix. Above 1
0% or less, and the remainder is essentially magsium (Mg)
As is clear from the results of experiments conducted by the present inventors, by using a magnesium alloy with It is possible to obtain a composite material that can withstand use at extremely high temperatures.

Magnesium alloys made by adding Nd to Mg as a matrix of composite materials have fairly high mechanical strength and heat resistance, but these properties are further improved when reinforced with β-type silicon nitride whiskers. However, if the Nd content is less than 1%, the effect is not sufficient, and if it exceeds 10%, the composite material becomes brittle and is not suitable for practical use. Therefore,
The Nd content of the magnesium alloy as a matrix in the composite material of the present invention is 1% to 10%, preferably 3 to 7%. In this case, the same effect can be obtained by using didymium containing up to 70% Nd instead of Nd. In addition, when containing 3 to 10% of Ce-based metal (mitshu metal), Mq-N
Strength, especially creep strength, greater than or equal to the Nd content of a β-type silicon nitride whisker-reinforced magnesium composite material with d-alloy as a matrix can be obtained.

Further, a composite material having a matrix of Nd-containing Mg-Nd alloy as described above and the above-mentioned 3 to 10% Ce
In a composite material whose matrix is a magnesium alloy containing a series metal, if the volume fraction of β-type silicon nitride whiskers is less than 5% by weight, sufficient strength and low coefficient of thermal expansion cannot be ensured. When the volume fraction is in the range of 5 to 25% by volume, the strength of the composite material increases almost linearly with the increase in volume fraction, but when the volume fraction exceeds 25% by volume, β-type silicon nitride resists the penetration of molten metal. Whisker resistance increases,
Manufacture of healthy composite materials becomes an option.

In addition, all percentages in this specification are weight % except in the case of fiber volume percentage, and in the expression of chemical components of magnesium alloy [substantially MgJ
"Zn, Si, Fe, Cu, Ni
This means that the total amount of impurities such as is 0.5% or less, and the remainder is Mg.

The present invention will be described in detail below with reference to examples.

Magnesium alloy AZ92, AZSlolo (alloy manufactured by Ube Industries), AS21, EZ33A, QE22A, M
g-5%Nd, Mg-5%Nd-1%Mn, Mq-5%
Nd-1%Y, Mg-4%Nd-2%MM% and Mg
-5%MM-2%Mn (Note: MM is Mitshu Metal) using a 250-ton vertical die-casting machine.
A β-type silicon nitride whisker-reinforced magnesium composite material was manufactured using a β-type silicon nitride whisker molded body. Chemical composition of matrix alloy used, manufacturing conditions, 250
A schematic diagram of the vertical die force machine mold cavity and a schematic diagram of the β-type silicon nitride whisker-reinforced magnesium composite material are shown in Table 2, Table 3, FIG. 1, and FIG. 2, respectively. The above-mentioned β-type silicon nitride whisker molded product is a β-type silicon nitride whisker manufactured by Ube Industries (average am length 10 to 50 μm, average fiber diameter 0.1 to 1.5 am, 100% β-3i3N4).
) was produced using a uniaxial press without using a binder.

The shape is a disc with a size of about 100 mφ x 20 mt, and the fiber volume percentage is about 10%, and the silicon nitride whiskers are three-dimensionally randomly oriented.

The manufacturing method will be specifically described below. First, a molten magnesium alloy [phase] is poured into the sleeve (2) of the 250-ton vertical die-casting machine shown in FIG. 1 using a ladle. Sleeve■
A ceramic vapor is placed inside to prevent the temperature of the molten metal [phase] from decreasing. Next, as shown in FIG. 1, a placing core is set, and the β-type chambered silicon whisker molded body (2) is placed thereon.

Immediately, as shown in Figure 1, the movable mold ■ is lowered from above.
Once the manufacturing conditions have been met, the cavity is closed, and the molten metal is pushed into the cavity by the push-up of the plunger. After the mold closing time of 45 seconds has elapsed, the movable mold (2) moves upward, and the β-type silicon nitride Usska-reinforced magnesium composite material shown in FIG. 2 is taken out.

In the β-type silicon nitride whisker compact-reinforced magnesium composite material shown in Fig. 2, a test piece was cut out parallel to the circular surface of the compact from the area where the disk-shaped compact was present, and JI
A tensile test was conducted at 200'C and a creep rupture test was conducted at 250C according to the S standard. The test results are shown in Table 4, and in both the tensile test and the creep rupture test, materials other than EZ33A relied on F materials (materials that were not heat treated).

, Overwhelming 9-15, Comparative Examples 6-9° In the same manner as in Examples 1-8, a β-type silicon nitride whisker molded body with a fiber volume ratio of about 10% by volume and a magnesium alloy with the chemical composition shown in Table 5 were prepared. A composite material was manufactured using a 250-ton vertical die-casting machine (in the case of fiber reinforcement). Further, a magnesium alloy having the chemical composition shown in Table 5 was cast alone using a 250-ton vertical die-casting machine (if not reinforced with fibers). From these two series products, test pieces were cut out in the same manner as in Examples 1 to 8, and the F material was cut out at 20°
A C tensile test and a 250°C creep rupture test were conducted. Table 6 shows the results without fiber reinforcement (reference example)
Table 7 shows the cases in which the fibers were reinforced. Also,
Among these experimental results, only the tensile test results are summarized in FIG. 3.

Table 5. Chemical composition diagram 3 of Mg-(1~20)%Nd alloy
From this, it can be seen that the appropriate content of Nd is 1% or more and 10% or less, particularly 3 to 7%.

, Cases 16-20, Hiki-10 From the fruiting results of Examples 9-15, an appropriate Nd content was found. Therefore, in order to find an appropriate fiber volume percentage of the molded product, first, the fiber volume percentage is 5% by volume, 10% by volume, 15% by volume, 2% by volume.
β-type silicon nitride whisker molded bodies of 0% by volume, 25% by volume, and 30% by volume were produced. This molding method used only a uniaxial press, or if the fiber volume ratio was insufficient, a rubber press was also used. Using the β-type silicon nitride whisker molded body prepared in this way, a composite material was manufactured in the same manner as in Examples 1 to 8 for Mg-5% Nd alloy,
A test piece was cut out from the composite material (F material) and heated to 200°C.
A tensile test and a creep rupture test were conducted at 250°C. The results are shown in Table 8 and FIG.

From FIG. 4, the tensile strength and yield strength increase as the fiber volume fraction increases up to a fiber/volume fraction of 25% by volume, but do not increase beyond that. This is thought to be because the penetration resistance of the molten metal into the molded body increases as the fiber volume fraction increases, and as a result, defects such as insufficient molten metal filling inside the composite material eventually surface when the fiber volume fraction is 3CI%. In addition, the fiber volume fraction is 5
The tensile strength is not much different from that of non-fiber reinforced alloys below 20%. Considering these results and the results of the creep rupture test, an average fiber volume fraction of 5 to 25% by volume is considered appropriate.

A molded body made by compression molding Natsuriri β-type silicon nitride whiskers,
By impregnating and solidifying a magnesium alloy containing Nd and the like under high pressure, a high-strength m-fiber reinforced magnesium composite material with excellent heat resistance was obtained. This composite material is 20
The 0°C tensile strength is approximately 30 kgf/s2, the 200°C tensile test values are well balanced, and the material has excellent creep strength.

Therefore, it is suitable for applications that require light weight, low thermal expansion, and heat resistance, such as automotive engine parts and general-purpose engine parts.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the mold cavity of a 250-ton vertical die force machine, Figure 2 is a schematic diagram of β-type silicon nitride whisker-reinforced magnesium composite material, and Figure 3 is a schematic diagram of Mg-N with different Nd contents.
Figure 4 shows the results of a 200°C tensile test when the d alloy is not reinforced with fibers and when the alloy is reinforced with fibers.
The relationship between temperature and tensile strength is shown. In FIGS. 1 and 2, ■...movable mold, ■...
Cavity, ■... Fixed mold, ■... Platen, ■
... Sleeve, ■... Plunger, ■... Core, ■... β-type silicon nitride whisker molded body, ■... Ceramic vapor, ■... Represents molten magnesium alloy. Patent applicant Ube Industries Co., Ltd. 48rb I6 good quality large straw 4 tons of 200'C 1 piece of cylindrical material

Claims (7)

[Claims] (1) Magnesium alloy 9 containing 1% or more and 10% or less of Nd or Nd-based metal, with the remainder being substantially Mg
A β-type silicon nitride whisker-reinforced magnesium composite material comprising 5-75% by volume of β-type silicon nitride whiskers and 5-25% by volume of β-type silicon nitride whiskers. (2) The β-type silicon nitride whisker-reinforced magnesium composite material according to claim (1), wherein the magnesium alloy further contains 3% or less of Mn. (3) The β-type silicon nitride whisker-reinforced magnesium composite material according to claims (1) and (2), wherein the magnesium alloy further contains 1.5% or less of Y. (4) The β-type silicon nitride whisker-reinforced magnesium composite material according to claims (1), (2), and (3), wherein the magnesium alloy further contains 5% or less of Sm. (5) Magnesium alloy further contains 8% or less Ce or Ce
The β-type silicon nitride whisker-reinforced magnesium composite material according to claims (1) to (4), which contains a metal. (6) β-type silicon nitride whisker-reinforced magnesium consisting of 95-75% by volume of a magnesium alloy containing 3-10% of Ce-based metal and the remainder being substantially Mg and 5-25% by volume of β-type silicon nitride whiskers Composite material. (7) The β-type silicon nitride whisker-reinforced magnesium composite material according to claim (6), wherein the magnesium alloy further contains 3% or less of Mn.