JP2647805B2 - Method for improving processing characteristics of intermetallic compound by surface treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an intermetallic compound, N
The present invention relates to a method for improving processing characteristics such as bending of i ₃ Al by surface treatment.

[0002]

2. Description of the Related Art Intermetallic compounds such as Ni ₃ Al have high hardness,
It has excellent properties such as high heat resistance, high strength, etc. that are not found in ordinary crystalline metals, and it has the inverse temperature dependence of strength, so it is expected to be applied as a heat resistant material, but in the ordinary polycrystalline state Because it is a very brittle material that is extremely difficult to process,
Practical application is hampered. In recent years, many studies for overcoming the brittleness of intermetallic compounds have been reported. They are,
It is divided into research on material reforming and research on processing processes.

Researches on material modification include: 1) addition of trace elements (boron, etc.) at the time of casting, 2) selection of alloy constituent elements, 3) control of texture by heat treatment or the like (structure adjustment, crystal grain size reduction). Researches have been made on miniaturization, directional solidification, single crystal recrystallization), 4) slight changes in the component ratio of the stoichiometric composition of intermetallic compounds, and the like.

[0004] On the other hand, there are the following studies on the processing process. 1) A method for finding optimum processing conditions (temperature, processing speed) (for example, Sendust has found a range that can be processed at high temperature and low strain rate), 2) Control of stress state such as ultra-high hydrostatic pressure conditions. Methods (extrusion at high temperature, HIP, etc.), 3) Utilization of powder molding method, 4) Method of repeatedly deforming a plurality of component materials or composite materials and then diffusing them to form an alloy are reported.

[0005] For intermetallic compounds which are difficult to process,
As described above, various studies for practical use have been advanced, but most of the studies are on material modification.
For example, there is a study that as a material modification method for Ni ₃ Al, it is possible to improve the processing characteristics by adding boron as a component of about 0.1% (for example,
Kiyoshi Aoki, Osamu Izumi, L1 ₂ type intermetallic compound Ni ₃ Al improved room temperature viscosity by boron addition of Japan Institute of Metals Journal, 43
('79) 359. ). However, in this method,
It is necessary to add boron in advance as a component for material modification, which is unsuitable for simple use. In addition, if the amount of boron added during melt solidification is increased, the high-temperature strength of Ni ₃ Al is impaired. There is also a problem.

On the other hand, the present inventors have studied the above-mentioned processing process in order to find out the optimum processing conditions for Ni ₃ Al processing.
Bending was investigated the effect of processing speed in the processing, Ni ₃ A
No suitable speed for processing 1 was found. Regarding the above-mentioned working process, no other practical method for improving the workability of Ni ₃ Al has been found.

[0007]

In view of the above situation, the present inventors have developed Ni ₃ A by a simple processing process.
We have been conducting research to overcome the brittleness of l, but in the course of that research, we could improve the processing characteristics by improving ductility etc. even if boron was locally diffused and infiltrated into the surface of the Ni ₃ Al material. Was found. The present invention is based on such knowledge, and therefore, its basic technical problem is to perform processing such as bending, shearing, and drawing by diffusing and infiltrating boron by surface treatment into a Ni ₃ Al material. To improve the performance. A more specific technical problem of the present invention is to omit the addition of boron at the time of material generation and to improve the processability of the Ni ₃ Al material by a simple treatment of diffusion and infiltration of boron into the material. Another technical object of the present invention is to locally improve the workability of a material of Ni ₃ Al by locally performing boron surface diffusion on the material.

[0008]

According to the method of the present invention for solving the above-mentioned problems, boron is locally or entirely diffused and penetrated into the surface of the Ni ₃ Al material, and the processing characteristics are improved by improving the ductility. It is characterized by the following.
When the boron is diffused and infiltrated, a liquid boron diffusing agent is applied to the surface of the Ni ₃ Al material, and the boron can be penetrated by thermal diffusion.

Ni ₃ A to be treated in the present invention
The raw material may be a material which is not melted and solidified, and the size of crystal grains is not particularly adjusted. The addition of boron at the time of forming the raw material may be omitted, and the amount of plastic deformation at the time of processing the Ni ₃ Al raw material may be reduced. The required amount or minimum of boron can be diffused and infiltrated locally on the surface of the large portion, or can be diffused and infiltrated over the entire surface of the material as necessary.

In the diffusion and infiltration of the boron, it is convenient and advantageous to use a liquid diffusing agent or the like which is extremely commonly used to infiltrate by thermal diffusion.
Various means including solid diffusion can be used.
In this case, as will be understood from the following examples, the optimum diffusion conditions for boron are a diffusion temperature of 900 ° C. and a diffusion time of 60 minutes.
An excellent diffusion effect can be obtained in 20 hours. In addition, since the diffusion depth can be changed by adjusting the diffusion temperature and the diffusion time, they can be appropriately adjusted according to the type of processing, and can be adapted to various types of processing.

The boron-diffused Ni ₃ thus obtained
The material of Al, without making it ultra high pressure or high temperature,
Processing can be performed at room temperature using a normal processing apparatus.

[0012]

EXAMPLES Examples of the method of the present invention will be described below. In the experiment, a liquid boron diffusing agent was applied to the surface of a thin Ni ₃ Al sample, and boron was permeated by thermal diffusion.
In order to confirm the effect of improving the processing characteristics, the Ni ₃ Al
Using a thin plate, a three-point bending test was performed to examine the optimal diffusion conditions and how the thermal diffusion and diffusion conditions of boron affect the bending characteristics. The Ni ₃ Al sample used had a stoichiometric composition of 87 wt% (75 at%) of nickel and 13 wt% (25 at%) of aluminum, and had dimensions of 0.2 mm thick × 20.0 mm wide × 30.0 m long.
m. Both surfaces were mirror-polished to R _{max of} about 0.2 μm in order to diffuse boron into the sample.

As a diffusing agent for diffusing boron, a general high-concentration diffusing agent for semiconductors was used and applied to one surface of the sample so as to have a uniform film thickness using a spin coater. This sample was baked at 200 ° C. for 20 minutes, and then subjected to a thermal diffusion process in an N ₃ atmosphere using an infrared gold image furnace.

Table 1 shows the boron diffusion conditions.

[Table 1]

The number of revolutions of the spin coater when applying the above-mentioned diffusing agent was determined by the following method. At a rotation speed of 600 rpm or less, a uniform film surface could not be obtained.
The sample was rotated at five different rotation speeds between pm and 1500 rpm for 20 seconds to apply a diffusing agent to the sample surface, and then the samples were subjected to diffusion treatment at 900 ° C for 60 minutes (heating rate 50 ° C per minute). Referring to the result of comparing stress-strain diagrams obtained from the three-point bending test, the number of rotations was set to 1100 rpm for 20 seconds to apply the diffusing agent. To determine the optimal diffusion conditions, the diffusion temperature is set to 700 ° C, 900 ° C, 110 ° C.
Diffusion time at 0 ° C. and at each temperature is 3
Boron was thermally diffused to one surface of the Ni ₃ Al sample under nine heat treatment conditions for 0, 60, and 120 minutes.

FIG. 1 shows the outline and dimensions of the bent portion in the three-point bending test. In the drawing, reference numeral 1 denotes a sample, 2 denotes a fulcrum roll, and 3 denotes an indentation punch. The bending speed was 0.1 mm per second, and the punch was bent up to 3 mm, that is, a bending angle of 90 ° with the diffusion surface of the sample outside. In addition to the samples subjected to the thermal diffusion of boron under the conditions shown in Table 1, N was used as a raw material for comparison.
An i ₃ Al sample and a sample subjected to only heat treatment with the same heat history as diffusion were also used. The bending characteristics were evaluated by observing the surface of the bending line, the bending stress, the maximum bending stress obtained from the nominal bending strain diagram, the nominal bending strain at that time, the bending angle of the sample, and the point at which microcracks occurred.

When surface analysis by ESCA was performed to confirm boron on the diffusion surface, about 10 at% of boron was detected on the surface. In addition, 90
The sample was bent at an angle and observed on a bending line with a microscope. Cracks occurred in the sample that was heat-treated only without using a boron diffusing agent. However, in the case of boron diffusion,
When diffusion is performed at 900 ° C for 120 minutes for 20 minutes,
The occurrence of cracks was relatively small. On the other hand, when the diffusion temperature was 700 ° C., cracks were observed in the samples treated at any diffusion time. This crack did not occur along the bending line, but when further enlarged and observed, it was found that it occurred at the crystal grain boundary. When the diffusion was performed at 900 ° C., cracks were hardly observed in the diffusion times of 30 minutes and 60 minutes. In the case of 1100 ° C., cracks occurred at all diffusion times,
Less than in ° C. At all the diffusion temperatures, many cracks occurred in the sample subjected to the diffusion treatment for 120 minutes.

FIGS. 2A to 2C show bending stress / nominal bending strain diagrams obtained by a three-point bending test (diffusion temperature: 60 minutes). As can be seen from these figures, the stress increases with increasing strain, but at some point goes beyond the peak and decreases. This is because cracks occur in the bent portion. Therefore, the bending ductility can be evaluated by comparing the strain corresponding to the maximum stress. Regarding the strain value at the time of the maximum stress, the diffusion treatment showed a larger value than the case where only the heat treatment was performed under any condition. The rate of decrease in stress after exceeding the peak indicates the degree of progress of the crack. The phenomenon is remarkable at 700 ° C., and is relatively slow at 900 ° C. and 1100 ° C., thereby suppressing the occurrence of cracks. I understand.

FIG. 3 shows the effect of diffusion temperature on the nominal bending strain at maximum bending stress. The flexural strain increased with increasing temperature, with a maximum nominal flexural strain value of 0.045 at 900 ° C., and decreased at higher temperatures. FIG. 4 shows the effect of the diffusion temperature on the maximum bending stress. There was not much change at 700 ° C and 900 ° C, but it decreased at 1100 ° C. There was no significant change compared to the case of only heat treatment.

FIG. 5 shows the effect of diffusion time on bending strain. The nominal bending strain values for boron diffusion at 900 ° C. and 1100 ° C. once increased with increasing diffusion time, but decreased again at 120 minutes.

FIG. 6 shows the bending angle of the sample processed to 90 ° by the three-point bending test after unloading. In the case where boron diffusion was performed, the variation was smaller than that in the case where only heat treatment was performed.
An angle close to 0 ° was obtained. Looking at the effect of the diffusion temperature on the bending angle, once the temperature rises, the bending angle once becomes 90 °.
However, at 1100 °, a large value was again shown due to the effect of springback.

From the results of the above-mentioned experiments, when the bending ductility of Ni ₃ Al is improved by diffusing boron to the surface, the effect of the diffusion temperature is great. The diffusion conditions of boron are 900 ° C., diffusion time Was found to be optimal for 60 minutes. FIG. 7 shows an example in which a bending stress / nominal bending strain diagram of a sample in which boron is diffused under these conditions is compared with a sample in which boron is added in advance.

In the raw Ni ₃ Al sample, cracks occurred in the elastic region, and no plastic strain was exhibited. On the other hand, the bending stress of the sample containing 0.16 wt% of boron from the melting stage was larger than that of the other samples, and the microcracks occurred when the nominal bending strain value was 0.034. 900
When only heat treatment was performed at 60 ° C. for 60 minutes, microcracks occurred when the nominal bending strain value was 0.03. This value is larger than the value of the sample containing 0.07 wt% boron,
It was smaller than the value of the sample containing 0.16 wt% boron.
However, the nominal bending strain value at the microcrack occurrence point of the sample in which boron was diffused on the surface (Example) is larger than that of any other sample, and the value of the Ni ₃ Al sample as raw material is regarded as 0.01. And a value of about 5 times 0.05.

[0024]

As described in detail above, the processing characteristics of the present invention
The method for improving the easiness is to melt Ni ₃ Al as in a known method.
Even if boron is not added at the stage of solidification, Ni ₃ Al
Just by diffusing boron locally into the surface of the material,
By improving its ductility, etc., it is possible to improve processing characteristics.
It is based on the knowledge of the present inventors that
Improved workability of Ni ₃ Al material such as bending, shearing and drawing.
And a simple treatment called diffusion and penetration of boron.
More locally or completely on the surface of boron
Can be diffused, and the partial workability of the material
Improvements can also be made.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an outline and dimensions of a bent portion in a three-point bending test for evaluating the processing characteristics of a sample.

FIGS. 2A to 2C are bending stress / nominal bending strain diagrams obtained by a three-point bending test for samples having different diffusion conditions.

FIG. 3 is a diagram showing the effect of diffusion temperature on nominal bending strain at maximum bending stress.

FIG. 4 is a diagram showing the effect of diffusion temperature on the maximum bending stress.

FIG. 5 is a diagram showing the effect of diffusion time on bending strain at the time of maximum bending stress.

FIG. 6 is a diagram showing the effect of diffusion conditions on bending angles.

FIG. 7 is a graph showing the bending stress and the processing characteristics of various samples in comparison.
It is a nominal bending strain diagram.

Claims (2)

(57) [Claims] 1. A method for improving the processing characteristics of an intermetallic compound by surface treatment, wherein boron is locally or entirely diffused and penetrated into the surface of a Ni ₃ Al material to improve processing characteristics by improving ductility. . 2. The method according to claim 1, wherein the diffusion and infiltration of boron into the surface of the Ni ₃ Al material is performed by applying a liquid boron diffusing agent to the surface of the material and performing thermal diffusion. Of improving the processing characteristics of an intermetallic compound by the method.