JPS58171542A - Functional cu-zn-al alloy - Google Patents

Abstract

PURPOSE:To obtain a functional Cu-Zn-Al alloy with especially stabilized temp. sensitivity and enhanced resistance to thermal fatigue due to repeated use, by adding a specified precentage of Fe and/or P to a Cu-Zn-Al alloy and by alloying them. CONSTITUTION:0.01-1.0% Fe, 0.01-0.05% P and/or 0.01-0.1% B are added to a Cu-Zn-Al alloy consisting of 68-72% Cu, 2.8-4.5% Al and the balance Zn to obtain a functional Cu-Zn-Al alloy. This alloy is a shape memory alloy contg. martensite having <=500mum, especially <=100mum average grain size. This shape memory alloy has remarkably improved temp. sensitivity, shape restoring power and fatigue resistance. Unsatisfactory shape restoring power and fatigue resistance are considered to be the maximum defects of a convertional alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shape memory alloy based on Cu-Zn-Al, and particularly relates to a shape memory alloy with stabilized temperature sensitivity and improved repeated thermal fatigue resistance.

In recent years, functional materials that can exhibit special properties have been gaining importance in the development of metallic materials, and among them, shape memory alloys are
It is attracting attention as a new alloy that can exhibit both temperature sensitivity and vibration damping properties.

Metal material vca, N1-At, which usually exhibits shape memory effect
More than a dozen types of alloys are known, such as alloys based on copper, Au-Cd, Cu-, At, Cu-Zn, and Ti-Ni.
Among these alloys, Ti has a particularly remarkable shape memory effect.
-Ni-based (trade name Nitinol) and its effect is TtL
The main target is the Cu--Zn--Al system, which is not as sensitive as the -N1 system but has low processability and is economical, and research and development on both of them is being carried out vigorously.

Shape memory alloys, in a broad sense, refer to a group of alloys whose shape reversibly changes through phase transformation, and in terms of phenomena, when a product formed at a temperature above the transformation point (hereinafter referred to as a "sub-formed product") is deformed after cooling. This is a phenomenon in which a deformed product (hereinafter referred to as a secondary molded product) maintains its deformed shape at temperatures below the transformation point, but returns to its original formed state at temperatures above the transformation point. It has been revealed that this is caused by the martensitic transformation of the alloy itself.

The present invention utilizes Cu-Zn-A among these shape memory alloys.
This relates to l-based alloys, and its purpose is to stabilize the temperature sensitivity and improve repeated thermal fatigue properties among the properties of the alloys.

In general, shape memory is expressed by a thermal transformation history curve in which displacement is plotted on the vertical axis and temperature is plotted on the horizontal axis, as shown in FIG.

In this case, a, the temperature at which martensite transformation begins during cooling is the Ms point, the ending temperature is the Mf point, the temperature at which martensite begins to disappear during heating is the A8 point, and the temperature at which it completely disappears is iA.
Assuming point f, each exhibits a characteristic thermoelastic hysteresis mainly due to composition-dependent differences in transformation point. .

The inventors have discovered that in Cu-Zn-Al alloys, Cu
70mm, mainly made of brass with 30% Zn, Cu68~7
All prototype alloys with At content changed from 2.8% (Ms point 80c) to 4.6chi (Me point -1oot:"), each subjected to normal heat treatment and processing conditions 17i
: Various types of plate materials and wire materials were prototyped, and their temperature sensitivity, so to speak, the state of displacement of the products during heating and cooling was investigated. However, it was confirmed that the martensite grain size is an important strength factor for both products in terms of displacement stability and repeated thermal fatigue resistance.

For example, when prototyping a product with M8 point 30 t: (Mf point 10 C), the composition is (: u 70%, At 3.5%
, the remaining zinc and the melting and casting temperatures were respectively 1080 t:,
1040C, 50 mm width x 40 mm length x 100111!
Make a Masa cake, 30 length x 40 length x 100m
A material with a thickness of m was cut out, hot rolled at 650 to 750C to a thickness of 5 mm, and annealing and cold rolling were repeated several times to create a thin plate of 10 mm width x 100 mm length x 1 mm thickness. Next, this flat thin plate was made into a secondary molded product, heated in a temperature range of ~850 C, and quenched in cold water to obtain a crystal grain size of 10.
A martensite composition of 00 to 3000 μm was obtained.

Finally, this quenched sample was bent at the center in the longitudinal direction with a radius of curvature of 20 mm and an angle of inclination of 10 degrees to form a secondary molded product. This sample was heated with 40~50C warm water and 0
~5C cold water showed full bending recovery, but it was about 5000
In this case, the bending displacement, so to speak, the recovery of the shape became weak.

The inventors focused on refining the crystal grain size in order to improve the shape recovery property, so to speak, repeated thermal fatigue resistance, and simultaneously added one or more of Fe, P, and B1Cu-Zn-Az gold alloy as additive elements. It was confirmed that the addition of this compound had an excellent effect on crystal refinement.

That is, when Fe, P, and B were individually added in amounts of 0.01 or less under the same manufacturing conditions as the sample, they all dissolved in the molten metal, and the resulting martensite crystal grain size was 600.
Although multiple refinement was performed to ~1000 μm, the results were weak. Similarly, 1cFe, 0.2%, P [1,Q5
%, 8011% or more is added individually, solid solution formation and partial dispersion precipitation occur, martensite crystal grain size is 5.
However, when the composition exceeds this composition, it rapidly becomes brittle and hardens considerably, which tends to impede workability and shape recovery. Regarding the addition of one element,
It is possible to achieve a certain degree of refinement, and a grain size of about 500 μm is guaranteed, but if possible, further refinement is desirable.
The inventors have Fe O, 01~1.0%, P O, 01~
By simultaneously adding 0.05% and BO in the range of 0.01 to 0.04%, it was possible to refine the vc grain size crystals to a total of 100 μm or less. In this case, FeO,01-1.
When adding 0 or 0.0% or 0.01 to 0.05% of Fe0.01 to 1.0% or 90% of Fe0.01 to 1.0%,
．． 01 to 0.05 chi or two, and further BO,
It has been found that when 0.01 to 0.04% of martensite is added in combination, the grain size of martensite can be advantageously refined.

Regarding the recovery properties of the target marks of the alloy specimens according to the present invention, it was possible to recover them over 10,000 times.

In order to further confirm the effect of crystal refinement, the inventors also conducted a fatigue test against repeated stress on the martensitic grain size of the thin plate itself, which was not subjected to primary and secondary forming. As a result, it was found that the yield strength of the material containing Fe, P, and B according to the present invention was about 2.5 times higher than that of the material containing only the Cu-Zn-At composition. In the example, a test piece (10 mm wide x 100 mm long x 1 mm thick) was used as a single support beam, and stress was repeatedly applied to the free end.
The crystal grain size is 1500 ttm (D 4 (
7) H30kMJT broke after 3 x 10' cycles, but
The P'e, P, and Bft-added product according to the present invention is 1
Even after reaching 0x105 times, it did not break.

As mentioned above, Fe O,01~CO%, po, according to the present invention
o1 to 0.05%, El O,01 to 0.1% all alone or simultaneously added to the shape memory alloy, regarding temperature sensitivity,
Furthermore, the shape recovery properties and fatigue resistance, which were considered to be the biggest drawbacks in the past, have been significantly improved, and this provides an epoch-making alloy manufacturing method.

The present invention will be explained in detail from Example VC below.
1 Cu 70%, At 5.5%, and the remainder Zn were melted in a graphite crucible at 1 o 80 C in an amount of 1.5 kg, cast in a graphite mold, and after cooling with water, a cake of 35 mm width x 45 mm length x 100 thickness was obtained. Next, from this cake, measure 30 mm wide x 40 mm long x 15 mm.
After cutting out the entire am-thick raw sample, the reduction rate was approximately 20%, 7
A plate with a thickness of 5 mm was produced by hot rolling at 00C. The plate was pickled with 10% sulfuric acid, cold-rolled, annealed, and cut several times to obtain a specimen (A) of 10 ll width x 100+ m length x 1 dragon thickness. This specimen was heated at 750 r: 5
The sample was heated for 10 minutes, quenched in cold water, and the quenched specimen was bent 10' at the center with a radius of curvature of 20 m1 to obtain a secondary molded product. The average crystal grain size of martensite in this case is approximately 1
It was 500 μm.

In order to confirm temperature sensitivity, the material was repeatedly immersed in 5°C hot water and 5C cold water, and its shape recovery properties were examined. After approximately 5,200 times7, the displacement change became uneven and structural defects were also observed. Ta.

The inventors noticed that the reason for this clearly depends on the crystal grain size, and added the following elements to refine the grain size.

In the above composition, Fe O, 05%, PO, 02%, B
Sample (B) of the same shape under the same manufacturing conditions with the addition of O.01%? The average grain size of martensite was 90 μm. This sample was repeatedly immersed in hot and cold water under the same temperature conditions, and its shape recovery properties were investigated. As a result, even after 15,000 cycles, the displacement change was smooth and no defects in the surface structure were found. .

Example 2 In order to reconfirm everything in Example 1, the inventors conducted a fatigue test against repeated stress on the same specimens A and ``E3'' used in Example 1vc.First, one end of the specimen was fixed, and the Hold it vertically to the other free end ゛Load 20 kg/
mtn, 30 kg/min 50 times/min
The rupture limit value was determined for all floors. The results are shown in Table-1.

Example 3 Additive element fFe1.1 under the same manufacturing conditions as Example 1
When CH, P O, 06%, B O, 2% (7)
−? /L/Tenside Although the grain size was refined to 1'1100 pm or less, it did not reach 10,000 cycles in the recovery test.

This is because the undissolved additive elements precipitate in the crystal grain size and the material becomes brittle.

Example 4 Under the same manufacturing conditions as Example 1, all added elements were Fe090
When two types of 5CH, PO, OS%, and BO, 03CH are added simultaneously, the martensite crystal grains (■) are refined in the range of 300 to 400 μm, and in the shape recovery test, they are all 12 ,000 or more repetitions were possible.

Example 5 Under the same manufacturing conditions as Example 1, the additive element was FeO, 0.
Martensite crystal grains IJ [ij 400 to 500 μm
In the shape recovery test, both in and
It was possible to repeat the test more than 000 times.

[Brief explanation of the drawings] Figure 1 is a diagram showing an example of a thermal transformation history curve of a shape memory alloy.
FIG. 2 is a diagram showing an example of the shape of the secondary molded product. Figure 1 Vorticity Figure 2 Continuation of page 1 Applicant Dowa Metal Industry Co., Ltd. 76 Matsunogijima, Toyooka Village, Iwata District, Shizuoka Prefecture Procedures Sleeve 11:, Calligraphy (self-motivated) Sleeve 1 Display of 1st grade cow 1982 Patent Application No. 53441 2 Issued Name Cu-Zn-A7 Functional Alloy 3 Person making the amendment Relationship to the case Patent applicant representative Nishi 1) Yao 4 Agent 〒162 6, Details of the amendment The detailed description of the invention is amended as follows. Note (a) “30 throat width x 40++ on length x 100 thickness material” on page 5, line 8 of the specification is “6Dwn width x 40 length x
Corrected to 15mm thick material. ←) "Results" on page 6, line 11 of the specification will be corrected to "effects." (c) Amend "knowledge" on page 9, line 10 of the specification to "r knowledge." ) page 10 line 7 of the specification [20kg/min, 5
0kg/min Jk “20kg/mJ 3okg/
Correct to m1fLJl. (E) “Table 1” on page 10 of the specification will be amended as follows (correction to klil/min″fkg/mti). Table 1 241-

Claims (1)

[Claims] m Cu-Zn-At alloy, 0.0
1-1.0% Fe or 0.01-0.05% P
Cu-Zn-Al with an average martensite grain size of 500 μm or less by alloying one or two of the following.
Functional alloys. (2) Cu-Zn-At according to claim 1, wherein the martensite average grain size is 100 μm or less
Functional alloys. (3) The cu-Zn-At alloy is Cu68
3. The Cu-Zn-Al based functional alloy according to claim 1 or 2, wherein the Cu-Zn-Al functional alloy comprises: 72% At, 2.8-4.5% At, and the balance Zn. (4) In Cu-Zn-Al alloy, 0.
01~1.0 inch Fe and 0.01~0.05 inch P
One or two of these and further 0.01 to 0.1% of B are alloyed to obtain martensite average grain size y soo
A Cu-Zn-At-based functional alloy with a thickness of less than μm. (5) Cu-Zn-A7 according to claim 4, wherein the martensite average grain size is 100 μm or less
Functional alloys. (6) 0u-Zn-At alloy is Cu68~72
%, At28 to 4.5%, and the balance is Zn.
-At-based functional alloy. (710,01~1.0% Fe, 0.01~0.05
% of P, 0.01 to 0.1% of one or more types of B'itC! Cu-Zn-Al is added to a u-Zn-At alloy, processed into a product with a desired shape by plastic working, and then completely quenched to reduce the martensite crystal grain size of the alloy to 500 μm or less.
A method for manufacturing functional alloys.