JPS596338A - Compound alloy and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain compound alloy excellent in ductility and strength, by a method wherein the second phase of boron compound is, in dispersion manner, precipitated in master phase by quenching molten metal of alloy from a semimolten state. CONSTITUTION:The molten metal of alloy is solidified by quenching it from a semimolten state at a temperature lower than the liquidus where crystalline phase is partially precipitated. Then, the second phase of boron compound is, in conversion manner, precipitated in the master phase composed of one or more phase, of amorphous phase, fine crystalline phase and supersaturated solid solusion. Thus, ductility is given accordint to the master phase, tensile strength being raised according to the dispersion precipitation of the second phase at the same time and composite alloy excellent in ductility and strength can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite alloy and a method for producing the same, and more particularly to a composite alloy and a method for producing the same suitable for obtaining a composite alloy with excellent ductility and strength in a simple process.

A precipitation dispersion type composite alloy is generally known as one type of composite alloy. Since this type of alloy utilizes precipitation from a solid phase, a certain amount of heat treatment is required.

Furthermore, if the heat treatment temperature is high, the crystal grains will become coarser due to recrystallization of the matrix phase, and a new processing heat treatment will be required to adjust the crystal grains, resulting in a complicated process. Furthermore, in some alloys, precipitates segregate at grain boundaries, which causes a problem of deterioration in ductility.

On the other hand, ultra-rapid cooling from the conventional molten state (molten metal rapid cooling method)
K, the amorphous and crystalline phases produced by Yoshishi contain a large amount of B and C compared to alloys that have been processed and heat treated.

Metalloids such as Si and P can be dissolved in solid solution. This large amount of semimetal has the advantage of increasing the hardness and strength of the ultra-rapidly solidified alloy. However, if this metalloid element is added in excess of the limit, compounds are formed in the conventional molten metal quenching method, resulting in a very brittle alloy. For example, in the case of B, the limit of the amount added in the conventional molten metal quenching method is about aoat%. However, a large amount of B is desired to be added in order to increase the neutron absorption capacity of spent nuclear fuel storage racks at a high density.

An object of the present invention is to provide a composite alloy and a method for producing the same, which can transform a conventional mechanically brittle alloy composition into a ductile structure without requiring complicated steps.

The present invention imparts ductility to the amorphous phase, which is either an amorphous phase, a fine crystalline phase, or a supersaturated solid solution, even if the alloy composition is conventionally mechanically brittle, and disperses and precipitates the second phase. This increases the hardness and tensile strength of the matrix composition of the alloy.When manufacturing such a composite alloy, the molten alloy is heated to a temperature close to the liquidus line where a part of the crystalline phase precipitates. 〃 is also rapidly solidified from a semi-molten state at low temperatures.

Hereinafter, the present invention will be explained in more detail based on the drawings.

FIG. 1 is an A-B binary system equilibrium state diagram schematically showing the principle of the present invention. In this binary alloy, a compound called AB is formed. Furthermore, there is a eutectic point e between A and AB. In the region (2) near this eutectic point composition, a ductile amorphous phase, a fine crystalline phase, or a supersaturated solid solution is formed by the molten metal quenching method. Looking at such a binary alloy with composition M, M has a larger amount of B than region II. Even when solidified, it becomes a brittle material.

The feature of the present invention is that the M alloy is rapidly solidified from a semi-molten state in a temperature range from the d point (liquidus line) T, which is much lower, to the eutectic point e, which is much higher. For example, when the M alloy is rapidly solidified from point C in FIG. 1, the semi-molten state is as follows. That is, at point C, the M alloy composition is in a state where point b, that is, the AB compound (solid phase) is crystallized and dispersed in the liquid phase of point a, that is, the M' composition. When this state is rapidly cooled and solidified, the liquid phase M' falls within the range (3) and becomes at least one of an amorphous phase, a fine crystalline phase, and a supersaturated solid solution. The alloy obtained by K in this manner becomes a composite alloy in which the AB compound is dispersed using at least one of a ductile amorphous phase, a microcrystalline phase, and a supersaturated solid solution as a parent phase. This composite alloy has greater hardness and tensile strength than alloys with a matrix composition due to precipitate dispersion strengthening. Therefore, a ductile composite alloy can be manufactured even outside the range where a ductile alloy can be manufactured by the conventional molten metal quenching method, that is, in a composition range that results in a brittle alloy.

In the present invention, generally known methods such as a single-roll quenching method, a twin-roll quenching method, a pendant drop method, and a melt extraction method can be applied to rapidly solidify the semi-molten molten metal. In these methods,
The molten metal in a semi-molten state is rapidly solidified on a directly rotating or moving cooling base, and the cooling rate is usually about 10'.
Extremely fast at over C/sec.

In the present invention, it is necessary for the molten alloy to be in a semi-molten state when it comes into contact with the cooled substrate surface in the above method, and for this purpose, the alloy composition is completely melted in the alloy melting tank. There is a method in which the distance between the nozzle and the cooling substrate surface, such as the roll surface, is changed and the temperature of the molten metal just before it contacts the roll surface is measured with an infrared thermometer. However, with this method, it is difficult to obtain a homogeneous ribbon with uniform thickness because the distance between the nozzle and the roll surface varies. Therefore, a thermometer such as a thermocouple is installed in the nozzle installed in the alloy melting tank, and the molten metal in the nozzle is maintained in a semi-molten state, and an inert gas is pressurized into the nozzle. It is better to squirt out. In this case, even if the molten alloy is in a semi-molten state, if the temperature of the molten alloy is too low, the viscosity of the molten metal will increase and it will be difficult to eject the molten metal, so it is necessary to maintain it in a semi-molten state that allows the molten metal to eject. be.

The present invention will be explained in detail below.

FIG. 2 is a schematic diagram of the single roll quenching method used in this example. A pre-molten alloy is inserted into a nozzle 1 made of transparent quartz tube, and after being remelted in a high frequency induction furnace 2, it is heated to a roll 3 using high pressure Ar gas.
The temperature of the molten metal at the time of ejection was measured by a thermocouple 5 inserted from the upper part of the nozzle.

In this example, a Cr-plated copper roll (diameter 20
01+1111) and set the rotation speed to 300Orpm.
, the slit at the tip of the nozzle is 0.5 x 5 mm.

Adjust the Ar gas pressure to 0.4 to 2 Kg/cm”,
The ribbon had a width of about 5 mm and a thickness of about 30 μm.

Figure 3 shows the Fe, 3-x Crl fabricated in this way.
? In the amorphous formation range (range indicated by the arrow) of the Bz rapidly solidified alloy and the range in which the precipitate is dispersed in the amorphous phase, the volume percentage (%) of the precipitate (CrB compound) is shown. In the method (conventional method) of rapidly cooling from a completely molten state (1300 t:'), the range of amorphous formation is limited to about 22 at %, and if the amount of B exceeds that amount, the amorphous phase does not form and becomes brittle.

On the other hand, in the method of the present invention, the temperature of the molten metal at the time of ejection is set to 115oC (semi-molten state) using a thermocouple 5, and when it is rapidly solidified, a crystalline phase is partially precipitated and dispersed in a composition range of about 20 to 30 at%, resulting in nine ductility. It becomes a composite alloy with This crystalline phase was found to be in υCrBCr by X-ray diffraction. This precipitate is
The particles were very fine, ranging from several μm to about 20 μm.

FIG. 4 shows the change in the amount of precipitated CrB compound depending on the F'4 & Cr17 &s gold alloy molten metal jetting temperature. Figure 4 is C
It is shown that the amount of rB compound precipitated can be controlled by the melt temperature and increases as the temperature decreases. However, if the temperature of the molten metal is too low, the viscosity of the molten metal will be high and it will be impossible to eject it. In FIG. 4, A is the temperature range where ejection is not possible.

FIG. 5 1dNi, , -ICr,. The range of amorphous phase formation of Pt, B, and alloys and the precipitation ratio (%) of precipitates are shown.

In the case of this alloy, the limit B content for amorphous formation by the conventional method is about 308 t%. On the other hand, according to the method of the present invention, B
The amount can be increased to about 36 at%, with up to about 5% precipitate. The precipitate is a CrB compound based on the results of X-ray diffraction and XMA. Even if such precipitation occurs, it remains in an amorphous phase, so it has toughness and excellent ductility. Furthermore, these high B-containing Nl-based alloys have good corrosion resistance and high neutron absorption ability, and are therefore suitable as neutron absorbing materials and radioactivity shielding materials for nuclear fuel storage rack materials.

As described above, according to the present invention, it is possible to impart ductility to the matrix phase and increase the strength and tensile strength by dispersing and precipitating the second phase. By increasing the amount of added elements that have been previously limited, the properties of the resulting alloy can be improved, and furthermore, complicated heat treatment is not required.

[Brief explanation of the drawing]

Fig. 1 is a schematic A-B binary system phase diagram for explaining the present invention in detail, Fig. 2 is a schematic diagram of a single roll quenching device applied to the present invention, and Fig. 3 is a Fe811-ECr1Jx Figure 4 shows the amorphous phase formation composition and precipitation ratio of precipitates by the method according to the present invention and the conventional method for alloys.
A diagram showing the change in the amount of precipitates depending on the molten metal ejection temperature of cr rtt13ts alloy, Figure 5 is N1vy, 5-8Cr16P
1. FIG. 2 is a diagram showing the amorphous formation composition and the proportion of precipitates in an sBx alloy. 1... Nozzle, 2... High frequency induction furnace, 3... Roll, 4 $ 1st, Q /'l' /
'7 A13 BByc$ amount 2nd item 5 $3 Menagaguchi/1 (d"/,) 4th circuit end Pt, temperature (゛ri thousand 5th item)

Claims (1)

[Scope of Claims] 1. A composite alloy characterized in that a second phase is dispersed and precipitated in a parent phase consisting of at least one of an amorphous phase, a fine crystalline phase, and a supersaturated solid solution. 2. The composite alloy according to claim 1, wherein the second phase is a boron compound. 3. A method for producing a composite alloy, which comprises rapidly solidifying a molten alloy from a semi-molten state at a temperature lower than the liquidus line at which a part of the crystalline phase precipitates.