JPS62263940A - Heat treatment of ti-fe sintered alloy - Google Patents

Abstract

PURPOSE:To provide excellent tensile strength and elongation percentage,by subjecting a Ti-Fe alloy to heat treatment under specific conditions and by forming a metallic structure in which a new-precipitated phase separates out from a solid solution and forms into laminar state along the cleavage planes of solid solution grains. CONSTITUTION:A high-purity iron powder is added to a high-purity titanium powder by a specific weight percentage up to the eutectoid composition, and they are sufficiently blended. The resulting powder mixture is compacted and then sintered in a high-temp. vacuum furnace for a prescribed period. The resulting sintered compact is held at a temp. in a beta single phase temp. region for a prescribed period and then hardened. The above compact is further held at a temp. within an (alpha+beta) two phases temp. region for a prescribed period, which is hardened or is allowed to stand to be cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a Ti--Fe sintered alloy, and more particularly to a method for heat treatment of a Ti--Fe sintered alloy.

Conventional technique II hammered titanium and titanium alloys have high specific strength (tensile strength/specific gravity) and excellent corrosion resistance, so they can be used as shape memory materials for mechanical structural materials such as various chemical industry parts and aircraft parts. It is widely used as a functional material such as alloys and hydrogen storage alloys.

Mainstream methods for manufacturing titanium products include ingot casting, rolling, cutting, and the like.

However, this method is expensive due to poor workability (rollability, machinability) of titanium and low yield, and in the case of titanium alloys with eutectoid structures, segregation tends to occur and the structure is non-uniform. There are some problems.

In order to solve the above problems, various methods for producing titanium alloys using powder metallurgy have been studied.

In this method, titanium powder and powder of another metal are mixed in a predetermined ratio, compression molded, and sintered.

This powder metallurgy method has the potential to solve all the problems of segregation and machining difficulties that occur with melt-sawn materials.

However, titanium-based alloys are sometimes used under harsh conditions, and one major problem is how to increase the sintered density.

Among these, a sintered material of a mixed powder of titanium powder and Group 8 element powder (iron, cobalt, nickel, palladium) that undergoes a eutectic reaction at relatively low temperatures has been studied.

-1- A certain weight % (several weight % to at most 10 weight %) of powder of the S3 group metal element is added, molded under high pressure, and sintered at a high temperature (100 (1 to 1400°C)). ,
The relative density reached nearly 100%, and densification was achieved.

However, among these sintered materials, Ti--Fe alloys have increased tensile strength but decreased elongation. According to some experimental results, the tensile strength was about 90 kgf/mm2 and the elongation was 0.25%. For this reason, it cannot be used practically as an alloy for mechanical structures. The above-mentioned problem applies not only to Ti-Fe but also to Tl-C01T.
This also occurs in the case of alloys with eutectoid structures such as i-Ni alloys.

In alloy systems that do not eutectoid, such as Ti-(I to I-4V alloys), the mixed powder of the alloy powder is compressed and pressed, then sintered for several hours, and the sintered alloy is heated to a temperature of, for example, 1050°C, which is in the β phase. When the alloy is held in the area for a predetermined period of time and water quenched, an alloy with mechanical properties of tensile strength of about 90 Kgf/mm2 and elongation of about 10% is obtained.
II
When the IP treatment is performed, the 111 grain phase does not exist, and an alloy with a homogeneous and fine (α and β) two-phase structure is obtained. The mechanical properties of this alloy include tensile strength of approximately 100Kgf/mm2,
The elongation rate was about 17%. These properties are sufficient to withstand use as an alloy for mechanical structures.

UI! As mentioned above, in the conventional technology, Ti-Fe.

Segregation occurs in the melting process of alloys such as Ti-Co and Ti-Ni that have a eutectoid structure. However, when a mixed powder of titanium and Group 8 elements is sintered, no large segregation occurs;
Moreover, a dense sintered material can be obtained. The sintered material (A) has considerable tensile strength, but has almost no elongation.On the other hand,
In addition, in alloy systems that do not eutectoid such as Ti -6AI -/lV alloy, the β phase is quenched and the l-I
IP treatment yields a tough material with high tensile strength as well as high elongation.

However, in the Ti-Fe based titanium alloy sintered material, which is a type of eutectoid alloy that occurs for eutectoid use, there are no proper heat treatment conditions to realize an alloy that is dense and has sufficient tensile strength and elongation. It wasn't obvious.

Therefore, an object of the present invention is to provide a method for heat treatment of a Ti-Fe-based sintered alloy, which enables production of a Ti-Fe-based titanium alloy sintered material having high tensile strength, high elongation, and dense and tough properties. Our goal is to provide the following.

I! As a result of various studies to solve the conventional problems, the inventors of the present invention have developed Ti-
It has been discovered that a tough material can be obtained by appropriately heat-treating Fe mixed powder, and the present invention has been completed based on this knowledge.

That is, the heat treatment method for a Ti-Be-based sintered alloy of the present invention involves adding high-purity iron powder to high-purity titanium powder in a specific weight percent below the eutectoid composition and thoroughly mixing the resulting mixture. After compacting the powder, it is sintered in a high-temperature vacuum furnace for a certain period of time, and the obtained sintered material is held at a temperature in the β single phase temperature range for a certain period of time, then quenched, and then it is further sintered into two (α and β) phases. It is characterized by being kept at a temperature within a temperature range for a certain period of time and then being quenched or left to cool.

In the method of the present invention described above, as-sintered Ti
-The metallographic structure of the Fe-based alloy is such that a new precipitated phase precipitates from the solid solution and becomes plate-like along the cleavage planes of the solid solution particles, so-called Widmannslatte.
n) structure, and this structure becomes finer as the amount of Fe element increases. When this sintered alloy is quenched from the β phase,
The result is a mixed structure of martensite α° and residual β phase, or a single structure of residual β phase. In addition, when the alloy quenched from the β phase is further kept at a constant temperature within the (α + β) two-phase region and cooled, the α phase precipitates from the martensite α″ or residual β phase, and the fine (α + β) two-phase The improvement in ductility was obtained by this series of heat treatments (α”−β)
This is obtained by improving the ratio of α/β phase in the phase structure and refining the structure.

To summarize the following -1-, a Ti--Fe based alloy has a fine and uniform metal structure.

Example Hereinafter, the present invention will be explained in more detail with reference to Examples.

The method for manufacturing the Fe-Ti based sintered alloy of the present invention will be explained.

First, T made by Osaka Titanium■ with a purity of 99.5% or more - 1 unit.
S P-350Ti (particle size: 350 mesh or less), Badishe-Anilin and 5or
Carbonyl Fe powder (average particle size 4-5 μm, purity 99.8% or more) sold by la-Fabrik AG, etc.
Add tJ at 2% by weight or 4% by weight, and then add lubricant and mix thoroughly. After molding each of the obtained mixed powders (molding pressure 6 tf/ci), the mixture was heated at 1200°C (1
473 K) for 1 hour.

The following method for processing the sintered body will be explained with reference to the attached FIG. 1. FIG. 1 is an equilibrium phase diagram of the Ti--Fe system, where the vertical axis is temperature (K>) and the horizontal axis is Fe content (wt%).

First, the sintered material is heated to 950℃ (1223K), which is the β single phase region.
After holding for 30 minutes, water quenching is performed. Furthermore, at 640°C (913K), which is the temperature of the (α10β) phase region, Fe
The mechanical strengths of the alloys are shown in Table 1 below, as measured for water-quenched alloys after holding the sintered bodies containing 2% by weight or 4% powder for 5 hours or 20 hours, respectively. The static tensile properties of these samples were measured using an Instron universal testing machine.

The values shown in Table 1 in Table 1 indicate (α + β) 2
This is a value that fully satisfies the tensile strength of 91 Kgf/...m or more and the elongation of 10% or more specified in ΔSTM B38, which is the standard for casting materials of Ti-6AI-4V alloy, which is a phase alloy. The tensile strength of the sintered body of the present invention exceeds 69.3 Kgf/mm2 of sintered titanium and 90.4 Kgf/mm2 of Ti-5tle sintered body, and has significantly better mechanical properties. It shows. The sintered material of item 1 has high tensile strength and high elongation, so it can be used as an alloy for machine structures.

As explained above, according to the heat treatment method for Ti-Fe-based sintered alloy according to the present invention, by molding and sintering a mixed powder of titanium and iron and heat-treating it, segregation in the molten material can be reduced. It has high tensile strength, high elongation, and can be used as a mechanical structural alloy.

This means that it is highly expected that its use as a titanium-based material for aircraft parts will expand.

[Brief explanation of drawings]

FIG. 1 is an equilibrium state diagram of the Ti-Fe system. Patent applicant Kei Sho Tsukasa Department 1] Yutomo Heavy Machinery Industry Co., Ltd.

Claims (1)

[Claims] High-purity iron powder is added to high-purity titanium powder in a specific weight percent below the eutectoid composition, mixed thoroughly, the resulting mixed powder is molded, and then sintered in a high-temperature vacuum furnace for a certain period of time. The obtained sintered material is held at a temperature in the β single-phase temperature range for a certain period of time, then quenched, and then held at a temperature in the (α + β) two-phase temperature range for a certain period of time, and then quenched or allowed to cool. A heat treatment method for a Ti-Fe based sintered alloy.